Limited benefit of electrophysiological studies during dorsal rhizotomy

Using a formula for standard deviation and several assumptions, the potential benefit of electrophysiological recording (ER) during dorsal rhizotomy for cerebral palsy is calculated and expressed in a ratio, the electrophysiological recording benefit ratio (ERBR). ERBR is approximately 1.1 in most of the examples, but other factors may reduce this ratio. Severing an additional rootlet appears to be a viable alternative to ER in most of the examples. Advantages of dorsal rhizotomy without ER include reduced expense and operative time. Prospective studies are recommended to evaluate further the benefit of ER during dorsal rhizotomy. If stimulation of dorsal rootlets is abandoned during dorsal rhizotomy, stimulation of whole dorsal and ventral roots may still be necessary to prevent inadvertent severing of motor fibers.