Effect of intrathecal baclofen bolus injection on ankle muscle activation during gait in patients with acquired brain injury

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Study examined activation of medial gastrocnemius (MG) and tibialis anterior (TA) muscles during gait before and after intrathecal baclofen (ITB) bolus injection in patients with resting hypertonia after acquired brain injury. Eight patients with hemorrhagic stroke and 11 patients with traumatic brain injury were assessed before and at 2, 4, and 6 hours after a 50-μg ITB injection via lumbar puncture. Measures included the lower-extremity Ashworth score, temporospatial gait parameters, characteristics of the linear relationship between electromyogram (EMG) and lengthening velocity (LV) in MG during stance, and the duration and magnitude of TA-MG coactivation. Results showed that temporospatial gait parameters did not significantly differ across the evaluation points. However, the Ashworth score, frequency and gain of significant positive EMG-LV slope, and duration of TA-MG coactivation significantly decreased in the more-affected leg after ITB bolus. EMG changes were not significantly different between patients who did and did not increase gait speed after the injection. The timing of the largest decrease in the Ashworth score and the largest decrease in EMG parameters coincided in 36 percent of cases, on average. Findings suggest that ITB bolus injection reduces the activation of ankle muscles during gait without affecting the pattern of coactivation or the overall gait performance. The authors conclude that the analysis of ankle-muscle activation during gait better characterizes the response to ITB bolus injection than gait kinematics.

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