• Mariano Serrao, Alberto Ranavolo, Ole Kaeseler Andersen, Romildo Don, Francesco Draicchio, Carmela Conte, Roberto Di Fabio, Armando Perrotta, Michelangelo Bartolo, Luca Padua, Valter Santilli, Giorgio Sandrini, and Francesco Pierelli.
• University of Rome La Sapienza, Polo Pontino, Latina, Italy. mariano.serrao@uniroma1.it
• Clin Neurophysiol. 2012 Mar 1; 123 (3): 527-40.

ObjectivesTo investigate the behavior of the nociceptive withdrawal reflex (NWR) in the upper limb during reaching and grasping movements in post-stroke hemiparetic patients.MethodsEight patients with chronic stroke and moderate motor deficits were included. An optoelectronic motion analysis system integrated with a surface EMG machine was used to record the kinematic and EMG data. The NWR was evoked through a painful electrical stimulation of the index finger during a movement which consisted of reaching out, picking up a cylinder, and returning it to the starting position.ResultsWe found that: (i) the NWR is extensively rearranged in hemiparetic patients, who were found to present different kinematic and EMG reflex patterns with respect to controls; (ii) patients partially lose the ability to modulate the reflex in the different movement phases; (iii) the impairment of the reflex modulation occurs at single-muscle, single-joint and multi-joint level.ConclusionsPatients with chronic and mild-moderate post-stroke motor deficits lose the ability to modulate the NWR dynamically according to the movement variables at individual as well as at multi-muscle and joint levels.SignificanceThe central nervous system is unable to use the NWR substrate dynamically and flexibly in order to select the muscle synergies needed to govern the spatio-temporal interaction among joints.Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

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