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Recurrent hypertensive brainstem encephalopathy
In hypertensive encephalopathy (HE), computerized tomography or magnetic resonance (MR) images usually exhibit predominantly posterior white matter involvement, similar to reversible posterior leukoencephalopathy syndrome (RPLS).1,2 Recurrent HE is rare.3 Here, we report a rare case of recurrent HE.
A 75 year old man with an unremarkable medical history presented with generalized convulsion and stupor following a headache in June 2003. On admission, his blood pressure (BP) was 200/120 mmHg. The T2 weighted MR images (T2WI) and fluid attenuated inversion recovery (FLAIR) images revealed hyperintense lesions and swelling in the brainstem (fig 1). There was no enhancement of these lesions after an injection of contrast media. Electroencephalography demonstrated no electric potentials of an epileptic discharge. Blood and cerebrospinal fluid analyses revealed normal findings without elevated levels of serum creatinine (18.0 mg/l) and urea nitrogen (200 mg/l). We treated the patient with antihypertensive drugs, after we noted that a decrease in his BP resulted in the rapid improvement of symptoms and the findings of T2WI and FLAIR images. One year later, he had a relapse of generalized convulsion. His BP was 230/100 mmHg. A funduscopic examination of the eyes revealed retinal hypertensive atherosclerosis with Keith-Wagener II changes. T2WI and FLAIR images exhibited recurrent hyperintense lesions in the brainstem (fig 1), accompanied by slight hyperintense changes in the bilateral occipital lobes. The serum creatinine level was 21 mg/l, and the urea nitrogen level was 270 mg/l. The creatinine clearance rate was 20.6 ml/min. A hormonal survey revealed a plasma aldosterone concentration of less than 1.0 pg/ml because of secretory suppression caused by severe hypertension. The levels of other hormones, such as urinary and blood catecholamines, urinary vanillylmandelic acid (VMA), 17-hydroxycorticosteroids, 17-ketosteroids, and plasma renin activity were within normal ranges: urinary noradrenaline 158.7 μg/day (normal range (NR), 48.6 to 168.4), plasma noradrenaline 0.15 ng/ml (NR 0.07 to 0.31), urinary adrenaline 5.6 μg/day (NR 3.4 to 26.9), plasma adrenaline <0.05 ng/ml (NR <0.10), urinary dopamine 378.8 μg/day (NR 365.0 to 961.5), plasma dopamine <0.10 ng/ml (NR <0.10), and urinary VMA 3.3 mg/day (NR 1.5 to 4.3). Abdominal MR angiography revealed the occlusion of the left renal artery and the stenosis of the right renal artery. Furthermore, abdominal MR images revealed that the left kidney was atrophied, but did not reveal adrenal tumour. Thus, we diagnosed the patient as having recurrent hypertensive brainstem encephalopathy because of renal vascular hypertension and renal dysfunction. After adequate antihypertensive treatment, his symptoms immediately improved and the MR images exhibited normal findings (fig 1). By January 2005, he did not exhibit any recurrent symptoms.
Our patient presented with headache and generalized convulsion associated with marked hypertension. MR imaging revealed brainstem hyperintense lesions on T2WI and FLAIR images. The prompt initiation and adequate administration of antihypertensive treatment led to a complete clinical recovery, with the disappearance of lesions on MR images. However, the patient’s symptoms and abnormal findings on MR images were recurrent, a feature that has been rarely reported to date.
HE and RPLS are disorders that have been similarly categorized based on their symptoms and imaging findings. They are acute disorders that occur in patients with marked hypertension associated with central nervous system (CNS) symptoms, such as headache, convulsion, and altered mental status.1 HE typically involves the posterior parieto-occipital lobes accompanied by some degree of brainstem and cerebellar involvements. However, HE has recently been reported to have a predominant involvement of the brainstem with minimal changes in the supratentorial structure.2 The clinical diagnosis of hypertensive brainstem encephalopathy is difficult. The pontine T2W hyperintense lesion observed in our patient indicates glioma, infarction, postinfectious encephalomyelitis, radiation changes, or central pontine myelinolysis. A previous study suggested that retinal hypertensive signs are important for identifying the CNS manifestations of HE. The signs also allow the differentiation of HE from brainstem tumour.2 Initially, we provisionally diagnosed the patient as having one of these conditions on the basis of his clinical symptoms. However, by simply decreasing his BP, the imaging findings became normal. Moreover, retinal examination demonstrated hypertensive changes, which are diagnostic features of hypertensive brainstem encephalopathy.
The proposed mechanism underlying HE involves the breakdown of autoregulation, resulting in the dilatation of cerebral arterioles, the disruption of the blood–brain barrier, and the breakthrough accumulation causing vasogenic oedema.1,2 As the vertebrobasilar system and posterior cerebral arteries are sparsely innervated by sympathetic nerves,4 the occipital lobes and other posterior brain regions may be particularly susceptible to the breakdown of autoregulation. In RPLS, most patients have hypertension as the precipitating factor, with comorbidities such as renal failure and numerous medications.1 In a patient with pheochromocytoma, it was suggested that direct catecholamine toxicity might also have a role in the generation of brain lesions and vasospasm.2 The levels of catecholamines in our case were within normal ranges; therefore, we ruled out the diagnosis of pheochromocytoma. A previously reported case of a patient with recurrent posterior reversible encephalopathy syndrome had an unknown aetiology, and was accompanied by only mild HT.3 Our patient may have developed susceptibility affected posterior circulation modified by renal failure. His recurrent HE might have been caused by a marked hypertension and renal dysfunction and his susceptibility to changes in BP, although we cannot rule out the possibility of the influence of other catecholamines that have not been evaluated.
In most patients with hypertension, renal stenosis is detected by angiography. In the chronic course of renal vascular hypertension, renal vascular changes lead to an acute increase in BP spontaneously. Renal vascular hypertension is sometimes diagnosed in hypertensive crisis accompanied by hypertensive encephalopathy.5 In our patient, percutaneous intervention and surgical treatment were not performed because of severe renal failure. However, clinicians have to suspect this possibility in renal vascular hypertension, when patients present with hypertension, to prevent renal vascular changes and control hypertension similar to our present patient.
In conclusion, we suggest that there are patients susceptible to an increase in BP and recurrent HE such as our present patient, and that doctors must make a prompt diagnosis and provide immediate treatment, even if the actual aetiology of recurrent HE is not evident.
Competing interests: none declared
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