Neurosurgical treatment of spasticity: selective posterior rhizotomy and intrathecal baclofen.

The pathophysiology of spasticity and the history of posterior rhizotomies are reviewed. The rationale for selective posterior rhizotomies is that electrical stimulation identifies afferent posterior rootlets that terminate on relatively uninhibited alpha motoneurons; if these uninhibited rootlets are divided, spasticity can be alleviated without loss of other posterior root functions. Indications, technique, and results of selective posterior rhizotomies are presented. The use of continuous intrathecal baclofen (CITB) is summarized. CITB at doses of approximately 300 micrograms/day consistently reduces lower extremity spasticity and diminishes or alleviates muscle spasms in adults with spasticity of spinal origin. Single doses of intrathecal baclofen significantly decrease lower extremity muscle tone in children with cerebral palsy, and the effects can be maintained in these patients by CITB infusions which diminish muscle tone not only in the lower extremities, but in the upper extremities as well. CITB is best accomplished via an externally programmable pump that allows titration of the daily dose to attain the desired reduction in spasticity. Factors influencing the decision for rhizotomy or CITB are presented.