Reversible cytotoxic brain edema and facial weakness in uremic encephalopathy

Abstract

Sirs, Neurological symptoms of uremic encephalopathy result from cerebral edema and include deterioration of conscious level, headache, myoclonus, tremor, and seizures [9]. To distinguish between vasogenic and cytotoxic edema, diffusion-weighted brain magnetic resonance imaging (MRI) can be performed. Because vasogenic edema is predominant in uremic patients, as opposed to cytotoxic edema, prompt treatment may allow regression of cellular damage and clinical symptoms [4, 11]. We report the first case of nondiabetic uremic encephalopathy with focal neurological deficits and cytotoxic edema. However, despite neuroradiological signs of cytotoxicity, immediate therapy resulted in full recovery of neurological signs and MR changes. A 46-year-old woman with no past medical history presented with subacute onset of left facial weakness, confusion, and nonfluent aphasia. Initial MRI showed bilateral confluent areas of T2 hyperintensity involving the complete supratentorial white matter without cortical involvement. Diffusion-weighted imaging (DWI) revealed hyperintense signal alterations with reduced apparent diffusion coefficient (ADC) values indicative of diffusion restriction (Fig. 1). Laboratory examination revealed excessive blood urea nitrogen (220 mg/dl) and creatinine levels (6.9 mg/dl); blood pressure was only slightly elevated (\140 mmHg). The neurological impairment of our patient rapidly improved after continuous hemodialysis over 12 h with full recovery after 1 day. Blood urea nitrogen level was 33 mg/ dl after 72 h. Follow-up MRI after 18 days demonstrated complete resolution of the diffusion abnormalities. The cause of renal failure remained unclear, as the patient refused renal biopsy. However, a hereditary glomerulonephritis was suspected, as several family members needed chronic hemodialysis or had proteinuria. Diabetes and rheumatologic kidney diseases were excluded. Only few reports describe brain DWI changes in uremic patients and the effect of hemodialysis on neuroimaging [4, 11]. They suggest the presence of interstitial vasogenic edema as opposed to cytotoxic edema. Thus, unusual for uremic encephalopathy, our patient presented with bilateral cytotoxic edema similar to brain ischemia. The distinction was possible by using diffusion-weighted MRI which revealed decreased ADC values indicative of diffusion restriction. In contrast, increased ADC values would have represented vasogenic edema. However, immediate therapy with hemodialysis resulted in full recovery of neurological symptoms. To our knowledge, similar reversibility of diffusion abnormalities has not been demonstrated for uremic encephalopathy. It is however known in other pathologies such as transient cerebral ischemia [6], methotrexate-induced neurotoxicity [7] or reversible posterior leukoencephalopathy syndrome [2]. Uremic encephalopathy may be a cause of reversible posterior leukoencephalopathy syndrome (RPL) [8]. Here, however, the patient not only lacked typical clinical symptoms such as headache, seizures or visual loss [8], but also characteristic cortical lesions on MRI [3] or predisposing factors such as high blood pressure, eclampsia, diabetes or immunosuppressive drugs [10]. Also, in most cases of RPL, vasogenic interstitial edema with increased H. Pruss (&) F. Masuhr Department of Neurology, Charite, University Medicine Berlin, Campus Mitte, Chariteplatz 1, 10117 Berlin, Germany e-mail: harald.pruess@charite.de