VARIATION BETWEEN CENTERS IN ELECTROPHYSIOLOGIC TECHNIQUES USED IN LUMBOSACRAL SELECTIVE DORSAL RHIZOTOMY FOR SPASTIC CEREBRAL-PALSY

The extent of variation between centers in the electrophysiologic tech niques used in lumbosacral selective dorsal rhizotomy (SDR) for spasti c cerebral palsy was studied using a questionnaire survey. Nineteen ce nters completed the The extent of variation between centers in the ele ctrophysiologic techniques questionnaire, and the responses were analy zed for those 16 centers in which the extent of dorsal root section wa s guided by intraoperative electrophysiologic responses. Consistent te chniques included: use of unipolar stimulating electrodes (11 of 15 re sponses); stimulation <4 cm from the root exit foramen (14 of 16); sep aration of dorsal roots into three to eight rootlets each (14 of 16); tetanic stimulation frequency of 50 Hz (11 of 16); tetanic stimulation at 100% of threshold (13 of 16); recording from multiple lower limb m uscles simultaneously (16 of 16), and using contralateral spread of th e response as a major criterion of electrophysiologic abnormality (13 of 16). There was more variation (<11 of 16 concurrence) with respect to the use of a constant current versus constant voltage stimulator; t he location of the cathode of the stimuIating electrode relative to th e anode; the definition of the threshold for a response; whether thres hold was determined from stimulation of a dorsal root or individual ro otlets; the type of recording electrodes (needle versus surface), and the relative importance of electrophysiologic versus clinical findings in determining how much of each dorsal root to cut. In 10 centers, SD R would proceed without the benefit of electrophysiologic guidance if the equipment should fail intraoperatively (only if quadriplegic in 4) , and this had happened in 6. The results indicate significant variati on in many aspects of electrophysioIogically guided SDR.