The blood-brain barrier and cerebral blood flow in acute hypertension

Uremic encephalopathy: A definite diagnosis by magnetic resonance imaging?

The aim of this study was to investigate the magnetic resonance imaging (MRI) findings for the diagnose uremic encephalopathy and describe the usefulness of MRI findings in the ultimate diagnosis of uremic encephalopathy (UE). A total of 20 patients with uremic encephalopathy admitted to the hospital were evaluated in this prospective study. The clinical manifestations, laboratory and MRI imaging findings, demographic information, and clinical outcome were analyzed for each patient. We observed that the 20 prospectively reviewed patients with UE had no involvement of the basal ganglia or the lentiform fork sign (LFS). However, two-thirds of the patients had white matter involvement, and 80% of the subjects had cerebral or cortical atrophy. The arterial blood gas (ABG) analysis revealed that 50% of the patients suffered from metabolic acidosis (n=10). The results of the present study demonstrated that although the observation of Lentiform Fork Sign and Basal Ganglia involvement in MRI of UE patients is a specific finding the absence of which does not rule out UE. Thus, simultaneous examination of clinical manifestation and laboratory test analyses, along with imaging findings, should also be taken into account.

Peripheral Anti-Angiogenic Imbalance during Pregnancy Impairs Myogenic Tone and Increases Cerebral Edema in a Rodent Model of HELLP Syndrome

Using an animal model of hemolysis elevated liver enzymes low platelets (HELLP) that has systemic inflammation and neuroinflammation we wanted to determine if blood brain barrier (BBB) permeability, cerebral edema, vascular tone, and occludin expression were altered in pregnant rats. Anti-angiogenic proteins sFlt-1 and sEng (4.7 and 7 µg/kg/day, respectively) were chronically infused into normal pregnant (NP) rats beginning on gestational day 12 via a mini-osmotic pump. On gestational day 19, blood pressure was measured via a carotid catheter and brains were collected. BBB permeability was assessed in select brain regions from rats infused with 0.5 mg/mL Texas Red Dextran and phenylephrine. Occludin, sFlt-1, and sEng were analyzed via western blot or ELISA. Infusion of sFlt-1 and sEng into NP rats increased hemolysis and liver enzymes, and decreased platelets and led to hypertension. HELLP rats had significant impairment in the myogenic response and increased BBB permeability in the posterior cortex and brainstem. Brain water content in the posterior cortex was increased and sEng protein expression in the brainstem was significantly increased in HELLP rats. The results from this study suggest that a peripheral anti-angiogenic imbalance during pregnancy is associated with decreased myogenic tone, vasogenic edema, and an increase in BBB permeability, but not anti-angiogenic imbalance in the brain.

Protective effect of unilateral vasospasm in the setting of HHH-associated posterior reversible encephalopathy syndrome: case report, review of the literature, and treatment considerations

Background

Hyperdynamic therapy, also called triple-H therapy, is the standard treatment and prophylaxis for aneurysmal-associated vasospasm. In patients who are able to tolerate cardiopulmonary stressors induced by this therapy, it is of benefit as a modality for prevention and treatment of delayed ischemic neurologic deficit. However, it can be a cause of significant cardiopulmonary or neurologic sequelae. In rare cases, it can be associated with posterior reversible encephalopathy syndrome (PRES), secondary to prolonged vasopressor and hypertensive therapies.

Case presentation

We present the case of a patient with right-sided aneurysmal-associated vasospasm who, after 10 days of triple-H therapy, experienced a seizure and was found to have left-sided PRES. Right-sided vasospasm served as a protective mechanism from triple-H therapy-associated PRES. It presented a treatment conundrum due to contradictory perfusion requirements. Hypertensive therapy was curtailed and in efforts to preserve local cerebral perfusion and vasodilation, local therapy with intrathecal nicardipine was initiated. We present our case, a review of the literature, and management considerations.

Conclusions

Therapies that have conventionally functioned as second line treatments for aneurysmal subarachnoid hemorrhage (intra-arterial vasodilators and intrathecal vasodilators) may be beneficial as earlier treatments in the setting of vasospasm given the systemic difficulties and complications associated with HHH therapy in patients with PRES.

Various Imaging Manifestations of Posterior Reversible Encephalopathy Syndrome (PRES) on Magnetic Resonance Imaging (MRI)

Background

Posterior reversible encephalopathy syndrome (PRES), also called the acute hypertensive encephalopathy and reversible posterior leukoencephalopathy syndrome (RPLS), is a neurotoxic syndrome of cerebral vasoregulation classically characterized by bilaterally symmetrical parieto-occipital edema. However, the imaging findings are variable and may occur in other locations such as the frontal lobes, thalami, basal ganglia and brainstem. Most commonly, PRES presents with hyperintense signals on T2 and FLAIR sequences. Restricted diffusion and hemorrhage are rare. This study presents the typical and atypical manifestations of PRES on 3T MR images.

Material/Methods

It is a retrospective study analyzing a radiology report database and MR images of 92 patients with a clinical and radiological diagnosis of PRES. The brain MRI images of these patients were evaluated. The regions involved and the signal intensity of the affected areas on T1, T2, FLAIR and DW sequences were recorded. The location of the abnormal signal intensity as well as the presence or absence of atypical features such as diffusion restriction and hemorrhage were also recorded.

Results

The most commonly affected region was the parieto-occipital lobes (100%), however, other atypical regions involved were the frontal lobes (30.4%), temporal lobes (8.69%), basal ganglia (22%), cerebellum(17.39%), brainstem(9%) and thalamus(4%). Some of the cases showed restricted diffusion (43%) and hemorrhage (9%).

Conclusions

The involvement of the parieto-occipital, frontal and temporal lobes is common in PRES. Occasionally, there may be an involvement of the basal ganglia, cerebellum and brainstem, with or without hemorrhage and restricted diffusion. Radiologists should be aware of the typical and atypical imaging manifestations of PRES in order to make an accurate diagnosis.

Tacrolimus associated posterior reversible encephalopathy syndrome - a case series and review

Tacrolimus is an immunosuppressive drug mainly used to lower the risk of transplant rejection in individuals who are post solid organ or hematopoietic transplantation. It is a macrolide which reduces peptidyl-propyl isomerase activity and inhibits calcineurin, thus inhibiting T-lymphocyte signal transduction and interleukin-2 (IL-2) transcription. It has been associated with Posterior Reversible Encephalopathy Syndrome (PRES), a disease of sudden onset that can present as a host of different symptoms, depending on the affected area of the brain. While infectious causes of encephalopathy must always be entertained, the differential diagnosis should also include PRES in the appropriate context. We report three cases of PRES in patients with acute myeloid leukemia (AML) placed on tacrolimus after receiving a bone marrow transplant (BMT). The focus of this review is to enhance clinical recognition of PRES as it is related to an adverse effect of Tacrolimus in the setting of hematopoietic transplantation.

Posterior Reversible Encephalopathy Syndrome in severe preeclampsia: case report and literature review

We describe a 23 year old primigravid patient with severe preeclampsia complicated by posterior reversible encephalopathy syndrome (PRES), who presented with sensory and motor deficits and amnesia in the postpartum period Cranial magnetic resonance imaging (MRI) showed abnormal areas in the white matter of bilateral parieto-occipital lobes, indicating brain edema which disappeared completely on the follow-up scan taken four weeks after delivery together with complete symptom regression. The development of PRES in preeclampsia is discussed and the importance of prompt postpartum blood pressure control is emphasized.

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 cat with neurological manifestations of systemic disease. Key conditions impacting on the CNS

PRACTICAL RELEVANCE

A number of systemic diseases are associated with neurological deficits. Most systemic diseases that impact on the nervous system result in multifocal neurological signs; however, isolated deficits can also be observed. This article reviews the clinical signs, pathophysiology, diagnosis, treatment and prognosis of four important systemic diseases with neurological consequences: feline infectious peritonitis, toxoplasmosis, hypertension and hepatic encephalopathy.

CLINICAL CHALLENGES

Early recognition of systemic signs of illness in conjunction with neurological deficits will allow for prompt diagnosis and treatment. While neurological examination of the feline patient can undoubtedly be challenging, hopefully the accompanying articles in this special issue will enable the clinician to approach these cases with more confidence.

EVIDENCE BASE

The veterinary literature contains numerous reports detailing the impact of systemic disease on the nervous system. Unfortunately, very few references provide detailed descriptions of large cohorts of affected cats. This review summarises the literature underpinning the four key diseases under discussion.

Posterior reversible encephalopathy syndrome in the pediatric renal population

Posterior reversible leukoencephalopathy syndrome (PRES) clinically presents with seizures, severe headaches, and mental and visual changes. Our goal was to describe the clinical features, triggering factors, neuro-imaging findings, and electroencephalogram (EEG) findings in a pediatric cohort with renal disease. We retrospectively analyzed the records of 18 children with the diagnosis of PRES between January 2001 and June 2006 at the University of Miami/Holtz Children's Hospital, USA. There were 22 PRES episodes. The most common clinical presentation was generalized tonic-clonic seizures in 59% (13/22). The most common identified trigger of PRES was hypertensive crisis in 59% (13/22). Almost half of the children had no evidence of on-going uncontrolled hypertension; 44% (8/18) had normal funduscopic examination findings, and 50% (9/18) had no or mild left ventricular hypertrophy. Two of the 18 patients had recurrent PRES episodes, three episodes each. Diffuse slowing was the most common finding on the EEGs. Atypical magnetic resonance imaging (MRI) findings were more prevalent in the imaged cases (62% vs 25%, P < 0.05). All the computerized tomography (CT) scans were normal, despite the positive MRI findings in four cases when both types of imaging was used. All the episodes had total clinical resolution. In conclusion, despite the diverse initial trigger, acute hypertension seems to be the common pathogenic pathway for pediatric PRES. MRI seems superior to CT, with better sensitivity due to its high resolution and diffusion-weighted imaging. The lesions do not necessarily have to be in the posterior white matter and may not be totally reversible.

Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings

OBJECTIVE

Posterior reversible encephalopathy syndrome (PRES) is classically characterized as symmetric parietooccipital edema but may occur in other distributions with varying imaging appearances. This study determines the incidence of atypical and typical regions of involvement and unusual imaging manifestations.

MATERIALS AND METHODS

Seventy-six patients were eventually included as having confirmed PRES from 111 initially suspected cases, per imaging and clinical follow-up. Two neuroradiologists retrospectively reviewed each MR image. Standard sequences were unenhanced FLAIR and T1- and T2-weighted images in all patients, with diffusion-weighted imaging (n = 75) and contrast-enhanced T1-weighted imaging (n = 69) in most. The regions involved were recorded on the basis of FLAIR findings, and the presence of atypical imaging findings (contrast enhancement, restricted diffusion, hemorrhage) was correlated with the severity (extent) of hyperintensity or mass effect on FLAIR.

RESULTS

The incidence of regions of involvement was parietooccipital, 98.7%; posterior frontal, 78.9%; temporal, 68.4%; thalamus, 30.3%; cerebellum, 34.2%; brainstem, 18.4%; and basal ganglia, 11.8%. The incidence of less common manifestations was enhancement, 37.7%; restricted diffusion, 17.3%; hemorrhage, 17.1%; and a newly described unilateral variant, 2.6%. Poor correlation was found between edema severity and enhancement (r = 0.072), restricted diffusion (r = 0.271), hemorrhage (r = 0.267), blood pressure (systolic, r = 0.13; diastolic, r = 0.02). Potentially new PRES causes included contrast-related anaphylaxis and alcohol withdrawal.

CONCLUSION

This large series of PRES cases shows that atypical distributions and imaging manifestations of PRES have a higher incidence than commonly perceived, and atypical manifestations do not correlate well with the edema severity.

Spectrum of radiological changes in hypertensive children with reversible posterior leucoencephalopathy

We prospectively studied 19 children with severe hypertension to evaluate the spectrum of radiological changes, severity and reversibility of this entity. All of them were subjected to clinical and biochemical evaluation, followed by magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA). Headache was seen in 17 children, 13 had confusion and drowsiness, 12 had nausea and vomiting, 10 patients had visual disturbances, seizure and dyspnoea. Only two had focal neurological deficit (one with right facial palsy and another with right lateral rectus palsy). Of these 19 children, 15 patients had hypertensive retinopathy and four had normal fundi. The positive MRI findings in 17/19 patients were: bilateral leukoencephalopathic changes in occipitoparietal region (9/17), diffuse white/grey matter lesion (3/17) patients, brain stem hyperintensity (2/17) and haemorrhagic lesions (3/17). On MRA, 12/19 patients had attenuation of cerebral arteries of different degree. On follow up, MRI findings resolved in all except three patients. All patients had normal MRA on follow up, except one with persistent minimal attenuation of middle cerebral artery and another had spasm in anterior, middle and posterior cerebral arteries. The intracranial abnormalities in these patients with severe hypertension were reversible in many of the cases after control of blood pressure was achieved. We therefore conclude that severe hypertension may lead to leuoencephalopathy, which had a wide radiological spectrum. A better understanding of this complex syndrome may obviate unnecessary investigations and allow management of associated problems in prompt and appropriate ways.

[Hypertensive encephalopathy: differential diagnosis of brain edema with midline shift]

Hypertensive encephalopathy is a severe complication of hypertensive crisis or malignant hypertonia. We report a case with grave clinical and radiological features. The patient was comatose, with pupillary dysfunction, and initial CT suggested a local intracranial mass with edema. Cranial MRI showed almost completely hyperintensive supratentorial white matter, with edema and midline shift, and hypertensities in cerebellum and brainstem. The patient recovered, and the radiological findings improved after antihypertensive therapy. Hypertensive encephalopathy may be differentiated by MRI, manifests acutely, and is potentially reversible when adequate therapy is rapidly performed.