[Cerebellar ataxia and unilateral asterixis caused by thalamic hematoma. Presumed mechanisms].

A 76 year-old hypertensive man developed an acute inability to stand due to a right cerebellar ataxia. Somatosensory performances were normal, but a transient and mild weakness of the right arm and leg with Babinski's sign was observed. There was a prominent asterixis of the right hand. CT scan showed a hemorrhage of the thalamus with surrounding edema of the adjacent internal capsule. Initial median nerve somatosensory evoked potentials showed a mild reduction of left parietal responses with absent left frontal SEPs (P22 and N30). Fourty days later the cerebellar ataxia was persisting while asterixis had disappeared. A second recording of SEPs showed a complete recovery of all cortical components. MRI performed at the same time showed a left postero lateral thalamic lesion. CT, MRI and SEPs findings suggested that asterixis could result from interruption of somatosensory fibres projecting to the motor cortex.