title: Effect of intrathecal baclofen bolus injection on ankle muscle activation during gait in patients with acquired brain injury.
abstract: BACKGROUND
  Intrathecal baclofen (ITB) bolus injection effectively decreases spinal excitability but the impact on lower limb muscle activation during gait has not been thoroughly investigated.
  
  
  OBJECTIVE
  Examine activation of medial gastrocnemius (MG) and tibialis anterior (TA) muscles during gait before and after ITB bolus injection in patients with resting hypertonia after acquired brain injury.
  
  
  METHODS
  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 were assessed before and at 2, 4, and 6 hours after a 50-µg ITB injection via lumbar puncture in 8 hemorrhagic stroke and 11 traumatic brain injury subjects.
  
  
  RESULTS
  Temporospatial gait parameters did not significantly differ across the evaluation points (P ≥ .170). However, Ashworth score (P < .001), frequency and gain of significant positive EMG-LV slope (P ≤ .020), and duration of TA-MG coactivation (P ≤ .013) significantly decreased in the more-affected leg after ITB bolus. EMG changes were not significantly different between patients who did (n = 10) and did not (n = 9) increase gait speed after the injection. The timing of the largest decrease in Ashworth score and the largest decrease in EMG parameters coincided in 36% of cases, on average.
  
  
  CONCLUSIONS
  ITB bolus injection alters the activation of MG and TA during gait. However, the changes in muscle activation are not closely related to the changes in gait speed or resting muscle hypertonia. The analysis of ankle muscle activation during gait better characterizes the response to ITB bolus injection than gait kinematics.
authors.affiliation: Methodist Rehabilitation Center, Jackson, MS, USA jchow@mmrcrehab.org.
authors.forename: John W
authors.initials: JW
authors.lastname: Chow
authors.affiliation: University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Yablon
authors.affiliation: Methodist Rehabilitation Center, Jackson, MS, USA.
authors.forename: Dobrivoje S
authors.initials: DS
authors.lastname: Stokic
mesh_terms: D000293:Adolescent; D000328:Adult; D000842:Ankle / Q000503:physiopathology; D001418:Baclofen / Q000008:administration & dosage*; D001696:Biomechanical Phenomena; D001930:Brain Injuries / Q000188:drug therapy / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D005684:Gait / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007278:Injections, Spinal; D020300:Intracranial Hemorrhages / Q000188:drug therapy / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009122:Muscle Hypertonia / Q000188:drug therapy* / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D020521:Stroke / Q000188:drug therapy / Q000503:physiopathology*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D009465:Neuromuscular Agents; D001418:Baclofen
keywords: coactivation; hypertonia; spasticity; stretch reflex; stroke; traumatic brain injury