Disorders of Nerves and Nerve Roots

Facial palsy
The incidence of facial nerve palsy (Bell's palsy) is substantially increased during pregnancy and the puerperium (as Bell himself described). The reason for this is not known. There have been no studies of treatment in this specific context but it is reasonable to treat promptly with prednisolone, beginning at 40 mg daily and reducing over a 2-week course.

Mononeuropathies
Carpal tunnel syndrome, due to compression of the median nerve in the wrist, is very common in pregnancy, characteristically causing pain and tingling in the hands at night and after use. Most cases can be managed with nocturnal wrist splints, although steroid injections into the carpal tunnel may tide the patient over into the puerperium, when symptoms usually remit.

Diuretics are of little value. Surgical decompression during pregnancy should be reserved for cases with severe pain, weakness, or wasting, when usually there have been symptoms either before pregnancy or early in the first trimester. In troublesome cases it is worth considering delayed surgery to prevent recurrence in subsequent pregnancies, which is common.

The lateral cutaneous nerve of the thigh can be compressed as it crosses the inguinal ligament. This is particularly common in the third trimester and causes tingling, hypersensitivity, or numbness in the midlateral thigh, which may be bilateral. Usually no treatment is required, but troublesome cases may respond to transcutaneous nerve stimulation or a local nerve block. Remission after delivery is the rule.

Lumbosacral root and plexus problems
Backache is very common in pregnancy, particularly in women with a past history of back pain or occupations that involve bending and lifting. It is traditionally blamed on changes in posture and hormonally mediated relaxation of spinal and sacroiliac joints. The pain is usually confined to the lumbar region but may radiate into the buttock or thigh. There may be tenderness over one or other sacroiliac joints. Radiological investigations are not needed if there are no abnormal neurological signs. Management is conservative.

Abrupt onset of pain that radiates below the knee with focal weakness, numbness, or reflex loss is most likely to be due to a prolapsed intervertebral disc. Provided that the signs are unilateral with no sphincter impairment, conservative management is again appropriate, with analgesia and advice to keep mobile. If this fails then magnetic resonance imaging is thought to be a safe method of investigation prior to consideration of lumbar microdiscectomy.

Obstetric nerve palsies are becoming less common with improvements in obstetric care, but still occur in cases of prolonged or complicated labour (for example due to cephalopelvic disproportion, dystocia, and primiparity), in difficult forceps deliveries, and as a result of traction or haematoma formation in caesarean section. Damage to the common peroneal nerve from incorrectly positioned leg holders is now rare.