A. A.J. Maillard
Historically, the best-known major surgical procedure of the head performed under regional anesthesia in the United States is the partial maxillectomy performed on President Grover Cleveland in 1893. This chapter is presented according to the anatomic sites and types of nerves (scalp and face, facial nerves, trigeminal nerve, midface, and mandibular nerve). For each site, the relevant anatomy and the corresponding blocks will be described. Since most head blocks involve cranial nerves or their branches, consideration will also be given to the bony anatomy and especially the neural foramina. All of these blocks can be performed with the patient in the sitting or supine position depending on the block and the condition of the patient.
A. Blocks of the Scalp and Face
Indications: Blocks of the cutaneous nerves supplying the scalp are indicated in the emergency room and for plastic surgery to avoid tissue distortion. Blocks of the frontal branch of the supraorbital and infraorbital nerves are indicated for anesthesia in or around the eye. These blocks are indicated for blepharoplasty or for other lid procedures, including traumatic and posttraumatic reconstructive surgical procedures. Blocks of the auriculotemporal, greater auricular nerves, and minor occipital nerves are indicated for ear surgery.
Needle Size: 25-gauge, 20-mm needle.
Volume: 1 to 2 mL.
Anatomic Landmarks: Cutaneous nerves supplying the scalp and face (Fig. 23-1): 1, frontal nerve; 2, supraorbital nerve; 3, zygomaticotemporal nerve (V2); 4, auriculotemporal nerve (V3); 5, greater auricular nerve; 6, minor occipital nerve; 7, greater occipital nerve; 8, supra- and infratrochlear nerve; 9, infraorbital nerve; 10, external nasal branches of the ethmoid nerve; 11, mental nerve.
Approach and Technique: The appropriate site is identified, and 0.5 to 1.0 mL of 1% lidocaine with 1/100,000 epinephrine is injected subcutaneously in small increments up to 2 mL per nerve to obtain adequate anesthesia.
1. Originally, these blocks were directed at specific cutaneous nerves to block their sensory distribution. However, as epinephrine came into general use, its hemostatic effects on the scalp became a great aid to neurosurgeons. Therefore, instead of electively blocking these nerves, surgeons started to infiltrate the scalp around their proposed incision sites.
Figure 23-1. Cutaneous nerves supplying the scalp and face.
B. Blocks of the Facial Nerve
Indications: Blocks of the facial nerve are indicated when cosmetic procedures are planned that require the injection of botulin toxin-A to produce nerve paralysis with subsequent removal of forehead rhytides. It is of utmost importance to test the effect of blocking the zygomaticotemporal branch of the facial nerve using a short-acting local anesthetic. If the botulin injection is not performed correctly, and the botulin toxin is infiltrated lower, then a paralysis of the eyelids occurs that can last 2 to 3 months (temporary motor denervation). Blocks of the facial nerve are also used for plastic surgery (to produce a temporary paralysis of the eyelids when performing CO2 laser resurfacing or dermabrasion) and for traumatic repairs as well as posttraumatic reconstructive surgery.
Needle Size: 25-gauge, 35-mm needle.
Volume: Up to 2 mL.
Anatomic Landmarks: The orbit.
Approach and Technique: 1% lidocaine with 1/100,000 epinephrine is injected in small increments (up to 2 mL) along the orbit posterior to the rim, laterally and inferiorly. The needle can come close to the midline without causing paralysis and affecting eye closure. The effects are not long lasting and can be used as a good test prior to injecting the botulin toxin.
1. The combination of a supraorbital nerve block and an infraorbital nerve block provides complete anesthesia of the periorbita (Fig. 23-2).
2. The advantages of this technique over infiltrating techniques are that the volume of the soft tissues is not augmented by these injections and that there is no soft tissue distortion. Therefore, the surgeon has much better perspective to plan and carry out the repairs.
Figure 23-2. The combination of a supraorbital nerve block and an infraorbital nerve block provides complete anesthesia of the periorbita.
C. Blocks of the Trigeminal Nerve and Associated Dermatomes for V1, V2, and V3
The first division of the trigeminal nerve (V1) gives rise to the supraorbital nerve, which exits the brain through the supraorbital fissure. This branch gives sensation to the forehead and parietal scalp. The second division (V2) exits through the infraorbital fissure to exit into the face through the infraorbital foramen, located at approximately the midpoint of the infraorbital rim. Figure 23-3 depicts the cutaneous dermatomes associated with the different sensory branches of the trigeminal nerve.
Indications: Plastic, ophthalmologic, and trauma surgery involving the eye and the nose (ethmoid sinus labyrinth).
Needle Size: Variable, depending on the depth.
Volume: Up to 2 mL per nerve.
Anatomic Landmarks: The ophthalmic nerve cannot be blocked directly because it is posterior to its branches (the lacrimal, nasociliary, and frontal nerves). The nasociliary nerve insinuates itself through the annulus of Zinn into the apex of the orbit and innervates the eye. Its two branches, the posterior and anterior ethmoids, leave the orbital apex and pass into the posterior and anterior ethmoid foramina. The frontal and lacrimal branches are not accessible to blocks in the posterior orbital apex because they lie entirely outside of the apex of the orbital wall.
Figure 23-3. Cutaneous dermatomes associated with the different sensory branches of the trigeminal nerve.
Approach and Technique: With a needle pointing to the anterior ethmoid foramen, the anterior and posterior ethmoid nerves are blocked, which innervates the conjunctiva. Up to 2 mL of 1% lidocaine with 1/100,000 epinephrine is then injected near the superior orbital fissure. With the insertion of the needle, the globe elevates as digital pressure increases. With a needle pointing to the posterior ethmoid foramen, the frontal and lacrimal nerves are blocked by injecting up to 2 mL of the same local anesthetic solution. The frontal nerve may be blocked forward, above the bulb.
1. The portions of the orbit that are straighter are best to guide the needle when blocking the orbital apex. These conditions are best exemplified along the lateral wall of the orbit and the superomedial wall. The lateral point of injection lies immediately above the outer canthus of the eye. The needle is passed with its point constantly in contact with the bone to an approximate depth of 4.5 to 5.0 cm.
2. To block the ciliary nerves and ciliary ganglion, the local anesthetic solution needs to be injected in the muscle boundaries. As a rule, the optic nerve is unaffected. After injection, a transient mild proptosis is not uncommon.
3. Finally, to obtain transient sensory de-innervation of the bulb, the injection must be made in the muscle boundaries to block the ciliary nerves and ciliary ganglion. As a rule, the optic nerve is unaffected. After injection, a transient mild proptosis is not uncommon.
D. Midface Blocks
Indications: For incision and drainage of dental abscesses in the outpatient setting, to remove hardware used in repairing maxillofacial fractures, and, occasionally, in sinus surgery in the elderly and in closed reduction of nasal fractures. Palatal blocks are also indicated to excise cysts, small benign tumors, and bony exostoses. They are also occasionally used as a conduit to the pterygopalatine foramen either to block V2 at the foramen rotundum or to therapeutically obtain hemostasis in posterior nosebleeds by placing the internal maxillary artery in spasm and using the hydrostatic pressure for vessel compression against the bony canal. Blocking the sphenopalatine ganglion is also valuable in evaluating contact neuralgia (Sluder type) prior to any definitive surgical procedure.
Needle Size: 22-gauge, 89-mm spinal needle.
Volume: 2 to 5 mL per nerve depending on the nerve.
Anatomic Landmarks: Anatomy—main trunk (V2) intraoral and infraorbital branches (Fig. 23-3).
Approach and Technique: To provide a complete block of the region it is necessary to block the peripheral branches of the second division of the trigeminal nerve (the infraorbital and superior, posterior, and medial alveolar nerves). The infraorbital nerve is approached by introducing the needle directly to the midpoint of the inferior orbital rim and infiltrating the area with approximately 1 to 2 mL of 1% lidocaine with 1/100,000 epinephrine. This block produces anesthesia of the lower eyelid, the upper lip, a large part of the nose, a part of the skin and mucosa of the cheek, the anterior portion of the superior alveolar process and its periosteum, the anterior wall of the maxilla, and the upper central and lateral incisors.
Anesthesia of the second division of the trigeminal nerve (V2) may be carried out externally by passing a 22-gauge, 89-mm spinal needle just below the zygomatic arch along the posterior surface of the ascending ramus of the mandible into the most superior portion of the pterygopalatine fossa. The point of insertion of the needle lies immediately behind the lower palpable angle of the malar bone (Fig. 23-4). First, a small amount of 1% lidocaine with 1/100,000 epinephrine is injected into the skin itself. From this point, the needle is pressed inward and upward. Its point passes through the masseter muscle until it comes in contact with the superior maxillary tubercle, and it is slid along this surface. Occasionally, the point of the needle strikes the wing of the sphenoid, in which case, the direction of the needle is changed, or, if necessary, withdrawn altogether, and another point of entrance made just posterior to the midpoint of the zygomatic arch. The appropriate location is assumed once the needle suddenly passes deeper into the pterygopalatine fossa and reaches the nerve at an approximate depth of 5 to 6 cm. Once the needle is in the appropriate position, the patient complains of radiating pain in the face. The needle is then withdrawn slightly, and 5 mL of 1% lidocaine with 1/100,000 epinephrine is injected, moving the needle back and forth.
Figure 23-4. The point of insertion of the needle lies immediately behind the lower palpable angle of the malar bone.
1. In the past, these blocks have been used for major surgery of the head.
2. When performing these blocks, it is very important not to perform an intraneural injection (a sharp “electric-like” pain during the injection), and therefore the patient should remain awake during the block.
E. Mandibular Nerve Blocks (V3)
Indications: Anesthesia of the lower third of the face. Mostly used by dentists and maxillofacial surgeons in the emergency room setting for repair of facial lacerations, animal bites, incision and drainage of dental or salivary gland abscesses, probing of salivary gland ducts, or in radiology. Indications also include biopsies of the tongue, labiodental sulcus, or inner table of the mandible, manipulation of the mandible in cases in which mandible fractures are suspected and the patient is uncooperative to intraoral exam because of pain, and in removal of hardware inserted for repair of Le Fort fractures. It is also useful in performing a number of cosmetic procedures on the lower third of the face.
Needle Size: 22-gauge, 89-mm spinal needle.
Volume: 5 to 10 mL per nerve.
Anatomic Landmarks: Shown in Figure 23-3.
Approach and Technique: There are two standard access routes to anesthetizing the third division of the trigeminal nerve (V3).
The first method consists of injecting the inferior alveolar and lingual nerves intraorally by injecting the inner surface of the ascending ramus of the mandible into the region of the lingula. This route is the one most commonly performed. The second method is by directly blocking the nerve trunk in the foramen ovale.
For the intraoral approach (inferior alveolar and lingual nerve blocks), the index finger is passed intraorally until it touches the ascending ramus of the mandible. At about 1.5 cm lateral to the third molar, the sharp edge of the coronoid process can be palpated. This runs inferiorly along the side of the third molar and becomes lost in the oblique line. Medially, from this edge, there is a small, concave bony area, with three corners, directed forward and inward and medially bounded by a bony ridge. This area is occasionally referred to by head and neck surgeons as the retromolar trigone. With the mouth closed, this area lies to the inner side of the third molar. With the mouth open, it lies laterally to the upper and lower teeth and is easily accessible. The lingual nerve lies immediately under the mucosa, and the inferior alveolar nerve is 1.5 cm in back of this point. A long 22-gauge, 89-mm spinal needle is introduced intraorally and is directed from opposite the lateral incisors toward the point of injection and held parallel to the biting surface of the lower teeth. The needle is then inserted 1 cm above and lateral to the biting surface of the last molar, into the retromolar trigone. The bone should be immediately felt. If this is not the case, then the point of the needle is too far from the median line, in which case the needle must be directed more to the median line until the border is felt. The needle is passed along the inner surface of the ascending ramus of the mandible into the deeper parts for approximately 2.0 to 2.5 cm. Once the needle is proximate to the lingual nerve, about 5 to 10 mL of 1% lidocaine with 1/100,000 epinephrine is injected. A long needle is always used so that the injection site is under direct visualization at all times.
The foramen ovale approach (block of the main trunk of the trigeminal nerve) has the advantage of providing a complete block of the branches originating from the main trunk of the trigeminal nerve, except for the lingual nerve. For the external approach to the foramen ovale, once again a long spinal needle is used. The point of injection is chosen by marking the inferior border of the zygomatic arch at its midpoint, and the needle is inserted almost in transverse fashion. At a depth of 4 to 5 cm, the end of the needle touches the pterygoid process. In this injection, the needle is approximately 1 cm anterior to the foramen ovale. The depth is then marked on the needle. The needle is then withdrawn to the subcutaneous tissue and is once again passed medially at a slight posterior angle and to the same depth or a few millimeters more. The characteristic radiating pains will then occur. At this point, the needle is withdrawn a few millimeters and the injection proceeds by instilling approximately 5 to 10 mL of 1% lidocaine with 1/100,000 epinephrine (Fig. 23-5).
Figure 23-5. The needle is withdrawn a few millimeters and the injection proceeds by instilling approximately 5 to 10 mL of 1% lidocaine with 1/100,000 epinephrine.
1. To provide a complete block of the branches originating from the trigeminal nerve, it is necessary to occasionally add a block of the distal branches, which exit through the mental foramina.
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