The validity of electrophysiological criteria used in selective functional posterior rhizotomy for treatment of spastic cerebral palsy

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Abstract
Although selective functional posterior rhizotomy (SFPR) is an established procedure for the treatment of spasticity, the electrophysiological criteria used to define which posterior rootlets should be cut have not been standardized. The purpose of this study was to determine the validity of the intraoperative electrophysiological criteria used to select posterior rootlets for sectioning in SFPR. Intraoperative stimulation of posterior lumbosacral nerve roots and rootlets, using a 50-Hz stimulus at threshold intensity, was performed in five nonspastic children (controls) undergoing laminectomy for spinal cord untethering and in 32 spastic patients undergoing SFPR. Electromyographic responses were recorded in the upper and lower limbs, the neck, and the face. The pattern of sustained responses was assessed in detail in 17 additional patients who had previously undergone SFPR and in the five controls. Sustained responses with ipsilateral lower limb extrasegmental spread occurred in both spastic patients and the control group. Contralateral lower limb spread and suprasegmental spread to the upper limbs, neck, and face were found only in spastic children. Sustained responses with an incremental pattern were restricted to the spastic population and correlated well with the extent of contralateral and suprasegmental spread, whereas decremental patterns were not associated with contralateral spread. It is concluded that contralateral and suprasegmental spread into the upper limbs, neck, and face, and incremental responses are probably valid criteria of abnormality.