Eclamptic encephalopathy: imaging and pathogenetic considerations

Cerebral Blood Flow Regulation in Pregnancy, Hypertension, and Hypertensive Disorders of Pregnancy

The regulation of cerebral blood flow (CBF) allows for the metabolic demands of the brain to be met and for normal brain function including cognition (learning and memory). Regulation of CBF ensures relatively constant blood flow to the brain despite changes in systemic blood pressure, protecting the fragile micro-vessels from damage. CBF regulation is altered in pregnancy and is further altered by hypertension and hypertensive disorders of pregnancy including preeclampsia. The mechanisms contributing to changes in CBF in normal pregnancy, hypertension, and preeclampsia have not been fully elucidated. This review summarizes what is known about changes in CBF regulation during pregnancy, hypertension, and preeclampsia.

Sleep/Wake Behaviors in Mice During Pregnancy and Pregnancy-Associated Hypertensive Mice

Study Objectives

In humans and other mammals, sleep is altered during pregnancy. However, no studies have been conducted on sleep/wakefulness during pregnancy in mice. In this study, we examined sleep/wakefulness in female C57BL/6 mice during pregnancy. We also examined sleep/wake behaviors in an animal model of preeclampsia, pregnancy-associated hypertensive (PAH) mice, in which increased angiotensin causes hypertension.

Methods

Sleep/wake behaviors of female C57BL/6 and PAH mice were examined based on electroencephalogram (EEG) or electromyogram recordings before, during, and after pregnancy. To examine whether high blood pressure disrupts the integrity of the blood-brain barrier in PAH mice, Evans blue dye was injected intravenously. Angiotensin II receptor blocker (olmesartan)-administered PAH mice and female Tsukuba hypertensive mice were also examined.

Results

C57BL/6 mice showed a decreased total wake time and increased nonrapid eye movement (NREM) sleep time during late pregnancy. Rapid eye movement (REM) sleep time did not change during the course of pregnancy. PAH mice exhibited a general slowing of EEG during late pregnancy and subsequently returned to apparently normal sleep/wakefulness after delivery. All PAH mice exhibited multiple focal leakages of Evans blue dye in the brain. Spike-and-wave discharges were observed in 50% of PAH mice. Olmesartan-administered PAH mice did not show general slowing of EEG. Tsukuba hypertensive mice showed a normal time spent in wakefulness and NREM sleep and a decreased total REM sleep time.

Conclusions

This study showed pregnant-stage-specific changes in sleep/wakefulness in C57BL/6 mice. Furthermore, PAH mice may be useful as an animal model for eclampsia.

Hypertensive Encephalopathy: Clinical and Neuroradiological Findings

Hypertensive encephalopathy is a syndrome consisting of headache, seizures, visual changes, and other neurologic disturbances in patients with elevated systemic blood pressure. The purpose of this study was to analyse the clinical and neuroradiological findings in nine patients with hypertensive encephalopathy, observed in five years.

CT (n = 13), and MR (n = 12), examinations performed in these patients before and after resolution of symptoms were reviewed. Six had the preeclampsia-eclampsia syndrome, and three had hypertensive encephalopathy due to other causes. CT and MR findings in all patients having these examinations were indicative of oedema in the cortex and subcortical white matter in the occipital lobes. Two of the nine patients also had similar findings in the cerebellum and frontal lobes.

The findings on the CT and MR studies resolved on follow-up examinations performed after the hypertension was corrected.

Our results suggest that the radiological findings associated with hypertensive encephalopathy in the appropriate clinical setting are very useful to achieve an early diagnosis.

Cerebrovascular Dysfunction in Preeclamptic Pregnancies

Preeclampsia is a hypertensive, multisystem disorder of pregnancy that affects several organ systems, including the maternal brain. Cerebrovascular dysfunction during preeclampsia can lead to cerebral edema, seizures, stroke, and potentially maternal mortality. This review will discuss the effects of preeclampsia on the cerebrovasculature that may adversely affect the maternal brain, including cerebral blood flow (CBF) autoregulation and blood-brain barrier disruption and the resultant clinical outcomes including posterior reversible encephalopathy syndrome (PRES) and maternal stroke. Potential long-term cognitive outcomes of preeclampsia and the role of the cerebrovasculature are also reviewed.

Placental ischemia in pregnant rats impairs cerebral blood flow autoregulation and increases blood-brain barrier permeability

Cerebrovascular events contribute to ~40% of preeclampsia/eclampsia‐related deaths, and neurological symptoms are common among preeclamptic patients. We previously reported that placental ischemia, induced by reducing utero‐placental perfusion pressure, leads to impaired myogenic reactivity and cerebral edema in the pregnant rat. Whether the impaired myogenic reactivity is associated with altered cerebral blood flow (CBF) autoregulation and the edema is due to altered blood–brain barrier (BBB) permeability remains unclear. Therefore, we tested the hypothesis that placental ischemia leads to impaired CBF autoregulation and a disruption of the BBB. CBF autoregulation, measured in vivo by laser Doppler flowmetry, was significantly impaired in placental ischemic rats. Brain water content was increased in the anterior cerebrum of placental ischemic rats and BBB permeability, assayed using the Evans blue extravasation method, was increased in the anterior cerebrum. The expression of the tight junction proteins: claudin‐1 was increased in the posterior cerebrum, while zonula occludens‐1, and occludin, were not significantly altered in either the anterior or posterior cerebrum. These results are consistent with the hypothesis that placental ischemia mediates anterior cerebral edema through impaired CBF autoregulation and associated increased transmission of pressure to small vessels that increases BBB permeability leading to cerebral edema.

Preeclampsia is associated with an increased risk for developing encephalopathies. A prevailing theory is that impaired cerebral blood flow autoregulation contributes to this process. Whether placental ischemia, commonly thought to be a major underlying factor in the development of preeclampsia, can cause impaired cerebral blood flow autoregulation is not clear. In this study, placental ischemia is experimentally induced to test this directly. The results show that placental ischemia in the pregnant rat causes marked impairment of cerebral blood flow autoregulation.

Posterior reversible encephalopathy syndrome

Posterior reversible encephalopathy syndrome (PRES) is a recently proposed cliniconeuroradiologic entity with several well-known causes, such as hypertensive encephalopathy, eclampsia, and the use of cytotoxic and immunosuppressive drugs, as well as some causes more recently described. PRES is characterized by neuroimaging findings of reversible vasogenic subcortical edema without infarction. The pathogenesis is incompletely understood. Two opposing hypotheses are commonly cited, but the issue is controversial: (1) the current more popular theory suggests that severe hypertension exceeds the limits of autoregulation, leading to breakthrough brain edema; (2) the earlier original theory suggests that hypertension leads to cerebral autoregulatory vasoconstriction, ischemia, and subsequent brain edema. The clinical syndrome of PRES typically involves headache, encephalopathy, visual symptoms, and seizures. The clinical presentation is often nonspecific, and therefore the diagnosis of PRES has come to increasingly rely on magnetic resonance imaging (MRI) abnormalities consistent with PRES with documented recovery clinically and on repeated neuroimaging. The diagnosis has important therapeutic and prognostic implications because the reversibility of the clinical and radiologic abnormalities is contingent on the prompt control of blood pressure and/or discontinuing the offending drug.

Role of neuroimaging in patients with atypical eclampsia

NEED

Despite availability of intensive care units and improved antenatal care, some women still die from Eclampsia. Eclampsia is associated with increased risk of maternal death varying from 1.8 % in developed countries to 14 % in developing countries. Cerebral complications are the major cause of death in eclampsia patients. Eclampsia along with hypercoagulopathy of pregnancy is a high risk fact for patient in respect of development of cerebrovascular thrombosis/ischemic strokes. Eclampsia patients who are refractory to the routine treatment have been found to have various CNS pathological conditions amenable to the medical treatment.

AIMS AND OBJECTIVES

(1) To study the neuropathophysiology behind an eclamptic seizure to reduce the morbidity associated with it. (2) To study the role of neuroimaging in patients with atypical eclampsia.

METHODOLOGY

Prospective study design included 30 patients for the study. All patients were admitted in the eclampsia room with h/o convulsions. All patients were put on MgSO4 therapy and antihypertensives. The patients who are refractory to the treatment such as having recurrent convulsions despite therapy MgSO4 were selected for neuroimaging with CT scan. Neuroimaging is done using Phillips Tomoscan CT scanner where slices of 10-mm thickness were taken through the entire brain in the transaxial plane. Abdomen shielding is done with lead shield to prevent radiation hazard.

RESULT

[Table: see text].

CONCLUSION

Eclampsia patients who were refractory to the treatment with MgSO4 and antihypertensives have been found to have very significant and morbid CNS pathological conditions. Neuroimaging in these patients have done a pivotal role in identifying the abnormality and rectifying it with medical means which had definitely improved patient's condition and have reduced morbidity.

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.

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.

Self-reported cognitive functioning in formerly eclamptic women

OBJECTIVE

Recently, persistent brain white matter lesions were demonstrated in eclamptic women when imaged 6 weeks after delivery. Moreover, many of these women complain about cognitive limitations years after the eclamptic pregnancy. Therefore, in a cohort of such women, we assessed cognitive failures in daily life.

STUDY DESIGN

Thirty formerly eclamptic women completed the Cognitive Failures Questionnaire. Scores were compared with scores of formerly preeclamptic (n = 31) and healthy parous control participants (n = 30) with the use of a priori Student t test. Groups were matched in terms of current age and years elapsed since index pregnancy.

RESULTS

Women who have had eclampsia scored significantly higher on the Cognitive Failures Questionnaire, compared with healthy parous control subjects (43.5 +/- 14.6 vs 36.1 +/- 13.9, respectively; P < .05).

CONCLUSION

Women who have had eclampsia reported significantly more cognitive failures years after the index pregnancy. It is hypothesized that this might be due to some degree of cerebral white matter damage. This subjective assessment of cognitive function must be confirmed with objective neurocognitive testing and related to neuroimaging findings.

Factors contributing to blood-brain barrier disruption following intracarotid injection of nonionic iodinated contrast medium for cerebral angiography: experimental study in rabbits

PURPOSE

This study was performed to investigate the role of injection methods and conditions under a fixed dose of radiographic contrast medium (CM) in respect to promoting blood-brain barrier (BBB) disruption.

MATERIALS AND METHODS

A total of 44 white rabbits (average body weight 2.7 +/- 0.4 kg) were used, and their carotid injection was performed with nonionic CM. The variables assessed for the carotid injections included the following: iodine content (300 or 150 mg I/ml), liquid temperature (37 degrees or 24 degrees C), and the injection time duration (1 or 30 s). The rabbits were divided into five groups. To evaluate BBB disruption, pre- and post-contrast-enhanced magnetic resonance (MR) studies were performed.

RESULTS

Abnormal enhancement of the brain parenchyma in MRI was noted in only one group, which consisted of high-iodine concentration CM injected at a low temperature over a short injection interval. Statistically significant increased values for the percentage of relative enhancement (RE%) were demonstrated (P < 0.05) in comparison with the saline-injected control group.

CONCLUSION

This result suggests variables that may need to be carefully considered to prevent BBB injury induced by nonionic CM for cerebral angiography, especially in the setting of a neurointerventional procedure.

Tumor lysis syndrome as a contributory factor to the development of reversible posterior leukoencephalopathy

INTRODUCTION

Reversible posterior leukoencephalopathy syndrome (RPLS) is a recently described clinical and radiological entity comprising headache, seizures, altered level of consciousness and visual disturbances in association with transient posterior cerebral white-matter abnormalities.

METHOD

We report a young woman with Burkitt's lymphoma who developed RPLS after combined chemotherapy administered during the tumor lysis syndrome.

RESULTS

The symptoms in this patient fitted well with those of RPLS; they included abrupt alterations in mental status, seizures, headache, visual changes and characteristic neuroradiological findings. She was given further combination chemotherapy without any neurological complications, at which time she had already recovered from both RPLS and tumor lysis syndrome.

CONCLUSION

Although many etiological factors have been reported in the development of RPLS, the underlying mechanism is not yet well understood. With prompt and appropriate management, RPLS is usually reversible, and chemotherapy can be continued after complete recovery from RPLS. We suggest that tumor lysis syndrome should be considered as a contributory factor to the development of RPLS in patients for whom treatment with combined chemotherapy for hematological malignancies is planned.

Comparison of cerebral magnetic resonance and electroencephalogram findings in pre-eclamptic and eclamptic women

OBJECTIVE

To compare the cerebral magnetic resonance (MR) and electroencephalogram (EEG) findings in pre-eclamptic and eclamptic pregnant women.

METHODS

A total of 38 pregnant women with mild pre-eclampsia (n = 15), severe pre-eclampsia (n = 11) and eclampsia (n = 12) were included in this study. Cranial MR without contrast and EEG were performed in these women on admission or within 3 days of onset. Follow-up control MR or EEG evaluations were performed 4-6 weeks postpartum in women with MR or EEG abnormalities in the initial examination. To compare differences, X(2) test, Fisher exact or Mann-Whitney U-tests were used.

RESULTS

Abnormal cranial MR findings were found in one (6%) pre-eclamptic woman, in four (36%) severe pre-eclamptic women, and in 11 (92%) eclamptic women. Cranial MR findings were consistent with ischaemia in 15 (39%) patients and haemorrhage in one (3%) case. Two (5%) severe pre-eclamptic women showed cerebral infarction during the follow-up period. MR and EEG abnormalities were totally resolved in 88% of cases. The MR findings of 12 (71%) patients were located in the occipital lobes followed by the parietal lobes in six (40%) cases. Three (20%) mild pre-eclamptic women, four (36%) severe pre-eclamptic women and 10 (83%) eclamptic women had abnormal EEGs. The EEG changes were totally resolved in 13 of 14 (93%) patients after the first month. In one patient with cerebral haemorrhage, the EEG changes lasted for a duration of 6 months.

CONCLUSIONS

A correlation between EEG abnormalities and MR findings was found in this study. The combined use of MR and EEG may help to determine the prognosis for these patients, but the interictal EEG findings recorded in eclampsia were non-specific.

Upward transtentorial herniation, hydrocephalus, and cerebellar edema in hypertensive encephalopathy

BACKGROUND

Edema of the cerebellum with secondary obstructive hydrocephalus is a rare presentation of hypertensive encephalopathy. The authors report an unusual case of isolated posterior fossa swelling with upward transtentorial herniation and hydrocephalus causing neurologic deterioration. These patients are often initially evaluated by a neurologist because of the acute neurologic symptoms. Prompt diagnosis with aggressive blood pressure control may obviate the need for emergent cerebrospinal fluid (CSF) diversion.

REVIEW SUMMARY

This is a case report of a 26-year-old man who presented to the emergency room with confusion and somnolence over a 2-day period. His initial blood pressure was 175/110 mmHg. On examination he was disoriented, with a Glasgow Coma Scale score of 12 points, opening his eyes only to loud verbal stimuli, verbalizing inappropriately, and he was only able to follow simple commands. Neuroimaging revealed edema of the cerebellar folia with noncommunicating hydrocephalus and upward transtentorial herniation. Differential diagnoses of posterior fossa tumor, rhombencephalitis, and hypertensive encephalopathy were entertained. A thorough literature review is included with the discussion of this case. The patient underwent emergent ventriculostomy for CSF drainage and prompt blood pressure control with nitroprusside. After 48 hours of CSF drainage and correction of his hypertension, his neurologic examination normalized. Repeat imaging revealed near resolution of the obstructive hydrocephalus and cerebellar edema.

CONCLUSION

Isolated edema of the cerebellum with upward transtentorial herniation and obstructive hydrocephalus is a rare presentation of hypertensive encephalopathy and should be considered in patients with an acute hypertensive crisis and mental status changes. This entity responds to prompt blood pressure control; however, emergent ventriculostomy by a neurosurgical team should be entertained for neurologic deterioration secondary to significant obstructive hydrocephalus, as illustrated in this case.

Permanent visual deficits secondary to the HELLP syndrome

A 34-year-old woman with eclampsia and the hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome developed encephalopathy, cardiomyopathy, pulmonary edema, liver failure, and disseminated intravascular coagulation (DIC), all of which resolved. She also had retinal hemorrhages in both eyes and a hemorrhagic infarct in the left occipital lobe that resulted in a permanent right homonymous hemianopia and a persistently depressed acuity of 20/100 OS. This case is unusual in demonstrating permanent visual deficits. In nearly all cases of preeclampsia or eclampsia, visual deficits are reversible. The superimposition of the HELLP syndrome may create more neurologic damage. Clinicians should be alert to patients at risk for HELLP syndrome and manage them aggressively.

Increased cerebral blood flow in preeclampsia with magnetic resonance imaging

OBJECTIVE

The purpose of this study was to compare third trimester and nonpregnant cerebral blood flow of women with preeclampsia to normotensive control subjects with the use of magnetic resonance imaging techniques.

STUDY DESIGN

Nine normotensive pregnant women and 12 untreated women with preeclampsia underwent velocity-encoded phase contrast magnetic resonance imaging of the bilateral middle and posterior cerebral arteries in the third trimester and at 6 to 8 weeks after delivery. The Student t test was used for comparison, with a probability value of <.05 considered significant.

RESULTS

Third-trimester large cerebral artery blood flow was significantly higher in preeclampsia. Mean vessel diameter was unchanged, except for the left posterior cerebral artery. There was no difference in mean vessel diameter or cerebral blood flow between the 2 groups while the women were not pregnant.

CONCLUSION

Cerebral blood flow is increased significantly in preeclampsia. We hypothesize that increased cerebral blood flow ultimately could lead to eclampsia through hyperperfusion and the development of vasogenic edema.

Posterior reversible encephalopathy syndrome (PRES) in critically ill obstetric patients

OBJECTIVE

To describe clinical, neuroradiological and evolutionary findings in obstetric patients with posterior reversible encephalopathy syndrome (PRES).

DESIGN

Retrospective case series.

SETTING

University intensive care unit (ICU).

PATIENTS

Four critically ill patients. Two patients experienced PRES in late postpartum without the classical pre-eclamptic signs. All patients showed impairment of consciousness and epileptic seizures; two of them presented cortical blindness and headache, too. True status epilepticus (SE) occurred in two cases. In all patients MRI showed the typical feature of gray-white matter edema, mainly localized to the temporo-parieto-occipital areas.

INTERVENTIONS

Normalization of high blood pressure (BP) and treatment of seizures. Two patients with SE and severe impairment of consciousness were treated with an intravenous valproate (ivVPA) bolus followed by continuous infusion.

MEASUREMENTS AND RESULTS

In three cases, neurological and MRI abnormalities completely resolved in about a week. Another patient died due to subarachnoid hemorrhage.

CONCLUSION

Posterior reversible encephalopathy syndrome is a well described clinical and neuroradiological syndrome characterized by headache, altered mental status, cortical blindness and seizures, and a diagnostic MRI picture; usually reversible, PRES can sometimes result in death or in irreversible neurological deficits, thus requiring early diagnosis and prompt treatment. PRES can have various etiologies, but pregnancy and postpartum more frequently lead to this condition. Treatment of seizures deserves special attention since the anti-epileptic drugs currently used in SE management may worsen vigilance as well as autonomic functions. Extensive research is needed to assess the role of ivVPA in this condition.

Posterior leukoencephalopathy in association with the tumour lysis syndrome in acute lymphoblastic leukaemia--a case with clinicopathological correlation

We report a case and autopsy findings of posterior leukoencephalopathy (PL) developing during induction chemotherapy for B-cell acute lymphoblastic leukaemia (B-ALL) complicated by tumour lysis syndrome. PL may present with seizures, headache, altered mental status and occipital blindness, associated with transient parieto-occipital abnormalities on neuro-imaging studies. Precipitants include immunosuppressive agents, renal insufficiency, hypertension and fluid retention. It has also been reported in association with pre-eclamptic and eclamptic states, nephrotic syndrome and following liver and bone marrow transplantation. Only rare cases of PL developing during treatment for haematological malignancy have been reported and to our knowledge it has not been previously reported in association with tumour lysis syndrome. Since the condition is generally regarded as being fully reversible few autopsy findings have been reported.

Posterior leukoencephalopathy syndrome

Posterior leukoencephalopathy syndrome is a newly recognised brain disorder that predominantly affects the cerebral white matter. Oedematous lesions particularly involve the posterior parietal and occipital lobes, and may spread to basal ganglia, brain stem, and cerebellum. This rapidly evolving neurological condition is clinically characterised by headache, nausea and vomiting, seizures, visual disturbances, altered sensorium, and occasionally focal neurological deficit. Posterior leukoencephalopathy syndrome is often associated with an abrupt increase in blood pressure and is usually seen in patients with eclampsia, renal disease, and hypertensive encephalopathy. It is also seen in the patients treated with cytotoxic and immunosuppressive drugs such as cyclosporin, tacrolimus, and interferon alfa. The lesions of posterior leukoencephalopathy are best visualised with magnetic resonance (MR) imaging. T2 weighted MR images, at the height of symptoms, characteristically show diffuse hyperintensity selectively involving the parieto-occipital white matter. Occasionally the lesions also involve the grey matter. Computed tomography can also be used satisfactorily to detect hypodense lesions of posterior leukoencephalopathy. Early recognition of this condition is of paramount importance because prompt control of blood pressure or withdrawal of immunosuppressive agents will cause reversal of the syndrome. Delay in the diagnosis and treatment can result in permanent damage to affected brain tissues.

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.

Hypertensive emergencies

A hypertensive emergency is a situation in which uncontrolled hypertension is associated with acute end-organ damage. Most patients presenting with hypertensive emergency have chronic hypertension, although the disorder can present in previously normotensive individuals, particularly when associated with pre-eclampsia or acute glomerulonephritis. The pathophysiological mechanisms causing acute hypertensive endothelial failure are complex and incompletely understood but probably involve disturbances of the renin-angiotensin-aldosterone system, loss of endogenous vasodilator mechanisms, upregulation of proinflammatory mediators including vascular cell adhesion molecules, and release of local vasoconstrictors such as endothelin 1. Magnetic resonance imaging has demonstrated a characteristic hypertensive posterior leucoencephalopathy syndrome predominantly causing oedema of the white matter of the parietal and occipital lobes; this syndrome is potentially reversible with appropriate prompt treatment. Generally, the therapeutic approach is dictated by the particular presentation and end-organ complications. Parenteral therapy is generally preferred, and strategies include use of sodium nitroprusside, beta-blockers, labetelol, or calcium-channel antagonists, magnesium for pre-eclampsia and eclampsia; and short-term parenteral anticonvulsants for seizures associated with encephalopathy. Novel therapies include the peripheral dopamine-receptor agonist, fenoldapam, and may include endothelin-1 antagonists.

Change in estimated cerebral perfusion pressure after treatment with nimodipine or magnesium sulfate in patients with preeclampsia

OBJECTIVE

Data are accumulating to suggest that cerebral perfusion pressure may be either abnormally high or low in preeclampsia and eclampsia. Little is known of the cerebral perfusion pressure effects of magnesium sulfate or nimodipine. Our objective in this study was to compare the change in cerebral perfusion pressure in patients with severe preeclampsia randomly selected to receive nimodipine or magnesium sulfate.

STUDY DESIGN

Patients with severe preeclampsia were randomly selected to receive magnesium sulfate (6 g bolus and 2 g/hr intravenous infusion) or nimodipine (60 mg taken orally every 4 hours). Transcranial Doppler ultrasonography was used to measure flow velocities in the right and left middle cerebral arteries, and the results were averaged. Measurements were obtained before treatment (baseline) and 30 minutes after the magnesium sulfate bolus was completely infused or 30 minutes after the nimodipine was ingested. Studies were performed before any other intervention. The person performing the ultrasonography was unaware of the patient's group assignment. Estimated cerebral perfusion pressure was calculated with the following formula: Estimated cerebral perfusion pressure = Velocity(mean) x [(Blood pressure(mean ) - Blood pressure(diastolic ))/(Velocity(mean) - Velocity(diastolic ))]. The difference between estimated cerebral perfusion pressure at baseline and after treatment was compared between the 2 groups by means of the Mann-Whitney rank sum test.

RESULTS

Nine patients were randomly selected to receive nimodipine and 12 to receive magnesium sulfate. Patient demographics and severity of condition were not significantly different between the 2 groups. The change in estimated cerebral perfusion pressure was significantly different between the groups. Estimated cerebral perfusion pressure increased after nimodipine use and decreased after magnesium sulfate use.

CONCLUSION

Shortly after administration to patients with severe preeclampsia, nimodipine resulted in increased cerebral perfusion pressure in comparison with magnesium sulfate.