Abstract
Transcranial magnetic stimulation (TMS) is emerging as a promising tool to non-invasively assess specific cortical circuits in neurological diseases. A number of studies have reported the abnormalities in TMS assays of cortical function in dementias. A PubMed-based literature review on TMS studies targeting primary and secondary dementia has been conducted using the key words “transcranial magnetic stimulation” or “motor cortex excitability” and “dementia” or “cognitive impairment” or “memory impairment” or “memory decline”. Cortical excitability is increased in Alzheimer’s disease (AD) and in vascular dementia (VaD), generally reduced in secondary dementias. Short-latency afferent inhibition (SAI), a measure of central cholinergic circuitry, is normal in VaD and in frontotemporal dementia (FTD), but suppressed in AD. In mild cognitive impairment, abnormal SAI may predict the progression to AD. No change in cortical excitability has been observed in FTD, in Parkinson’s dementia and in dementia with Lewy bodies. Short-interval intracortical inhibition and controlateral silent period (cSP), two measures of gabaergic cortical inhibition, are abnormal in most dementias associated with parkinsonian symptoms. Ipsilateral silent period (iSP), which is dependent on integrity of the corpus callosum is abnormal in AD. While single TMS measure owns low specificity, a panel of measures can support the clinical diagnosis, predict progression and possibly identify earlier the “brain at risk”. In dementias, TMS can be also exploited to select and evaluate the responders to specific drugs and, it might become a rehabilitative tool, in the attempt to restore impaired brain plasticity.
Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
KEYWORDS:
Brain stimulation; Cognitive dysfunction; Cortical excitability; Differential diagnosis; Intracortical circuitry; Motor impairment; Neuromodulation
- PMID: 24840904
- Clin Neurophysiol. 2014 Aug;125(8):1509-32. doi: 10.1016/j.clinph.2014.04.010. Epub 2014 Apr 30.
Giovanni Di Pino is MD/PhD, Neurologist, Associate Professor of Human Physiology and Head of the “NeXT: Neurophysiology and Neuroengineering of Human-Technology Interaction” Research Unit at Campus Bio-Medico University of Rome. Giovanni Di Pino current fields of interest regard clinical neurophysiology and bio-engineering and all the possible matches. Giovanni Di Pino is primarily involved in: - Clarifying the mechanisms at work behind the sensorimotor control loop and the brain representation of the hand - Developing neural interfaces to control sensorized cybernetic prostheses and to improve bioelectronic hybridity, with particular attention to related brain plasticity. - Investigating which features in an artificial limb favor its embodiment and the related brain processes subtending the embodiment. - Developing novel methods for noninvasive neuromodulation in health and disease. He is European Research Council Starting Grant 2015 grantee with the project RESHAPE: REstoring the Self with embodiable HAnd ProsthesEs.
Giovanni Di Pino 
Leave a comment