Short latency afferent inhibition in Vascular Cognitive Impairment-No Dementia

Background: Unlike Alzheimer disease (AD), the role of cholinergic involvement in Vascular Dementia (VaD) is still under debate, and data on patients at risk for VaD are lacking. By coupling peripheral nerve stimulation with Transcranial Magnetic Stimulation (TMS), it is possible to test the short-latency afferent inhibition (SAI) which is considered a putative marker of central cholinergic transmission. Aim: to evaluate SAI in patients with leukoaraiosis and cognitive profile of Vascular Cognitive Impairment-No Dementia (VCI-ND). Materials and Methods: a sample of VCI-ND patients age-matched with healthy were evaluated for cognitive, functional status and white matter lesions (WMLs) load. Single-pulse TMS measures and SAI were recorded from the right first dorsal interosseous muscle using a figure-of-eight coil. Results: no significant difference was found for the mean SAI value between patients and controls. However, in the patients group abnormal SAI showed a positive correlation with worse scores at neuropsychological tests evaluating frontal lobe abilities. SAI also positively correlated with the vascular lesion burden, but not with the WMLs severity. Discussion: central cholinergic circuitry seems to be not clearly involved in VCI-ND patients, suggesting a distinctive profile of the cholinergic pathway with respect to primary cholinergic forms of dementia, even in the early stage. VCI may exhibit considerable interindividual variation in the location of subcortical infarcts and, therefore, in the distribution and magnitude of the resultant cholinergic denervation. SAI might provide useful insight in the diagnosis and prognosis of different dementing process and in identifying the responders to treatment with cholinergic agents.