Stroke - Disorders of the central Nervous System

There is probably an increased incidence of stroke during pregnancy and the puerperium, although it remains rare. There are some causes of stroke which seem to be more common in pregnancy, but most cases are due to one of the usual causes of stroke in non-pregnant young women. Cerebral infarction due to large cerebral artery occlusion may be slightly more common. Possible explanations for this include the mild hypercoagulable state that develops in the later stages of pregnancy and persists for a few weeks afterwards, also the phenomenon of paradoxical embolism from the leg or pelvic veins. Cerebral infarction may occur as a result of hypoxia-ischaemia or disseminated intravascular coagulation in the context of major obstetric emergencies such as amniotic fluid embolism. Unless the cause is obvious, ischaemic stroke in pregnancy should be investigated comprehensively in the same way that it would in a young non-pregnant woman.

There is a rare syndrome of segmental cerebral vasoconstriction in the puerperium, which usually presents with headaches, seizures, or focal deficits (especially visual field defects). It has a predilection for the posterior cerebral circulation and can give rise to multiple infarcts or haemorrhages. The condition, generally termed postpartum angiopathy, can occur spontaneously but has also been described in women taking bromocriptine. There are reports of successful treatment with corticosteroids and vasodilators, but there have been no prospective studies. The condition can recur in subsequent pregnancies.

Cerebral venous thrombosis, like deep vein thrombosis of the legs, is commoner in the puerperium, and the two conditions may coexist. Classically it gives rise to headache and neurological deficit that evolves over several hours and may become bilateral, with seizures and papilloedema; other cases present with the syndrome of benign intracranial hypertension. The diagnosis can usually be made with magnetic resonance imaging, including magnetic resonance venography. Although venous infarcts frequently undergo haemorrhagic transformation, the currently available evidence favours treatment with heparin. If the patient survives then recovery may be surprisingly complete.

The incidence of aneurysmal subarachnoid haemorrhage is not increased during pregnancy but its management is difficult. In general, neurosurgical considerations take precedence over obstetric ones and the aneurysm is treated in the usual way. If it is not technically possible to isolate the aneurysm then conventional wisdom is to deliver the baby (once it is mature) by caesarean section, although there is no definite evidence to suggest an increased risk of rebleeding during vaginal delivery. Intracranial and subarachnoid haemorrhage from arteriovenous malformations is much less common but the same principles of management apply. Women with untreatable vascular malformations (including cavernomas) should be counselled about the increased risk of bleeding (perhaps due to a mixture of hormonal and vascular factors) throughout pregnancy.