Variation between centers in electrophysiologic techniques used in lumbosacral selective dorsal rhizotomy for spastic...

The extent of variation between centers in the electrophysiologic techniques used in lumbosacral selective dorsal rhizotomy (SDR) for spastic cerebral palsy was studied using a questionnaire survey. Nineteen centers completed the questionnaire, and the responses were analyzed for those 16 centers in which the extent of dorsal root section was guided by intraoperative electrophysiologic responses. Consistent techniques included: use of unipolar stimulating electrodes (11 of 15 responses); stimulation < 4 cm from the root exit foramen (14 of 16); separation 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 muscles simultaneously (16 of 16), and using contralateral spread of the 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; the location of the cathode of the stimulating electrode relative to the anode; the definition of the threshold for a response; whether threshold was determined from stimulation of a dorsal root, or individual rootlets; 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, SDR 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 variation in many aspects of electrophysiologically guided SDR.