Whether the newly modified rhizotomy protocol is applicable to guide single-level approach SDR to treat spastic quadriplegia and diplegia in pediatric patients with cerebral palsy?

Abstract

Purpose Our aim was to test whether the newly modified rhizotomy protocol which could be effectively used to guide single-level approach selective dorsal rhizotomy (SL-SDR) to treat spastic hemiplegic cases by mainly releasing those spastic muscles (target muscles) marked pre-operatively in their lower limbs was still applicable in spastic quadriplegic or diplegic cerebral palsy (CP) cases in pediatric population. Methods In the current study, we retrospectively conducted a cohort review of cases younger than 14 years of age diagnosed with spastic quadriplegic or diplegic CP who undergone our modified protocol-guided SL-SDR in the Department of Neurosurgery, Children’s Hospital of Shanghai since July 2016 to November 2017 with at least 12 months post-op intensive rehabilitation program (pre-op GMFCS level-based). Clinical data including demographics, intra-operative EMG responses interpretation, and relevant assessment of included cases were taken from the database. Inclusion and exclusion criteria were set for the selection of patients in the current study. Muscle tone (modified Ashworth scale) and strength of those spastic muscles (muscle strength grading scale), range of motion (ROM) of those joints involved, the level of Gross Motor Function Classification System (GMFCS), and Gross Motor Function Measure 66 items (GMFM-66) score of those cases were our focus. Results A total of 86 eligible cases were included in our study (62 boys). Among these patients, 61.6% were quadriplegic. Pre-operatively, almost 2/3 of our cases were with GMFCS levels II and III. Mean age at the time of surgery in these cases was 6.2 (3.5–12) years. Pre-op assessment marked 582 target muscles in these patients. Numbers of nerve rootlets tested during SDR procedure were between 52 and 84 across our cases, with a mean of 66.5 ± 6.7/case. Among those tested (5721 in 86 cases), 47.9% (2740) were identified as lower limb-related sensory rootlets. Our protocol successfully differentiated sensory rootlets which were considered to be associated with spasticity of target muscles across all our 86 cases (ranged from 3 to 21). Based on our protocol, 871 dorsal nerve rootlets were sectioned 50%, and 78 were cut 75%. Muscle tone of those target muscles reduced significantly right after SL-SDR procedure (3 weeks post- vs. pre-op, 1.7 ± 0.5 vs. 2.6 ± 0.7). After an intensive rehabilitation program for 19.9 ± 6.0 months, muscle tone continued to decrease to 1.4 ± 0.5. With the reduction of muscle tone, strength of those target muscles in our cases improved dramatically with statistical significance achieved (3.9 ± 1.0 at the time of last follow-up vs. 3.3 ± 0.8 pre-op), and as well as ROM. Increase in GMFCS level and GMFM-66 score was observed at the time of last follow-up with a mean of 0.4 ± 0.6 and 6.1 ± 3.2, respectively, when compared with that at pre-op. In 81 cases with their pre-op GMFCS levels II to V, 27 (33.3%) presented improvement with regard to GMFCS level upgrade, among which 4 (4.9%) even upgraded over 2 levels. Better results with regard to upgrading in level of GMFCS were observed in cases with pre-op levels II and III when compared with those with levels IV and V (24/57 vs. 3/24). Upgrading percentage in cases younger than 6 years at surgery was significantly greater than in those older (23/56 vs. 4/25). Cases with their pre-op GMFM-66 score ≥ 50 had greater score increase of GMFM-66 when compared with those less (7.1 ± 3.4 vs. 5.1 ± 2.8). In the meanwhile, better score improvement was revealed in cases when SDR performed at younger age (6.9 ± 3.3 in case ≤ 6 years vs. 4.7 ± 2.7 in case > 6 years). No permanent surgery-related complications were recorded in the current study. Conclusion SL-SDR when guided by our newly modified rhizotomy protocol was still feasible to treat pediatric CP cases with spastic quadriplegia and diplegia. Cases in this condition could benefit from such a procedure when followed by our intensive rehabilitation program with regard to their motor function.

Intraoperative neurophysiological monitoring in selective dorsal rhizotomy (SDR)

“…Park's method put more focus on the EMG spreading pattern instead of the EMG discharge pattern, making its repeatability more reliable. In addition, such EMG interpretation [11,12]. could guide the selection of dorsal roots (rootlets) that are thought to be more closely associated with spasticity just beneath the conus level, which means the selection could be fully achieved without the need to identify the level of those nerve roots (rootlets).…”

“…Studies have shown that different anesthetics can affect intraoperative electrophysiological outcomes [16][17][18], including changes in threshold, latency to stimulus, and EMG response patterns. Because, to date, there is no proven anesthetic protocol used specifically for SDR, clinical practitioners have either just applied those protocols conducted in other neurosurgical procedures requiring IONM or simply developed their own [2][3][4][5][6][7][8][9][10][11][12][13].…”

“…Since Fasano's setup, intraoperative electrical stimulation has typically included both singlepulse stimulation and train stimulation. Singlepulse stimulation, which contains a constant current with a duration that varies from 0.05 to 0.5 ms and an intensity starting at 0.01 mA [2][3][4][5][6][7][8][9][10][11][12][13], is used mainly (1) to differentiate dorsal roots from ventral ones, (2) to identify those rootlets associated with the sphincter, and (3) to determine the electrical intensity for the following train stimulation. In both Browd's and our team's setups, single-pulse stimulation was also used to determine whether such rootlet stimulation initially evokes EMG responses in those target muscles.…”

“…The purpose of performing train stimulation in SDR is to determine whether the dorsal rootlet stimulated has matched rhizotomy criteria [1][2][3][4][5][6][7][8][9][10][11][12][13]. At present, most centers performing SDR set the train stimulation to a frequency of 50 Hz for 1 s. The reasons for setting this frequency are the following: (1) electrically stimulating a dorsal nerve root at a rate greater than 10 Hz usually leads to the gradual attenuation of EMG responses, and (2) when the frequency of train stimulation is between 30 and 50 Hz, motor neurons in the spinal cord respond only to the first stimulus [2].…”

“…The word "selective" refers to the intraoperative selection and dissection of the afferent nerve rootlets in the spinal cord that are considered to be more involved in spasticity, decreasing the afferent signaling to the motor neurons in the anterior horn of the spinal cord, so as to achieve a reduction in muscle tone after surgery. At present, some centers that perform SDR use intraoperative neurophysiological monitoring (IONM) to assist or even fully guide the operation [2][3][4][5][6][7][8][9][10][11][12][13]. Because the role of IONM in SDR has never been fully discussed, its importance and necessity have been long questioned.…”