[A case of portal-systemic shunt with progressive ataxia]

A 66-year-old man was admitted to Tokyo Metropolitan Geriatric Hospital because of progressive speech disturbance and ataxic gait. He had no history of abdominal surgery, liver disease, heavy drinking nor blood transfusion. One day before the admission, he showed confusional behavior for 6 hours, but he had no other history of consciousness disturbance. Neurological examination revealed slurred speech, fixation nystagmus, limb and gait ataxia, and hyperreflexia with pathological reflexes. Extrapyramidal signs were not identified. Laboratory examination showed marked hyperammonemia (118-292 micrograms/dl) with poor ICG excretion (ICG15 min = 30.8%). Percutaneous portography showed a large shunt vessel between the portal vein and the left hepatic vein. The plasma ammonium level of the right hepatic vein is normal (15 micrograms/dl), but that of the left one is very high (298 micrograms/dl). Therefore we concluded that hyperammonemia of the systemic circulation was resulted from portal-systemic shunt. A T2 weighted MRI image demonstrated symmetrical high signal intensity in the deep cerebral white matter. Unique lesions were observed in the bilateral middle cerebellar peduncles, and shown as low signal intensity in T1 weighted image and as high signal intensity in T2 weighted image. Hyperammonemia and neurological impairments of this patient did not improve with medical treatment. Three months after occlusion of the shunt vessel, fixation nystagmus and extensor plantar responses abolished and unsteadiness gait improved. Hyperammonemia might cause the cerebellar ataxia in the present case.