Familial and sporadic chronic progressive degenerative parietal ataxia

Background & objective: Parietal ataxia has been mainly reported as a consequence of acute ischemic stroke, while degenerative parietal ataxia has not been reported. Methods: We investigated clinical characteristics, neuroimaging data, and genetic analysis of patients with cerebellar ataxia plus parietal atrophy. Results: We identified seven patients, including five patients from two families, with chronic progressive cerebellar ataxia due to degenerative parietal atrophy but not stroke. Age at onset of ataxia was 57.6 ± 6.9 years. All patients showed chronic progressive cerebellar ataxia with severity of ataxic gait > limb ataxia > dysarthria. Patients showed no cognitive dysfunction, muscle weakness, or parkinsonism, and only two patients showed mild sensory disturbances. The seven patients showed lateralized limb ataxia with greater contralateral parietal lobe atrophy by magnetic resonance imaging, and hypoperfusion by single photon emission computed tomography, without any abnormal cerebellar pathology (i.e., crossed cerebellar diaschisis). Pathogenic mutations in the microtubule-associated protein tau gene were not found using two single nucleotide polymorphisms. Conclusions: This is the first description showing unique clinical features of familial and sporadic chronic progressive degenerative parietal ataxia.