Frequency distribution in intraoperative stimulation-evoked EMG responses during selective dorsal rhizotomy in children with cerebral palsy-part 1: clinical setting and neurophysiological procedure

Comparison of EMG Waveforms versus Degree of Spread in Selective Dorsal Rhizotomy

Selective dorsal rhizotomy (SDR) is a treatment for lower-extremity spasticity in disorders such as cerebral palsy (CP). "Selective" refers to sectioning nerve rootlets with the most abnormal responses on electromyography (EMG) upon intraoperative stimulation. EMG abnormalities can be classified by waveform appearance or by degree of spread throughout lower extremity muscles. We examine the relationship between different EMG waveforms and grades of spread. Intraoperative SDR EMG records from November 2009 through December 2021 were analyzed for waveform types and degrees of spread. Irregular, incremental, multiphasic, sustained, and clonic waveform patterns were considered more abnormal. Decremental, squared decremental, and squared waveforms were less abnormal. Degrees of spread were graded 0-4+, 4+ signifying the most abnormal spread. Distribution of grades of spread was compared between waveform patterns using pairwise Cochran-Armitage tests with Holm-Bonferroni correction. We hypothesized that more abnormal EMG waveform patterns would correlate with higher grades of spread. Sixty-three patients were included, with an average age of 8 years. Most had cerebral palsy (86%, n = 54). The remainder had brain malformations (8%, n = 5) and other etiologies (6%, n = 4). Higher grades of spread significantly increased the likelihood of multiphasic, sustained, or clonic patterns, compared to decremental, irregular, and squared patterns (p < .05). Squared waveforms decreased with higher grades of spread relative to other patterns (p < .05). Different EMG waveform patterns are associated with varying grades of spread in SDR, suggesting that evaluating both waveform pattern and degree of spread together can be useful in guiding rootlet sectioning.

Postoperative outcomes and stimulation responses for sectioned nerve roots during selective dorsal rhizotomy in cerebral palsy

BACKGROUND

Cerebral palsy (CP) is the most cause of motor dysfunction in children. Selective dorsal rhizotomy (SDR) plays a major role in long term spasticity control. However, limited data exists on the effect of SDR on postoperative spasticity treatment requirements and supraspinal effects, and the stimulation responses of dorsal nerve roots in those with CP.

METHODS

The current study included the outcome for 35 individuals undergoing SDR for motor functional outcome, spasticity, baclofen dose changes, botulinum toxin injection frequency, and spasticity related orthopedic procedures. We also report on the stimulation responses in 112 individuals who underwent SDR at our institution.

RESULTS

There was a significant difference in gross motor function measures (GMFM)-66 scores at last follow up that remained present when considering only ambulatory children but not with non-ambulatory children. Ashworth scores were significantly decreased for both upper and lower extremities after SDR at all follow up points. There was a significant decrease in Baclofen dose and botulinum toxin injections requirements after SDR, but no significant difference in the need for orthopedic intervention. A total of 5502 dorsal nerve roots were tested showing a decrease in stimulation intensity and increase in grade on the right side and for descending lumbosacral levels.

CONCLUSIONS

SDR improves gross motor scores during short term follow up but has additional benefits in decreasing baclofen dosing and botulinum toxin injections requirements after surgery. They stimulation responses of sectioned dorsal nerve roots adds to the limited available data and our understanding of the pathological changes that occur in CP.

Selective dorsal rhizotomy: Analysis of two rootlet sectioning techniques

OBJECTIVE

To analyze and compare the efficacy of two selective dorsal rhizotomy (SDR) techniques with intraoperative neurophysiological monitoring, using instrumented three-dimensional gait analysis.

INTRODUCTION

SDR is a common, irreversible surgical treatment increasingly used to address gait disturbances in children with chronic non-progressive encephalopathy by reducing spasticity. Various techniques have been used, which mainly differ in the percentage of rootlets selected for sectioning. A greater proportion of rootlets sectioned leads to a more effective reduction of spasticity; however, there is a potential risk of unwanted neurological effects resulting from excessive deafferentation. While there is evidence of the short- and long-term benefits and complications of SDR, no studies have compared the effectiveness of each technique regarding gait function and preservation of the force-generating capacity of the muscles.

MATERIALS AND METHODS

Instrumented three-dimensional gait analysis was used to evaluate two groups of patients with spastic cerebral palsy treated by the same neurosurgeon in different time periods, initially using a classic technique (cutting 50% of the nerve rootlets) and subsequently a conservative technique (cutting no more than 33% the nerve rootlets).

RESULTS

In addition to an increase in knee joint range of motion (ROM), in children who underwent SDR with the conservative technique, a statistically significant increase (p = 0.04) in the net joint power developed by the ankle was observed. Patients who underwent SDR with the conservative technique developed a maximum net ankle joint power of 1.37 ± 0.61 (unit: W/BW), whereas those who were operated with the classic technique developed a maximum net ankle joint power of 0.98 ± 0.18 (unit: W/BW). The conservative group not only showed greater improvement in net ankle joint power but also demonstrated more significant enhancements in minimum knee flexion during the stance phase and knee extension at initial contact.

CONCLUSION

Our results show that both techniques led to a reduction in spasticity with a positive impact on the gait pattern. In addition, patients treated with the conservative technique were able to develop greater net ankle joint power, leading to a better scenario for rehabilitation and subsequent gait.

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.

Clinical Relevance of State-of-the-Art Analysis of Surface Electromyography in Cerebral Palsy

Surface electromyography (sEMG) can be used to assess the integrity of the neuromuscular system and its impairment in neurological disorders. Here we will consider several issues related to the current clinical applications, difficulties and limited usage of sEMG for the assessment and rehabilitation of children with cerebral palsy. The uniqueness of this methodology is that it can determine hyperactivity or inactivity of selected muscles, which cannot be assessed by other methods. In addition, it can assist for intervention or muscle/tendon surgery acts, and it can evaluate integrated functioning of the nervous system based on multi-muscle sEMG recordings and assess motor pool activation. The latter aspect is especially important for understanding impairments of the mechanisms of neural controllers rather than malfunction of individual muscles. Although sEMG study is an important tool in both clinical research and neurorehabilitation, the results of a survey on the clinical relevance of sEMG in a typical department of pediatric rehabilitation highlighted its limited clinical usage. We believe that this is due to limited knowledge of the sEMG and its neuromuscular underpinnings by many physiotherapists, as a result of lack of emphasis on this important methodology in the courses taught in physical therapy schools. The lack of reference databases or benchmarking software for sEMG analysis may also contribute to the limited clinical usage. Despite the existence of educational and technical barriers to a widespread use of, sEMG does provide important tools for planning and assessment of rehabilitation treatments for children with cerebral palsy.