CONGENITAL ANOMALIES AND PEDIATRIC PLASTIC SURGERY
CHAPTER 28 MISCELLANEOUS CRANIOFACIAL CONDITIONS: FIBROUS DYSPLASIA, MOEBIUS SYNDROME, ROMBERG SYNDROME, TREACHER COLLINS SYNDROME, DERMOID CYST, AND NEUROFIBROMATOSIS
ROBERT J. HAVLIK
This chapter describes several disorders that do not “fit” in with other conditions in plastic surgery, or for that matter, with other conditions in medicine. With the exception of neurofibromatosis, these conditions are distinctly uncommon. With the rapid developments in molecular biology, two of these disorders have been shown to be caused by disorders in intracellular second messenger systems—fibrous dysplasia and neurofibromatosis 1 (NF-1).
Fibrous dysplasia is a benign disorder of the bone that affects both the axial and the craniomaxillofacial skeleton. Fibrous dysplasia is not “classically” a congenital disorder, since it is not usually evident at birth, but becomes clinically evident during late childhood or adolescence. It occurs sporadically and genetic transmission has not been documented. Fibrous dysplasia has been traditionally divided into three main categories: monostotic (or monocystic), polyostotic, and the McCune-Albright syndrome. The majority of patients (~70% to 80%) present with a single area of bony involvement (monostotic or monocystic fibrous dysplasia).1 Of the patients with polyostotic fibrous dysplasia (20% to 30%), approximately 3% present with a triad of polyostotic fibrous dysplasia, precocious puberty, and skin pigmentation known as the McCune-Albright syndrome.1 This skin pigmentation presents as “café-au-lait” spots with irregular borders, described as being similar to the coastline of Maine. In addition to this classic triad, McCune-Albright syndrome is also associated with several different endocrine disorders, all caused by autonomous hormonal overproduction, such as growth-hormone producing pituitary adenomas, hyperthyroid goiters, and adrenal hyperplasia.
The craniomaxillofacial structures are involved in approximately 25% of cases with monostotic fibrous dysplasia and up to 50% of cases with polyostotic involvement. The most common presentation in the craniofacial skeleton is that of a painless, enlarging mass of bone. The maxilla is the bone most often involved, followed in frequency by the frontal bone, but all bones of the craniomaxillofacial skeleton may show involvement. The clinical manifestations of fibrous dysplasia include expansive growth leading to aesthetic and functional compromise. Maxillary lesions can lead to dental malocclusions, tilting of the occlusal plane, or significant facial deformity and asymmetry. In lesions with orbital involvement, visual disturbance, ocular proptosis, and orbital dystopia can occur. In lesions with sphenoid involvement, blindness may occur as a result of impingement on the optic nerve.
The difficulty in the diagnosis of fibrous dysplasia varies with the extent of presentation of the disease. The polyostotic and McCune-Albright forms of fibrous dysplasia are relatively easily diagnosed based on clinical and radiologic investigation, whereas establishing the diagnosis of the monostotic form is more difficult because of the number of other important lesions that are included in the differential diagnosis. In the axial skeleton the lesions frequently appear as well-circumscribed radiolucent lesions with a thin sclerotic periphery. In contrast, the lesions of the craniofacial skeleton are more poorly defined and more radiopaque. Bone biopsy in many areas of the axial skeleton in fibrous dysplasia is generally avoided, especially where the risk of pathologic fracture is high. However, in the mandible, where monostotic involvement is most frequent in the craniomaxillofacial skeleton and therefore there is the greatest difficulty differentiating this from other solitary bony lesions, bone biopsy has not been reported to cause a pathologic fracture in fibrous dysplasia. Malignant degeneration of fibrous dysplasia has been reported to occur in 0.5% of cases with monostotic involvement, and up to 4% of cases with McCune-Albright syndrome. Notably, the most frequent site for sarcomatous degeneration is the craniofacial skeleton.
This disorder is centered around a structural and functional change in the cellular transduction mechanism involving G-proteins.1 The G-protein is a membrane-bound intracellular signaling mechanism that carries the message of extracellular hormone binding into the cell to create an effect. The G-proteins themselves have an intrinsic activity that causes hydrolysis of GTP to GDP. In fibrous dysplasia, the G-protein has a decreased ability to hydrolyze GTP, resulting in the G-protein remaining in an activated state, leading to continued stimulation of cAMP and multiple other effects.1 Significantly, many of the adrenal, hypophyseal, thyroid, and gonadal cells of patients with McCune-Albright syndrome show the same mutations, thereby leading to increased “on” activity, and constitutively increased hormone production.
It has been postulated that the timing at which this mutation occurs in embryologic development may determine the clinical extent of the disease. In other words, a mutation that occurs late in embryologic development or even a postnatal one will lead to a decreased cellular complement with the mutation and therefore lead to the development of monostotic bone involvement. In contrast, a somatic mutation that occurs in early embryologic development would lead to a larger portion of afflicted cells within the individual, and this leads to multicentric involvement (polyostotic fibrous dysplasia). If the mutation occurs early enough in development, it may also lead to the involvement of additional tissues (endocrine disorders, McCune-Albright syndrome, etc.). As noted above, there have been no documented cases of genetic transmission of fibrous dysplasia, it is believed to be a lethal mutation.
Treatment of fibrous dysplasia in the craniofacial skeleton is determined by the functional or aesthetic problems created by the disease process. The mere existence of fibrous dysplasia does not mandate treatment. In bones of the axial skeleton, the expansile process, coupled with cortical resorption, can lead to decreased structural strength and pathologic fracture. This is seldom the case in the craniomaxillofacial skeleton, and indications for treatment are more frequently related to aesthetic imbalance, facial disfigurement, distortion of the functional occlusion, ocular proptosis, and impingement on neural foramina. Impingement on the optic nerve has led to visual disturbance and blindness.
Treatment recommendations for fibrous dysplasia have occasionally been made based on the clinical observation that the disease will “burn out” in the post-pubertal adolescent state as skeletal maturity is reached. Unfortunately, there are no data to support this contention.
Surgical treatment is often designed to counter the effects of mass expansion and the consequent deformity that occurs in the facial skeleton. Therefore, in most cases, surgery of the craniofacial skeleton will consist of either a contour reduction of the afflicted area, or resection and replacement of the affected bone. Contour reduction is a more limited operation, but the lesion always recurs. A decision is made between contour reduction versus resection and replacement based upon the rate of tumor growth, or the “aggressiveness” of this benign process, and the location and potential complications of continued growth and expansion. Resection is followed by reconstruction with either prosthetic materials or bone autograft.
In the cranial vault, bone involvement is frequently both expansile and hyperostotic. The frontal bone is the most frequently involved bone, followed by the sphenoid bone. In the case illustrated inFigure 28.1 both resection and contour reduction techniques were used for hyperostotic fibrous dysplasia in the right frontoorbital region and the right parietal region. The resection and cranial bone autograft reconstruction were performed in the right orbit and frontal bone, where the potential problems with recurrent tumor and repeat resection would be more complicated. In contrast, the parietal bone was completely removed, and contour reduction was performed down to the level of the cortical plate. When fibrous dysplasia involves the skull base, surgical resection is not possible.
Fibrous dysplasia of the orbit raises several special considerations. First, the mass effect of bone growth can lead to dystopia and visual disturbances. The potential problems of recurrence in this area, particularly with the potentially more difficult surgery in the recurrent field from scarring, often swing the balance toward resection of the afflicted bone and replacement. Second, specific to the orbit is the concern that growth of fibrous dysplasia can lead to optic nerve compression, subsequently leading to visual change and blindness. Visual loss has been cited as the most common neurologic complication of fibrous dysplasia involving the skull.
Although optic nerve decompression in patients with fibrous dysplasia of the sphenoid surrounding the optic canal and with documented changes in vision is widely accepted, “prophylactic” decompression of the optic nerve is not recommended. Furthermore, decompression after visual decrement or visual loss will not restore the visual deficit.2 The risks involved with surgical decompression of the nerve include a lack of improvement in vision, which occurs in anywhere from 5% to 33% of cases, and blindness resulting from the surgery.2
Fibrous dysplasia of the mandible presents as a mass lesion with cortical expansion. Because the presentation with mandibular disease is frequently monostotic, bone biopsy may be indicated to establish or confirm the diagnosis. As noted previously, biopsy of the mandible can be safely accomplished in fibrous dysplasia without a significant risk of fracture. Depending on the severity of the involvement, either contour reduction or resection can be performed. In lesions involving the ramus in which the temporomandibular joint (TMJ) is spared, every effort should be made to plan the resection and reconstruction maintaining the existing joint. In larger lesions, resection of the tumor with free fibula reconstruction is a reasonable approach.
Until recently, surgical treatment was the only option for the treatment of fibrous dysplasia. Recently, several small series have been published using medical therapy with pamidronate, an aminobisphosphonate.3 This treatment has resulted in an increase in bone mineral density and radiologic signs of healing with the thickening of the cortical bone in some cases. In many cases, there has also been a significant decrease in pain with pamidronate therapy. Bisphosphonate therapy can be complicated by the formation of bony sequestra. Figure 28.2 shows a bony sequestrum of the maxilla that eroded through the palate. Radiation therapy is contraindicated because of an increased propensity for malignant transformation.
Moebius syndrome is a rare disorder characterized by absence of certain cranial nerves. Classically, Moebius syndrome is defined by the absence of the sixth and seventh cranial nerves resulting in masklike facies, incapable of animation, and an inability to laterally deviate the eyes (abducens palsy). The inability to show a facial response to verbal and nonverbal communication is a devastating deficiency. In the United Kingdom, there were approximately 90 cases of Moebius syndrome in a population of 50 million people, yielding a prevalence of 1 in 550,000. By extrapolation, in the United States there would be expected to be approximately 500 cases. In some publications, Moebius syndrome is defined more broadly, including patients with additional facial nerve palsies. Involvement of nearly all of the facial nerves has been documented, but the third, ninth, tenth and twelfth nerves are most commonly involved.4 In addition to the characteristic facies associated with the sixth and seventh nerve palsies, ptosis, nystagmus, or strabismus may be present, and epicanthal folds are frequent (Figure 28.3). The nose typically has a high, broad nasal bridge, and this increased breadth extends downward to the nasal tip. The mouth opening is typically small. In addition, there can be hypoplasia of the tongue, either unilaterally or bilaterally. There frequently is poor palatal mobility, poor suck, inefficient swallowing, and drooling. The mandible tends to be hypoplastic. These factors can contribute to difficulty feeding during the first year of life, frequently leading to poor growth. A coarse voice and speech impairment can be present, although hearing is usually normal. As the child grows, the ability to open the mouth and feed improves slowly and significantly. The facial paralysis and masklike facies may tend to bias early estimates of psychomotor activity, which tend to be low. Despite the perception created by the lack of facial expression, only 10% to 15% are mentally retarded.4
Etiology and Pathogenesis
The etiology of this disorder has not been clearly elucidated. It occurs sporadically, and in cases of “classic Moebius syndrome” involving only sixth and seventh cranial nerves, genetic transmission is rare. For Moebius syndrome, four separate and distinct, though not mutually exclusive, pathogenetic mechanisms have been advanced: (1) aplasia/hypoplasia of the cranial nerve nuclei; (2) destruction of the cranial nerve nuclei; (3) peripheral nerve abnormalities; and, (4) primary myopathy. Operative findings and postmortem examinations have supported each of these four mechanisms.4,5 In those patients with cranial nerve nuclei deficits, as with other central deficits, “downstream” changes in nerve and muscle would be expected to occur.
FIGURE 28.1. Fibrous dysplasia. A. Preoperative lateral view of fibrous dysplasia involving right orbit, frontal bone, and parietal bone. B. Preoperative “worm’s eye” view. C. Preoperative axial CT image. D. Intraoperative view showing increased density of fibrous dysplasia involving right frontal and right parietal bones. E. Planned split graft donor site using metallic template fabricated in 1F (illustration by Min Li MD). F. Intraoperative view following completed resection of tumor and reconstruction of orbital roof and supraorbital bar using split cranial bone grafts from left parietal bone and contour reduction of right parietal bone. G. CT scan showing completed reconstruction. H. Three-year postoperative frontal view. I. Three-year postoperative “worm’s eye” view.
FIGURE 28.2. A. Axial and (B) coronal images of bony sequestrum of maxilla in patient with fibrous dysplasia that eroded through palate.
Treatment has progressed more rapidly than our understanding of this rare disorder. This treatment is focused on alleviating one of the most socially devastating problems of this disorder—the inability to show a facial response. Facial reanimation surgery, which employs microvascular free muscle transfer innervated through the use of a suitable motor nerve, is effective in restoring function in many different etiologies of facial nerve deficits, and this treatment has been extended to Moebius syndrome. Zuker et al. report a series of 10 patients who had an average movement of their oral commissures following bilateral microvascular transfers of 1.37 cm, allowing for meaningful and deliberate facial animation.5 In addition, the children showed improvement with drooling and improved ability to drink. The surgery also has a definite benefit on speech.5
FIGURE 28.3. Child with Moebius syndrome with typical masklike facies and downslanted oral commissures.
ROMBERG DISEASE (PROGRESSIVE HEMIFACIAL ATROPHY)
Progressive hemifacial atrophy (PHA) is widely known by the eponym Romberg disease. In an era of molecular and genetic analysis, PHA remains the most enigmatic of the craniofacial disorders. The etiology of this disorder remains unknown.
PHA may involve any or all of the facial tissues, typically involving skin and subcutaneous tissue, but also potentially muscle, cartilage, and bone. Although there is new evidence that the trigeminal nerve (V) is involved, Pensler et al.6 have reviewed the clinical course in 41 patients and report that the initial presentation included the distribution of V1 in 35% of cases, the distribution of V2 in 45% of cases, and the distribution of V3 in the remaining 20% of cases. Facial involvement is unilateral in 95% of all cases, and either side of the face is equally likely to be involved. The initial presentation typically involves the skin and may be quite subtle, sometimes including pigment changes in which there may be either a brownish or bluish color to the skin, or even hypopigmentation. Alternatively, the disorder may present as a limited area of atrophy of the subcutaneous fat. A striking archetypal presentation often includes a nearly vertical linear depression of the forehead extending into the eyebrow and frontal hairline, known as the coup de sabre, or “cut of the saber” (Figure 28.4). This clinical sign was thought to be pathognomonic for Romberg disease, but can also be noted in linear scleroderma, a subtype of localized scleroderma, and this has led to a potential overlap of these diagnoses.
FIGURE 28.4. Progressive hemifacial. A. Frontal view of 14-year-old female with onset at 10 years. There is a large area of alopecia of scalp, mild soft tissue depression, loss of medial eyebrow, and vertical deficiency of right alar rim consistent with a mild “coup de sabre” type deformity. The nose not only shows vertical deficiency, but also thinning and collapse. Radiographic evaluation revealed no evidence of skeletal irregularity. B. Intraoperative view showing dermal fat graft in position for grafting soft tissue deficiency of forehead. An ear cartilage conchal bowl composite graft was used to reconstruct the alar deficiency after the rim was dissected free. C. Initial postoperative result of ala reconstruction. D. Postoperative result. The dermal fat graft initially led to significant overcorrection of the deficiency, but now yields a favorable result. The alar correction was diminished by the late presentation of a Pseudomonal infection of the cartilage.
PHA is not a congenital disorder, with the typical onset being in the first or second decade of life. The hallmark of the disorder is a slowly progressive course, with an “active phase” of disease characterized by involution, or “wasting away” of the skin, subcutaneous tissue, and muscle. This active phase lasts from 2 to 10 years. The subcutaneous tissue is the most severely involved, followed by substantial involvement of the skin and muscle. The facial musculature undergoes thinning, but usually maintains sufficient power to animate the face. The muscle involvement commonly includes atrophy of the tongue and palatal tissues. Patients with an early age of onset (during facial growth) are much more likely to have significant skeletal involvement. Pensler et al.6 report that 65% of their patients had osseous involvement, and they found a strong correlation between the age at onset and the degree of bone hypoplasia. However, in their review, they noted no correlation between the other findings of severity of soft tissue atrophy, the duration of the disease, the initial site of skin changes, and the eventual location or magnitude of the skeletal involvement.
In cases where the disease occurs during the first decade of life, profound skeletal hypoplasia is usually present. This stands in distinct contrast to those cases that present initially in the second decade of life. In these latter cases, there is typically limited, if any, impact on the facial skeleton with the gross morphologic changes being limited to the skin and subcutaneous tissue. The patient in Figure 28.4had disease onset at 10 years of age. There is clinical involvement of the skin, eyebrow, and periocular tissues. There is clearly hypoplasia or atrophy of the right nasal sidewall and cartilaginous atrophy of the nasal ala. Her dental development and occlusal relations show no signs of involvement. In view of this strong correlation of the severity of this disorder with the age of onset, it is unclear whether the facial skeleton actually undergoes atrophy. More likely, the bone fails to develop fully in the field of overlying atrophy of the skin and subcutaneous tissue. The skeletal “atrophy” in PHA is more accurately termed hypoplasia.
In early onset cases, the skeletal involvement often includes the mandible and midface, with concomitant implications for the occlusal relationships and facial appearance. There can be hypoplasia of the mandible, including significant vertical undergrowth of the ramus and a deficiency in posterior facial height. The mandible may also show significant sagittal undergrowth. The maxilla may also manifest both vertical and sagittal undergrowth in the sagittal plane. Because the involvement is unilateral, profound tilting of the occlusal plane develops. When PHA involves periorbital tissues enophthalmos is a frequent finding. Pensler et al., based on radiographic orbital measurements, suggest that the enophthalmos is not due to a skeletal change in the orbital volume, but that it is related to atrophy of the periorbital soft tissues.6
PHA can be associated with many other findings, including areas of skin and subcutaneous atrophy elsewhere on the body distinct from the face. The disorder is associated with nervous system dysfunction including Horner syndrome, trigeminal neuralgia, and unilateral mydriasis. Central nervous system involvement has been reported in smaller series by several authors, ranging from MRI changes to seizure disorders. However, the relative paucity and inconsistency of data at this point precludes any definitive correlation between these reports.
The etiology of PHA is unknown. PHA does not show any genetic predilection, is found in all races, and there is no evidence of a hereditary basis. It does occur more frequently in females in most series. Patients will frequently remember an “initiating event” in PHA and the onset of the disorder is often linked to an episode of trauma or infection. However, it is unclear whether this is simply an event that calls attention to a subtle area of initial clinical involvement, or whether there are true pathogenetic associations. Traditionally, three theories have been advocated for the etiology of Romberg disease: the infection hypothesis, the trigeminal-peripheral neuritis hypothesis, and the sympathetic hypothesis. The infectious hypothesis was historically linked to an irritation of nerves. In the current era of a new understanding of infectious agents (viruses, prions, mad cow disease, chronic wasting disease of deer, etc.), the infectious hypothesis may be remain a tenable etiology until a definitive understanding of this disorder is truly established. The trigeminal-peripheral neuritis hypothesis suggests a neuritis involving the trigeminal nerve, and is supported by episodes of pain in the involved areas prior to the onset of tissue involution. The sympathetic hypothesis is based on an association of Horner syndrome, pilomotor reflex changes, unilateral mydriasis, vasomotor disorders, unilateral migraine, and perspiration disorders. Based on current evidence, no definitive etiology has been established.
The insightful work of Pensler et al. has provided some enhanced understanding.6 First, in their clinical review, they found no evidence of sensory, sympathetic, parasympathetic, or sudomotor dysfunction. Muscles of mastication and facial expression were found to be fully functional. Biopsies revealed epidermal atrophy and a variable perivascular mononuclear cell infiltrate, with morphologic characteristics of lymphocytes and monocytes, that were grouped around dermal neurovascular bundles. Many of the venules were noted to have striking degenerative alteration in the lining epithelium with reduplication of the basal lamina. Significantly, they also noted that elastic fibers were present and morphologically intact (in contrast to linear scleroderma). They interpret these findings as being consistent with a lymphocytic neurovasculitis, and they advance this theory as a pathogenetic mechanism.
Understanding the pathogenesis of this disease is complicated further by the apparent overlap between the disorder of linear scleroderma and PHA. It is very likely that many of the cases that have historically been termed Romberg disease may include cases of linear scleroderma, since differentiating the two clinically is difficult, if not impossible. Linear scleroderma may also show monocytic infiltrates. The only finding that has been reported as useful to differentiate these two disorders is the absence of elastic fibers in the scleroderma group, and their preservation in the PHA group.6 The fact is that these two diagnoses may be describing the same entity.
Many surgeons will defer treatment until the disease “burns out,” or reaches a stable plateau phase. For milder asymmetry and atrophy of the skin and subcutaneous tissue, injection of collagen and hyaluronic acid derivatives or fat injection can provide some benefit.
For small areas of asymmetry, dermal grafts, fat grafts, or dermal-fascial-fat grafts can be considered. These can be tailored to smaller defects and provide an acceptable improvement with a limited operative approach and limited operative time and risk (see Figure 28.4). However, because of the variability in graft survival, overcorrection is necessary. In addition, there is typically a postoperative period that is characterized by induration. The technique of serial mini-graft “threading,” as described by Coleman, has enhanced the reliability of autologous fat grafting.7 Overall, the experience in the literature with larger nonvascularized transfer of fat tissue has been inconsistent.
Microvascular free tissue transfer is the gold standard in reconstruction for Romberg disease. Upton et al.8 reported microvascular transfer of scapular and parascapular flaps in 30 patients, five of whom had Romberg disease. They utilized long fat-fascial extensions with these transfers to fill isolated areas. They noted no postoperative atrophy in the 30 flaps, but they did note that in patients who gained weight, the flap volume increased. In addition, there were isolated areas, such as the upper lip, that tended to be undercorrected. They also noted no evidence that free tissue transfer altered the natural history of the disease process in PHA.
In children with the early onset of the disorder, there is often distortion of the orbit and the zygomaticomaxillary complex, leading to vertical orbital dystopia. Depending on the severity, this can be corrected either through corrective osteotomies and vertical repositioning of the orbit, or through bone grafting of the orbital floor. Involvement of the lower face leads to severe maxillary and mandibular asymmetries, with distortion of both the facial midline and occlusal plane. Bimaxillary surgery is necessary to correct the occlusal plane.
TREACHER COLLINS SYNDROME
Treacher Collins syndrome, or mandibulofacial dysostosis, is a craniofacial disorder that has an incidence of between 1 in 25,000 to 50,000 births and is characterized by a range of clinical presentations. The full clinical presentation is characterized by hypoplasia/aplasia of the body and arch of the zygoma, a significantly increased facial convexity, mandibular hypoplasia, a retrusive chin with increased vertical height, and external ear anomalies. A key distinguishing feature of this entity is that it is bilateral and symmetrical. The periorbital soft tissues show an antimongoloid slant of the palpebral fissures. The lower eyelid is hypoplastic with a coloboma located at the junction of the medial two-thirds and lateral third of the lower lid. The deficiency involves both the skin of the eyelid and the cartilage of the tarsal plate. The lower eyelid also lacks eyelashes typically over the medial third, and the lower eyelid is vertically deficient. These findings, along with the hypoplastic zygoma, lead to a striking clinical appearance (Figure 28.5). The nose is broadened in the midnasal dorsum, and can have a slightly elongated appearance. The midface is hypoplastic, particularly at the level of the zygomatic body and arch, but also in the maxillae. The mandible is characteristically hypoplastic, with a chin that has the unusual combination of findings of being both increased in vertical height but deficient in sagittal projection. An anterior open bite is often present. This combination exacerbates the overall clinical appearance of a facial profile that is much too convex. Cephalometric analysis has revealed that this facial convexity is attributable to the mandibular hypoplasia and position, since the relationship between the midface and the anterior cranial base is essentially within the normal range (SNA angle). In addition, the occlusal plane tends to be quite steep, with a clockwise rotation of the plane (hypoplastic posteriorly with decreased posterior facial height). There are characteristically significant deformities of both the external and middle ear present, with a low lying hairline with tongue-shaped caudal extensions of hair-bearing scalp in the preauricular areas.
FIGURE 28.5. Treacher Collins syndrome. A. Characteristic facies with orbital findings including vertically deficient lower lid, lateral eyelid coloboma, downslanting palpebral fissures (antimongoloid slant), and hypoplastic malar eminences. B. Five-year-old male with result of lid switch procedure with conjunctival grafting and canthopexy performed at age 3 shows improvement in the orientation of the palpebral fissure following resolution of edema and flap prominence (with no further surgery or treatment) reveals favorable eyelid and palpebral fissure position with deficiency over lateral malar eminence. C. Approximately 1 year result after dermal fat grafting shows improved contour in the malar eminence in 7-year-old.
Treacher Collins is an autosomal dominant disorder, with a markedly variable penetrance. While up to 60% of cases are thought to arise de novo, the variability in penetrance occurs at both the interfamilial and the intrafamilial level. All known cases of Treacher Collins result from mutations in the TCOF 1 gene. The TCOF 1 gene has been mapped to the 5q31.3-5q33.3 gene locus. Identification of family-specific mutations and tracing these specific mutations through family pedigrees have shown that the actual number of cases arising de novo may be less, and the familial transmission rate may actually be higher, since family members previously thought to be unaffected may in fact show the genetic mutation.
Patients with Treacher Collins syndrome often require a life-saving tracheostomy at birth. The cranial vault may show a mild deficiency in bitemporal diameter, but this is never of the magnitude to merit surgical intervention. The orbital changes, however, are striking and pathognomonic for this disorder. The orbital changes are consistent with the hypoplasia of the zygoma that characterizes the disorder. Treatment goals include the correction of both the lower eyelid and the craniofacial skeleton.
No perfect procedure exists for the lower eyelids. The cutaneous deficiency can be corrected through a lid switch operation. The lid switch operation, with a laterally based banner flap consisting of skin and orbicularis oculi muscle, has the advantage of providing vascularized tissue with an excellent skin color match (Figure 28.5). The lid switch also has a salutary benefit of vertical repositioning of the lateral canthus contributing to the correction of the antimongoloid slant of the palpebral fissure. This flap, however, may become edematous and remain “prominent” for a prolonged period of time.
Several different techniques have been described for reconstruction of the hypoplastic zygoma, including both split thickness and full thickness cranial bone grafts, vascularized calvarial grafts based on a temporalis muscle pedicle, and rib grafts. The cranial bone grafts are typically cut as one-piece T-shaped grafts that serve to reconstruct the body of the zygoma, the zygomatic arch, and the inferior orbital rim. Rib grafts are joined through the use of plates. Technical problems include the paucity of soft tissue in the malar eminence that is available for coverage of the skeletal reconstruction, a soft tissue problem exacerbated by the net volume expansion required with the reconstruction of this area. Bone grafts in this area of craniofacial skeleton, however, eventually undergo resorption. This may be partially due to the overlying soft tissue “matrix” in this disorder, and partially attributable to the inherent tendency of onlay bone grafts to undergo resorption with revascularization. The deficiency of soft tissue coverage may also influence the problems with graft revascularization.
A component of the controversy regarding reconstruction of the zygoma includes a consideration of the timing of reconstruction of the zygoma and the age of the patient. Posnick et al.9 reported favorable results with reconstruction of the zygoma using full thickness bicortical grafts for reconstruction of the zygoma at an age of 5-7 years. An alternative in the younger child about to start school is the use of dermal fat grafts to help correct the soft tissue deficiency and effectively camouflage the skeletal deficiency (Figure 28.5). Siebert has employed bilateral soft tissue free flaps to camouflage the skeletal deficiency with results that rival or exceed any skeletal reconstruction.
The nasal deformity in Treacher Collins includes a broad midnasal dorsal hump, further accentuated by the retrusive chin. The nasal dorsum is correctable through conventional rhinoplasty approaches and procedures, with the usual caveats regarding avoiding airway obstruction.
Approximately one-third of Treacher Collins patients have a cleft of the palate. Strict attention is directed to ventilatory status before considering repair of the cleft palate to avoid ventilatory obstruction. In many cases, this requires correction of the hypoplastic mandible or tracheostomy prior to attempts at closure of the palatal cleft.
Ears. The ears are characteristically involved in Treacher Collins syndrome, and this includes the auricle, the external auditory canal, and the middle ear. Both left and right sides are afflicted, and the deficiencies tend to be symmetrical. Middle ear malformations are common, and include aplasia, hypoplasia, and/or ankylosis of the ossicles. Middle ear deformities accounted for the majority of the hearing loss in these patients. Most patients (96%) have a moderate or greater degree of hearing loss. This is critical to recognize and treat appropriately since adequate hearing is essential for speech development and speech production. External hearing assistance through hearing aids is often necessary.
The external ear deformities pose unique problems. First, the low-set hairline and “tongue” of hair-bearing scalp that descends in the preauricular area often precludes reconstruction with native mastoid skin and requires the alternative use of a temporoparietal fascial flap with skin graft for adequate reconstruction. Second, the external auricle reconstruction must be coordinated with the mandibular reconstruction and the reconstruction of the zygoma. If there is inadequate non–hair-bearing mastoid skin for ear reconstruction, as is often the case, incisions in proximity to the ear must be carefully planned to preserve the superficial temporal artery, including incisions for any exposure at the level of the TMJ and also coronal incision for reconstruction of the zygoma. If there is favorable mastoid skin for reconstruction, no incisions should be planned prior to placement of the cartilage framework, as these violate the blood supply and can contribute to skin breakdown above the tension of a cartilage framework reconstruction. Because the mandibular reconstruction must take into consideration obstructive airway concerns and the timing of palatal closure, careful planning of each step in the child’s reconstruction is necessary. The mandibular deformity in Treacher Collins syndrome is extremely variable and can include the entire spectrum of mandibular hypoplasia. The deformity can certainly be as complex as the midfacial deformity. There is typically an exaggerated antegonial notch, clockwise rotation to an anterior open bite deformity, and the appearance of excess facial convexity. There is a decreased posterior facial height and an increased height of the lower anterior face, partly due to the increased vertical height of the chin. The mandibular body is also foreshortened in sagittal dimension. The Kaban/Mulliken modification of the Pruzansky classification of the mandibular deformity in hemifacial microsomia is directly applicable and widely used to characterize the deficiency in Treacher Collins syndrome (Figure 28.6).10
FIGURE 28.6. Kaban/Mulliken classification of hemifacial microsomia that can be extended to classify and discuss Treacher Collins patients. Hypoplasia of the mandible is broken into four groups: type I – normal architecture but smaller dimensional size of mandible and TMJ; type IIA – moderate hypoplasia of mandible with hypoplasia of ramus and condyle but some TMJ development adequately positioned for symmetrical opening of the joint; type IIB – moderate to severe hypoplasia of ramus, condyle, and TMJ joint that is malpositioned inferiorly, medially, and anteriorly and is “operationally equivalent” to a type III child; type III – total absence of mandibular ramus behind dentition not suitable for bone distraction.
In general, patients with type I and IIA deformities have normal TMJ function that should be preserved. Mandibular deficiency in most of these patients can be corrected during adolescence using conventional orthognathic procedures including sagittal split osteotomy of the mandibular ramus and Le Fort I osteotomy of the midface to correct the angle of the occlusal plane and close any anterior open bite. In addition, an osseous genioplasty designed to decrease the vertical height of the chin and improve the sagittal projection of the chin is routinely added.
In patients with type IIA mandibles with a significant loss of posterior facial height and in patients with type IIB mandibles, reconstruction can often best be obtained using the technique of mandibular distraction osteogenesis. The technique uses a mandibular osteotomy, followed by application of an external framework, and slow lengthening of the bone segments. It has the advantages of predictably lengthening bone with a minimal degree of relapse, unlike conventional bone-grafting techniques.
In type III mandibles, there is only a cortical shell of a mandible behind the dentition. This anatomy precludes distraction osteogenesis. These children often require a tracheostomy in the perinatal period for mandibular hypoplasia. These children require reconstruction of the mandibular ramus using a costochondral graft designed and positioned to abut against the skull base, because there is hypoplasia of the glenoid fossa. The costochondral rib grafts are harvested and positioned through Risdon (neck) incisions. Incisions in the preauricular area are frequently necessary to assist in reconstruction of the zygomatic arch and glenoid fossa. This creates a posterior “stop” for the costochondral graft and facilitates mandible function. This surgery can be performed at 6 to 10 years of age, as the costochondral grafts are of adequate caliber to perform the surgery at that age. Significantly, these steps should be postponed until after ear reconstruction is completed, for the reasons of skin tension and vascularity previously noted. Ultimately, these children will require secondary double jaw surgery to correct the malpositioned midface, correct the occlusal plane angle, and correct the facial height discrepancies discussed above. A Le Fort I osteotomy and a sagittal split osteotomy of the rib graft can be utilized, but obvious care must be taken in the rib graft osteotomy.
CONGENITAL DERMOID TUMORS
Congenital dermoid inclusion cysts of the face are common entities most commonly located in the upper lateral orbit and the upper lateral orbital rim, although they also can be found in the forehead and nasal areas.11 These lesions are benign, and embryologically these cysts represent displacement or retention of dermal and epidermal cells into embryonic lines of development. These benign tumors are more common in females than males.11 Surgical removal is the only effective treatment, and complete resection is necessary for successful management.
Congenital dermoid inclusion cysts can be subdivided into two groups, those involving the orbital/periorbital area (including the midline lower forehead) and those involving the nasal area. The lesions typically present as firm, but not hard, nodular lesions involving the upper lateral orbital rim or upper lateral orbit that slowly increase in size. They range in size from a few millimeters to a few centimeters, but most are between 1 and 2 cm in diameter. In lesions in the orbital and periorbital areas, the presence of an external ostium or punctum is uncommon, whereas in the nasal dermoid lesions the presence of a punctum occurs frequently. In a recent large series of patients, 80% of the lesions in this series were located in either the upper lateral orbit or the upper lateral orbital rim;12 10% of the lesions involved the upper medial orbit. The nasal lesions account for approximately 5% to 10% of all dermoid lesions, and have a distinct clinical presentation and a distinct etiology. Nasal dermoid cyst/sinuses are typically located in the midline and they can have multiple presentations, including nasal pits, hair growth within a punctum, intermittent drainage of sebaceous material, chronic draining sinus tracts, abscess, and soft tissue infections including cellulitis. They can also present as recurrent lesions after failed incision and drainage procedures (Figure 28.7A).
Etiology and Pathogenesis
The etiology of orbital and periorbital congenital dermoid inclusion cysts is thought to be related to migrating tissue being “trapped” below the surface along lines of embryologic fusion as embryologic development progresses. Dermoid inclusion cysts are distinguished from simple epidermoid inclusion cysts by the presence of dermis and skin adnexa in the wall of the lesion. Because the cysts have skin adnexa present, the cysts or sinuses can contain cellular debris, sebum, and hair. The lesions subsequently enlarge over time. The etiology of nasal dermoid inclusion cysts and sinuses is distinct from that of orbital or periorbital dermoids. Although three separate theories have been advocated to account for these nasal dermoid sinus/cysts, the one that has been most often acknowledged is the “nasocranial deep trilaminar” theory. During normal embryogenesis the nasal and frontal bones develop by intramembranous ossification, but remain separated by a small fontanelle called the fonticulus nasofrontalis. A prenasal space between the nasal bones and cartilaginous nasal capsule extends from the skull base to the nasal tip. Dura extends through the fonticulus nasofrontalis, into the prenasal space, and comes into contact with skin. Normally, the dura and skin separate as the nasal process of the frontal bone grows. The dura recedes and the fonticulus nasofrontalis and foramen cecum fuse, forming the cribriform plates. Nasal dermoid cysts and sinuses are formed when the dura remains fused to the overlying skin, instead of separating. As the dura recedes intracranially, it pulls ectodermal tissue with it, most frequently along the tract through the foramen cecum. A sinus tract is formed when the misplaced dermal and epidermal lined tract maintains a connection with the skin, whereas a cyst is formed when ectoderm is trapped without egress to the skin, trapping the sloughed contents below the surface. Nasal dermoids require a distinct evaluation and treatment that are discussed separately below.
FIGURE 28.7. Dermoid sinus/cysts. A. Infected dorsal nasal dermoid sinus after local attempt at excision – this lesion extended intra-cranially. B. Patent foramen cecum in anterior skull base that transmitted dermoid sinus intracranially. C. Bifid crista galli on coronal CT scanD. Intra-operative photograph of intra-cranial extension of nasal dermoid sinus cyst after “keystone” portion of supraorbital bar was removed.
Complete surgical removal of these benign lesions is the only successful therapeutic strategy. For the 90% of these lesions that are located in the orbital or periorbital areas, no further diagnostic evaluation is warranted. Surgical excision is performed in straightforward fashion. The lesions can be approached through a supratarsal fold upper eyelid incision. Dissection is carried through the orbicularis muscle and directly down onto the cyst wall. The dissection then meticulously proceeds on the cyst wall around the lesion. For those in the periorbital area, the lesions are frequently below the periosteum, so incision of this slightly tougher layer must occur as part of the complete excision of the cyst.
For the 10% of these lesions that are nasal dermoids, the critical issue in management is to establish whether or not there is intracranial extension of the cyst/sinus. The midline location is a harbinger of the potentially more complicated problem. If the lesion extends intracranially, then a formal craniotomy is often necessary. Preoperative imaging with fine cut CT scan through the anterior cranial base is essential and can differentiate whether there is a patent foramen cecum and a bifid crista galli present, two signs of intracranial extension (Figure 28.7B and C). Although the presence of a bifid crista galli and an open cecum does not confirm intracranial extension, it is agreed that a normal size and appearance of the crista galli and foramen cecum rules out intracranial extension. If the CT findings are positive, an MRI may provide additional insight. If the MRI is positive with an obvious intracranial extension, then surgical planning should include neurosurgical involvement and a formal craniotomy. If a coronal incision and formal craniotomy are required, then the majority of the dissection and retrieval should be accomplished from the coronal approach. This can be facilitated by outfracture of the “keystone” portion of the supraorbital bar12 (Figure 28.7D). If the MRI findings are equivocal or absent but the CT findings are positive, a frequent clinical scenario, then planning should still include the possible need for a craniotomy and neurosurgical consultation and evaluation. In this case, the nasal lesion can be approached by an incision around the lesion and dissection cephalad, or through an open rhinoplasty approach with a small incision around the base of the nasal punctum. The dissection then proceeds cephalad, meticulously dissecting the stalk of the lesion up dorsal to the cartilage but deep to the nasal bones. If the stalk can be completely removed, there is no need for the craniotomy. Otherwise, the craniotomy is required to ensure complete removal (Figure 28.7D). Recurrence rates have been reported to be as high as 12%, and incomplete removal can be associated with complications such as infection and osteomyelitis.
Neurofibromatosis is a common disorder, with an estimated 100,000 cases in the United States alone. The disorder can involve both the central and peripheral nervous systems. The clinical hallmark of the disorder is the development of multiple cutaneous and subcutaneous nodular tumors. The disease has protean manifestations, a variable age of onset, a variable presentation, variability in clinical findings, and a variable but progressive course. Over the past 25 years, our understanding of neurofibromatosis has advanced significantly. Critical to this advance was a National Institutes of Health Consensus Statement in 1987 that established the diagnostic criteria for “peripheral neurofibromatosis,” now known as neurofibromatosis 1 (NF1), and “central neurofibromatosis,” now known as neurofibromatosis 2 (NF2) (see Table 28.1). While refinements of these criteria have been proposed, the establishment of the criteria in 1987 has effectively focused thought about neurofibromatosis throughout the world. Surgical resection remains the mainstay of treatment for enlarging or symptomatic tumors.
Etiology and Pathogenesis
Plastic surgeons and craniofacial surgeons are primarily concerned with the manifestations of NF113 which occurs over 10 times more frequently than NF2. The gene for NF1 has been localized to band 11.2 of the long arm of chromosome 17, clearly distinct from that for NF2, which has been localized to the middle of the long arm of human chromosome 22. NF1 is a tumor suppressor gene that encodes the tumor suppressor protein neurofibromin, which accelerates the conversion of Ras-GTP to Ras-GDP in various cell types.14 In patients with NF1, there is decreased production of neurofibromin and therefore decreased inactivation of RAS-GTP to RAS-GDP. Therefore, at the molecular level, NF1 is grouped with the set of developmental disorders known as RASopathies.14 Interestingly, NF1 also involves an alteration in intracellular messaging involving the GTP to GDP conversion, similar to fibrous dysplasia. NF1 is transmitted as an autosomal dominant disorder with a complete penetrance but variable expressivity. Families must be counseled that there is a 50% chance of an afflicted individual having an affected child.
Diagnosis and Clinical Presentation
Despite the localization of the gene for NF1, the diagnosis of NF1 remains based upon establishing the presence of clinical features (Table 28.1). The clinical presentation of NF1 is most commonly heralded by the appearance of café-au-lait spots. These lesions are cutaneous hyperpigmented areas, typically 20 to 30 mm in diameter, and are the most common manifestation of NF1, with greater than six lesions found in 90% to 99% of all cases.15 These lesions can sometimes be clinically difficult to differentiate from congenital nevi, but this can be readily accomplished by a simple dermal punch biopsy. Most children present with café-au-lait spots as the earliest and as the only manifestation of NF1, but greater than 80% will develop additional signs of the disorder. Axillary freckling generally appears before age 5 and is seen in approximately 80% of all cases of NF1.15 Lisch nodules are pigmented, dome-shaped nodules seen on the surface of the iris that are best seen by ocular exam with slit lamp microscopy.15 They usually have an onset by 10 years of age and are present in nearly all NF1 cases by 20 years of age. As noted above, the NF1 gene is a tumor suppressor gene that regulates cell proliferation, and intracranial tumors are frequent occurrences in these NF1 patients. Optic pathway gliomas are the most common central nervous system tumors in patients with NF1, occurring in approximately 15% of cases, and are histologically identified as low-grade pilocytic astrocytomas.16 NF1 patients also have an increased incidence of brainstem gliomas, as well as an apparent increase in the occurrence of benign and malignant astrocytomas, ependymomas, meningiomas, medulloblastomas, and malignant schwannomas. Skeletal abnormalities associated with NF1 include sphenoid wing dysplasia, macrocephaly, scoliosis, and thinning of long bone cortex—frequently manifest as anterior tibial bowing. The sphenoid wing dysplasia is present in 5% to 7% of NF1 cases and is characterized by unilateral agenesis of the greater wing of the sphenoid (Figure 28.8A and B). This agenesis creates a large communication between the middle temporal fossa of the brain and the orbit, and can lead to ocular proptosis, pulsatile exophthalmos, and exposure problems for the eye. It can be associated with neurofibromas within the cone of periocular tissues.
Neurofibromas, the hallmark of the NF1 disease, are nerve sheath tumors that may arise anywhere along a nerve sheath from the dorsal root ganglion to the terminal nerve branches.15 They are composed of Schwann cells, fibroblasts, mast cells, and perineural cells. Neurofibromas occur in five main types: localized cutaneous neurofibromas, diffuse cutaneous neurofibromas, localized intraneural neurofibromas, massive soft tissue neurofibroma and plexiform neurofibromas. Plexiform neurofibromas are virtually unique to NF1 and are composed of nerve sheath cells that proliferate along the length of a nerve. Plexiform neurofibromas are frequently associated with hypertrophy of the soft tissue and hyperpigmentation or hypertrichosis of the overlying skin. Their growth can cause destruction or compression of local tissue, causing significant morbidity. Plexiform lesions occur in between 16% and 40% of patients with NF1, and are found on the trunk in 43% to 44%, the extremities in 15% to 38%, and the head and neck in 18% to 42% of patients. Craniofacial plexiform neurofibromas most frequently involve the second and third divisions of the fifth cranial nerve and each of these occur in approximately 5% of patients with NF1. In contrast to the other types of neurofibromas, these plexiform neurofibromas are believed to be congenital in origin, and usually become evident by 2 years of age. Their growth is unpredictable, but occurs frequently during early infancy and times of hormonal change such as preadolescence/adolescence or pregnancy. Craniofacial neurofibromas cause significant facial disfigurement.
Malignant degeneration of peripheral nerve sheath tumors is more frequent than may be appreciated by conventional wisdom, occurring in up to 13% of patients with NF1.15 Malignant peripheral nerve sheath tumors, formerly known as neurosarcomas or malignant schwannomas, arise from Schwann cells. Over 50% of patients with malignant nerve sheath tumors have NF1. Only the plexiform neurofibromas have a high propensity for malignant degeneration. Medium and large nerves such as those involving the thigh, the buttock, the brachial plexus, and the paraspinal nerves are most frequently involved. Pain is the most reliable indicator of malignant degeneration. Prompt medical attention is warranted and surgical biopsy is indicated. Once diagnosed, management consists of an aggressive attempt at total surgical resection. Metastases are common. Malignant soft tissue neoplasms occur approximately 34 times more frequently than in a control group, and accounted for 9.4% of the deaths of patients with NF1.15 Despite treatment, the 5-year survival rate of malignant peripheral nerve sheath tumors is estimated to be between 16% and 52%.
The craniofacial problems associated with NF1 typically are of two types—the orbitopalpebral neurofibromas associated with sphenoid wing dysplasia (cranioorbital neurofibromatosis) and the plexiform neurofibromas involving the soft tissue of the face, largely in the distribution of the trigeminal nerve. These two types may exist together in the same patient, but most frequently occur separately. Several core issues must be addressed in treatment planning. First, the surgery is treating the deformity only. The underlying process of neurofibromatosis remains, and the recurrence of the neurofibromas is common. Second, both the timing of surgery and the extent of surgery must be carefully considered. Third, neurofibromas of the face and cranioorbital region tend to bleed significantly during surgery, the bleeding is difficult to control with electrocautery, and blood loss can be substantial. Jackson has even reported the option of packing the facial wound open with compression, and returning in 48 hours to complete the operation.16 Appropriate patient monitoring and intravenous access must be a component of preoperative planning, and consideration should be given to hypotensive anesthesia.16Fourth, the correction of the soft tissue structures is prone to recurrence of the initial deformity. The soft tissue of the face in neurofibromatosis, including the skin, ligaments, tendons and subcutaneous tissues appear to have a decreased tensile strength, and there is a strong tendency toward stretch and “relaxation,” with recurrence of the original deformity. Finally, the surgical management of this disorder must balance aesthetic outcome with the preservation of function. While these considerations are acknowledged, surgery is the most powerful tool for helping these patients, and these patients are often extremely grateful and appreciative of surgical intervention, even though the aesthetic result may be less than what the surgical team had desired. Surgical approaches vary from limited surgery at intervals to massive “one-stage” surgical resections of the involved tissues. It is likely that the optimal approach lies somewhere between these two ends of the spectrum, and should be decided by the surgeon based upon the degree of the deformity and in consultation with the patient and family.
FIGURE 28.8. Neurofibromatosis. A. Preoperative 3D CT Scan demonstrating large defect in sphenoid wing. B. Coronal CT scan of orbit revealing expanded orbit, vertical dystopia, and intraorbital neurofibromas. C. Postoperative 3D CT scan showing decrease in size of aperture between orbit and middle fossa. This aperture allows passage of the ophthalmic nerve and contents of the superior orbital fissure. D. CT Scan of Orbit Postoperative showing titanium and bone graft composite reconstruction of posterior sphenoid wing. E. Massive plexiform neurofibromatosis of right face showing significant overgrowth with extensive distortion evident on frontal view. F. Postoperative result following staged resection and suspension of soft tissue from zygomatic arch using sutures and fascia lata suspension demonstrates substantial improvement, but also continued ptosis from laxity of soft tissues.
Management of Cranioorbital Disorders. The orbital-palpebral neurofibromas associated with sphenoid wing dysplasia form a discrete subtype of neurofibromatosis, frequently described as cranioorbital neurofibromatosis. The principal findings in this disorder are pulsatile exophthalmos, an enlarged bony orbit, orbital neurofibroma, dysplasia or aplasia of the sphenoid wing with the presence of a herniation of the temporal lobe of the brain into the orbit, and a bulging temporal fossa. In addition to the exophthalmos, there is also frequently vertical dystopia of the globe. Overall, cranioorbital-temporal neurofibromatosis has been found to exist in from 1% to 10% of patients with NF1. While several etiologies have been advocated for the sphenoid dysplasia, including a direct effect of the orbital neurofibroma on the bone versus a congenital mesodermal maldevelopment with defective ossification of the sphenoid bone, the etiology of the sphenoid defect has not been clearly demonstrated.
The management of the orbital structures is one of the most complex issues in neurofibromatosis. In most cases, when vision exists in the affected eye, although potentially compromised, the eye should be preserved.16 In patients with functional vision, Jackson approaches mild cases with little change in orbital volume through the upper eyelid, whereas in cases with significant bony enlargement, he recommends use of a coronal flap, and a C-shaped osteotomy through the lateral orbital wall, zygoma, and horizontally through the maxilla below the inferior orbital nerve. The neurofibroma is resected through either approach, although he notes that it may be inadvisable to remove the tumor completely in the plexiform variety where there is significant involvement of the neuromuscular structures, as this may cause a disturbance of eye movement and resultant diplopia. The sphenoid wing can then be bone grafted, using either split rib grafts or cranial bone graft. He also recommends identifying the greatly stretched levator aponeurosis and repairing this directly to the tarsal plate, but cautions against excess shortening of the levator aponeurosis and also against excess skin resection. In patients with a loss of vision, an orbital exenteration is performed. The temporal lobe is reduced into the middle cranial fossa, and the entire defect in the sphenoid wing is bone grafted. The eyelid skin is then invaginated into the orbit and used as skin cover. Once healing is complete, the orbital defect is fitted with prosthesis.
An alternative way to approach these ocular problems is through the use of a coronal incision and a frontal craniotomy. The incision placement can be selected to allow for a forehead lift and direct excision of skin in those cases with involvement of the forehead and eyebrow and resultant ptosis of the eyebrow. The supraorbital bar and orbital roof can be removed, allowing both direct exposure of the entire orbit and the opportunity to reposition the supraorbital bar in cases of dystopia or orbital volume change. The coronal approach allows for excellent visualization and separation of the dura from the periorbital structures. It also allows favorable visualization as dissection proceeds medially and the ophthalmic nerve and vessels are approached. The cranial bone graft is cut precisely and placed to allow for separation of the middle cranial fossa from the orbital contents, minimizing the area of defect which must remain to allow passage of the structure in the superior orbital fissure (Figure 28.8Band C). Many surgeons have commented about the tendency for these grafts to absorb over time, and the use of a “composite” graft of cranial bone and titanium mesh is often useful to tolerate the pulsations of the brain and provide osseous healing and stability (Figure 28.8D).
As difficult as the skeletal reconstruction may be, the soft tissue structures are more problematic as they have decreased tensile strength, tend to stretch and “relax,” and recreate the original deformity. The management of the medial and lateral canthal structures is performed using standard techniques, but it should be noted that these tissues always relapse. Similarly, this same problem can occur with ptosis correction, which frequently must be repeated. One must avoid overcorrection of the ptosis, as a foreshortened eyelid with ocular exposure is a disastrous complication. It is much better to repeat the surgery and readvance the levator aponeurosis. As is true of many aspects of management of neurofibromatosis, improvement can be significant, but correction is both difficult to achieve and harder yet to maintain.
Management of Plexiform Neurofibromas of the Face. Plexiform neurofibromas involving the face typically involve either the temporal fossa, or originate from one or more divisions of the trigeminal nerve. Grabb et al. have eloquently described that neurofibromas “are woven into the normal fabric of the face and usually defy all but partial treatment.” The plexiform neurofibromas that originate from one or more divisions of the trigeminal nerve cause significant distortion of the facial soft tissue and skeletal framework. The characteristic overgrowth of the soft tissue leads to distortion of the eyebrow, thickening of the eyelids, ptosis, visual obstruction, dysconjugate gaze, glaucoma, ectropion, and can lead to visual loss. Epiphora is frequently present. The cheek is usually grossly involved and ptotic. There can be hypertrophy of the nose and distortion of the nasal soft and cartilaginous tissue (Figure 28.8E and F). There can be significant dental involvement and distortion of the maxillary and mandibular occlusal plane. Plexiform infiltration of the mandibular division of the trigeminal nerve can lead to compromise of buccal, oropharyngeal, and retropharyngeal tissue causing speech apraxia and oropharyngeal dysfunction. These patients have profound disfigurement and suffer from profound psychosocial problems related to the deformity, and they are desperate for any improvement in appearance.
Surgical management of neurofibromatosis of the temporal fossa requires an assessment of risks and expected outcomes. These are benign tumors that seldom cause major problems. Certainly, the simple presence of a neurofibroma in this location, as elsewhere, does not warrant surgery. If pain and considerable enlargement supervene, then surgery can be considered. Occasionally, these lesions will cause deformity of the mandible and maxilla by a mass effect. The temporalis muscle can be densely infiltrated by the neurofibromas. The caveat of blood loss during these procedures in NF1 patients must be acknowledged and planned for in these corrective skeletal procedures. Following resection, the most obvious problem is frequently a soft tissue deficiency. Reconstruction can be performed using microvascular free tissue transfer, dermal- fascial-fat grafts, or onlay of the skull using bone substitutes. The exact method for reconstruction depends on the severity of the soft tissue deficit, with free tissue transfer typically being reserved for larger deficiencies.
Soft tissue plexiform neurofibromas of the forehead can be approached through a coronal or “hairline” frontal incision. These approaches allow excellent exposure, and can be used to lift the redundant skin vertically as needed, thereby allowing correction of eyebrow ptosis. Separate incisions may be necessary to address orbital changes.
Surgery to correct the hypertrophy of the cheek, the nose, and the lips should follow skeletal correction, if this is planned. Similar to the principles for reconstruction of congenital defects, the skeletal framework correction should be performed first if this is planned as a component of treatment. In general, this consists of reduction of osseous structures with leveling of the occlusal plane through modifications of standard orthognathic approaches and techniques. The correction of the soft tissue of the cheek, nose, and lip can then be undertaken. The redundancy of the cheek skin can be approached through a facelift incision/approach or through a Weber-Ferguson approach. If the facelift incision is used, every attempt should be made to preserve the function of the facial nerve.15Although many of the facial muscles may have limited function due to involvement by a neurofibroma, the nerve should be preserved wherever possible. Direct full thickness excision of redundant tissue is frequently necessary. The skin incisions usually heal favorably and do not tend to be either prominent or noticeable after surgery. The tendency toward relapse should be counteracted by using permanent sutures to anchor the tissue to the bony skeleton at the zygomatic arch and wherever possible. In severe cases of redundancy, it may be worthwhile considering the use of tensor fascia lata slings to suspend the soft tissue structures and minimize the tendency toward relapse of the position of the soft tissue. In cases with significant redundancy of the soft tissue, facial animation may not occur to any appreciable extent, and static suspension of the soft tissues is appropriate and yields a significant clinical improvement. The redundancy of the tissue of the lip and nose should be addressed through direct excision. Both vertical and horizontal excisions may be necessary to obtain the desired position of these structures, and considerable improvement can reliably be obtained. Surgery for plexiform neurofibromas of the face must consider the initial deformity, the blood loss, the aesthetics of the expected result, and the likely durability of that result, given the laxity of the soft tissues and the inevitable recurrence of the deformity. Surgery can provide tremendous improvement both aesthetically and functionally. Although we can seldom provide complete correction, amelioration is a desirable and significant goal.
While surgery remains the mainstay of treatment for plexiform neurofibromas, there has been some success in the development of chemotherapeutic agents. Recent success has been obtained using imatinib mesylate (Gleevec and Novartis), a potential inhibitor of c-kit. Initial results have been encouraging, and the role of this agent in treatment of plexiform neurofibromas is in evolution at present.
1. Marie PJ. Review. Cellular and molecular basis of fibrous dysplasia. Histol Histopathol. 2001;16:981-988.
2. Chen Y-R, Breidahl AMS, Chang C-N. Optic nerve decompression in fibrous dysplasia: Indications, efficacy, and safety. Plast Reconstr Surg. 1997;99(1):22-30.
3. Matarazzo P, et al. Pamidronate treatment in bone fibrous dysplasia in children and adolescents with McCune-Albright syndrome. J Pediatr Endocrinol Metab. 2002;15:929-937.
4. Gorlin RJ, Cohen MM, Levin LS. Syndromes of the Head and Neck. 3rd ed. Oxford, England: Oxford University Press; 1990:642-671.
5. Zuker RM, Goldberg CS, Manktelow RT. Facial animation in children with Moebius syndrome after segmental gracilis muscle transplant. Plast Reconstr Surg. 2000;106:1-8.
6. Pensler JM, Murphy GF, Mulliken JB. Clinical and ultrastructural studies of Romberg’s hemifacial atrophy. Plast Reconstr Surg. 1990;85:669-674.
7. Coleman SR. Facial recontouring with lipostructure. Clin Plast Surg. 1997;24:347-367.
8. Upton J, et al. The use of scapular and parascapular flaps for cheek reconstruction. Plast Reconstr Surg. 1992;90:959.
9. Posnick JC, Goldstein JA, Waitzman A. Surgical correction of the Treacher Collins malar deficiency: quantitative CT scan analysis of long term results. Plast Reconstr Surg. 1993;92:12-22.
10. Kaban LB, Moses MH, Mulliken JB. Surgical correction of hemifacial microsomia in the growing child. Plast Reconstr Surg. 1980;82:9-19.
11. Bartlett SP, et al. The surgical management of orbitofacial dermoids in the pediatric patient. Plast Reconstr Surg. 1993;91:1208-1215.
12. van Aalst JA, et al. “Keystone” approach for intracranial nasofrontal dermoid sinuses. Plast Reconstr Surg. 2005;116:13-19.
13. NF1. Online Mendelian Inheritance of Man no 162200. http://www.ncbi.nim.nih.gov/omim
14. Jouhilahti S, Peltonen S, Heape AM, Peltonin J. The pathoetiology of Neurofibromatosis 1. Am J Pathol. 2011;178(5):1932-1939.
15. Friedman JM. Neurofibromatosis 1: Clinical manifestations and diagnostic criteria. J Child Neurol. 2002;17:548-554.
16. Jackson IT. Neurofibromatosis of the skull base. Clin Plast Surg. 1995;22(3):513–530.