Changes of intracortical excitatory neuronal circuits in patients with Vascular Cognitive Impairment-No Dementia

Introduction. Several clinical and neuroradiological studies have associated the brain white matter lesions (WMLs) to cognitive decline of elderly patients, even in absence of dementia, and to non cognitive symptoms such as depression, apathy and gait disorder [1]. In line with the “disconnection hypothesis”, these manifestations probably result from ischemic interruption of prefrontal–subcortical loops [2]. Few studies have investigated the neurophysiological relevance of WMLs in patients with Vascular Cognitive Impairment-no dementia (VCI-ND). Aim. To evaluate early changes in intracortical inhibition and facilitation by means of Transcranial Magnetic Stimulation (TMS) in elderly patients with VCI-ND compared to age-matched controls. Methods. Twelve VCI-ND patients and ten age-matched controls underwent to bilateral single and paired-pulse TMS. The clinical evaluation, the neuropsychological profile and the vascular burden at brain magnetic resonance imaging were concomitantly explored. Results. Patients reported abnormal scores at tests evaluating executive control functions (Tab. 1). No statistically significant difference was found in motor threshold, cortical silent period and intracortical inhibition between patients and controls and between the two hemispheres in patients (Tab. 2). We observed a significant bilateral enhancement of mean intracortical facilitation in pairedpulse excitability curves (Fig. 1). Conclusions. Our study provides the first evidence of enhanced intracortical excitatory neuronal circuits in patients with subcortical vascular disease and clinical features of VCI-ND [3]. This change might be part of a plastic compensatory remodeling process or represent a subclinical marker of cognitive and/or motor impairment in a “brain at risk” for vascular dementia. TMS is a valuable tool in the further understanding of the neurophysiological mechanisms underlying WMLs and their cognitive consequences.