Neurologic Signs in Alzheimer's Disease

Neurologic signs and their neuropathologic correlates were examined in a sample of 56 patients with autopsy-proved Alzheimer's disease (13 men, 43 women; mean age at death, 83.1 years; range, 67 to 96 years) from a prospective longitudinal study. Full-range regular rigidity with cog-wheeling was found in 20 patients and was significantly associated with lower neuron counts in the substantia nigra and with the presence of Lewy bodies in the brain stem and neocortex. Twelve patients with myoclonus had a younger age at onset, a lower age at death (mean, 78.6 years), and lower neuron counts in the serotoninergic dorsal raphe nucleus and in the noradrenergic locus coeruleus than did the patients without myoclonus. Generalized motor seizures were reported in six patients, and they had significantly lower counts of pyramidal cells in cortical layers III through IV of the parietal cortex (area 7) and slightly decreased pyramidal cell numbers in the parahippocampal gyrus (area 28). The 19 patients with a positive grasp reflex had an earlier onset of illness and a significantly inferior performance on the Mini-Mental State examination and Cambridge Cognitive Examination tests. They, and 25 patients with a positive snout reflex, had significantly lower counts of large pyramidal cells in layers III through V of the frontal cortex (area 32). These results indicate that different neurologic symptoms in Alzheimer's disease can be related to disproportionate neuronal degeneration in functionally different brain areas.