Persistence of cerebral hemodynamic changes in patients with eclampsia: A report of three cases

Unusual Presentation of Reversible Transient Vision Loss After Caesarean Section Under Subarachnoid Block: A Case Report

A transient vision loss is not commonly encountered during the postoperative period following a caesarean section. Although numerous causes have been suggested for transient vision loss, when loss of vision is associated with seizures and headaches, the differential diagnoses include hemolysis, elevated liver enzymes, low platelet syndrome, reversible cerebral vasoconstriction syndrome, posterior reversible encephalopathy syndrome (PRES), dural venous thrombosis, and central retinal arteriolar occlusion. We report a case of a 35-year-old patient who underwent an elective caesarean section under spinal anaesthesia and developed a headache followed by loss of vision and seizures during the postoperative period. An MRI scan of the brain on the same day revealed subtle hyperintensity in bilateral parieto-occipital lobes in the cortical and subcortical areas and bilateral cerebral hemispheres, which indicates PRES. Rapid and complete resolution of symptoms was observed with supportive treatment. Therefore, prompt suspicion and effective management of PRES are of paramount importance to prevent short- and long-term neurological deficits.

Cerebral haemodynamics in early puerperium: A prospective study

AIM

Prospective study on 900 consecutive puerperae to assess normal values and range of the blood flow velocity in the middle cerebral artery in both hemispheres.

MATERIAL AND METHOD

M1 and M2 segments of both middle cerebral arteries were assessed in all subjects within 96 hours of delivery. Mean flow velocity was recorded after adjusting for insonation angle. Lindegaard index (LI = middle cerebral artery-Internal Carotid Artery mean flow velocity ratio) was calculated whenever the mean flow velocity exceeded 100 cm/second. Asymmetry indexes were calculated inter hemispherically for M1 and M2 segments separately.

RESULTS

Mean flow velocities were 74 ± 17 and 72 ± 17 in right and 73 ± 17 and 72 ± 17 cm/second in the left M1 and M2, respectively. A total of 136 subjects (12.1%) exceeded the threshold of 100 cm/second, but LI was consistently <3 in all of them. Mean flow velocity was inversely and independently correlated to haemoglobin levels and to parity. Mean asymmetry indexes were 0.25 ± 23 in M1 and 0.45 ± 25 in M2.

CONCLUSION

Mean flow velocity in the middle cerebral artery of healthy subjects in early puerperium is higher than in age-matched non-puerperal women and may exceed the threshold of 100 cm/second with no evidence of intracranial spasm, because of blood loss during delivery. Mean flow velocity is independently correlated with parity. Right-to-left mean flow velocity asymmetry may reach 50% as a consequence of a transient imbalance in vascular tone regulation.

Magnesium Sulfate Provides Neuroprotection in Eclampsia-Like Seizure Model by Ameliorating Neuroinflammation and Brain Edema

Eclampsia is a hypertensive disorder of pregnancy that is defined by the new onset of grand mal seizures on the basis of preeclampsia and a leading cause of maternal and fetal mortality worldwide. Presently, magnesium sulfate (MgSO₄) is the most effective treatment, but the mechanism by which MgSO₄ prevents eclampsia has yet to be fully elucidated. We previously showed that systemic inflammation decreases the seizure threshold in a rat eclampsia-like model, and MgSO₄ treatment can decrease systemic inflammation. Here, we hypothesized that MgSO₄ plays a neuroprotective role in eclampsia by reducing neuroinflammation and brain edema. Pregnant Sprague-Dawley rats were given an intraperitoneal injection of pentylenetetrazol following a tail vein injection of lipopolysaccharide to establish the eclampsia-like seizure model. Seizure activity was assessed by behavioral testing. Neuronal loss in the hippocampal CA1 region (CA1) was detected by Nissl staining. Cerebrospinal fluid levels of S100-B and ferritin, indicators of neuroinflammation, were detected by enzyme-linked immunosorbent assay, and ionized calcium binder adapter molecule 1 (Iba-1, a marker for microglia) and glial fibrillary acid protein (GFAP, a marker for astrocytes) expression in the CA1 area was determined by immunofluorescence staining. Brain edema was measured. Our results revealed that MgSO₄ effectively attenuated seizure severity and CA1 neuronal loss. In addition, MgSO₄ significantly reduced cerebrospinal fluid levels of S100-B and ferritin, Iba-1 and GFAP activation in the CA1 area, and brain edema. Our results indicate that MgSO₄ plays a neuroprotective role against eclampsia-like seizure by reducing neuroinflammation and brain edema.

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.

Cytotoxic Edema in Posterior Reversible Encephalopathy Syndrome: Correlation of MRI Features with Serum Albumin Levels

BACKGROUND AND PURPOSE

Posterior reversible encephalopathy syndrome is a clinicoradiologic entity with typical MR imaging showing predominant vasogenic and occasional cytotoxic edema. It is unclear whether MR imaging correlates with levels of serum albumin. We determined potential risk factors for development of cytotoxic edema in posterior reversible encephalopathy syndrome.

MATERIALS AND METHODS

Seventy-nine cases with typical clinical symptoms and characteristic neuroradiologic findings conformed to posterior reversible encephalopathy syndrome diagnostic criteria and were included in this study. FLAIR, DWI, and ADC maps were interpreted to evaluate the severity and type of edema. MR imaging was correlated with the levels of serum albumin, and cytotoxic edema was compared with the location and severity of brain edema.

RESULTS

Pure vasogenic edema was found in 53 cases (67.09%), and vasogenic edema complicated with cytotoxic components, in 26 patients (32.91%). There was no difference in serum albumin levels between patients with cytotoxic components and those with vasogenic edema (P = .983). There was a significant difference in the edema scale scores between patients with cytotoxic edema and those with vasogenic edema (P = .006). The percentage of cytotoxic edema located in the area with higher scale scores of edema was significantly larger than that in areas with lower scale scores of edema (P = .002).

CONCLUSIONS

Serum albumin may contribute to the development of edema in PRES but is not a decisive factor for edema type. Cytotoxic edema in posterior reversible encephalopathy syndrome is probably related to regional decreased perfusion and arteriolopathy. Further work should be undertaken to discover the pathophysiologic mechanisms involved.

Cerebro vascular reactivity (CVR) of middle cerebral artery in response to CO2 5% inhalation in preeclamptic women

OBJECTIVE

To compare the cerebro vascular reactivity (CVR) of middle cerebral artery (MCA) in response to CO2 5% inhalation between preeclamptic and normotensive pregnant women, also, between mild and severe preeclampsia.

STUDY DESIGN

A comparative study was performed on 61 women with preeclampsia and 65 normotensive pregnant women who were in the third trimester of gestation. MCA transcranial Doppler ultrasound was used to measure CVR in response to CO2 5% inhalation. Pulsatility index (PI), resistance index (RI), blood pressure, maternal age, gestational age and gravidity were also recorded.

RESULTS

Baseline PI and RI were lower in the preeclamptic group (p < 0.05). Inhalation of CO2 5% caused significant increase in CVR among normotensive pregnant women in comparison with preeclamptic group (1.006 ± 0.229 versus 0.503 ± 0.209, p = 0.0001). Significantly, more cerebral vasodilatation was found among mild preeclamptic women in comparison with severe preeclamptic women (0.583 ± 0.193 versus 0.383 ± 0.173, p = 0.0001). The receiver operating characteristics curve analysis revealed acceptable difference between CO2 stimulation test of preeclamptic and normotensive women (Area under curve = 0.973, p = 0.0001).

CONCLUSION

CVR in response to CO2 5% is less in preeclamptic pregnant women than normotensives, also, in severe preeclampsia, it is less than mild 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.

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.

Is High Cerebral Perfusion Pressure and Cerebral Flow Predictive of Impending Seizures in Preeclampsia? A Case Report

Transcranial Doppler ultrasound was used to demonstrate elevated estimated cerebral perfusion pressure (CPP) and cerebral flow index (CFI) in a preeclamptic patient. She subsequently developed eclampsia. After magnesium sulfate therapy her CPP and CFI were within the normal range and she did not experience further seizures. This finding suggests that cerebral overperfusion may be at least one of the etiologies involved in the pathogenesis of eclampsia.

Advances in the understanding of eclampsia

Preeclampsia, a serious hypertensive complication of pregnancy characterized by new-onset hypertension and proteinuria after midpregnancy, is a multisystem disorder that often involves the central nervous system. Neurologic signs and symptoms include hyperreflexia, headaches, visual disturbance, seizures, and cerebral hemorrhage. Eclampsia-new-onset seizures in the setting of preeclampsia-usually occurs before or within 48 hours of delivery, but can present as late as 1 month postpartum (late postpartum eclampsia). Magnesium sulfate is the drug of choice to prevent and treat eclampsia, a recommendation validated through large, randomized, and placebo-controlled trials. This review describes the pathogenesis, clinical features, and treatment of eclampsia, focusing on recent observations regarding roles of circulating antiangiogenic factors in the pathogenesis of the neurologic complications of eclampsia.

Posterior reversible encephalopathy syndrome, part 2: controversies surrounding pathophysiology of vasogenic edema

Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic state accompanied by a unique brain imaging pattern typically associated with a number of complex clinical conditions including: preeclampsia/eclampsia, allogeneic bone marrow transplantation, solid organ transplantation, autoimmune diseases and high dose cancer chemotherapy. The mechanism behind the developing vasogenic edema and CT or MR imaging appearance of PRES is not known. Two theories have historically been proposed: 1) Severe hypertension leads to failed auto-regulation, subsequent hyperperfusion, with endothelial injury/vasogenic edema and; 2) vasoconstriction and hypoperfusion leads to brain ischemia and subsequent vasogenic edema. The strengths/weaknesses of these hypotheses are reviewed in a translational fashion including supporting evidence and current available imaging/clinical data related to the conditions that develop PRES. While the hypertension/hyperperfusion theory has been most popular, the conditions associated with PRES have a similar immune challenge present and develop a similar state of T-cell/endothelial cell activation that may be the basis of leukocyte trafficking and systemic/cerebral vasoconstriction. These systemic features along with current vascular and perfusion imaging features in PRES appear to render strong support for the older theory of vasoconstriction coupled with hypoperfusion as the mechanism.

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.

Pregnancy prevents hypertensive remodeling and decreases myogenic reactivity in posterior cerebral arteries from Dahl salt-sensitive rats: a role in eclampsia?

Previous studies have demonstrated that pregnancy prevents protective hypertension-induced remodeling of cerebral arteries using nitric oxide synthase (NOS) inhibition to raise mean arterial pressure (MAP). In the present study, we investigated whether this effect of pregnancy was specific to NOS inhibition by using the Dahl salt-sensitive (SS) rat as a model of hypertension. Nonpregnant ( n = 16) and late-pregnant ( n = 17) Dahl SS rats were fed either a high-salt diet (8% NaCl) to raise blood pressure or a low-salt diet (<0.7% NaCl). Third-order posterior cerebral arteries were isolated and pressurized in an arteriograph chamber to measure active responses to pressure and passive remodeling. Several vessels from each group were stained for protein gene product 9.5 to determine perivascular nerve density. Blood pressure was elevated in both groups on high salt. The elevated MAP was associated with significantly smaller active and passive diameters ( P < 0.05) and inward remodeling in the nonpregnant hypertensive group only. Whereas no structural changes were observed in the late-pregnant hypertensive animals, both late-pregnant groups had diminished myogenic reactivity ( P < 0.05). Nerve density in both the late-pregnant groups was significantly greater when compared with the nonpregnant groups, suggesting that pregnancy has a trophic influence on perivascular innervation of the posterior cerebral artery. However, hypertension lowered the nerve density in both nonpregnant and late-pregnant animals. It therefore appears that pregnancy has an overall effect to prevent hypertension-induced remodeling regardless of the mode of hypertension. This effect may predispose the brain to autoregulatory breakthrough, hyperperfusion, and eclampsia when MAP is elevated.

Cerebral blood flow autoregulation and edema formation during pregnancy in anesthetized rats

Eclampsia is considered a form of hypertensive encephalopathy in which an acute elevation in blood pressure causes autoregulatory breakthrough, blood-brain barrier disruption, and edema formation. We hypothesized that pregnancy predisposes the brain to eclampsia by lowering the pressure of autoregulatory breakthrough and enhancing cerebral edema formation. Because NO production is increased in pregnancy, we also investigated the role of NO in modulating autoregulation. Cerebral blood flow autoregulation was determined by phenylephrine infusion and laser Doppler flowmetry. Four groups were studied: untreated nonpregnant (n=7) and late-pregnant (days 19 to 21; n=8) Sprague-Dawley rats and nonpregnant (n=8) and late-pregnant (n=8) animals treated with an NO synthase inhibitor (N(G)-nitro-l-arginine methyl ester; 0.5 to 0.7 g/L). Brain water content and blood-brain barrier permeability to sodium fluorescein were determined after breakthrough. Pregnancy caused no change in autoregulation or the pressure of breakthrough. However, treatment with the NO synthase inhibitor significantly increased the pressure of autoregulatory breakthrough (nonpregnant: 183.6+/-3.0 mm Hg versus 212.0+/-2.8 mm Hg, P<0.05; late-pregnant: 180.8+/-3.2 mm Hg versus 209.3+/-4.7 mm Hg, P<0.05). After autoregulatory breakthrough, only late-pregnant animals showed a significant increase in cerebral edema formation, which was attenuated by NO synthase inhibition. There was no difference in blood-brain barrier permeability between nonpregnant and late-pregnant animals in response to acute hypertension, suggesting that pregnancy may predispose the brain to eclampsia by increasing cerebral edema through increased hydraulic conductivity.

Cerebral Hemodynamics in Preeclampsia: Cerebral Perfusion and the Rationale for an Alternative to Magnesium Sulfate

Preeclampsia and eclampsia continue to be major causes of maternal death. Currently, approximately 18% of U.S. maternal deaths are attributed to hypertensive disorders and eclampsia, and several hundred women die from eclampsia and its complications every year. In the United States, preeclamptic women have received magnesium sulfate as a seizure prophylaxis agent for 3 decades, and this practice is becoming more widely accepted internationally. In addition to a recognized failure rate, there are financial, logistic, and safety concerns associated with the universal administration of magnesium sulfate. Many institutions in the developing world lack the necessary equipment and expertise to administer the medication, and many preeclamptic patients thus do not receive magnesium sulfate before their first seizure. As effective as it has been in reducing mortality from eclampsia, magnesium sulfate is also associated with appreciable morbidity and mortality from administration errors and magnesium toxicity. The availability of an easily administered, cheap, safe, and orally administered alternative to magnesium sulfate would be welcomed in the developing world and would provide an extremely useful alternative therapy to the current standard of care. Recent advances in the understanding of the pathophysiology of preeclampsia and eclampsia, primarily related to cerebral perfusion and blood flow, could allow us to reduce the seizure rate in treated preeclamptic women even further than what is currently reported. This article deals with the rationale behind the use of labetalol as an alternative to magnesium sulfate for the prevention of eclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to recall that hypertensive diseases of pregnancy contribute a significant portion of today's maternal mortality, explain that methods of preventing eclampsia are not applicable worldwide, and state that understanding of the pathophysiology of preeclampsia/eclampsia may assist in developing safe and effective medications that can be used universally.

Cerebral edema on MRI in severe preeclamptic women developing eclampsia

OBJECTIVE

The aim of this study is to identify suitable applications for cerebral MR (magnetic resonance) scanning in cases of severe preeclampsia and eclampsia through comparison of clinical course and easily accessible parameters.

METHODS

From January 2001 to December 2003, cerebral MR scans were performed on 43 women with severe preeclampsia; of those 41 were enrolled in data analyses. Twenty clinical parameters, including age, body mass index, blood pressure, liver and renal function, and coagulation status, were compared for each patient. Data were analyzed using the SPSS program on a VAX main frame.

RESULTS

Among 41 severe preeclamptic women, abnormal MR images were observed in 11 cases including six with systemic seizures. Predictive accuracy of eclampsia with abnormal cerebral MR imaging was 84.9% (P=0.00001), while only 14.3% of severe preeclampsia cases had been diagnosed radiologically. Statistical analysis suggests diastolic BP and serum AST as predictive parameters for abnormal MR images with 82.9% predictive accuracy (P=0.0007).

CONCLUSIONS

Cerebral edema can be observed in preeclamptic patients developing eclampsia. Rapid delivery is indicated when diastolic BP and AST are elevated. MR scanning is useful when delivery is delayed due to fetal immaturityin cases of severe preeclampsia.

Pregnancy-induced up-regulation of aquaporin-4 protein in brain and its role in eclampsia

Neurologic complications of eclampsia are thought to be similar to hypertensive encephalopathy in which an acute, excessive elevation in blood pressure causes blood-brain barrier (BBB) disruption and edema formation. Because women who develop eclampsia are in general normotensive and asymptomatic prior to pregnancy, we hypothesized that pregnancy alone predisposes the brain to edema formation by up-regulation of aquaporin 4 (AQP4), a water channel in the brain that has been shown to positively correlate with edema formation. To test this hypothesis, we compared localization (immunohistochemistry), mRNA (RT-PCR), and protein levels (Western analysis) of AQP4 in brains from Sprague Dawley rats that were nonpregnant (NP, proestrous), mid-pregnant (MP, days 9-10), late-pregnant (LP, days 19-20), and postpartum (PP, days 3-4). AQP4 mRNA was detected in the brains of all the animals and was localized primarily around the brain parenchymal blood vessels, strongly implicating its role in BBB function. Western analysis revealed that the major AQP4 band at approximately 32 kDa was significantly elevated in MP, LP, and PP animals compared with NP by 9-, 22-, and 17-fold, respectively. These results suggest that pregnancy and the postpartum state up-regulate AQP4 protein located around the intraparenchymal blood vessels, a consequence that could promote edema formation when blood pressure is acutely and excessively elevated, as during eclampsia.-Quick, A. M., Cipolla, M. J. Pregnancy-induced up-regulation of aquaporin-4 protein in brain and its role in eclampsia.

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.

Late postpartum eclampsia: a common presentation of an uncommon diagnosis

We present two cases of late postpartum eclampsia. Both patients presented with a chief complaint of headache, and were diagnosed with eclampsia after the onset of seizures. Neither patient had proteinuria or edema. Further evaluation did not yield another diagnosis for the seizures, and treatment with i.v. magnesium sulfate was successful in stopping the seizures. No further seizure activity occurred in either patient.

Neuroimaging of delayed eclampsia. Report of 3 cases and review of the literature

Computed tomography and magnetic resonance imaging findings consistent with eclampsia were recently encountered in 3 patients who developed severe headache days to weeks after uncomplicated delivery. The neurologic presentation was nonspecific, and pre-eclamptic symptoms were not present, including significant hypertension. Variable expression of pre-eclampsia occurred during the course of their observation. Conventional angiography obtained in 2 patients because of a concern for aneurysm demonstrated central and peripheral vasospasm. Magnetic resonance angiography demonstrated central vasospasm in the third patient.

Impaired dynamic cerebral autoregulation in eclampsia

Eclampsia is frequently associated with brain edema, cerebral infarction or hemorrhage. Its underlying cerebrovascular pathophysiology is still poorly understood. We examined cerebral autoregulation by a non-invasive multimodal assessment in a 28-year-old primaparous woman with postpartal eclampsia. Transcranial Doppler sonography showed considerably increased cerebral blood flow velocity (CBFV) of all basal cerebral vessels. Magnetic resonance imaging demonstrated multifocal vasogenic brain edema. Using transfer function analysis, a severely decreased phase shift between respiratory-induced 0.1-Hz oscillations of arterial blood pressure and CBFV was observed, indicating substantial disturbance of dynamic cerebral autoregulation (DCA). In contrast, CO(2)-vasomotor reactivity of the right middle cerebral artery was only slightly reduced. We therefore assume that the cerebral arteriolar dysfunction in eclampsia leads primarily to an impairment of the autoregulatory mechanism that is followed by different degrees of arteriolar vasodilation. Because of its probably high sensitivity to hemodynamic disturbances, assessment of DCA might be of great value in early pre-eclampsia for risk prediction of cerebral arteriopathy and eclampsia.

Maternal transcranial Doppler in pre-eclampsia and eclampsia

Pre-eclampsia affects 3-7% of women and is associated with significant maternal and perinatal morbidity and mortality. Transcranial Doppler (TCD) has been used in pre-eclampsia/eclampsia to evaluate non-invasively the cerebrovascular hemodynamics in the maternal middle cerebral artery. TCD has demonstrated in pre-eclamptic women maternal cerebral vasospasm, which does not correlate with mean arterial pressure assessed simultaneously. Estimated cerebral perfusion pressure, assessed using a modified formula, has been shown to be increased in women with severe and non-severe pre-eclampsia. However, in severe pre-eclampsia, elevated cerebral perfusion pressure is counterbalanced by increases in cerebrovascular resistance and cerebral blood flow is unaffected. In eclampsia a significant fall in cerebral vascular resistance occurs which, in the presence of increases in cerebral perfusion pressure, leads to hyperperfusion. Cerebral vascular changes to date have not been sensitive enough to predict the development of pre-eclampsia or eclampsia. Longitudinal studies with the aim of predicting the onset of pre-eclampsia and to assess the effects of various drugs on the maternal cerebral circulation need to be designed.

[Brain oedema following blood-brain barrier disruption: mechanisms and diagnosis]

Brain oedema following blood-brain barrier (BBB) disruption, or vasogenic oedema, is present in most cases of brain oedema. According to the Starling's law, water, ions and plasma proteins cross the BBB toward the interstitium if the driving forces for transmural bulk flow are excessive (mechanical origin) and/or if the BBB permeability is enhanced (chemical origin). Both mechanisms coexist in most cases. Excessive elevation of the gradient of hydrostatic pressure with lost of cerebral autoregulation has been proved in ischaemia/reperfusion and trauma, and suggested in acute mountain sickness and eclampsia. The BBB permeability can be enhanced by immediate (chemical mediators) or delayed (cellular infiltration) inflammatory response, or by alteration of the membrane integrity. This later can be transient (hyperosmolar BBB disruption), or permanent by activation of matrix metalloproteinase or by neovascularization with BBB breakdown. The reference method for the diagnosis of vasogenic oedema is the MRI diffusion-weighted imaging.

Cerebral perfusion pressure, and not cerebral blood flow, may be the critical determinant of intracranial injury in preeclampsia: a new hypothesis

OBJECTIVE

The relationship between cerebral perfusion pressure (CPP) and cerebral blood flow is unclear in preeclampsia. Our objective was to clarify this issue by comparing normal pregnant women to those with mild and severe preeclampsia.

STUDY DESIGN

Patients with mild (n = 72) and severe (n = 120) preeclampsia underwent transcranial Doppler (TCD) imaging of the maternal middle cerebral artery (MCA). At the same time, blood pressure was taken with a Dinamap monitor (Dinamap; Criticon Inc, Tampa, Fla). CPP, resistance area product (RAP), and the cerebral flow index (CFI) were calculated by standard formulas. Data were plotted on normative curves for pregnancy (5% and 95%) and compared by chi(2) and Mann-Whitney U tests.

RESULTS

CFI is usually normal in both severe (75%) and mild (72%) cases. If CFI is abnormal in severe cases, it may be either increased (14%) or decreased (10%), although in mild cases almost all abnormal CFI (25%) is lower than normal. In those cases with low or normal CFI, severe cases are associated with a significantly higher CPP, RAP, and MAP than mild cases (P <.05), although the CFI is not significantly different. A significant proportion of severe cases have high CPP (52%), whereas in mild cases the CPP is almost always normal (87%). Overall, in severe cases the RAP is abnormally high, although it is within the normal range in mild cases.

CONCLUSIONS

One of the fundamental differences between mild and severe cases relates to the degree of cerebral perfusion pressure that the MCAs are subjected to. Because most preeclamptic women, regardless of degree of severity, have a normal CFI, it appears that autoregulation is generally intact. Because women with severe cases are more prone to cerebral catastrophe than those with mild preeclampsia, uncontrolled CPP may cause barotrauma and vessel damage, leading to hypertensive encephalopathy and overperfusion injury. Therapeutic strategies that ensure reduction of the CPP with maintenance of the CFI seem most likely to prevent the cerebral injuries (overperfusion or underperfusion) that cause seizures or death in women with preeclampsia.

Hyperperfusion encephalopathies: hypertensive encephalopathy and related conditions

BACKGROUND

Hypertensive encephalopathy (HTE) is a syndrome typified by headache, seizures, and neurologic signs associated with increased systemic blood pressures; edema in the subcortical white matter is seen on imaging studies and is usually reversible, although infarction or hemorrhage may supervene. Based on previous work, we theorize that HTE is associated with increased perfusion to the brain. Syndromes related to HTE may also be encountered in clinical situations in which perfusion to the brain is acutely increased without systemic hypertension (i.e., after treatment of high-grade carotid stenoses or large intracranial arteriovenous malformations, or in high altitude mountain sickness). We therefore refer to these conditions more generally as hyperperfusion encephalopathies (HPE).

REVIEW SUMMARY

The clinical and radiographic data of 110 patients (average age, 50.1 years) who presented at the Brigham and Women's Hospital with clinical and radiographic signs of HPE were reviewed; 104 had systemic hypertension and 6 had postcarotid endarterectomy hyperperfusion syndrome. Edema involved the subcortical white matter and occasionally the cortex in all patients. In patients with systemic hypertension, the edema was usually bilateral and located predominantly in the occipital lobes; other brain regions included the parietal lobes, posterior frontal lobes, cerebellum, and splenium of the corpus callosum. The six patients with postcarotid endarterectomy hyperperfusion syndrome had edema in the hemisphere ipsilateral to the operated side involving the anterior and middle cerebral artery territories. The edema in HPE was associated with: increased low attenuation on CT; decreased T(1) and increased T(2) signal on MR imaging; increased cerebral perfusion on single emission computed tomography (SPECT) and perfusion MR imaging;did not show restricted diffusion on MR imaging. The syndrome resolved completely in most cases after the administration of antihypertensive agents, although rarely small infarcts and hemorrhages occurred. Three patients with thrombocytopenia developed large fatal intracranial hemorrhages.

CONCLUSION

The symptoms of HPE are usually nonspecific, but the radiographic findings are consistent. Treatment should be instituted rapidly and patients should be followed until the condition resolves either clinically or radiographically; hemorrhagic complications, although rare, can be serious.

The neurologic consequences of eclampsia

BACKGROUND

Toxemia of pregnancy (preeclampsia/eclampsia) is a syndrome characterized by pregnancy-induced hypertension, edema, and proteinuria, although it is often associated with more generalized multisystem abnormalities that affect the nervous system, the liver, kidneys, and coagulation. For the most part, preeclampsia/eclampsia is a reversible process that almost always improves after delivery of the baby. Despite recent advances in diagnosis and management, eclampsia remains the second most common cause of maternal death in the United States. Because of the often severe repercussions on the nervous system, neurologists can make important contributions to the management of patients with eclampsia. Although preeclampsia is largely under the purview of obstetrics, neurologists can provide input to the management of intracranial vascular problems, seizures, and raised intracranial pressure. Input on the severity and nature of neurologic problems will enable the obstetrician to determine whether to expedite or to delay child birth.

REVIEW SUMMARY

There is an increasing body of evidence on the associated endothelial dysfunction, breakdown of the blood-brain barrier, and failure of cerebrovascular autoregulation with vasospasm, ischemia, and cerebral edema. Therapy is directed at controlling blood pressure, giving magnesium sulfate to treat the preeclamptic/eclamptic process itself, and instituting antiseizure medicines (e.g., diazepam or phenytoin) when uncontrolled seizures or status epilepticus supervene.

CONCLUSION

Cerebrovascular accidents occur more frequently in young women during pregnancy and the puerperium, and there is an unmet need for basic and clinical research directed at the pathophysiology of the eclamptic process so as to provide more directed therapy.

New insights in hypertensive disorders of pregnancy

Research reported during the past year has enhanced our understanding of conditions that lead to the complex changes that are observed in hypertensive disorders of pregnancy. An association between placental pathology and a multisystem disorder that is characterized by endothelial dysfunction which involves genetic and immunological investigations has been identified. On the basis of these findings, promising screening tools for early detection of pre-eclampsia were identified. No marked changes in anaesthetic approach to hypertensive disorders of pregnancy occurred during the period of review, apart from a reappraisal of spinal anaesthesia as a safe technique in caesarean section, even in patients with severe pre-eclampsia. A multidisciplinary approach to management and therapy is needed and the right balance must be sought between the needs of the mother and baby, both of which are jeopardized by the hypertensive disorders of pregnancy.

Management and monitoring of severe preeclampsia

Preeclampsia is associated with increased maternal and perinatal morbidity and mortality. Preeclampsia is more than pregnancy-induced hypertension. The hypertension is only one manifestation of an underlying multifactorial, multisystem disorder, initiated early in pregnancy. In established severe disease there is volume contraction, reduced cardiac output, enhanced vascular reactivity, increased vascular permeability and platelet consumption. Medical treatment of severe hypertension in pregnancy is required. The more controversial issues are the role of pharmacological treatment in conservative management of severe preeclampsia aiming at prolongation of pregnancy, the ability of such therapy to modify the course of the underlying systemic disorder and the effects on fetal and maternal outcome. This paper presents an overview concerning the current developments in management and monitoring of severe preeclampsia. Controversial topics such as the role of plasma volume expansion in preeclampsia, expectant versus aggressive management of severe preeclampsia remote from term, and pharmacological interventions in the management of eclampsia and the HELLP syndrome are addressed.

Preeclampsia-eclampsia: clinical and neuroradiographic correlates and insights into the pathogenesis of hypertensive encephalopathy

PURPOSE

To investigate the clinical parameters that are associated with the development of brain edema of hypertensive encephalopathy in patients with preeclampsia-eclampsia.

MATERIALS AND METHODS

Twenty-eight patients with preeclampsia-eclampsia and neurologic symptoms underwent magnetic resonance (MR) imaging. Clinical parameters recorded at the time of MR imaging included serum electrolytes and various indices of hematologic, renal, and hepatic function. Several data were available 1 week prior to the development of neurologic symptoms in 11 patients. Univariate analysis and multivariate logistic regression analyses were performed to study possible associations between these parameters and brain edema at MR imaging.

RESULTS

The 20 patients with brain edema at MR imaging had a significantly greater incidence of abnormal red blood cell morphology (14 [82%] of 17 patients vs two [25%] of eight, P: <.005) and higher levels of lactic dehydrogenase (LDH) (339 U/L +/- 65 [SD] vs 258 U/L +/- 65, P: =.007) than the eight with normal MR imaging findings; multivariate logistic regression analysis showed a strong association with red blood cell morphology only. Moreover, LDH levels were elevated before the development of neurologic abnormalities (P: <.05). Blood pressures were not significantly different between groups at any time.

CONCLUSION

Brain edema at MR imaging in patients with preeclampsia-eclampsia was associated with abnormalities in endothelial damage markers and not with hypertension level.