In vivo functional evaluation of central cholinergic circuits in vascular dementia

Objective Central cholinergic circuits of human brain can be tested non-invasively by coupling peripheral nerve stimulation with transcranial magnetic stimulation of motor cortex. This test, named short latency afferent inhibition (SAI) has been shown in healthy subjects to be sensitive to the blockage of muscarinic acetylcholine receptors and it is impaired in Alzheimer disease (AD) patients, a cholinergic form of dementia, while it is normal in non-cholinergic forms of dementia such as fronto-temporal dementia. The objective of present study was to evaluate central cholinergic circuits in patients with Vascular Dementia (VaD). Methods We evaluated SAI in a group of patients with VaD and compared the data with those from a group of AD patients and a control group of age-matched healthy individuals. Results Mean SAI was normal in VaD patients while it was significantly reduced in AD patients. The analysis of individual data showed abnormal SAI in 75% of AD and in only 25% of VaD. Conclusions SAI is normal in most of VaD patients in contrast with AD patients. This test might be used for the functional evaluation of central cholinergic circuits in VaD patients. Significance SAI testing may represent a useful additional tool for the evaluation of patients with VaD however, further studies are required in order to evaluate whether this method can be used for the differential diagnosis between pure VaD and different forms of dementia.