Short latency afferent inhibition: A biomarker for mild cognitive impairment in Parkinson's disease?
Financial disclosures: Alison Yarnall is supported by grants from the Newcastle University Lockhart Parkinson's Disease fund and MJ Fox Foundation. She has received honoraria from Teva-Lundbeck and sponsorship from Teva-Lundbeck and UCB for attending conferences. Lynn Rochester receives funding from Medical Research Council, MJ Fox Foundation, Parkinson's UK, Welcome Trust and European Union 7th Framework. Mark Baker is a NIHR Clinical Lecturer and is supported by grants from the National Institute for Health Research (NIHR), UK Medical Research Council, Wellcome Trust and Academy of Medical Sciences. Rachel David has no conflicts of interest. Tien K Khoo was supported by the Lockhart Parkinson's Disease fund. He has received honoraria and educational grants from Teva-Lundbeck and sponsorship from GlaxoSmithKline and UCB Pharma for attending conferences. Gordon Duncan is supported by a grant from the Lockhart Parkinson's Disease Fund. He has received funds from UCB for attending conferences. Brook Galna has received funds from UCB for attending conferences. David Burn has received grants from NIHR, Wellcome Trust, GlaxoSmithKline Ltd, Parkinson's UK and Michael J Fox foundation. He has received honoraria from Teva-Lundbeck and UCB in the past two years and acted as consultant for GSK and Archimedes. The authors have no conflicts of interest related to the research in this article.
Funding agencies: The study was supported by the Michael J. Fox Foundation and Parkinson's UK. The funding agencies had no direct involvement with the contents of the study. This research was supported by the National Institute for Health Research (NIHR) Newcastle Biomedical Research Centre based at Newcastle upon Tyne Hospitals National Health Service (NHS) Foundation Trust and Newcastle University.
Relevant conflicts of interest/financial disclosures: Nothing to report.
Full financial disclosures and author roles may be found in the online version of this article.
Corresponding author: Dr. Alison J Yarnall, Institute for Ageing and Health, Clinical Ageing Research Unit, Campus for Ageing and Vitality, Newcastle University, Newcastle upon Tyne, NE4 5PL, UK; firstname.lastname@example.org
Mild cognitive impairment in Parkinson's disease (PD) is common and predicts those at risk of dementia. Cholinergic dysfunction may contribute to its pathophysiology and can be assessed using short latency afferent inhibition.
Twenty-two patients with PD (11 cognitively normal; 11 with mild cognitive impairment) and 22 controls participated. Short latency afferent inhibition was measured by conditioning motor evoked potentials, which were elicited by transcranial magnetic stimulation of the motor cortex with electrical stimuli delivered to the contralateral median nerve at varying interstimulus intervals.
There was no significant difference between cognitively normal PD and controls for short latency afferent inhibition (62.8±30.3% vs. 55.7±21.7%; P=0.447). The PD-mild cognitive impairment group had significantly less inhibition (88.4±25.8%) than both cognitively normal PD (P=0.021) and controls (P=0.01).
Cholinergic dysfunction occurs early in those with PD-mild cognitive impairment. Short latency afferent inhibition may be a useful biomarker of increased risk of dementia in PD patients. © 2013 Movement Disorder Society