Facial nerve

Bell palsy, the most common disorder of the facial nerve and of idiopathic etiology , has a slightly higher incidence of involvement in women. The risk for developing Bell palsy during pregnancy or directly after gestation is three times higher than in nonpregnant women. The third trimester or the 2 weeks immediately postpartum is most common .

Hypertension, gestational edema, viral infections, and hypercoagulability are suggested etiologies. Hypertensive disorders during pregnancy are more frequent, because they occur in Bell palsy .

The course of Bell palsy during pregnancy is similar to that seen in all cases. There is sudden weakness of the entire ipsilateral face and sometimes subjective numbness. No objective sensory loss is found. The patients rarely have bilateral involvement; however, they may have ear pain, hyperacusis, and absence of taste ipsilaterally. Onset of maximum weakness is within hours to days. When some motor function is preserved it is a good prognostic sign. Complete or near complete recovery of facial strength occurs in most cases. Recurrence of Bell palsy in subsequent pregnancies is unusual.

Electrophysiologic studies can be useful during this period. They may be helpful in predicting recovery. Facial stimulation as a therapeutic measure has not been consistently demonstrated to be helpful in recovery.

Treatment of Bell palsy includes prednisone for a short course and acyclovir . Obviously this is of less risk when it occurs in the third trimester or postpartum period insofar as causing harm to the fetus. When patients are treated with steroids, blood pressure and blood glucose levels must be monitored closely. The eye must be lubricated to protect the cornea from abrasions, and recovery during pregnancy seems to be at the same rate as in nonpregnant patients. Residual problems from this paralysis include incomplete recovery, facial synkinesis, and crocodile tears.

Auditory nerves

On rare occasions, women during pregnancy lose their ability to hear. This seems to be vascular in etiology and can be severe. The exact etiology has not been determined and prognostication is difficult. Women often require head MRI evaluation to rule out a cerebellopontine angle tumor or other compressive etiology. Viral etiologies also occur.

Oculomotor nerve

Diplopia may occur in pregnant women, but it is rare. It may occur with cranial nerve III involvement and may be transient. Persistent isolated paresis should prompt a search for causes, as it would in any nonpregnant woman. Obviously, cranial nerve III involvement with pupil sparing would suggest nerve infarctions, such as occurs in diabetes mellitus, and pupillotonia might suggest aneurysm involving the posterior communicating artery. This is not unique to pregnancy, however.

Myasthenia gravis may present during pregnancy with external ocular muscle dysfunction and may mimic isolated muscle paresis. Involvement of the cranial nerve IV is extremely uncommon in pregnancy and is rarely caused by a structural abnormality.

Abducens nerve

Diplopia may occur during pregnancy because of an abducens nerve (VI) palsy from elevated intracranial pressure, such as that seen in idiopathic intracranial hypertension. Abrupt hypertension can cause increased intracranial pressure and VI nerve palsy. This may also be seen in pre-eclampsia. It may occur postpartum, and if associated with headaches or focal symptoms, one might be concerned with sinus thrombosis .

Optic nerve

Visual loss during pregnancy is rare. Optic neuritis (retrobulbar; disc edema) may occur during pregnancy, particularly in the second trimester, and may produce visual loss and subsequent optic atrophy. This can be bilateral and severe. The clinician should be concerned for possibility of demyelinating disease. Idiopathic intracranial hypertension causing visual loss, although uncommon in pregnancy, is important to recognize and manage, even with shunt procedures.

Neuroimaging is important in this situation to evaluate for orbital apex masses, such as meningioma, glioma, or aneurysmal compression, and to look for more diffuse evidence of demyelinating plaques. Aneurysms and meningiomas sometimes enlarge during pregnancy.

Median nerve and carpal tunnel syndrome

Carpal tunnel syndrome is a frequent problem in pregnancy. Key presenting features are pain at night with sensory disturbance in a median nerve distribution. Clinical findings may include loss of sensation and thenar atrophy or weakness in a median nerve distribution. One of the challenges is distinguishing carpal tunnel syndrome from hand discomfort in pregnancy. It is estimated that 30% to 35% of all pregnant women have hand discomfort during pregnancy at one point in the gestation. What distinguishes this from carpal tunnel syndrome is that it is most often bilateral, it is not in a specific nerve distribution, and usually there is less burning and no night pain .

The etiology of carpal tunnel syndrome in pregnancy is not completely understood. It is known that the incidence is higher in nonpregnant females than in males. Whether this is attributable to a smaller carpal canal, hormonal differences that occur during pregnancy, or degree of adipose tissue is not clear. The incidence is also higher in perimenopausal women. This is believed to relate to increased fluid retention, the effects of relaxin and other hormonal changes on ligamentous laxity, altered amounts of adipose tissue, and perhaps to altered sleep position . Butterworth and colleagues found increased sensitivity to a lidocaine block in pregnant women, and this may imply changes in the nerve itself during pregnancy. Another important point is the incidence of carpal tunnel syndrome that occurs in the postpartum period. This is most typically associated with individuals who are breastfeeding and is believed to be caused by awkward positions often necessary to successfully breastfeed .

Stevens and colleagues found that up to 50% of pregnant women have some nocturnal symptoms in the third trimester. Of those who have carpal tunnel syndrome, 2.3% to 4.6% are pregnant, and in the 15- to 44-year age group, carpal tunnel syndrome is two to three times more frequent in pregnant than nonpregnant females. Stolp-Smith and colleagues found in a large retrospective study of 10,873 women who experienced 14,579 pregnancies in Olmsted County, Minnesota, that in less than 1% who had carpal tunnel syndrome recorded in the medical record, 8% of the cases occurred in the first trimester, 32% in the second trimester, and 35% in the third trimester. There was no correlation with weight gain, onset and gestation interval, or pre-eclampsia. Symptoms in these patients were typically paresthesias, which were bilateral in 68%, and pain in 67%, with a positive median Tinel sign in 95%. Most had some degree of generalized edema by the third trimester.

Melvin and colleagues performed serial nerve conduction studies in pregnant women. No changes were seen in the control group of asymptomatic women. In pregnant women, 7% had prolonged median motor or sensory distal latencies. Findings returned to normal as early as the eighth month of pregnancy or as late as 10 months postpartum. Seror studied 52 carpal tunnel syndrome hands in 30 pregnancies. More than 20 demonstrated motor or sensory “conduction blocks” and 5 had “severe denervation changes.” Prospective median and ulnar nerve conduction studies matched by age and parity to control subjects found prolonged medial distal latencies in the pregnant group, more so in those with symptoms, and that the interpalmar latency was the best comparison for positive electrodiagnosis .

Given the high likelihood that carpal tunnel symptoms resolve in the immediate postpartum period, management is typically conservative. Avoiding aggravating factors, which includes taking a thorough history of occupational and other activities of daily living, wearing wrist hand orthoses, and controlling edema, are all important. Beyond that, it is not clear if it is necessary to use modalities or injections or to pursue surgery. Attention should be given to postpartum activities if there are persistent symptoms, and in particular if surgery is performed; this may have implications for positional changes in hand and arm use in the postpartum period. Al Qattan reported that 76% of carpal tunnel resolved 1 month postpartum. Ninety-three percent of pregnant patients ceased nocturnal awakening from pain, and seven women required surgery 2 to 16 years later . Wand noted that 40% of pregnant women who had carpal tunnel syndrome who were followed had signs but not symptoms of median nerve dysfunction postpartum. It is believed that conservative therapy may fail if symptom onset is before pregnancy or if it occurs in the first two trimesters. Also, a positive Phalen sign within 30 seconds and abnormal two-point discrimination combined indicate a poor prognosis for response to conservative treatment.

In summary, carpal tunnel syndrome in pregnancy has a higher incidence than in the general population, and the etiology is uncertain. Symptoms are more severe than the typical hand pain in pregnancy. Electrodiagnosis can be used to differentiate between pregnancy hand pain and carpal tunnel syndrome. Conservative treatment is usually successful. Care should be taken in the postpartum period to avoid activities and postures that could aggravate carpal tunnel syndrome, and patients should be reassured that most have resolution of symptoms in the immediate postpartum period.

Ulnar nerve

Sensory distribution in the medial (ulnar) aspect of the palm dorsally and ventrally with sensory dysfunction and pain occur infrequently during pregnancy and certainly less commonly than median involvement. The ulnar nerve is most commonly injured at the olecranon groove or in the cubital tunnel. Sometimes it may be involved more distally at Guyon canal. Search for some traumatic mechanism is of value in this situation, as is the association of women having previous fractures of their proximal radius (“tardy ulnar palsy”).

Electrophysiologic diagnosis may be extremely helpful in localizing the etiology of the involvement to the wrist, elbow, or even in between. Involvement bilaterally must be ruled out, and the clinician must be sure that there is not more diffuse involvement of the nerves with only symptoms localized to the ulnar distribution.

Therapy usually involves care to not traumatize the olecranon groove or other site of compression .

Brachial plexus

Idiopathic brachial plexus involvement and hereditary brachial plexus neuropathy may occur in the postpartum period and less frequently during pregnancy. Some re-occur in subsequent pregnancies. Early, there is pain in the shoulder and upper arm, followed by weakness, atrophy, and occasional localized isolated axillary sensory loss.

Most of these patients recover, but this may take up to 2 to 3 years .

Electrodiagnostic tests may be performed to confirm the diagnosis. Usually axonal damage is a predominant feature.

Peroneal nerve

This peroneal neuropathy during pregnancy is rare, except in the situation of trauma at delivery. Weakness in the anterior compartment muscles or paresthesias in the anterolateral part of the leg would prompt the clinician to evaluate for this etiology, particularly if no low back pain or radicular symptoms are present. Most common concern is trauma at the fibular head and neck, but neuromas and cysts may also localize to this area . Electrodiagnostic tests and ultrasound may help determine the etiology or localize the level of the lesion.

Tibial nerve

Tibial nerve may be involved with various reports of tarsal tunnel syndrome during pregnancy. There is pain at the ankle and foot and paresthesias over the sole of the foot, just inferior to the medial malleolus. With increasing edema during pregnancy, local trauma is a concern similar to problems that occur in nonpregnant women. The symptoms often abate after delivery .

Involvement at the tibial nerve in the popliteal fossa must be distinguished from tarsal tunnel syndrome; this is best done by electrodiagnostic studies. Baker cyst in the popliteal fossa has been known to produce symptoms during pregnancy from enlargement.

Lumbosacral plexus

Involvement of the lumbosacral plexus may rarely develop during the third trimester and is suspected to be caused by compression from the fetus. Rarely, a lumbosacral plexopathy occurs during pregnancy as part of hereditary brachial plexus neuropathy. Usually involvement of the plexus resolves well following delivery .

Electrodiagnostic tests are invaluable to help determine the extent of the involvement, prognostic issues, and to rule out other etiologies, such as radicular involvement.

Lateral femoral cutaneous nerve of the thigh

Numbness and paresthesias in the anterolateral thigh and sometimes significant pain may result from damage to the lateral femoral cutaneous nerve. Known as “meralgia paresthetica,” this occurs during pregnancy, most commonly in the third trimester. Location of the involvement of the nerve has been associated with at least nine specific possible points of compression along the route. Most likely increased abdominal size and weight gain may cause stretch injury to the nerve and may alter the angle of the nerve at various locations, including the inguinal ligament or as the nerve enters or exits the tensor fossa lata.

Electrodiagnostic tests are rarely needed during this situation, but they can be performed. Usually this is a clinical diagnosis, often with resolution of symptoms postpartum .

Medical treatment during pregnancy, beyond reassurance, may include lidocaine patches. With severe pain, oral medications can be considered after the third trimester. Anesthetic injections sometimes are used.

Acute immune demyelinating polyneuropathy

Acute or subacute motor neuropathy with a monophasic course is seen during pregnancy (acute immune demyelinating polyneuropathy [AIDP] or Guillain-Barre syndrome) . Although generally considered an ascending symmetric weakness with paresthesias, strength may be lost proximally greater than distally on some occasions. Reflexes are usually lost, except in early cases, and spinal fluid demonstrates the cytoalbuminologic dissociation. Sensation is usually spared on examination despite the profound weakness.

Electrophysiologic studies are important, but early on they may be fairly normal. Later they typically show prolonged F-wave latencies, then slowed conduction velocities and prolonged distal latencies.

AIDP during pregnancy has a similar incidence to the nonpregnant state. Women may develop this weakness at any time during the pregnancy, but most commonly in the third trimester. This is an immune-mediated illness, but viral syndromes do precede onset in almost two thirds of all cases. Screening for cytomegalic virus, Epstein Barr virus, HIV, Campylobacter jejune , varicella zoster, and other viral infections may be performed.

During late gestation, respiratory decompensation may occur because of diminished lung volumes and an elevated diaphragm and may restrict the mother’s vital capacity . The respiratory function should be serially evaluated to follow the mother’s course. When mechanical ventilation is required, the mother may be at higher risk for premature labor, thromboembolic complications, respiratory distress, or even sepsis.

Treatment is multifaceted and includes good nutrition, prevention of embolic complications, observation for autonomic dysfunction, and good fluid management. Plasmapheresis or intravenous immune globulin is effective in nonpregnant patients and can be used safely during pregnancy .

Because AIDP has no effect on uterine contraction, patients may undergo vaginal delivery. These patients, however, are considered an at-risk group of women. Respiratory and pain control and general anesthesia issues should be maintained carefully by the anesthesiologist. The fetal survival rate is 96%.

Chronic immune demyelinating polyneuropathy

A chronic form of demyelinating polyneuropathy (CIDP) involves sensory and motor neuropathy of autoimmune character. The onset may be more subacute, occurring over months, and sometimes it may take on a relapsing course. The incidence of relapse may increase during pregnancy or the patient may worsen and may be progressively weak during the third trimester or postpartum period .

Treatment considerations include plasmapheresis, intravenous Ig (IVIg), and possibly even steroids . Women who have known CIDP on immunosuppression who wish to become pregnant should be educated about the risks for herself and the fetus and perhaps switch to less harmful agents prophylactically.

Diabetes mellitus

Diabetic neuropathy is a diffuse distal chronic sensorimotor neuropathy. There are other manifestations seen in patients who have diabetes mellitus, which include diabetic amyotrophy, autonomic neuropathy, and thoracolumbar radiculopathy. These may be more frequent in diabetic women during pregnancy . Neuropathy caused by diabetes mellitus does not necessarily worsen during pregnancy and is seldom a major issue of concern, other than the mother’s discomfort .

Postpartum the incidence of peripheral neuropathy may increase, perhaps as much as tenfold . This suggests that the neuropathy during pregnancy can worsen in certain situations, particularly with insulin-dependent diabetes. Electrophysiologic tests have failed to demonstrate induction or worsening; however, there does seem to be a direct correlation with glycemic control.

Electrophysiologic abnormalities show slowed nerve conductions with reduced amplitudes. Sometimes when small-fiber neuropathy is predominant, they are normal.

Porphyria

Hepatic porphyria occurs in young women and occasionally occurs while they are pregnant . Acute intermittent porphyria, variac porphyria, or even hereditary porphyria have enzymatic defects that affect the keen synthesis pathway. Precipitating factors then may lead to excessive production of porphobilinogen or delta aminolevulinic acid in young women. Oral contraceptives during the menstrual cycle may produce exacerbations of neuropathy or other symptoms, including psychiatric disturbance or abdominal pain. In a young woman known to have porphyria, proper medication during the pregnancy is essential to prevent an attack. Elimination of exacerbating medications and giving glucose and carbohydrate meals should be instituted as treatment. Sometimes treatment with hematin prevents subsequent neurologic problems .

Electrodiagnostic testing assists in determining the severity and prognosis and usually shows a diffuse sensorimotor and sometimes autonomic neuropathy.