Clinical and Neurophysiologic Assessment of Strength and Spasticity During Intrathecal Baclofen Titration in Incomplete Spinal Cord Injury: Single-Subject Design

Background/Objective:

Spasticity after spinal cord injury (SCI) is commonly managed with oral and intrathecal baclofen (ITB), with less attention to the effects on voluntary motor control. Studies combining clinical and neurophysiologic assessments during dose optimization are rare. Study aims (a) systematically evaluate effects of varied doses of oral and ITB on clinical and neurophysiologic measures of strength and spasticity and (b) relate clinical and neurophysiologic findings.

Methods:

A 41-year-old man with an incomplete T11-ASIA D SCI was studied during ITB titration. Spasticity and strength in the lower extremities were assessed clinically and neurophysiologically at 5 different daily dosages of baclofen: (a) 80 mg oral, (b) 80 mg oral/50 μg ITB, (c) 80 mg oral/125 μg ITB, (d) 30 mg oral/125 μg ITB, and (e) 125 μg ITB only.

Results:

A dose-dependent change in the Ashworth score and lower limb motor score was observed during titration of oral and ITB. Whereas the Hoffman (H)-reflex was abolished after the introduction of ITB, the flexion withdrawal reflex approximated a dose-dependent pattern. Changes in the motor score and EMG during voluntary muscle activation were proportionally smaller than the corresponding changes in clinical and neurophysiologic measures of spasticity. Neurophysiologic assessment largely paralleled clinical findings.

Conclusions:

This single-subject study shows that the control of spasticity can be achieved without detrimental effects on strength in incomplete SCI and suggests the need for including strength testing in comprehensive clinical assessment of spasticity. The study shows convergent validity between clinical and neurophysiologic assessments during ITB dose titration. Adding neurophysiologic assessment to clinical assessment may provide objectivity and sensitivity and facilitate decision-making during ITB titration.