Article

An understanding of the mechanical effects of botulinum toxin type A
(BoNT A) on spastic and voluntary muscle contraction may help predict functional
responders. OBJECTIVE: To compare the effect of BoNT A on the voluntary and
stretch reflex-related torques produced by activation of the rectus femoris (RF).
METHODS: This was a prospective open study where 15 incomplete spinal cord injury
patients, impaired by a stiff-knee gait, with RF hyperactivity in mid-swing
quantified by formal gait analysis (GA), were assessed before and after RF BoNT A
injection (Botox, 200 UI). MAIN OUTCOME MEASURES: Included isokinetic peak torque
(and angle at peak torque) at 0 degrees (supine) and 90 degrees (seated) during
passive stretch (10 deg/s, 90 deg/s, and 150 deg/s), and voluntary contraction
(60 deg/s) of the quadriceps. Secondary measures included impairment by Modified
Tardieu Scale (MTS), peak knee flexion and spatial-temporal data by GA, activity
(6-minute walking test, timed stair climbing), and discomfort (Verbal Rating
Scale). RESULTS: Voluntary torque decreased (-16%; P = .0004) but with only a
trend toward a decrease in stretch reflex-related torque. The angle at spastic
torque increased at 90 deg/s (+5 degrees ; P = .03), whereas MTS, peak knee
flexion (+4 degrees ; P = .01), spatial-temporal data, timed stair climbing test
(25%; P = .02), and discomfort were significantly improved. CONCLUSION: BoNT A
appeared to delay the stretch-reflex angle at peak torque, whereas the voluntary
torque decreased. After strict patient selection, BoNT A injection into the RF
muscle led to improvements in impairment, activity, and discomfort.

Langue : ANGLAIS