Invited Review: The Brain in Eclampsia

Efficacy of Magnesium Sulfate on Maternal Mortality in Eclampsia

Eclampsia is a common complication of preeclampsia patients and can be life-threatening for both the mother and the fetus. Hence, timely intervention and appropriate management of this detrimental condition are extremely crucial. Eclampsia is described as the occurrence of generalized convulsions in patients with preeclampsia. Magnesium sulfate (MgSO₄) is the drug of choice for treating and preventing eclampsia. This review aims to study and analyze the available literature on the pathogenesis of eclampsia, the pharmacology of MgSO₄, and its effectiveness in the management of eclampsia. Other proposed treatments and their comparative study with MgSO₄ are also discussed. Additionally, we examine the data regarding the impact of eclampsia, its public health burden, and the cost-effectiveness of MgSO₄. One of the major drawbacks associated with the use of MgSO₄ in low-income countries has been the cost of treatment and the lack of resources. We have analyzed the trials that have proposed alternate treatment regimens which could shape new guidelines to resolve these issues. For this review, we extensively studied abstract and full-text articles from multiple databases. This article discusses the pathophysiology of eclampsia, the pharmacology of MgSO₄, the issues surrounding eclampsia management, and how MgSO₄ benefits these patients.

Posterior Reversible Encephalopathy Syndrome: A Review

Radiologists may be the first to suggest the diagnosis of posterior reversible encephalopathy syndrome (PRES). PRES is associated with many diverse clinical entities, the most common of which are eclampsia, hypertension, and immunosuppressive treatment. Radiologists should be aware of the spectrum of imaging findings in PRES. When promptly recognized and treated, the symptoms and radiological abnormalities can be completely reversed. When unrecognized, patients can progress to ischemia, massive infarction, and death. In this review, we present an overview of the unique signs observed on computed tomography and magnetic resonance images in PRES that can help in the early diagnosis and treatment that is highly effective in this syndrome.

The Contribution of Normal Pregnancy to Eclampsia

Eclampsia, clinically defined as unexplained seizure in a woman with preeclampsia, is a life threatening complication unique to the pregnant state. However, a subpopulation of women with seemingly uncomplicated pregnancies experience de novo seizure without preeclamptic signs or symptoms, suggesting pregnancy alone may predispose the brain to seizure. Here, we hypothesized that normal pregnancy lowers seizure threshold and investigated mechanisms by which pregnancy may affect seizure susceptibility, including neuroinflammation and plasticity of gamma-aminobutyric acid type A receptor (GABA_AR) subunit expression. Seizure threshold was determined by quantifying the amount of pentylenetetrazole (PTZ) required to elicit electrical seizure in Sprague Dawley rats that were either nonpregnant (Nonpreg, n = 7) or pregnant (Preg; d20, n = 6). Seizure-induced vasogenic edema was also measured. Further, activation of microglia, a measure of neuroinflammation (n = 6-8/group), and GABA_AR δ- and γ2-subunit protein expression in the cerebral cortex and hippocampus (n = 6/group) was determined. Seizure threshold was lower in Preg compared to Nonpreg rats (36.7±9.6 vs. 65.0±14.5 mg/kg PTZ; p<0.01) that was associated with greater vasogenic edema formation (78.55±0.11 vs. 78.04±0.19% water; p<0.05). The % of active microglia was similar between groups; however, pregnancy was associated with downregulation of cortical GABA_AR-δ and hippocampal GABA_AR-γ2 expression. Overall, pregnancy appears to be a state of increased seizure susceptibility that is not due to neuroinflammation, but rather is associated with reduced expression of GABA_AR subunits and greater edema. Understanding neurophysiological changes occurring in normal pregnancy could allow for better prevention and management of de novo seizure, including pathologic states such as eclampsia.

Magnesium sulfate treatment reverses seizure susceptibility and decreases neuroinflammation in a rat model of severe preeclampsia

Eclampsia, defined as unexplained seizure in a woman with preeclampsia, is a life-threatening complication of pregnancy with unclear etiology. Magnesium sulfate (MgSO₄) is the leading eclamptic seizure prophylactic, yet its mechanism of action remains unclear. Here, we hypothesized severe preeclampsia is a state of increased seizure susceptibility due to blood-brain barrier (BBB) disruption and neuroinflammation that lowers seizure threshold. Further, MgSO₄ decreases seizure susceptibility by protecting the BBB and preventing neuroinflammation. To model severe preeclampsia, placental ischemia (reduced uteroplacental perfusion pressure; RUPP) was combined with a high cholesterol diet (HC) to cause maternal endothelial dysfunction. RUPP+HC rats developed symptoms associated with severe preeclampsia, including hypertension, oxidative stress, endothelial dysfunction and fetal and placental growth restriction. Seizure threshold was determined by quantifying the amount of pentylenetetrazole (PTZ; mg/kg) required to elicit seizure in RUPP+HC±MgSO₄ and compared to normal pregnant controls (n = 6/group; gestational day 20). RUPP+HC rats were more sensitive to PTZ with seizure threshold being ∼65% lower vs. control (12.4±1.7 vs. 36.7±3.9 mg/kg PTZ; p<0.05) that was reversed by MgSO₄ (45.7±8.7 mg/kg PTZ; p<0.05 vs. RUPP+HC). BBB permeability to sodium fluorescein, measured in-vivo (n = 5–7/group), was increased in RUPP+HC vs. control rats, with more tracer passing into the brain (15.9±1.0 vs. 12.2±0.3 counts/gram ×1000; p<0.05) and was unaffected by MgSO₄ (15.6±1.0 counts/gram ×1000; p<0.05 vs. controls). In addition, RUPP+HC rats were in a state of neuroinflammation, indicated by 35±2% of microglia being active compared to 9±2% in normal pregnancy (p<0.01; n = 3–8/group). MgSO₄ treatment reversed neuroinflammation, reducing microglial activation to 6±2% (p<0.01 vs. RUPP+HC). Overall, RUPP+HC rats were in a state of augmented seizure susceptibility potentially due to increased BBB permeability and neuroinflammation. MgSO₄ treatment reversed this, increasing seizure threshold and decreasing neuroinflammation, without affecting BBB permeability. Thus, reducing neuroinflammation may be one mechanism by which MgSO₄ prevents eclampsia during severe preeclampsia.

Seizures in Women with Preeclampsia: Mechanisms and Management

Eclampsia is defined in the obstetrical literature as the occurrence of unexplained seizure during pregnancy in a woman with preeclampsia. In the Western world, the incidence of eclampsia is ~1 per 2000 to 1 per 3000 pregnancies, but the incidence is 10-fold higher in tertiary referral centers and undeveloped countries where there is poor prenatal care, and in multi-fetal gestations. Nearly 1 in 50 women with eclampsia die as do 1 in 14 of their offspring, and mortality rates are considerably higher in undeveloped countries. Eclampsia is also associated with significant life-threatening complications, including neurological events. Seizure acutely can cause stroke, haemorrhage, oedema and brain herniation and thus lead to epilepsy and cognitive impairment later in life.

Cerebral vascular adaptation to pregnancy and its role in the neurological complications of eclampsia

The cerebral circulation has a central role in mediating the neurological complications of eclampsia, yet our understanding of how pregnancy and preeclampsia affect this circulation is severely limited. Here, we show that pregnancy causes outward remodeling of penetrating arterioles and increased capillary density in the brain due to activation of peroxisome proliferator-activated receptor-γ (PPARγ), a transcription factor involved in cerebrovascular remodeling and highly activated in pregnancy. Pregnancy-induced PPARγ activation also significantly affected cerebral hemodynamics, decreasing vascular resistance and increasing cerebral blood flow by ∼40% in response to acute hypertension that caused breakthrough of autoregulation. These structural and hemodynamic changes in the brain during pregnancy were associated with substantially increased blood-brain barrier permeability, an effect that could promote passage of damaging proteins into the brain and cause the neurological complications of eclampsia, including seizure.

The Cerebral Endothelium During Pregnancy: A Potential Role in the Development of Eclampsia

The authors investigated the influence of pregnancy on cerebral endothelial cell permeability in response to an acute elevation in intravascular pressure that caused forced dilatation of myogenic tone. Third-order branches of the posterior cerebral artery (PCA) were dissected from nonpregnant (NP) and late-pregnant (LP, days 19 to 20) Sprague-Dawley rats and mounted on glass cannulas in an arteriograph chamber that allowed control over intravascular pressure and measurement of both diameter and permeability to fluorescent dextran (3000 Da). Permeability was determined at 75 mm Hg and after a step increase in pressure to 200 mm Hg. The extent of pinocytosis and transcellular transport in response to pressure was evaluated separately in the same groups of animals at 75 and 200 mm Hg using transmission electron microscopy. All arteries developed myogenic tone at 75 mm Hg that was lost when pressure was increased to 200 mm Hg to cause forced dilatation. The increased pressure caused a significant increase in permeability to dextran and enhanced pinocytosis in arteries from LP animals, but not in NP animals whose permeability remained constant at both pressures. These results suggest a pregnancy-specific effect on the cerebral endothelium that may promote enhanced vascular permeability during acute hypertension and may contribute to the edema formation and neurologic complications of eclampsia.

HAEMODYNAMIC CONTRIBUTIONS TO THE PATHOGENESIS OF PREECLAMPSIA AND ECLAMPSIA

Current hypotheses regarding the origins of preeclampsia have focused on the “Two stage model”. This model suggests that the primary steps in the pathophysiologic sequence of preeclampsia are initiated by abnormal placentation including the classic finding of abnormal trophoblast invasion of maternal decidual spiral arteries. The second stage of the sequence includes the elaboration of a single or multiple substances from these disordered placentas which contribute to the generalized maternal systemic illness, eventually manifesting as endothelial injury, hypertension and proteinuria. Recent studies have focused on the role of pro and anti-angiogenic peptides as potential placentally derived aetiologic agents in this pathophysiologic sequence, although other placental products have been highlighted in recent research. Despite the fact that this modeling of preeclampsia has widespread support significant limitations to this hypothesis can be identified.

Postoperativ aufgetretene reversible posteriore Enzephalopathie bei einem Patientin mit Morbus Crohn

Posterior encephalopathy (PE) is a rare condition with different origins and unknown pathogenesis. We report on a case of a 16-year-old boy with Crohn's disease who developed PE after peridural anesthesia with ropivacain. A possible connection between PE, ropivacain and Crohn's disease is discussed on the basis of the current literature.

Cerebral artery reactivity changes during pregnancy and the postpartum period: a role in eclampsia?

Eclampsia is thought to be similar to hypertensive encephalopathy, whereby acute elevations in intravascular pressure cause forced dilatation (FD) of intrinsic myogenic tone of cerebral arteries and arterioles, decreased cerebrovascular resistance, and hyperperfusion. In the present study, we tested the hypothesis that pregnancy and/or the postpartum period predispose cerebral arteries to FD by diminishing pressure-induced myogenic activity. We compared the reactivity to pressure (myogenic activity) as well as factors that modulate the level of tone of third-order branches (<200 μm) of the posterior cerebral artery (PCA) that were isolated from nonpregnant (NP, n = 7), late-pregnant (LP, 19 days, n = 10), and postpartum (PP, 3 days, n = 8) Sprague-Dawley rats under pressurized conditions. PCAs from all groups of animals developed spontaneous tone within the myogenic pressure range (50–150 mmHg) and constricted arteries at 100 mmHg (NP, 30 ± 3; LP, 39 ± 4; and PP, 42 ± 7%; P > 0.05). This level of myogenic activity was maintained in the NP arteries at all pressures; however, both LP and PP arteries dilated at considerably lower pressures compared with NP, which lowered the pressure at which FD occurred from >175 for NP to 146 ± 6.5 mmHg for LP ( P < 0.01 vs. NP) and 162 ± 7.7 mmHg for PP ( P < 0.01 vs. NP). The amount of myogenic tone was also significantly diminished at 175 mmHg compared with NP: percent tone for NP, LP, and PP animals were 35 ± 2, 11 ± 3 ( P < 0.01 vs. NP), and 20 ± 7% ( P < 0.01 vs. NP), respectively. Inhibition of nitric oxide (NO) with 0.1 mM Nω-nitro-l-arginine (l-NNA) caused constriction of all vessel types that was significantly increased in the PP arteries, which demonstrates significant basal NO production. Reactivity to 5-hydroxytryptamine (serotonin) was assessed in the presence of l-NNA and indomethacin. There was a differential response to serotonin: PCAs from NP animals dilated, whereas LP and PP arteries constricted. These results suggest that both pregnancy and the postpartum period predispose the cerebral circulation to FD at lower pressures, a response that may lower cerebrovascular resistance and promote hyperperfusion when blood pressure is elevated, as occurs during eclampsia.

Untoward effects of rapid-acting antihypertensive agents

Cerebral haemorrhage remains a major cause of hypertensive cerebral mortality. Lowering of raised blood pressure is therefore crucial in the clinical management of hypertensive disorders of pregnancy. This article reviews rapid-acting agents employed in life-threatening situations.

Maternal cerebral hemodynamics in pregnancy-related hypertension. A prospective transcranial Doppler study

AIM

To compare maternal cerebral hemodynamics, as assessed by transcranial Doppler studies, with the clinical and radiological findings in different types of pregnancy-related hypertension and to determine their pathophysiology.

METHODS

A prospective study of 66 consecutive pregnant women with hypertensive disorders (eclampsia, n = 3; pre-eclampsia, n = 41; isolated hemolysis, elevated liver enzymes, and low platelet count (HELLP)-syndrome, n = 12; pre-eclampsia superimposed on chronic hypertension, n = 5; chronic hypertension, n = 5) and 21 women with uncomplicated pregnancies. Mean blood flow velocities (Vmean) were assessed serially by means of transcranial Doppler in all basal arteries and correlated with changes in mean arterial blood pressure (MABP) and the clinical course.

RESULTS

Patients with the pre-eclampsia/eclampsia syndrome showed significantly elevated Vmean values as compared to controls. In the course of the illness Vmean over the whole length of all insonated basal arteries rose simultaneously. The three eclamptic patients showed the highest Vmean values (156, 182, 192 cm/s, respectively), of the middle cerebral artery (MCA) while MABP was 135, 135, and 150 mmHg, respectively. In pre-eclamptic patients the maximal Vmean MCA ranged from 80 (67, 93) to 145 (114, 151) cm/s [median (25th, 75th percentile)] depending on the severity of clinical presentation. In patients with isolated HELLP-syndrome changes in Vmean were either mild (5/12 cases) or absent (7/12 cases).

CONCLUSIONS

Considerable differences in cerebral hemodynamics were observed in the various types of pregnancy-related hypertensive disorders examined in this study. Our findings in patients with pre-eclampsia/eclampsia syndrome suggest a breakdown of autoregulation with hyperperfusion and vasogenic edema being the most probable pathophysiological mechanism.

Dynamic susceptibility contrast enhanced MRI in reversible posterior leukoencephalopathy syndrome associated with haemolytic uraemic syndrome

We describe a case of reversible posterior leukoencephalopathy associated with haemolytic uraemic syndrome. Following remission confirmed on MRI, the patient relapsed several months later. Neuroimaging findings on conventional MRI and FLAIR sequences and dynamic susceptibility contrast enhanced MRI are described. White matter abnormalities may be shown on CT or MRI in this syndrome. However, dynamic susceptibility contrast enhanced MRI showed far more extensive abnormality within the brain. In addition, phase contrast angiographic measurement of flow in the carotid and basilar arteries indicated a significant elevation of cerebral blood flow, suggesting a decrease in global cerebrovascular resistance. These observations support existing theories that the disorder is manifested by autoregulatory disturbance in small cerebral vessels. Our findings suggest that this abnormality is far more extensive than is demonstrated on T2 weighted MR images and that it is associated with global abnormality of cerebrovascular autoregulation.

Management of acute severe hypertension and encephalopathy

We still do not have an ideal drug to treat acute severe hypertension in pregnancy. Hydralazine and labetalol are the safest agents, but they are inadequate to control blood pressure in some women. Both hypertensive encephalopathy and eclampsia now appear to be forms of an acute process known as reversible posterior leukoencephalopathy syndrome.

Fatal leukoencephalopathy in a patient with non-Hodgkin's lymphoma treated with CHOP chemotherapy and high-dose steroids

Leukoencephalopathy syndromes encompass a variety of neurologic abnormalities that affect cerebral white matter. Known etiologies include malignant hypertension, eclampsia, renal failure, CNS infection, and drug therapy with cyclosporine, tacrolimus (FK506) and interferon-alpha. Symptoms vary according to sites of involvement; they include altered mentation, visual disturbances, focal neurologic signs, and seizures. Characteristic radiologic findings are hypodense areas without contrast enhancement on CT and an increased T2 signal on MRI. The hypodense areas are often symmetric. The clinical symptoms and neuroimaging abnormalities are often reversible with treatment of the underlying condition or removal of the offending drug. We describe a patient with non-Hodgkin's lymphoma treated with conventional cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy and high-dose steroids who developed a rapidly progressive fatal leukoencephalopathy. Her neurologic symptoms and findings on CT are consistent with reported cases of leukoencephalopathy; however, in this instance, the syndrome was not reversible and was ultimately fatal. None of the previously described etiologies could be demonstrated in association with the patient's illness. There are no prior reports of fatal leukoencephalopathy in adult patients treated with standard-dose CHOP. We believe the concurrent immunosuppression from chemotherapy and high-dose steroids resulted in this patient's fatal complication.

The electroencephalogram during normal third trimester pregnancy and six months postpartum

In 1942 Gibbs and Reid described a slowing of the electroencephalogram (EEG) at the end of a normal pregnancy. To the best of our knowledge this is the only report that addresses the modification of the EEG in normal pregnancy. We performed a spectral multichannel EEG analysis and revealed no differences during third trimester pregnancy and six months postpartum. Therefore EEG changes seen during pregnancy, which were previously regarded as 'subtle changes of pregnancy', may turn out to be clinically relevant changes which indicate either pre-existing EEG dysfunction or EEG abnormalities in the context of a pregnancy-related disorder.

A reversible posterior leukoencephalopathy syndrome

BACKGROUND AND METHODS

In some patients who are hospitalized for acute illness, we have noted a reversible syndrome of headache, altered mental functioning, seizures, and loss of vision associated with findings indicating predominantly posterior leukoencephalopathy on imaging studies. To elucidate this syndrome, we searched the log books listing computed tomographic (CT) and magnetic resonance imaging (MRI) studies performed at the New England Medical Center in Boston and Hôpital Sainte Anne in Paris; we found 15 such patients who were evaluated from 1988 through 1994.

RESULTS

Of the 15 patients, 7 were receiving immunosuppressive therapy after transplantation or as treatment for aplastic anemia, 1 was receiving interferon for melanoma, 3 had eclampsia, and 4 had acute hypertensive encephalopathy associated with renal disease (2 with lupus nephritis, 1 with acute glomerulonephritis, and 1 with acetaminophen-induced hepatorenal failure). Altogether, 12 patients had abrupt increases in blood pressure, and 8 had some impairment of renal function. The clinical findings included headaches, vomiting, confusion, seizures, cortical blindness and other visual abnormalities, and motor signs. CT and MRI studies showed extensive bilateral white-matter abnormalities suggestive of edema in the posterior regions of the cerebral hemispheres, but the changes often involved other cerebral areas, the brain stem, or the cerebellum. The patients were treated with antihypertensive medications, and immunosuppressive therapy was withdrawn or the dose was reduced. In all 15 patients, the neurologic deficits resolved within two weeks.

CONCLUSIONS

Reversible, predominantly posterior leukoencephalopathy may develop in patients who have renal insufficiency or hypertension or who are immunosuppressed. The findings on neuroimaging are characteristic of subcortical edema without infarction.

Randomised study assessing the effect of phenytoin and magnesium sulphate on maternal cerebral circulation in eclampsia using transcranial Doppler ultrasound

OBJECTIVE

To assess maternal middle cerebral artery flow velocity patterns as measured by transcranial Doppler ultrasound (TCD) in eclampsia and to investigate the effect of the anticonvulsants magnesium sulphate (MgSO4) and phenytoin on cerebral circulation.

DESIGN

Prospective randomised study.

SETTING

High care obstetric unit, King Edward VIII Hospital, Durban, South Africa.

PARTICIPANTS

Twenty-four eclamptic patients: 13 received MgSO4 and 11 phenytoin.

INTERVENTION

Middle cerebral artery flow velocity waveforms were measured using 2 MHz pulsed Doppler ultrasound via the transtemporal approach in eclamptic patients, before and 15 minutes after the loading dose of anticonvulsant.

RESULTS

Magnesium sulphate significantly reduced the pulsatility index (P = 0.002) and mean flow velocity (P = 0.02) in the middle cerebral artery, whereas phenytoin failed to produce any statistically significant effect. However, differences between groups were not statistically significant. Systolic and diastolic blood pressures were reduced in both the MgSO4 and phenytoin groups.

CONCLUSION

These findings provide firm evidence that MgSO4 relieves cerebral vasospasm, compared with phenytoin, and may therefore be the better drug for the prevention of eclamptic convulsion.