TASK:
Selective dorsal risotomy using a single-level approach (SL-SDR) for the treatment of spasticity is 100% based on the interpretation of the results of intraoperative neuroelectrophysiological monitoring. This study is devoted to the role that the interpretation of EMG plays during the SL-SDR procedure in the choice of nerve roots for partial dissection in pediatric cases with spastic cerebral palsy (cerebral palsy).

METHODS:
A retrospective study was conducted in pediatric patients with spastic CP who suffered our modified SL-SDR using the risotomy protocol from May 2016 to March 2019 in our hospital. Our study focused on the intraoperative interpretation of EMG and its correlation with the results of the preoperative assessment and the difference in the choice of the dorsal root, when the data of our intraoperative EMG records were interpreted using different risotomy protocols.

RESULTS:
Data from clinical and intraoperative neuroelectrophysiological monitoring were analyzed in total of 318 successive cases, which included 231 boys and 87 girls with 32 hemiplegia, 161 diplegia and 125 quadriplegias.
The age at the time of SL-SDR in these cases was 3.0-14.0 (5.9 ± 1.9) years. The number of target muscles varied from 2 to 8 in these cases (muscles of the lower extremities with preoperative muscle tone ≥ 2 points, modified Ashworth scale). Of the 21,728 tested nerve roots (68.3 ± 8.2 / case), 6272 (28.9%) had a sphincter associated with our intraoperative neuromonitoring. In the remaining 15,456 (48.6 ± 7.6 / case) nerve roots, which, according to neuromonitoring, were associated with the lower extremities, 11,009 were taken as dorsal (34.6 ± 7.4 / case).
A total of 3,370 (10.6 ± 4.7 / case) roulettes met our rhizotomy criteria with 3061 (9. 6 ± 4.1 / case) cross-section 50% and 309 (1.0 ± 1.0 / case) reduction 75%. The ratio of rhizotomy (partially crossed nerve roots / all dorsal roots associated with the lower extremities in a particular case) was 15.8%, 22.3%, 33.4%, 41.8% and 45.7% in all cases with the pro-op GMFCS level from I to V, respectively. Root crops requiring a cut of 75% tended to increase and in our cases, with their level of GMFCS in pro-op from I to V, which is 1.5%, 4.8%, 8.5%, 14.1% and 15.2% of all crossed roulettes, respectively, the muscle tone of 2068 target muscles in these cases 3 weeks after SL-SDR revealed a significant decrease compared to the preoperative period (1.7 ± 0.5 against 2.7 ± 0.6).
Further studies that compared the choice of our roulettes with the choice based on traditional rhizotomy criteria using our EMG intraoperative records in 318 cases showed that the overlap coefficient tended to increase when their level before GMFCS surgery increased (39.5%, 41.3%, 52.2%, 54.1% and 62.8% in cases with levels IV, respectively). While our modified rhizotomy protocol successfully identified 2-23 roulettes for partitioning in all our 318 cases, the traditional rhizotomy protocol could not distinguish any for cutting in about 20% of cases with levels I and II before GMFCS surgery.

CONCLUSIONS:
The criteria of rhizotomy are entirely based on the interpretation of EMG, which makes intraoperative neuroelectrophysiological monitoring decisive when SDR is performed using a single-level approach. Our modified rhizotomy protocol is feasible, safe and effective to guide SL-SDR to treat all types of spastic cases of CP by reducing muscle tone in certain groups of spastic muscles in the lower extremities. Data from EMG responses during the SL-SDR procedure, as well as clinical results based on their interpretation, can help doctors better understand how neural chains work in the spinal cord of these patients.

Keywords:
Spinal rhizotomy; EMG interpretation; Intraoperative neurophysiology; Spastic cerebral palsy