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

Single-level laminoplasty approach to selective dorsal rhizotomy with conus localization by rapid spine MRI

INTRODUCTION

While selective dorsal rhizotomy (SDR) was originally described as a multilevel approach, single-level approaches are now popularized. Conus localization is beneficial for operative planning in single-level selective dorsal rhizotomy. Our approach to SDR involves minimal exposure for a single-level laminoplasty, preserving one attached interspinous ligament. Pre-operative conus localization is required for this tailored approach to determine the laminoplasty level and dictate rostral or caudal division of the superior spinus ligament. While rapid MRI sequences have been popularized for pediatric cranial imaging, its utility for spinal imagining is less well-described, and specific application for conus localization has not been reported.

OBJECTIVE

Illustrate that rapid MRI without sedation is sufficient to identify conus level for tailored single-level laminoplasty SDR.

MATERIAL AND METHODS

Patients undergoing SDR from 2014 to 2022 at one institution were reviewed for type of pre-operative MRI (rapid vs full), conus level, procedural time for MRI, and radiology report. The typical rapid MRI has four sequences utilizing single-shot technique (scout, sagittal T2, axial T2, and axial T1) that typically take less than 1 min each of acquisition time, with non-single-shot sequences added periodically in cooperative patients. To include time for patient positioning, pre-scan shimming, procedural incidentals, and other patient-specific variations, MRI procedure length was recorded as documented in the electronic medical record.

RESULTS

N = 100 patients had documentation of an MRI for pre-operative imaging. Seventy-nine of these had a rapid MRI, and 21 required a full MRI with anesthesia for their treatment plan. Mean total procedure time for rapid MRI was 21.5 min (median 17). Mean procedure time for MRI under general anesthesia was 91.2 min (median 94). Of patients with rapid MRI imaging, 2/79 had an ambiguous conus level (1 from motion artifact, 1 from spinal hardware) vs 1/21 with a full MRI under anesthesia (due to spinal hardware).

CONCLUSION

Rapid spinal MRI without sedation can be used for conus localization in a pediatric population. This may be routinely used as pre-operative imaging for a single-level approach to selective dorsal rhizotomy, without sedation or intubation procedures.

Modified Selective Dorsal Rhizotomy Exposure Method for Adults With Spastic Paralysis of the Lower Limbs

BACKGROUND AND OBJECTIVES

Spinal deformities are a common complication after selective dorsal rhizotomy (SDR). In this article, we introduce a more minimally invasive SDR procedure in adult patients with spastic paralysis of the lower limbs.

METHODS

In this retrospective analysis of SDR in 8 adult patients with spastic paralysis of the lower limbs, a modified exposure method was used during the surgery. Only the lower part of the L1 spinous process, upper part of the L2 spinous process, and part of the lamina were resected through L1-2 interlaminar approaches. The motor and sensory roots were found to be completely dependent on electrophysiological monitoring. The sensory roots of the target muscle groups were partially transected. All patients were followed up for 2-4 years. The degree of lower extremity spasm was assessed using the Gross Motor Function Classification Scale, Ashworth grading, Gross Motor Function Measure-66, joint range of motion, and electromyography analysis.

RESULTS

All 8 patients were successfully operated with the help of intraoperative electrophysiological monitoring. The Ashworth score of the target muscles, Gross Motor Function Measure-66 score, and range of motion of the joints improved significantly after surgery. Two patients achieved cross-grade improvement in their Gross Motor Function Classification Scale scores. No persistent incision pain or spinal deformities were observed during follow-up.

CONCLUSION

The interspinous process approach provides sufficient surgical space and reduced the damage to the bone structure of the spine. The electrophysiological monitoring protocol is suitable for adult patients with lower extremity spasm.

Neuromodulation Therapies for Spasticity Control: Now and Beyond

Spasticity is a major cause of disability following upper motor neuron (UMN) injury. The diagnosis and treatment of spasticity has been a focus of clinicians and researchers alike. In recent years, there have been significant advances both in strategies for spasticity assessment and in the development of novel treatments. Currently, several well-established spasticity management techniques fall into the major categories of physiotherapy, pharmacotherapy, and surgical management. The majority of recent developments in all of these broad categories have focused more on methods of neuromodulation instead of simple symptomatic treatment, attempting to address the underlying cause of spasticity more directly. The following narrative review briefly discusses the causes and clinical assessment of spasticity and also details the wide variety of current and developing treatment approaches for this often-debilitating condition.

Conus-level combined dorsal and ventral lumbar rhizotomy for treatment of mixed hypertonia: technical note and complications

Combined dorsal and ventral rhizotomy is an effective treatment for patients with concurrent spasticity and dystonia, with the preponderance of complaints relating to their lower extremities. This operative approach provides definitive relief of hypertonia and should be considered after less-invasive techniques have been exhausted. Previously, the surgery has been described through an L1-S1 laminoplasty. In this series, 7 patients underwent a conus-level laminectomy for performing a lumbar dorsal and ventral rhizotomy. Technical challenges included identifying the appropriate-level ventral roots and performing the procedure in children with significant scoliosis. Techniques are described to overcome these obstacles. The technique was found to be safe, with no infections, CSF leaks, or neurogenic bladders.

The selective dorsal rhizotomy technique for spasticity in 2020: a review

This review looks at the advances in the surgical technique, selective dorsal rhizotomy, used for the management of spasticity in children.

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.

The progress in the treatment of spastic cerebral palsy with selective dorsal rhizotomy (SDR)

Spasticity is the main disabling clinical manifestation of children with cerebral palsy (CP). Selective dorsal rhizotomy (SDR) has been performed for the treatment of spastic CP in Asia for quite some time from 1990. The purpose of this review is to discuss the historical origin and development of SDR. Our goal here is to identify the current patient selection criteria for SDR and to point out indications and contraindications based on the patients with CP, age from 2 to 18 years-old, over 6000 cases, who received SDR surgery with spasticity of muscle tension more than 3 degrees in our center. We also discuss evidence-based approaches on how to evaluate postoperative patient outcomes of SDR and how complications can be avoided. Finally, we mention progress made in terms of SDR technical advances and how improvements can be made in the future. In conclusion, SDR surgery is a reliable way to improve outcomes of patients with spastic CP and can be done carefully in patients as long as stringent selection criteria are used. However, more research and technological advancements are needed to help address associated complications.

Selective dorsal rhizotomy: an illustrated review of operative techniques

OBJECTIVE

Selective dorsal rhizotomy (SDR) is a procedure primarily performed to improve function in a subset of children with limitations related to spasticity. There is substantial variability in operative techniques among centers and surgeons. Here, the authors provide a technical review of operative approaches for SDR.

METHODS

Ovid MEDLINE, Embase, and PubMed databases were queried in accordance with PRISMA guidelines. All studies included described a novel surgical technique. The technical nuances of each approach were extracted, including extent of exposure, bone removal, and selection of appropriate nerve roots. The operative approach preferred at the authors' institution (the "2 × 3 exposure") is also detailed.

RESULTS

Five full-text papers were identified from a total of 380 articles. Operative approaches to SDR varied significantly with regard to level of exposure, extent of laminectomy, and identification of nerve roots. The largest exposure involved a multilevel laminectomy, while the smallest exposure involved a keyhole interlaminar approach. At the Hospital for Sick Children, the authors utilize a two-level laminoplasty at the level of the conus medullaris. The benefits and disadvantages of the spectrum of techniques are discussed, and illustrative figures are provided.

CONCLUSIONS

Surgical approaches to SDR vary considerably and are detailed and illustrated in this review as a guide for neurosurgeons. Future studies should address the long-term impact of these techniques on functional outcomes and complications such as spinal deformity.

Electrophysiology of Sensory and Motor Nerve Root Fibers in Selective Dorsal Rhizotomies

AIMS

Spasticity remains a major impediment in the treatment of cerebral palsy (CP). The single-level selective dorsal rhizotomy (SDR) is a minimally invasive intervention that reduces spasticity in select patients. We provide a descriptive set of normative data that practitioners can utilize to help guide the single-level SDR procedure, including (1) physiological threshold values used to dissociate ventral from dorsal roots; (2) response characteristics of muscles; (3) descriptions of abnormal physiological responses; and (4) percentage of rootlets transected during surgery.

METHODS

We examined data from 38 patients with CP who underwent SDR. Dorsal and ventral roots were classified based on the amplitude of electromyographic (EMG) responses, number of muscles activated, and abnormal response characteristics.

RESULTS

Ventral roots activated more muscles at significantly lower stimulus thresholds and demonstrated larger EMG responses than did dorsal roots. Of the transections made, 64.72 ± 1.69% of each rootlet was transected. Ventral and dorsal roots can be readily separated based on a few key physiological characteristics including response thresholds and the spread of muscle activation. It was observed that a threshold of approximately 0.4 mA could be used to dissociate ventral and dorsal roots during surgery.

CONCLUSIONS

These data illustrate the range of physiological variance observed while performing SDR in patients with spastic CP. Notably, we encountered outlier patients whose roots demonstrated aberrant response characteristics and displayed uncharacteristically low dorsal root thresholds or abnormally high ventral root thresholds. Practitioners should be prepared to individualize their threshold criteria and customize treatment on a patient-by-patient basis.

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?

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.

Feasibility and effectiveness of a newly modified protocol-guided selective dorsal rhizotomy via single-level approach to treat spastic hemiplegia in pediatric cases with cerebral palsy

PURPOSE

It still remains challenging to treat CP cases with spastic hemiplegia using SDR via a single-level approach when guided by the traditional EMG response grading system. Our aim was to assess the feasibility and effectiveness of a newly modified protocol-guided single-level laminectomy SDR to treat such pediatric patients.

METHODS

A retrospective cohort review was conducted in the CP cases with spastic hemiplegia undergone our newly modified protocol-guided single-level approach SDR since May 2016 to October 2017, and followed by intensive rehabilitation program for at least 12 months in both Shanghai Children's Hospital and Shanghai Rehabilitation and Vocational Training Center for the Disabled. Inclusion and exclusion criteria were set for the selection of patients in the current study. Our study focused on the setup, EMG recording interpretation, and outcome measures for this newly modified rhizotomy scheme.

RESULTS

Eleven cases were included in the current study. Based on our new rhizotomy protocol, a total of 34 rootlets over our 11 cases were cut (2 in 4, 3 in 4, 4 in 1, and 5 rootlets in 2 cases, respectively). After SDR and the following rehabilitation program at a mean duration of 19 months, muscle tone of those "target muscles" in affected lower extremities which identified during pre-op assessment decreased by a mean of 1.4 degrees (Modified Ashworth Scale) in our cases. Strength of those target muscles and ROM of joints involved in their lower limbs were reported to have improved significantly as well. All cases showed major progress with regard to their motor function. A mean of about 10-point increase of GMFM-66 score was reported, and five of six cases who were with GMFCS level II preoperatively improved their GMFCS level at the last assessment. Kinematics of joints of hip, knee, and ankle on the affected side in our cases demonstrated a major correction, along with improvement of their foot pressure patterns to the ground during their gait cycles. Surgery-related complications, such as cerebral-spinal fluid leak/infection, long-term hypoesthesia, or urinary/bowel incontinence were not recorded in the current study.

CONCLUSION

Single-level SDR when guided by our simplified rhizotomy protocol is feasible and effective to treat pediatric CP cases with spastic hemiplegia.