Amyotrophic lateral sclerosis and parkinsonism-dementia on Guam: a 30-year evaluation of clinical and neuropathologic trends.

We reviewed the records of 279 Guamanian Chamorro patients with amyotrophic lateral sclerosis (ALS) and 293 patients with parkinsonism-dementia (PD), who had onset of symptoms between 1950 and 1979, to determine if there were changes in the clinical and neuropathologic features that might clarify the declining incidence rates in the past decade. There were no major temporal changes in the frequencies of physical findings or histopathologic features, but in the past three decades, an increase in age at onset was observed for both ALS and PD. There was also a shorter duration of illness in ALS and a longer duration in PD. Good correlation was found between the clinical and pathologic findings for both ALS and PD throughout this period.