Ataxia and middle cerebellar peduncle lesions in hepatic encephalopathy

Abstract

Sir,Brain MRI in patients with hepatic encephalopathy (HE)shows hyperintensity in the globus pallidus on T1-weightedimages, which is thought to reflect manganese andammonia accumulation in situ [1, 2]. Those patientscommonly have asterexis, disturbed consciousness, andextrapyramidal features [1, 2]. In contrast, ataxia in HE israre [3], and MRI correlates for ataxia have not beenentirely clear [4, 5]. We recently had a woman who, duringa course of HE, presented with bilateral, middle cerebellarpeduncle lesions and ataxia, both of which ameliorated afterbranched amino acid treatment.A 57-year-old woman suffered from primary biliarycirrhosis and hepatocellular carcinoma for the past 7 years.One year after the onset of diseases, she developedasterexis and disorientation to time and place. An intrave-nous administration of branched amino acid ameliorated hersymptoms. She was then started on kanamycin andlaxatives. However, 1 month before admission to ourhospital, an abdominal MRI revealed a recurrence ofhepatocellular carcinoma; in addition, she developedunsteadiness of the gait but without flapping tremor. Onadmission, she had slight disorientation to place. She hadcerebellar ataxia on finger to nose test, diadochokinesis,and heel-to-knee test. She had no extrapyramidal features orflapping tremor. Blood tests showed increased serum levelsof ammonia 183μg/dl (30–80) and total bilirubin 1.5 mg/dl(0.2–1.0). Brain MRI revealed high signal intensity in theglobus pallidus on T1-weighted image, and markedly highsignal intensity in the middle cerebellar peduncle bilaterally(Fig. 1a) and slightly high signal intensity in the cerebralwhite matter on T2-weighted image. We started her on anintravenous administration of 500 ml/day (valine 0.84%,leucine 1.10%, isoleucine 0.90%) intravenous branchedamino acid and low protein diet. Three weeks later, herataxia ameliorated significantly, and serum ammonia levelsdecreased to 113μg/dl. A post-treatment MRI scan, whichwas performed 1 month later, showed reduction inhyperintense signal (Fig. 1b).Previously, four reports of brain MRI imaging for ataxiain HE are available [4–7]. Park and Heo [4] reported a46-year-old man with acquired hepatocerebral degenerationwho developed ataxia and bilateral, middle cerebellarpeduncle lesions. In a review article, Uchino and colleagues[5] showed similar MRI findings. Nagura and colleagues[6] reported a 66-year-old man with portal-systemic shunt,with irreversible middle cerebellar peduncle involvement,attributed to hyperammonemia. Deguchi and colleagues [7]reported a 58-year-old woman with similar MRI findings,which improved by intravenous branched amino acids. Todate, no pathology studies are available accounting for theMRI abnormalities in the middle cerebellar peduncle.However, in cases of HE, demyelination has been demon-strated in the cerebral white matter [8], pontine base [9],and corticospinal tract [10]. Since myelinated axon is themain histological constituent in the cerebellar peduncle, theMRI findings in the middle cerebellar peduncle mightreflect demyelination. Since intravenous branched aminoacid soon ameliorated ataxia and the MRI lesions, togetherwith reversal of serum ammonia levels, cytotoxic edema