Neurophysiological basis and clinical applications of the H-reflex as an adjunct for evaluating response to intrathecal baclofen for spasticity.

Implanted programmable pumps that infuse intrathecal baclofen (ITB) markedly enhance the ability of clinicians to manage severe spasticity in appropriately selected patients. Studies addressing the efficacy of this treatment modality have primarily used clinical outcome measures of impairment, particularly reduction in stiffness as measured by the Ashworth scale. Several recent studies, however, highlight comparalively higher sensitivity of neurophysiologic techniques, especially the H-reflex, as an objective index of spinal cord response to ITB administration. We review the conceptual, physiological, and methodological hases for use of the H-reflex as an adjunct to clinical evaluation among patients receiving ITB infusion, including published reports and selected case studies that address the potential advantages and limitations of such techniques when applied to dose titration and system "troubleshooting" scenarios, We also address the implications of such findings in the context of reported complications such as "tolerance" to ITB administration and catheter "microfracture". The accumulated knowledge suggests that H-reflex is a sensitive method for documenting altered spinal cord responsiveness in the presence of ITB delivery. We therefore recommend using H-reflex as an adjunct to clinical evaluation when judging the overall effectiveness of ITB administration.