MULTIPLE SCLEROSIS
In the United States, multiple sclerosis (MS) is second to trauma as a cause of neurological disability. Because MS affects women twice as often as men and usually begins in the 20s and 30s, women of reproductive age are most susceptible. The familial recurrence rate is 15 percent and the incidence in offspring is increased 15-fold. Shown in Figure 78-1 is the relationship of pregnancy to relapse of MS. The demyelinating characteristic of this disorder results from (predominately) T cell-mediated autoimmune destruction of oligodendrocytes that synthesize myelin. There is a genetic susceptibility and likely an environmental trigger such as exposure to certain bacteria and viruses.
FIGURE 78-1 Pregnancy in multiple sclerosis study: Annualized relapse rates for women with multiple sclerosis in the year before, during, and the 2 years after pregnancy. (Reproduced, with permission, from Cunningham FG, Leveno KJ, Bloom SL, et al (eds). Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010.)
Clinical Features
Classical symptoms include loss of vision, diplopia, and optic neuritis. Other common symptoms are weakness, hyperreflexia, spasticity, paresthesia, ataxia, intention tremor, nystagmus, dysarthria, diminished vibratory sense, and bladder dysfunction. The diagnosis is one of exclusion, and is confirmed by cerebrospinal fluid analysis (increased protein) and magnetic resonance imaging showing multifocal white matter plaques.
Management
Corticosteroids may diminish the severity of acute flares, but they have no effect on permanent disability. Symptomatic relief can be provided by analgesics; carbamazepine, phenytoin, or amitriptyline are used for neurogenic pain; baclofen for spasticity; α-adrenergic blockade to relax the bladder neck; and cholinergic and anticholinergic drugs to stimulate or inhibit bladder contractions. Immunosuppressive therapy with cyclosporine, azathioprine, and cyclophosphamide is often prescribed for severe cases. Both interferon-β-1a and a4-integrin antagonists have been shown to favorably modify the course of disease.
Women with MS who become pregnant may become fatigued more easily, and those with bladder dysfunction are prone to urinary infection. Labor is unaffected, and cesarean delivery is performed only for obstetrical indications. Women with lesions at or above T-6 are at risk for autonomic dysreflexia, and they should receive epidural anesthesia accordingly. Perinatal outcome is not altered significantly.
MYASTHENIA GRAVIS
This immune-mediated neuromuscular disorder affects about 1 in 7500 persons and has a predilection for women of childbearing age. The etiology is unknown. The disease is characterized by weakness resulting from IgG-mediated damage to acetylcholine receptors. Myasthenia gravis worsens in about 20 percent of pregnant women with this disease. The acetylcholine-receptor IgG antibodies cross the placenta, but only 10 to 20 percent of fetuses will have symptoms of myasthenia. Symptoms include a feeble cry, poor suckling, and respiratory distress. These symptoms resolve within 2 to 6 weeks as the antibodies are cleared.
CLINICAL FEATURES
Myasthenia gravis is characterized by easy fatigability of facial, oropharyngeal, extraocular, and limb muscles. Cranial muscles are involved early, and diplopia and ptosis are common. Facial muscle weakness causes difficulty in smiling, chewing, and speech. In 85 percent of patients, the weakness becomes generalized. The course of the disease is variable, but it tends to be marked by exacerbations and remissions. Remissions seldom are complete or permanent. Systemic diseases, concurrent infections, and even emotional upset may precipitate myasthenic crises.
Management
About 75 percent of patients have thymic hyperplasia or a thymoma and may respond to thymectomy. Anticholinesterase medications such as pyridostigmine bring about improvement by impeding degradation of acetylcholine. Ironically, the sign of overdosage is increased weakness, which is sometimes difficult to differentiate from the actual myasthenic symptoms. Nearly all women respond to immunosuppressive therapy. Short-term clinical improvement has been reported following intravenously administered immunoglobulin or plasmapheresis.
Management during pregnancy includes close observation with liberal bed rest and prompt treatment of infection. Most women respond well to pyridostig-mine administered every 3 to 4 hours. Those in remission who become pregnant while taking corticosteroids or azathioprine should continue these medications. Acute onset of myasthenia or its exacerbation demands prompt and supportive care. Plasmapheresis should be used for emergency situations, taking care not to provoke maternal hypotension or hypovolemia. Most women with myasthenia gravis tolerate labor without difficulty. Because the disease does not affect smooth muscle, labor usually proceeds normally. Oxytocin can be administered as necessary. Narcotics must be used with care, and any drug with a curare-like effect must be avoided—examples include magnesium sulfate, muscle relaxants used for general anesthesia, and aminoglycoside antibiotics. Amide-type local anesthetic agents are used for epidural analgesia for labor. Cesarean delivery is reserved for obstetrical indications. Forceps delivery may be necessary for women with impaired expulsive efforts.
GUILLAIN–BARRÉ SYNDROME
This syndrome is an acute demyelinating polyradiculoneuropathy. In over two-thirds of cases, it follows viral infections, especially cytomegalovirus and Epstein-Barr virus. There does not appear to be an increased incidence of Guillain–Barré syndrome (GBS) during pregnancy; however, the incidence appears to increase postpartum.
Clinical Features
The full syndrome takes 1 to 3 weeks to develop and includes areflexic paralysis with mild sensory disturbances and occasionally autonomic dysfunction.
Management
When GBS develops during pregnancy, its clinical course does not seem to be changed. Women should be hospitalized during the worsening phase. Management is supportive and may require ventilator assistance in up to 25 percent. If begun within 1 to 2 weeks of motor symptoms, intravenous high-dose immunoglobulin or plasmapheresis is beneficial, but does not decrease mortality rates. Almost 85 percent of patients recover fully, but the remainder are disabled or suffer relapses.
BELL PALSY
This acute facial paralysis, thought to be a viral-induced mononeuropathy, is common in pregnancy. It is uncertain if pregnancy alters the spontaneous recovery from facial palsy. There is evidence that suggests that pregnant women recover to a satisfactory level slower than nonpregnant women and men. Prognostic markers for incomplete recovery are bilateral disease, recurrence in a subsequent pregnancy, faster rate of nerve function loss and the extent of the loss. The onset is usually abrupt and painful, with maximum weakness within 48 hours. In some cases, hyperacusis and loss of taste accompany varying degrees of facial muscle paralysis. Corticosteroid therapy (prednisolone) given early in the course of disease improves outcomes. Acyclovir has not been shown to be beneficial. Supportive care includes prevention of injury to the constantly exposed cornea, facial muscle massage, and reassurance.
CARPAL TUNNEL SYNDROME
This syndrome is characterized by hand and wrist pain extending into the forearm and sometimes into the shoulder. It is caused by compression of the median or (less frequently) ulnar nerve, both of which are especially vulnerable to compression within the carpal tunnel at the wrist. Typically, the woman awakens with burning, numbness, or tingling in the inner half of one or both hands, and the fingers feel numb and useless. Symptoms are bilateral in 80 percent of affected pregnant women and 10 percent have signs of severe denervation. Although some symptoms of carpal tunnel syndrome are experienced by up to half of pregnant women, new onset of the full syndrome is much less frequent.
Carpal tunnel syndrome is self-limited, and treatment is symptomatic. A splint applied to the very slightly flexed wrist and worn during sleep usually provides relief. The signs and symptoms most often regress after delivery, although surgical decompression and corticosteroid injections are occasionally necessary.
SPINAL CORD INJURY
Cervical or thoracic spine injuries in pregnant women are not uncommon and are frequently complicated by urinary tract infections, anemia, pressure necrosis of the skin, worsening constipation, and preterm delivery.
If the lesion is higher than T-10, the cough reflex will be impaired and respiratory function may be compromised. In women with lesions above T5–6, autonomic hyperreflexia can occur. In this potentially life-threatening event, splanchnic nerves are excited by some stimulus and are not dampened because of lack of central inhibition. The resultant sudden sympathetic stimulation of nerves below the cord lesion causes a throbbing headache, facial flushing, sweating, bradycardia, and paroxysmal hypertension. A variety of stimuli, including urethral, bladder, rectal, or cervical distention, catheterization, cervical dilatation, uterine contractions, or examination of pelvic structures, may precipitate dangerous hypertension, which must be treated immediately. Spinal or epidural analgesia can prevent or avert dysreflexia and is recommended at the start of labor. General anesthesia is not preferred because the depth of anesthesia necessary to control the spasms and dysreflexia can cause hypotension and respiratory dysfunction.
Uterine contractions are not affected by cord lesions. Labor is often easy, even precipitous, and comparatively painless. If the lesion is below T-12, then contractions are felt normally. There is great concern that women with lesions above T-12 may deliver at home unattended before they realize that labor has begun. However, these women can be taught to palpate uterine contractions. Serial examinations with admission for advanced cervical dilatation or effacement may also be helpful. Delivery is preferably vaginal. Continuous cardiac rhythm monitoring along with intra-arterial pressure monitoring is recommended.
For further reading in Williams Obstetrics, 23rd ed.,
see Chapter 55, “Neurological and Psychiatric Disorders.”