Intrafusal effects of botulinum toxin in post-stroke upper limb spasticity.
A previous study in subjects with focal dystonia suggested that the greater and longer-lasting effect induced by botulinum toxin type A (BoNT-A) on the tonic vibration reflex (TVR) than on the maximal M-wave (M-max) might be the physiological marker of the toxin's action at the level of intrafusal muscle fibres. With this approach, we investigated the possible effect of BoNT-A on fusimotor synapses in eight patients with post-stroke spasticity (four with no residual motor capacity before treatment and four with partially spared muscle strength and residual motor capacity). TVR and M-max were recorded from the wrist and finger flexor muscles before treatment and at 1, 4 and 7 months afterwards. The TVR reduction was greater than the M-max reduction and remained fairly constant over time only in the subjects with a residual motor capacity before the treatment. This pilot study suggests that some degree of strength and active movement is necessary for the action of BoNT-A on intrafusal fibres.
Trompetto
C
C
Department of Neurosciences, Ophthalmology & Genetics, University of Genoa, Genoa, Italy.
Bove
M
M
Avanzino
L
L
Francavilla
G
G
Berardelli
A
A
Abbruzzese
G
G
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular / Q000379:methods; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009128:Muscle Spasticity / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology*; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D012026:Reflex, Stretch / Q000187:drug effects; D020521:Stroke / Q000150:complications; D034941:Upper Extremity
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A