An Investigation of the Late Excitatory Potentials in the Hand following Transcranial Magnetic Stimulation in Early Alzheimer's Disease.

BACKGROUND

Recent neuroimaging studies in humans support the clinical observations that the motor cortex is affected early in the course of Alzheimer's disease (AD).

PATIENTS AND METHODS

We measured the silent period (SP) induced by transcranial magnetic stimulation in AD patients in the very early stage of the disease, and we explored whether and in which way the pharmacologic manipulation of the cholinergic system could modify it.

RESULTS

An increase in the duration of the SP was observed in AD patients in the early stage in comparison to controls. After 2 months of treatment with donepezil, the duration did not differ significantly from that of normal subjects. The results of our study show a fragmentation and an enlargement of the SP in the presence of multiple late excitatory potentials (LEPs) in early untreated AD patients. These LEPs were also modulated by donepezil.

CONCLUSIONS

The results suggest an early functional impairment of cholinergic neurotransmission in AD. The disturbance in acetylcholine output in early AD leads to a decrease in excitability of the motor system.