[Progressive ataxic hemiparesis with asymmetric cortical and cerebral peduncular atrophy--report of two cases].

We report two patients, 73- and 70-year-old men, characterized by progressive hemiparesis and homolateral limb ataxia as the main clinical symptoms; magnetic resonance (MR) imaging of the brain revealed asymmetric cerebral cortical and peduncular atrophy; 99mTc-ECD single photon emission computed tomography (SPECT) of brain showed decreased RI uptake in the cerebral hemisphere correlated with clinical deficits. Brain SPECT of case 1 showed decreased RI uptake in the cortex of the right hemisphere and the left cerebellar hemisphere ("crossed cerebellar diaschisis; CCD"). These findings indicate that ataxia of our patients may depend on the lesions of the corticopontocerebellar tracts, although it is possible that ataxia may be related to lack of spatial orientation associated with parietal lobe lesion. The mechanism of the occurrence of asymmetric cerebral peduncular atrophy would be explained by wallerian degeneration of the pyramidal tract and other cortically originated fibers associated with the cortical degeneration. From these clinical and radiologic features, it seems likely that our two patients are categorized in the "asymmetric cortical degeneration syndromes", and we propose the term "progressive ataxic hemiparesis" for our patients.