INTRAOPERATIVE LOWER-EXTREMITY REFLEX MUSCLE-ACTIVITY AS AN ADJUNCT TO CONVENTIONAL SOMATOSENSORY-EVOKED POTENTIALS AND DESCENDING NEUROGENIC MONITORING IN IDIOPATHIC SCOLIOSIS

Study Design. Lower extremity polysynaptic reflexes and descending neu rogenic motor and ascending somatosensory activity were recorded. Obje ctive. Two cases are presented to illustrate the intraoperative use of lower extremity reflex recordings for detecting compromise of spinal cord function. Summary of Background Data. Lower extremity reflex proc essing can be used to measure integrated spinal cord activity, whereas descending neurogenic and ascending somatosensory potentials measure only long tract function. Methods. Eight channels of lower extremity p olysynaptic reflex activity were recorded simultaneously after unilate ral lower extremity mixed nerve stimulation. Sequential descending neu rogenic and ascending somatosensory activity was recorded simultaneous ly with reflex recordings. Results. In these two patients with idiopat hic scoliosis, intraoperative reflexes changed before descending neuro genic and before ascending somatosensory activity changed. High-amplit ude synchronous persistent reflex activity correlated with a postopera tive neurologic deficit. Low-amplitude asynchronous transient reflex a ctivity was not associated with a postoperative neurologic deficit.Con clusion. Intraoperative lower extremity reflex changes are more sensit ive to spinal cord compromise than are changes in long tract function. Lower extremity polysynaptic reflexes monitor the integrated activity of the spinal cord that is responsible for the control of complex mot or behavior.