Functional evaluation of cerebral cortex in dementia with Lewy bodies

Neurochemical investigations have demonstrated central cholinergic dysfunction in patients with dementia with Lewy bodies (DLB). Central cholinergic circuits of the human brain can be tested noninvasively by coupling peripheral nerve stimulation with transcranial magnetic stimulation of the contralateral motor cortex. This test, named short latency afferent inhibition has been shown in healthy subjects to be sensitive to the blockage of muscarinic acetylcholine receptors and it is impaired in patients with Alzheimer disease (AD), a cholinergic form of dementia, while it is normal in non-cholinergic forms of dementia such as fronto-temporal dementia. We evaluated short latency afferent inhibition in a group of patients with DLB and compared the data with that from a group of AD patients and a control group of age-matched healthy individuals. Short latency afferent inhibition was significantly reduced in DLB and AD patients. The findings suggest that this method can be used as a non-invasive test for the assessment of cholinergic pathways in patients with dementia and may represent a useful additional tool for discriminating between cholinergic and non-cholinergic forms of dementia.