The Neurology of Pregnancy
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J Neurol Neurosurg Psychiatry 1998;64:711–725 717 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.64.6.717 on 1 June 1998. Downloaded from NEUROLOGY AND MEDICINE The neurology of pregnancy Guy V Sawle, Margaret M Ramsay The neurology of pregnancy can be split into headache, visual disturbances (typically pho- two. On the one hand, there are women who topsia), epigastric pain, or vomiting. This pro- develop neurological symptoms during preg- dromal state is typical, but the convulsions of nancy. Some have simple neurological disor- eclampsia may arise apparently unheralded ders such as carpal tunnel syndrome, which are and at what seems to be normal blood pressure. more common during pregnancy. Others have Eclampsia is most common during the third disorders that are either peculiar to or very trimester of pregnancy or during labour, but much commoner during pregnancy, such as can also occur after delivery, typically within eclampsia, pelvic neural compression, or even the first 48 hours. tumours arising from the placenta. The most common, serious, and important of these con- ditions is eclampsia. Other women have PRODROMAL FEATURES AND DIAGNOSIS Certain clinical features, indicating pre- neurological problems such as epilepsy or eclampsia of significant severity, are typical in myasthenia first and then become pregnant. patients who subsequently develop generalised For these patients, pregnancy may aVect the convulsions. It is di cult to know whether and course of the disease, and there may be impor- Y over what time scale this progression may occur tant issues with respect to investigation, in an individual patient. Such patients typically treatment, and prognosis. have high and rapidly rising or extremely labile blood pressure, proteinuria (sometimes in the Eclampsia nephrotic range), visual disturbances (especially Eclampsia is one of the commonest causes of photopsia or cortical blindness), headache, maternal death. In the United Kingdom, recent malaise, new onset of peripheral oedema (espe- figures show that 15.5% of direct maternal cially periorbital or facial), oliguria, restlessness, deaths were due to the hypertensive disorders shivering, and clonus. Laboratory evidence of of pregnancy, and more than half of these multisystem disease (such as hyperuricaemia, women had eclampsia.1 As many as 50 000 thrombocytopaenia, raised liver enzymes, or maternal deaths annually world wide are haemolysis) is also common. thought to be as a consequence of eclampsia.2 Other patients fail to show these warning http://jnnp.bmj.com/ The incidence of eclampsia during a recent signs and clinicians may not recognise impend- nationwide survey in the United Kingdom was ing eclampsia or may even fail to make the about one in 2000 maternities, with a case diagnosis when convulsions ensue. Examples fatality ratio of almost one in 50.3 We do not include patients who present during the second know how many women presenting with the trimester of pregnancy or in association with fulminating features described below will go on molar degeneration of the placenta. In other to have convulsions, or whether drug treatment cases the prodromal features are distracting, Division of Clinical can reduce the chance of progression. In one such as predominantly epigastric pain and on October 1, 2021 by guest. Protected copyright. Neurology GVSawle observational study, only one in 75 women vomiting, rather than headache and visual dis- with severe pre-eclampsia developed eclamptic turbance. The diagnosis may also be missed 4 Department of convulsions. when patients present in labour or the early Obstetrics and puerperium, when the blood pressure has Gynaecology, Queens DEFINITIONS always been normal (but beware rapidly rising Medical Centre, Pregnancy induced hypertension (also known blood pressure or onset of proteinuria peripar- Nottingham NG7 2UH, UK as pre-eclampsia and pregnancy toxaemia) tum). In other cases the blood pressure may M M Ramsay develops after 20 weeks of gestation in not be particularly raised or else there may be previously normotensive women and resolves no information about the patient’s “normal” Correspondence to: by three months postpartum; the pressure is prepregnancy blood pressure. Sometimes the Dr GV Sawle, Division of Clinical Neurology, Queens considered raised if greater than 140/90 mm patient or her medical attendants do not know Medical Centre, Nottingham Hg, or if the diastolic blood pressure rises that she is pregnant; other times the convul- NG7 2UH, UK. 15–25 mm Hg above prepregnancy values.5 sions begin late in the puerperium (>48 hours Telephone 0044 115 970 9792; fax 0044 115 970 When such a patient has a convulsion, they after delivery). Rarely, in an obtunded patient, 9738. should be considered to have eclampsia unless the seizures may not have been witnessed. proved otherwise. Such patients are likely also Important diVerential diagnoses in a preg- Received 22 May 1997 and to have significant proteinuria (>0.5 g/24 nant woman having her first seizure are intrac- in final revised form 2 March 1998 hours, or at least + with urine dipstick testing), erebral (particularly subarachnoid) haemor- Accepted 3 March 1998 facial or generalised oedema, and symptoms of rhage and cerebral venous thrombosis. Other 718 Sawle, Ramsay J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.64.6.717 on 1 June 1998. Downloaded from possibilities are tumours, intracerebral infec- which show increased T2 signals on MRI.14–17 tion, metabolic disturbances, and autoimmune Abnormalities are more common in patients disorders (particularly systemic lupus with eclampsia.16 There is a predilection for erythematosus).6 abnormalities in the occipital and parietal lobes, in the watershed area between middle PATHOPHYSIOLOGY and posterior cerebral artery territories.15 16 It is always diYcult to know how best to treat or The distribution of lesions shows good correla- prevent a disease when its underlying patho- tion in most cases with the patient’s clinical physiology is incompletely understood. Our features, such as occipital pole lesions in understanding of the cerebral changes occur- women with cortical blindness.14 15 Enhance- ring in pre-eclampsia and eclampsia has ment of T1 signals after injection of gadolin- changed with the improvement of neuroradio- ium has been documented in regions with logical techniques. The traditional view was increased T2 signals.17 The lesions are inter- that eclampsia was due to intracerebral haem- preted as indicating areas of abnormal water orrhage, because that is what was typically content—that is, focal cerebral oedema. There 6 found postmortem. Yet proposed pathophysi- is much debate about whether such oedema is ological mechanisms must provide explana- intracellular, indicating areas of focal ischae- tions for several clinical findings: firstly, that mia, or whether it is extracellular, secondary to eclamptic convulsions can arise suddenly in a capillary leakage and breakdown of cerebral patient with little or no prodrome; secondly, autoregulation.14–17 that eclampsia does not always occur with It is, however, important to determine which extremely high blood pressure or prolonged is the more important mechanism, as this will increase in blood pressure; and thirdly, that determine pharmacological strategies to amel- there may be transient focal neurological iorate or prevent eclampsia. The proponents of defects (such as cortical blindness or hemipare- the breakdown of cerebral autoregulation sis) yet most women who survive eclampsia do theory argue that eclampsia is simply hyperten- so neurologically intact. sive encephalopathy and that the keystone of It has variously been proposed that eclamp- treatment should be good control of blood tic convulsions result from intracerebral haem- pressure.18 This leaves a dilemma in a patient orrhage, hypertensive encephalopathy, cerebral 67 with “normal” or only marginally raised blood oedema, or cerebral vasospasm. DiVerent mechanisms may be operating in diVerent pressure as to what should be the target blood patients, with the compounding eVects of pressure. If focal ischaemic areas develop as a cerebral hypoxia, intravenous fluid and drug consequence of cerebral vasospasm, then administration, and varying degrees of hyper- specific vasodilator agents are likely to be more tension. The women who die are likely to be at beneficial and lowering blood pressure in some the worst end of the range. Those who die of circumstances could further aggravate ischae- eclampsia have significantly higher blood pres- mic processes. sure, but no worse renal function or more pro- An increasing body of evidence points to the teinuria than those who survive.8 presence of cerebral vasospasm in eclampsia and Typical postmortem cerebral findings are also in severe pre-eclampsia. Cases have been fibrinoid necrosis of vessels, thrombosed pre- reported where cerebral angiography and mag- 19 20 http://jnnp.bmj.com/ capillaries, perivascular ring haemorrhages, netic resonance angiography, performed subarachnoid, intraventricular, and intracer- after eclamptic seizures, have shown diVuse ebral haemorrhages (including patches of vasospasm. Similar images have also been noted 21 22 petechial haemorrhage in the cerebral cortex), in women with severe pre-eclampsia. Follow hypoxic-ischaemic damage, and perivascular up images documented resolution of vasospasm microinfarcts.67910 Studies with CT have in association with clinical recovery. Is cerebral shown that eclamptic patients with evidence