Reliability of intraoperative electrophysiological monitoring in selective posterior rhizotomy

Gabapentin as part of a multimodal pain protocol for selective dorsal rhizotomy does not impact percentage of rootlets transected

PURPOSE

We aim to determine whether preoperatively initiated gabapentin for pain control impacts the percentage of rootlets cut during monitored, limited laminectomy selective dorsal rhizotomy (SDR) procedure.

METHODS

This retrospective cohort study includes participants with cerebral palsy who had SDR for treatment of spasticity between 2010 and 2019 at a single-institution tertiary care center. One-level laminectomy SDR aimed to evaluate the cauda equina roots from levels L2-S1 with EMG monitoring. Gabapentin titration began 3 weeks prior to SDR. Data was analyzed using simple linear regression. Thirty-one individuals met inclusion criteria. Mean age was 7 years, 4 months. Eighteen participants (58%) identified as male, 12 (39%) female, and one (3%) non-binary. Thirty (97%) had bilateral CP. Sixteen (52%) were GMFCS II, four (13%) GMFCS III, five (16%) GMFCS IV, and six (19%) GMFCS V.

RESULTS

Mean percentage of rootlets transected was 50.75% (SD 6.00, range 36.36-60.87). There was no relationship between the dose of gabapentin at time of SDR and percentage of rootlets cut with a linear regression slope of - 0.090 and an R2 of 0.012 (P = 0.56).

CONCLUSION

Results indicate that preoperative initiation of gabapentin did not impact the percentage of rootlets transected. Thus, gabapentin can be initiated prior to SDR at moderate dosages without impacting SDR surgical outcomes.

Excitability of the radiculo-medullary circuitry in spastic cerebral palsy: An intraoperative neurophysiological study in children undergoing selective dorsal rhizotomy

AIM

To explore - through intraoperative neurophysiology mapping and recordings - the comparative distribution of the reflexive excitability of the L2 to S2 radiculo-metameric segments of the spinal cord in a series of children with bilateral spastic cerebral palsy (CP) who underwent selective dorsal rhizotomy (SDR).

METHOD

Our series included 46 consecutive children (36 males, 10 females; aged 5-16 years, mean 8 years) who underwent SDR, using keyhole interlaminar dorsal rhizotomy. The procedure allowed access to all L2 to S2 roots independently, while preserving the posterior architecture of the lumbar spine. Dorsal roots were stimulated selectively to test reflexive excitability of the corresponding radiculo-metameric levels. Stimulation parameters were identical for all roots for optimal comparison between root levels, with an intensity just above threshold to avoid excessive diffusion. The responses in the main muscular groups in each lower limb were clinically observed and electromyograms recorded. Degrees of excitability were quantified according to Fasano's scale.

RESULTS

The difference between root levels was highly significant. Median values of excitability were 1, 2, 3, 3, 3, and 3 for the L2, L3, L4, L5, S1, and S2 levels respectively. Lower root levels exhibited significantly more excitability.

INTERPRETATION

In addition to insight into the spasticity of children with CP, the profile of segmental excitability can be useful in establishing surgical planning when programming SDR.

WHAT THIS PAPER ADDS

Keyhole interlaminar dorsal rhizotomy modality allowed selective stimulation of all L2-S2 dorsal roots for testing excitability. There were significant differences in reflexive excitability of L2-S2 radiculo-medullary segments. Lower segments of L2-S2 medullary levels have higher excitability. Interindividual variability in excitability of lumbosacral segments justifies intraoperative neurophysiology. This original article is commented on by Young on pages 9-10 of this issue.

Dorsal rhizotomy in cerebral palsy: how root sectioning is influenced by intraoperative neuromonitoring

INTRODUCTION AND OBJECTIVE

Dorsal rhizotomy is a controversial procedure for treating spasticity in children with cerebral palsy, particularly regarding the influence of intraoperative neuromonitoring (ION). The objective of this study was to evaluate the influence of ION in adjusting root sectioning compared the preoperative program established by the multidisciplinary team.

MATERIAL AND METHODS

Twenty-four consecutive children with spastic diplegia or quadriplegia, operated on between 2017 and 2020 in the University Hospital of Nancy, France, were studied. All underwent the same procedure: Keyhole Intralaminar Dorsal rhizotomy (KIDr) with enlarged multilevel interlaminar openings to access all roots from L2 to S2. The Ventral Root (VR) was stimulated to map radicular myotomes, and the Dorsal Root (DR) to test excitability of the segmental circuitry. Muscle responses were observed independently by the physiotherapist and by EMG-recordings. The study compared final root sectioning per radicular level and per side after ION versus the preoperative program determined by the multidisciplinary team.

RESULTS

ION resulted in significant differences in final percentage root sectioning (p<0.05), with a decrease for L2 and L3 and an increase for L5. ION modified the symmetry of sectioning, with 32% instead of 5% in preoperative program. Only 5 children showed change in GMFC score 6 months after surgery.

CONCLUSION

The use of ION during dorsal rhizotomy led to important modifications of root sectioning during surgery, which justifies individual control of each root, level by level and side by side, to optimize the therapeutic effect.

Improvement of the gait pattern after selective dorsal rhizotomy derives from changes of kinematic parameters in the sagittal plane

OBJECTIVE

Selective dorsal rhizotomy (SDR) can decrease spasticity in children suffering from spastic cerebral palsy (SCP) and thus improve their moving ability when supplemented with the post-operational rehabilitation program. In this case, the study aims to investigate the gait changes in children with mild SCP after SDR in short-term follow-up.

METHODS

The information of ambulatory SCP cases who underwent SDR in our center was retrospectively reviewed, and comparisons of changes in spasticity, motor function and data of gait analysis before and after SDR were analyzed.

RESULTS

In total, 32 cases were included in this study, with a mean age of 5.9 ± 2.1 years old. Noticeable decrease was found in the median value of the pre-operational MAS score after SDR at last follow-up in both sides of adductors, gastrocnemius, soleus, and left hamstrings. The Gross Motor Function Measure-66 score increased from 70.6 ± 9.2 to 73.4 ± 8.2, and the gait deviation index increased after SDR compared with the pre-operational data (right side: 65.8 ± 8.8 vs. 60.1 ± 10.7; left side: 63.5 ± 10.1 vs. 57.0 ± 9.9). Noticeable changes were found that the maximum angle of affected ankles in the sagittal plane (the dorsal-flexion angle) increased from 2.5° to 8.2°, the angles at initial contact (1% gait cycle) of affected knees in the sagittal plane decreased from 34.0° to 27.8°, and the angles at the end of swing phase (100% gait cycle) of affected knees in the sagittal plane decreased from 35.8° to 28.3°.

CONCLUSION

In short-term follow-up, SDR can lower spasticity in children with SCP. Post-operational gait analysis showed improvements in gross motor function and gait, which derived from the changes in the sagittal plane (ankle and knee). A longer follow-up duration is thus needed to clarify the long-term outcome.

Usefulness of external anal sphincter EMG recording for intraoperative neuromonitoring of the sacral roots-a prospective study in dorsal rhizotomy

BACKGROUND

In conus medullaris and cauda equina surgery, identification of the sacral nerve roots may be uncertain in spite of their anatomical/radiological landmarks. Mapping the sacral roots by recording the muscular responses to their stimulation may benefit from EMG recording of the External Anal sphincter (EAS) in addition to the main muscular groups of the lower limbs.

METHOD

In a consecutive series of 27 lumbosacral dorsal rhizotomy (DRh), authors carried out a prospective study on the reliability of the EMG recording of the EAS for identification of the S1 and S2 sacral roots.

RESULTS

An EAS-response was recorded in all the 27 (bilaterally) explored individuals, testifying good sensitivity and selectivity of the method. EAS-responses were obtained in 96.3% of the 54 stimulated sides of the S2 root versus in only 16.66% for the S1 root, so that an absence of response would indicate S1 rather than S2 level. Furthermore, comparison between myotomal distribution of the S1 and S2 roots showed a significant difference (p < 0.00001), so that myotomal profile may help to identify root level.

CONCLUSIONS

EMG recording of the EAS can be recommended for current intraoperative neuromonitoring. This simple method also provides-indirectly by extrapolation-information on the sacral motor pathways of the external urethral sphincter (EUS), as the later has the same somatic innervation via the pudendal nerve and related S2, S3, and S4 roots. Method can be helpful not only for DRh, of all varieties, but also for spine surgery, correction of dysraphisms, lipomas and/or tethered cord, and tumor resection.

Selective dorsal rhizotomy: functional anatomy of the conus-cauda and essentials of intraoperative neurophysiology

INTRODUCTION

Spasticity is the result of an exaggeration of the monosynaptic muscle stretch reflex due to lesions affecting the central nervous system, in particular an upper motor neuron lesion. Selective dorsal rhizotomy (SDR) is a surgical technique developed to treat spastic diplegia, one of the common forms of cerebral palsy, resulting from the lack of supraspinal inhibitory controls. The aim of SDR is to identify and cut a critical amount of the sensory rootlets, in particular those contributing the most to spasticity, in order to relieve the patient from lower limb spasticity while preserving motor strength and sphincter control. Various surgical techniques to perform SDR have been proposed over time. Similarly, intraoperative neurophysiology (ION)-first introduced by Fasano and colleagues in 1976-is a safe and effective tool to guide the surgeon in the procedure of SDR, but different ION strategies are used by different authors, and the value of ION itself has been questioned.

METHODS

The purpose of this paper is to review the anatomo-physiological background of SDR, the historical development of the surgical technique, and the essential principles of ION.

RESULTS

While some surgeons privilege a single-level approach and others a multi-level approach, nowadays, there are still neither agreement nor guidelines on the percentage of roots to be cut. Rather, a tailored approach based on both the preoperative functional status as well as intraoperative ION findings seems reasonable. ION is considered not essential to decide the percentage of roots to cut, but it assists to distinguish between ventral and dorsal roots, and to preserve sphincterial function, whenever S2 rootlets are included in SDR.

CONCLUSIONS

To optimize the balance between reduction of spasticity and preservation of motor strength while minimizing the neurological damage remains the main goal of SDR.

The role of intra-operative neuroelectrophysiological monitoring in single-level approach selective dorsal rhizotomy

OBJECTIVE

Selective dorsal rhizotomy via a single-level approach (SL-SDR) to treat spasticity 100% relies on the interpretation of results from the intra-operative neuroelectrophysiological monitoring. The current study is to investigate the role EMG interpretation plays during SL-SDR procedure with regard to the selection of nerve rootlets for partially sectioning in pediatric cases with spastic cerebral palsy (CP).

METHODS

A retrospective study was conducted in pediatric patients with spastic CP undergone our modified rhizotomy protocol-guided SL-SDR from May 2016 to Mar. 2019 in our hospital. Our study focused on intra-operative EMG interpretation and its correlation with pre-op evaluation results, and dorsal rootlet selection difference when data of our intra-operative EMG recordings interpreted using different rhizotomy protocols.

RESULTS

Clinical and intra-operative neuroelectrophysiological monitoring data of a total of 318 consecutive cases were reviewed, which include 231 boys and 87 girls with 32 hemiplegias, 161 diplegias, and 125 quadriplegias. Age at the time of SL-SDR in those cases was between 3.0-14.0 (5.9 ± 1.9) years. The number of targeted muscle ranged from 2 to 8 over these cases (the muscle in lower limbs with its pre-op muscle tone ≥ 2 grade, Modified Ashworth scale). Among 21,728 nerve rootlets tested (68.3 ± 8.2/case), 6272 (28.9%) were identified sphincter related by our intra-operative neuromonitoring. In the rest of 15,456 (48.6 ± 7.6/case) nerve rootlets which neuromonitoring suggested associated with lower limbs, 11,009 were taken as the dorsal ones (34.6 ± 7.4/case). A total of 3370 (10.6 ± 4.7/case) rootlets matched our rhizotomy criteria with 3061 (9.6 ± 4.1/case) sectioned 50% and 309 (1.0 ± 1.0/case) cut 75%. The rhizotomy ratio (partially transected nerve rootlets/all dorsal rootlets associated with lower limbs in a particular case) was 15.8%, 22.3%, 33.4%, 41.8%, and 45.7% across cases with their pro-op GMFCS level from I to V, respectively. Rootlets required 75% cut had a tendency to increase as well in our cases with their pro-op GMFCS level from I to V, which comprising 1.5%, 4.8%, 8.5%, 14.1%, and 15.2% of all rootlets transected, respectively. The muscle tone of 2068 targeted muscles in these cases at the time of 3 weeks after the SL-SDR was revealed a significant decrease when compared to pre-op (1.7 ± 0.5 vs. 2.7 ± 0.6). Further investigation to compare our rootlet selection with the one guided by the traditional rhizotomy criteria using our intro-operative EMG recordings in 318 cases, revealed that the overlap ratio had a tendency to increase in cases when their pre-op GMFCS level increased (39.5%, 41.3%, 52.2%, 54.1%, and 62.8% in cases with levels I-V, respectively). While our modified rhizotomy protocol successfully identified 2-23 rootlets for sectioning in all of our 318 cases, the traditional rhizotomy protocol failed to distinguish any for cutting in about 20% of cases with their pre-op GMFCS levels I and II.

CONCLUSIONS

The rhizotomy criteria fully rely on the EMG interpretation making intra-operative neuroelectrophysiological monitoring crucial when SDR is performed via a single-level approach. Our modified rhizotomy protocol is feasible, safe, and effective to guide SL-SDR to treat all types of spastic CP cases by decreasing muscle tone in particular spastic muscle groups in their lower limbs. Data of EMG responses during SL-SDR procedure and as well as the clinical outcomes based on their interpretation could help clinicians to further understand how neuronal circuits work in the spinal cord of these patients.

Intraoperative neurophysiological monitoring in selective dorsal rhizotomy (SDR)

For decades, intraoperative neurophysiological monitoring (IONM) has been used to guide selective dorsal rhizotomy (SDR) for the treatment of spastic cerebral palsy (CP). Electromyography (EMG) interpretation methods, which are the core of IONM, have never been fully discussed and addressed, and their importance and necessity in SDR have been questioned for years. However, outcomes of CP patients who have undergone IONM-guided SDR have been favorable, and surgery-related complications are extremely minimal. In this paper, we review the history of evolving EMG interpretation methods as well as their neuroelectrophysiological basis.

Intraoperative electrophysiology during single-level selective dorsal rhizotomy: technique, stimulation threshold, and response data in a series of 145 patients

OBJECTIVE

Selective dorsal rhizotomy (SDR) is effective at permanently reducing spasticity in children with spastic cerebral palsy. The value of intraoperative neurophysiological monitoring in this procedure remains controversial, and its robustness has been questioned. This study describes the authors' institutional electrophysiological technique (based on the technique of Park et al.), intraoperative findings, robustness, value to the procedure, and occurrence of new motor or sphincter deficits.

METHODS

The authors analyzed electrophysiological data of all children who underwent SDR at their center between September 2013 and February 2019. All patients underwent bilateral SDR through a single-level laminotomy at the conus and with transection of about 60% of the L2-S2 afferent rootlets (guided by intraoperative electrophysiology) and about 50% of L1 afferent roots (nonselectively).

RESULTS

One hundred forty-five patients underwent SDR (64% male, mean age 6 years and 7 months, range 2 years and 9 months to 14 years and 10 months). Dorsal roots were distinguished from ventral roots anatomically and electrophysiologically, by assessing responses on free-running electromyography (EMG) and determining stimulation thresholds (≥ 0.2 mA in all dorsal rootlets). Root level was determined anatomically and electrophysiologically by assessing electromyographic response to stimulation. Median stimulation threshold was lower in sacral compared to lumbar roots (p < 0.001), and 16% higher on the first operated (right) side (p = 0.023), but unrelated to age, sex, or functional status. Similarly, responses to tetanic stimulation were consistent: 87% were graded 3+ or 4+, with similar distributions between sides. This was also unrelated to age, sex, and functional status. The L2-S2 rootlets were divided (median 60%, range 50%-67%), guided by response to tetanic stimulation at threshold amplitude. No new motor or sphincter deficits were observed, suggesting sparing of ventral roots and sphincteric innervation, respectively.

CONCLUSIONS

This electrophysiological technique appears robust and reproducible, allowing reliable identification of afferent nerve roots, definition of root levels, and guidance for rootlet division. Only a direct comparative study will establish whether intraoperative electrophysiology during SDR minimizes risk of new motor or sphincter worsening and/or maximizes functional outcome.

Muscle responses to radicular stimulation during lumbo-sacral dorsal rhizotomy for spastic diplegia: Insights to myotome innervation

OBJECTIVE

Most of knowledge on muscle radicular innervation was from explorations in root/spinal cord pathologies. Direct and individual access to each of the lumbar-sacral -ventral and dorsal- nerve roots during dorsal rhizotomy for spastic diplegia allows precise study of the corresponding muscle innervation. Authors report the lumbo-sacral segmental myotomal organization obtained from recordings of muscle responses to root stimulation in a 20-children prospective series.

METHODS

Seven key-muscles in each lower limb and anal sphincter were Electromyography (EMG)-recorded and clinically observed by physiotherapist during L2-to-S2 dorsal rhizotomy. Ventral roots (VR), for topographical mapping, and dorsal roots (DR), for segmental excitability testing, were stimulated, just above threshold for eliciting muscular response.

RESULTS

In 70% of the muscles studied, VR innervation was pluri-radicular, from 2-to-4 roots, with 1 or 2 roots being dominant at each level. Overlapping was important. Muscle responses to DR stimulation were 1.75 times more extended compared to VR stimulation. Inter-individual variability was important.

CONCLUSIONS

Accuracy of root identification and stimulation with the used method brings some more precise information to radicular functional anatomy.

SIGNIFICANCE

Those neurophysiological findings plead for performing Intra-Operative Neuromonitoring when dealing with surgery in the lumbar-sacral roots.

Clinically practical formula for preoperatively estimating the cutting rate of the spinal nerve root in a functional posterior rhizotomy

OBJECTIVE

A functional posterior rhizotomy (FPR) ideally involves minimal cutting of the posterior root while providing maximal reduction of disabling spasticity. However, the ideal cutting rate has yet to be determined. It was hypothesized that the cutting rate of the posterior root would negatively correlate with preoperative motor function in children with spasticity.

METHODS

Children who underwent an FPR between March 1996 and March 2017 and whose pre- and postoperative data were followed more than a year were enrolled. The preoperative Gross Motor Function Measure (GMFM) score and the overall cutting rate of the posterior root were plotted on a scatter plot, and a simple linear regression analysis was performed. The rationale for the cutting rate of the posterior root was tested by postoperative chronological changes in the GMFM score up to 5 years after the FPR. The Gross Motor Function Classification System (GMFCS) was used to group the children. The postoperative and preoperative GMFM were compared at each GMFCS level.

RESULTS

One hundred thirty-seven children (aged 2 to 19 years old, mean 5.9 years old) met the selection criteria. The cutting rate of the posterior root ranged from 17 to 83%, (mean 48.3%). A scatter plot was then made using GMFM scores between 10 and 90. The formula for the simple linear regression analysis was y = - 0.5539x + 73.896 (x, GMFM score; y, overall cutting rate (%)). The formula was further approximated based on the scatter plot findings as y = 100 - x. The postoperative GMFM showed an improved average score for all GMFCS levels although statistically significant improvement at postoperative 5 years was confirmed in only the GMFCS level 1 group.

CONCLUSIONS

The findings of this study supported the hypothesis of the negative correlation of the cutting rate of the posterior root with preoperative motor function in children with spasticity. The amount of posterior nerve root/rootlet cutting during FPR negatively correlated with the preoperative GMFM score. The approximated formula is simple, practical for clinical use, and helpful for preoperatively estimating the required overall cutting rate for the posterior root. The suggested cutting rate induced by the approximated formula should be used as a reference value and be modified according to preoperative motor function, severity and distribution of spasticity, the result of intraoperative neurophysiology, and other factors.

Dorsal rhizotomy for children with spastic diplegia of cerebral palsy origin: usefulness of intraoperative monitoring

OBJECTIVE The utility of intraoperative neuromonitoring (ION), namely the study of muscle responses to radicular stimulation, remains controversial. The authors performed a prospective study combining ventral root (VR) stimulation for mapping anatomical levels and dorsal root (DR) stimulation as physiological testing of metameric excitability. The purpose was to evaluate to what extent the intraoperative data led to modifications in the initial decisions for surgical sectioning established by the pediatric multidisciplinary team (i.e., preoperative chart), and thus estimate its practical usefulness. METHODS Thirteen children with spastic diplegia underwent the following surgical protocol. First, a bilateral intradural approach was made to the L2-S2 VRs and DRs at the exit from or entry to their respective dural sheaths, through multilevel interlaminar enlarged openings. Second, stimulation-just above the threshold-of the VR at 2 Hz to establish topography of radicular myotome distribution, and then of the DR at 50 Hz as an excitability test of root circuitry, with independent identification of muscle responses by the physiotherapist and by electromyographic recordings. The study aimed to compare the final amounts of root sectioning-per radicular level, established after intraoperative neuromonitoring guidance-with those determined by the multidisciplinary team in the presurgical chart. RESULTS The use of ION resulted in differences in the final percentage of root sectioning for all root levels. The root levels corresponding to the upper lumbar segments were modestly excitable under DR stimulation, whereas progressively lower root levels displayed higher excitability. The difference between root levels was highly significant, as evaluated by electromyography (p = 0.00004) as well as by the physiotherapist (p = 0.00001). Modifications were decided in 11 of the 13 patients (84%), and the mean absolute difference in the percentage of sectioning quantity per radicular level was 8.4% for L-2 (p = 0.004), 6.4% for L-3 (p = 0.0004), 19.6% for L-4 (p = 0.00003), 16.5% for L-5 (p = 0.00006), and 3.2% for S-1 roots (p = 0.016). Decreases were most frequently decided for roots L-2 and L-3, whereas increases most frequently involved roots L-4 and L-5, with the largest changes in terms of percentage of sectioning. CONCLUSIONS The use of ION during dorsal rhizotomy led to modifications regarding which DRs to section and to what extent. This was especially true for L-4 and L-5 roots, which are known to be involved in antigravity and pelvic stability functions. In this series, ION contributed significantly to further adjust the patient-tailored dorsal rhizotomy procedure to the clinical presentation and the therapeutic goals of each patient.

ELECTROMYOGRAPHY AND INSTRUMENTATION IN PATIENTS WITH IDIOPATHIC SCOLIOSIS

ABSTRACT Objective: The objective of this study is to relate the use of intraoperative electromyography with surgical time, proper placement of screws, type of curve and time spent per screw in idiopathic scoliosis correction surgery in a group of surgeons from Belo Horizonte. This study used the database of protocol evaluation of patients operated in the service, and separately analyzed the results of motor and somatosensory potentials. Methods: Retrospective study of 80 patients undergoing surgery for correction of idiopathic scoliosis between December 2008 and January 2015. A single group of Belo Horizonte spine surgeons performed the intraoperative electromyographic (EMG) monitoring. EMG was performed with stimulation of pedicle screws in patients undergoing instrumentation with pedicle screws as fixation elements. Results: The sample consisted of 85% females (mean age 17 years) and 37.5% of cases had classification type 1AN of Lenke. Of the total surgical cases, 60% had EMG changes. Of the total cases analyzed, 66.3% were true positives for the result. Conclusion: Intraoperative monitoring with EMG is a very important tool for the surgical treatment of patients with scoliosis undergoing instrumentation with pedicle screws. It enables to check if the screw is located on the correct path, helping to decrease the error rate and providing corrections to the surgical approach through a change of strategies. Moreover, it contributes to decrease the time to screw positioning and the total surgical time.

Selective dorsal rhizotomy: A multidisciplinary approach to treating spastic diplegia

Background:

Spasticity is a motor disorder that interferes with mobility and affects the quality of life. Different approaches have been utilized to address patients with spastic diplegia, among which is selective dorsal rhizotomy (SDR). Although SDR has been shown to be efficacious in treating spastic patients, many neurologists and neurosurgeons are not well aware of the procedure, its indications, and expected outcomes due to the limited number of centers performing this procedure.

Objectives:

The aim of this study is to describe the collaborative multidisciplinary approach between neurosurgeons, neurophysiologists, and physiotherapists in performing SDR. In addition, we delineate three illustrative cases in which SDR was performed in our patients.

Materials and Methods:

A retrospective review and analysis of the clinical records of our three patients who underwent SDR was conducted and reported. Patients’ outcomes were evaluated and compared to preoperative measurements based on clinical examination of power, tone (Ashworth scale), gait, and range of motion, as well as subjective functional assessment, gross motor function classification system, and gross motor function measure with follow-up at 6, 12, and 24 months postoperatively. A detailed description of our neurosurgical technique in performing SDR in collaboration with neurophysiology and physiotherapy monitoring is provided.

Results:

The three patients who underwent SDR using our multidisciplinary approach improved both functionally and objectively after the procedure. No intraoperative or postoperative complications were encountered. All patients were doing well over a long postoperative follow-up period.

Conclusion:

A multidisciplinary approach to treating spastic diplegia with SDR can provide good short-term and long-term outcomes in select patients suffering from spastic diplegia.

Monosegmental laminoplasty for selective dorsal rhizotomy--operative technique and influence on the development of scoliosis in ambulatory children with cerebral palsy

PURPOSE

Selective dorsal rhizotomy (SDR) reduces spasticity in children with cerebral palsy (CP) and is performed either through a lumbosacral multilevel laminectomy or a single-level laminectomy at the medullary conus. Spinal interventions generally involve the risk of subsequent instability depending on the extent of structural weakening. Destabilizing spasticity in CP might further increase this risk for both options. Laminoplasty is frequently applied to reduce instability through anatomical restoration, although the unavoidable interruption of interspinous ligaments might be a reason for inconsistent results. We report on a novel technique of laminoplasty, achieving complete restoration of the dorsal column.

METHODS

One hundred sixteen ambulatory children with gross motor function classification scale (GMFCS) level I to III were submitted to SDR through a single-level approach. The lamina was reinserted with a previously unreported technique of laminoplasty. Osseous reintegration of the excised lamina was supposed, if its spinous process was located in place on late follow-up radiographs. Scoliosis was described via Cobb's angle.

RESULTS

At a mean follow-up of 33 months, radiographs were available from 72 children with a mean age at surgery of 7.2 years. Sixty-two out of the 72 reinserted laminae were supposed to be vital and reintegrated. Seven children developed a predominantly mild scoliosis. No association was found between development of scoliosis and GMFCS level or age.

CONCLUSIONS

This novel laminoplasty technique provides the least invasive approach for SDR. The incidence of scoliosis after this single-level approach is comparable to the natural history of ambulatory CP children.

Infra-Conus Single-Level Laminectomy for Selective Dorsal Rhizotomy: Technical Advance

BACKGROUND/AIMS

Selective dorsal rhizotomy for spastic cerebral palsy is an effective and well-validated surgical approach. Multiple techniques have been described in the past including multiple laminectomies and a single-level laminectomy at the level of the conus. There is considerable technical challenge involved with a single-level laminectomy approach.

METHODS

We report here a modification of the single-level laminectomy that selectively analyzes each individual nerve root with electromyography to separate dorsal and ventral nerve roots through comparison of stimulus responses.

RESULTS

In 18 children with cerebral palsy who underwent this operation there was a mean improvement in the Modified Ashworth Scale of 2.0 with no reported incidence of muscle weakness, sensory loss, or neurogenic bladder.

CONCLUSION

This approach allows for a modification of selective dorsal rhizotomy through a single-level laminectomy and tailors the selection of nerve root sectioning to the individual patient of interest while still maintaining its effectiveness.

Neurosurgical Management of Childhood Spasticity: Functional Posterior Rhizotomy and Intrathecal Baclofen Infusion Therapy

A paradigm shift is currently ongoing in the treatment of spasticity in childhood in Japan. Functional posterior rhizotomy (FPR), which was first introduced to Japan in 1996, is best indicated for children with spastic cerebral palsy, regardless of the clinical severity of spasticity. Surgery is generally carried out in the cauda equina, where the posterior root is separated from the anterior one, and neurophysiological procedures are used to judge which nerve root/rootlet should be cut. The outcome of FPR is favorable for reducing spasticity in the long-term follow-up. Intrathecal baclofen (ITB) treatment for childhood spasticity was approved in 2007 in Japan and the number of children undergoing ITB pump implantation has been gradually increasing. ITB treatment is best indicated for children with severe spasticity, especially those with dystonia, regardless of the pathological background. Since it is a surgery performed to implant foreign bodies, special attention should be paid to avoid perioperative complications such as CSF leakage, meningitis, and mechanical failure. Severely disabled children with spasticity would benefit most from ITB treatment. We would especially like to emphasize the importance of a strategic approach to the treatment of childhood spasticity. The first step is to reduce spasticity by FPR, ITB, and botulinum toxin injection. The second step is to aim for functional improvement after controlling spasticity. Traditional orthopedic surgery and neuro-rehabilitation form the second step of treatment. The combination of these treatments that allows them to complement each other is the key to a successful treatment of childhood spasticity.

Keyhole interlaminar dorsal rhizotomy for spastic diplegia in cerebral palsy

BACKGROUND

The efficiency and safety of dorsal rhizotomies for cerebral palsy lie in the accuracy of radicular identification together with selectivity of root sectioning. Two different exposures are currently in use. The first is extended laminotomy/laminectomy from the upper lumbar level to the sacrum, which allows accurate identification of all L2-S2 roots/rootlets. The second is limited laminotomy exposing the conus/cauda equina at the thoracolumbar junction; this less invasive method limits accessibility to the roots. To optimize the accuracy and selectivity while minimizing invasiveness, the authors developed a tailored interlaminar procedure targeting the radicular levels involved in the harmful components of spasticity directly and individually.

METHODS

Six patients with spastic diplegia at different levels of the Gross Motor Functional Classification System were selected. In each patient, two to three interlaminar spaces, preselected according to planning, were enlarged in the "keyhole" fashion, respecting the spinous processes and interspinous ligaments. Ventral root stimulation identified the radicular level. Dorsal root stimulation evaluated its implication in the hyperactive segmental circuits, helping quantify the percentage of rootlets to be cut.

RESULTS

There were neither wound-related nor general complications. At 1 year of follow-up, X-ray examination did not reveal kyphosis or instability. In all children, the excess of spasticity was reduced. The Ashworth score decreased from 3.2 on average to 0.6 postoperatively (range: 2-4 to 0-2). Regarding the functional status at 1 year of follow-up for the three ambulatory children, the Gillette ability-to-walk score increased from 3/10 on average to 7.3/10 postoperatively (range: 2-4 to 7-8). For the three non-ambulatory children, abnormal postures, painful contractures and ease of care were much improved.

CONCLUSION

Keyhole interlaminar dorsal rhizotomy (KIDr) offers direct intradural access to each of the ventral/dorsal roots, thus maximizing the reliability of anatomical mapping and allowing individual physiological testing of all targeted roots. The interlaminar approach minimizes invasiveness by respecting the posterior spine structures.

Histological evidence of intraoperative monitoring efficacy in selective dorsal rhizotomy

PURPOSE

It has been advocated that intraoperative electrophysiological monitoring is mandatory in selective dorsal rhizotomy (SDR). However, it is still uncertain whether the monitoring procedure effectively differentiates dysfunctional rootlets. We histologically analyzed sectioned rootlets in SDR, in order to confirm the efficacy of the monitoring.

METHODS

Seven children with cerebral palsy underwent SDR on the same protocol. The pieces of their sectioned nerve rootlets from L5 were examined histologically using an electron microscope. In each patient, two nerve rootlets, one with the most abnormal response to intraoperative electrical stimulation and the other with the least abnormal response, were examined. The electron microscope findings of the rootlets were compared with the electromyography (EMG) findings in the intraoperative stimulation.

RESULTS

Among 14 examined nerve rootlets, definite abnormal EMG findings were seen in 5, which were 4 clonuses and one bilateral spread. All five rootlets with abnormal EMG findings showed axonal degenerations except one case, whose finding was dysmyelination. On the contrary, in the nine rootlets with normal EMG findings, eight rootlets had histologically minimum changes limited to the myelin sheath and one rootlet had dysmyelination without axonal degeneration.

CONCLUSIONS

The nerve rootlets with abnormal EMG findings in the intraoperative stimulation have definite histological abnormalities. This indicates that intraoperative monitoring is a meaningful method for identifying the nerve rootlets to be sectioned. This finding should be reminded as a precaution when considering nonselective dorsal rhizotomy, especially, for children who are expected to stand up after the surgery.

Peripheral sensory neuropathy observed in children with cerebral palsy: is chronic afferent excitation from muscle spindles a possible cause?

INTRODUCTION

Peripheral sensory neuropathy is known to be associated with several medical conditions; however, it has not been reported in patients with cerebral palsy. Authors have observed pathological changes in the sensory nerve rootlets taken during selective dorsal rhizotomy. This paper reports a possible novel cause of peripheral sensory neuropathy: the chronic afferent excitations from muscle spindles.

CASE REPORT

Sensory nerve rootlets on L5 were taken for histological evaluation from two children with cerebral palsy during selective dorsal rhizotomy, performed for their leg spasticities. Rootlets with clonus reaction against intraoperative electrical stimulation show dysmyelination, and in one child, axonal degeneration can also be observed. Rootlets with normal reaction have only minimum changes on their myelin sheath.

CONCLUSION

As cerebral palsy is a typical upper motor neuron disorder, peripheral sensory neuropathy is unexplained. Since observed neuropathy is mainly on the myelin sheath, the etiology is considered to be the chronic overload of afferent impulses from muscle spindles in the spastic muscle.

Comparação entre o teste de despertar e a monitoração neurofisiológica intra-operatória com potencial evocado somato-sensitivo nas cirurgias de escoliose

OBJETIVO: comparar a incidência de lesões neurológicas em cirurgias corretivas de curvas rígidas de escoliose idiopática, utilizando-se somente o teste do despertar e utilizando-se a monitoração neurofisiológica intra-operatória por meio dos Potenciais Evocados Somato-Sensitivo (PESS). MÉTODOS: foram realizadas 111 cirurgias para correção de escoliose idiopática, com curvas rígidas por meio de instrumentação e artrodese pela via posterior, no período de janeiro de 1985 a maio de 2001. Os procedimentos foram divididos em dois grupos, sendo 80 pacientes operados sem a monitoração intra-operatória, utilizando somente o teste do despertar, no período de janeiro de 1985 a janeiro de 1998. A partir de maio de 1998, as cirurgias passaram a ser monitoradas com potencial evocado somato-sensitivo (PESS), para prevenção de lesão neurológica, formando um segundo grupo de 31 pacientes. RESULTADOS: no primeiro grupo, um paciente teve lesão neurológica irreversível e quatro pacientes tiveram lesão neurológica reversível. Entre os 31 pacientes do segundo grupo, com monitoração neurofisiológica sensitiva durante a cirurgia, oito apresentaram lesão neurológica reversível constatada no intra-operatório, sem nenhuma repercussão clínica após o procedimento. CONCLUSÃO: os resultados apresentados sugerem a eficácia da monitoração intra-operatória, com o potencial evocado somato-sensitivo, para a prevenção de lesões neurológicas, nas cirurgias corretivas de curvas rígidas na escoliose idiopática.

Prevention of brisk hyperactive response during selective dorsal rhizotomy in children with spasticity: isoflurane versus sevoflurane maintenance anesthesia

In children with spasticity, deep tendon reflexes are hyperactive and even stimulation of normal dorsal rootlets can produce exaggerated full-strength, single-twitch responses in the muscles they innervate. This phenomenon is called the brisk hyperactive response (BHR). The aim of this study was to compare the efficacy of 2 volatile anesthetics, isoflurane and sevoflurane, for suppressing the confounding effect of BHR during selective dorsal rhizotomy (SDR) in children with spasticity. The subjects were 54 consecutive children of American Society of Anesthesiology physical status III who were scheduled for SDR. After tracheal intubation, each child was randomly assigned to Group I (isoflurane; n=27) or Group S (sevoflurane; n=27). There was no significant difference between the mean operation times in Groups I and S (200+/-40 vs. 220+/-35 minutes, respectively; p=0.0559). Thirteen patients in Group I (48.1%) and 5 in Group S (18.5%) exhibited BHR during stimulation of the dorsal rootlets (odds ratio 4.086; p=0.0418). Three of these 18 patients (2 in Group I and 1 in Group S) experienced hypertension and tachycardia simultaneously with BHR (odds ratio 4.086; p=1.0). The results suggest that sevoflurane is more effective at preventing BHR and might be a better choice for anesthetic management of children with spasticity undergoing SDR.

Comprehensive short-term outcome assessment of selective dorsal rhizotomy

This study retrospectively evaluated the safety and efficacy of selective dorsal rhizotomy (SDR) in participants who underwent a rigorous selection process, uniform surgical procedure, and a standardized postoperative rehabilitation process. Outcome measures assessed were the Ashworth scale for spasticity, the Gillette Gait Index (GGI) for overall gait pathology, oxygen cost for gait efficiency, and the Gillette Functional Assessment Questionnaire (functional walking ability scale; [FAQ]) for functional mobility. Outcomes were evaluated for 136 children (81 males, 55 females; mean age 7y 3mo [SD 2y 1mo], range 3y 5mo-18y 9mo) for an average of 18.3 months (SD 4.4mo) postoperatively. All participants had a diagnosis of cerebral palsy (CP): 10 quadriplegia, 19 triplegia, and 107 diplegia. Preoperative Gross Motor Function Classification System levels were: Level I n=6; Level II n=64; Level III n=59, and Level IV n=7. All outcome measures improved for the group as a whole. Spasticity improved with 66 to 92% of possible gain in Ashworth scores; GGI was 7.5 times more likely to have a good as opposed to a poor outcome; energy efficiency improved in over half of the participants, and the FAQ demonstrated a statistically significant improvement of 0.9 levels (p<0.001). The rate of complications was low, with peri- and postoperative complications resolved by time of discharge.

Does ketamine affect intraoperative electrophysiological monitoring in children undergoing selective posterior rhizotomy?

OBJECTIVE

Direct dorsal rootlet stimulation with intraoperative electrophysiological monitoring is an adjunct to clinical evaluation during selective posterior rhizotomy. The purpose of this study was to evaluate the impact of ketamine on intraoperative electrophysiological monitoring during selective posterior rhizotomy. Specifically, we sought to determine if low dose ketamine given as part of the anesthesia was associated with changes in intraoperative electrophysiological monitoring in patients who underwent selective posterior rhizotomy.

METHODS

A retrospective cohort study was conducted using anesthetic records and electrophysiological records of 32 children who had intraoperative electrophysiological monitoring during selective posterior rhizotomy under general anesthesia. Administration and dosage of ketamine preceding the stimulation of dorsal roots was determined from the anesthetic record. A pediatric neurologist, blinded to patient, and to ketamine exposure, evaluated different electrophysiological criteria.

RESULTS

Eight children received ketamine and 24 did not receive it. The mean average dose of ketamine was 0.18 mg x kg(-1) (sd: 0.04). We did not find any statistically significant difference in intraoperative electrophysiological response between the ketamine and the control groups. However, we noted some trends: Administration of ketamine preceding the stimulation of dorsal roots was associated with a lower maximal threshold (2.7 mA vs 3.5 mA, P = 0.663) and root thresholds compared with children who did not receive ketamine. In addition, the train response following delivery of the suprastimulation tended to last longer with the presence of ketamine.

CONCLUSIONS

Administration of low dose ketamine preceding the stimulation of dorsal roots during selective posterior rhizotomy might be associated with lower maximal thresholds and a more sustained train response following stimulation. Physicians should be aware of this finding in order to avoid misinterpreting intraoperative electrophysiological monitoring.

Functional posterior rhizotomy: the Tokyo experience

PURPOSE

The author describes the history of functional posterior rhizotomy (FPR), the surgical procedure currently used, and the results together with its future perspective in Japan. The modern form of FPR was introduced to Japan in 1995, and the first surgery was carried out in 1996. Despite initial resistance from orthopedic surgeons, the procedure has eventually gained wide recognition in the country.

MATERIALS AND METHODS

The author has operated on 98 patients (60 boys and 38 girls, aged from 2 to 19 years old) by the end of 2006. Most patients were mild to severely disabled children with spastic hypertonia because of cerebral palsy and other diseases. The surgical procedure used is based on the Peacock's procedure with some modification for the mildly disabled children whose spasticity was predominantly the muscles of the ankle joint. Intraoperative neurophysiology was an indispensable tool for preserving urogenital function and for judging which root/rootlet to be cut.

RESULTS

Seventeen to 83% of the root/rootlets were found to be abnormal and were cut, clearly correlating with the degree of disability. However, there was a wide difference in the cutting rate, even in children with the same degree of disability. The result of surgery in this group of patients was the same as in previously published data. Twenty out of 51 patients (39%) followed for more than a year at the current institute showed improved locomotion after FPR. Thirty patients (59%) demonstrated suprasegmental effects after FPR.

CONCLUSION

The role of FPR will grow in importance as a treatment for spasticity in Japan in the future.

Selective dorsal rhizotomies in the treatment of spasticity related to cerebral palsy

RATIONALE

Selective dorsal rhizotomy (SDR) is a surgical technique developed over the past decades to manage patients diagnosed with cerebral palsy suffering from spastic diplegia. It involves selectively lesioning sensory rootlets in an effort to maintain a balance between elimination of spasticity and preservation of function. Several recent long-term outcome studies have been published. In addition, shorter follow-up randomized controlled studies have compared the outcome of patients having undergone physiotherapy alone with those that received physiotherapy after selective dorsal rhizotomy.

MATERIALS AND METHODS

In this account, we will discuss the rationale and outcome after SDR. The outcome is addressed in terms of the gross motor function measurement scale (GMFM), degree of elimination of spasticity, strength enhancement, range of motion, fine motor skills, activity of daily living, spastic hip, necessity for postoperative orthopedic procedures, bladder and sphincteric function, and finally possible early or late complications associated with the procedure.

CONCLUSION

We conclude that SDR is a safe procedure, which offers durable and significant functional gains to properly selected children with spasticity related to cerebral palsy.

Spinal deformities following selective dorsal rhizotomy

OBJECT

Selective dorsal rhizotomy (SDR) has been shown to provide considerable benefit to children with spastic cerebral palsy (CP). The authors sought to evaluate the risks of postoperative spinal deformities in patients following SDR.

METHODS

All patients who underwent SDR at McGill University between 1991 and 2001 were identified. Hospital charts and radiographic spinal studies (both preoperative and the latest postoperative) were systematically reviewed. Univariate and multivariate regression analyses were conducted to test all independent variables of potential interest to determine risk factors more likely to be associated with spinal deformity. There were 98 patients whose mean age at surgery was 5.1 years; the mean radiographic follow-up duration was 5.8 years. Thirty-nine (44.8%) of 87 patients in whom postoperative weight-bearing radiographs were obtained had mild scoliosis, and 17 in whom standing radiographs were acquired had hyperlordosis. In all, 18 of 94 patients (19.1%) who had postoperative radiographs on which the lumbosacral junction was visible were found to have spondylolisthesis. Regression analysis identified the severity of preoperative CP as an important predictor, and less ambulatory patients were more likely to have scoliotic curves. Younger age at surgery and male sex were factors associated with a lower rate of hyperlordosis. Spondylolisthesis developed only in ambulatory children. None of the patients experienced clinically significant deficits.

CONCLUSIONS

There was a high rate of radiologically documented deformities in patients with CP who underwent SDR. Ambulatory function, CP severity, age at surgery, and sex may be contributing factors.

Functional performance following selective posterior rhizotomy: long-term results determined using a validated evaluative measure

Object. Selective posterior rhizotomy (SPR) may result in considerable benefit for children with spastic cerebral palsy. To date, however, there have been few studies in which validated functional outcome measures have been used to report surgical results beyond 3 years. The authors analyzed data obtained from the McGill Rhizotomy Database to determine long-term functional performance outcomes in patients who underwent lumbosacral dorsal rhizotomy performed using intraoperative electrophysiological monitoring.

Methods. The study population was composed of children with debilitating spasticity who underwent SPR and were evaluated by a multidisciplinary team preoperatively and at 6 months and 1 year postoperatively. Quantitative standardized assessments of activities of daily living (ADL) were obtained using the Pediatric Evaluation of Disability Inventory (PEDI). Of 57 patients who met the entry criteria for the study, 41 completed the 3-year assessments and 30 completed the 5-year assessments.

Statistical analysis demonstrated significant improvement in the mobility and self-care domains of the functional skills dimension at 1 year after SPR. The preoperative and 1-, 3-, and 5-year postoperative scaled scores for the mobility domain were 56, 64, 77.2, and 77.8, respectively. The scaled score for the self-care domain increased from 59 presurgery to 67.9, 81.6, and 82.4 at the 1-, 3-, and 5-year postoperative assessments, respectively.

Conclusions. The results of this study support the presence of significant improvements in functional performance, based on PEDI scores obtained 1 year after SPR. The improvements persisted at the 3- and 5-year follow-up examinations. The authors conclude that SPR performed using intraoperative stimulation is valuable in the augmentation of motor function and self-care skills essential to the performance of ADL.

Long-term functional outcome after selective posterior rhizotomy

OBJECT

Selective posterior rhizotomy (SPR) is a well-recognized treatment for children with spastic cerebral palsy (CP). Few investigators have used quantitative outcome measures to assess the surgical results beyond 3 years. The authors analyzed data obtained from the McGill Rhizotomy Database to determine the long-term functional outcome of children who had undergone selective dorsal rhizotomy accompanied by intraoperative electrophysiological monitoring.

METHODS

The study population was composed of children with spastic CP who underwent SPR and were evaluated by a multidisciplinary team preoperatively, and at 6 months and 1 year postoperatively. Quantitative standardized assessments of lower-limb spasticity, passive range of motion, muscle strength, and ambulatory function were obtained. Of the 93 patients who met the entry criteria for the study, 71 completed the 3-year and 50 completed the 5-year assessments, respectively. Statistical analysis demonstrated significant improvements in spasticity, range of motion, and functional muscle strength at 1 year after SPR. The preoperative, 1-, 3-, and 5-year values for the global score of the Gross Motor Function Measure were 64.6, 70.8, 80, and 85.6, respectively. The greatest improvement occurred in the dimensions reflecting lower-extremity motor function, where the mean change was 10.1% at 1 year, 19.9% at 3 years, and 34.4% at the 5-year follow-up review in comparison with the baseline value. This was associated with a lasting improvement in alignment and postural stability during developmental positions, as well as increased ability to perform difficult transitional movements.

CONCLUSIONS

The results of this study support the presence of significant improvements in lower-limb functional motor outcome 1 year after SPR, and the improvements persist at 3 and 5 years. The authors conclude that SPR in conjunction with intraoperative stimulation is valuable for permanently alleviating lower-limb spasticity while augmenting motor function.

Intraoperative neuromonitoring

BACKGROUND

Intraoperative neuromonitoring (IONM) has been a valuable part of surgical procedures for over 25 years. Insight into the nervous system during surgery provides critical information to the surgeon allowing reversal or avoidance of neural insults.

REVIEW SUMMARY

Electrophysiological tests including electroencephalography, electromyography, and multiple types of evoked potentials (somatosensory, auditory, and motor) are monitored during surgeries that involve risk to the nervous system. Deterioration of signals suggests a surgical insult and is associated with an increased risk of postoperative deficit. Intraoperative identification of this risk allows corrective action. In addition, IONM teams make use of their armamentarium of tests to evaluate anatomy or function of the nervous system in response to specific questions posed by the surgical team.

CONCLUSIONS

Intraoperative recordings are now a routine part of many surgical procedures. Their correct application leads to improved surgical outcome.