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Botulinum toxin changes intrafusal feedback in dystonia: A study with the tonic vibration reflex
Author(s) -
Trompetto Carlo,
Currà Antonio,
Buccolieri Alessandro,
Suppa Antonello,
Abbruzzese Giovanni,
Berardelli Alfredo
Publication year - 2006
Publication title -
movement disorders
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.352
H-Index - 198
eISSN - 1531-8257
pISSN - 0885-3185
DOI - 10.1002/mds.20801
Subject(s) - tonic (physiology) , reflex , botulinum toxin , stretch reflex , medicine , muscle spindle , h reflex , anesthesia , physical medicine and rehabilitation , afferent
To investigate the possible role of botulinum toxin (BT‐A) injection in reducing muscle afferent feedback, we evaluated electrophysiologically 10 right‐handed patients with writer's cramp before and 3 weeks after treatment. The ratio between pre‐ and postinjection values of maximal M‐wave (M‐max), maximal voluntary contraction (MVC), and tonic vibration reflex (TVR) were measured in the injected muscles (wrist flexors or extensors). In all the subjects, BT‐A injection reduced the TVR more than the M‐max and MVC (mean ratio ± SD: TVR, 0.24 ± 0.22; MVC, 0.59 ± 0.32; M‐max, 0.68 ± 0.24; P = 0.003). Long‐term evaluation of 2 patients disclosed that, after 7 months, when some clinical benefits persisted, M‐max and MVC had fully recovered, whereas the TVR was still depressed. This special sensitivity of the TVR to suppression by BT‐A injection could be mediated by the chemodenervation of intrafusal muscle fibers, leading to a reduction in spindle inflow to the central nervous system during vibration. The action on intrafusal fibers could alter sensorimotor integration, thus contributing to the clinical benefits of BT‐A injection. © 2006 Movement Disorder Society