Progressive frontal gait disturbance with atypical Alzheimer's disease and corticobasal degeneration.

OBJECTIVES The clinical neuropsychological, neuroradiological, and neuropathological description of two patients presenting with a frontal gait disturbance. METHODS Clinical case note review, neuropsychological assessment, functional imaging with (15)O(2) and (18)F-fluorodopa PET, and neuropathology. RESULTS Both patients presented with frontal gait impairment and only later developed more widespread cognitive impairment. In both cases (15)O(2) PET disclosed focal hypometabolism in the medial frontal lobes and in one patient (18)F-fluorodopa uptake into the caudate and putamen was normal. The neuropathological examination in one patient showed Alzheimer's histopathology together with large swollen eosinophilic neurons characteristic of corticobasal degeneration, which were particularly prominent in the medial frontal lobes. CONCLUSION Focal degeneration of the medial frontal lobes may present as an isolated gait disturbance and should be considered in the differential diagnosis of patients who present without an obvious structural abnormality on neuroimaging.