Before selective dorsal rhizotomy can be judged as beneficial for cerebral palsy, long-term results and controlled studies are needed

We read with interest Wang et al.’s article about a retrospective study of 143 pediatric patients with cerebral palsy who underwent selective dorsal rhizotomy (SDR) between July 2019, and November 2022 and were examined pre- and post-operatively (1). It was found that SDR significantly reduced the muscle tone of the lower limb muscle groups, the range of motion of the joints in the lower limbs and the transmalleolar angle (TMA) increased after surgery, and the preoperative internal tibial torsion before SDR decreased and changed to a normal angle post-operatively in 21% of limbs (1). Improvement with SDR was observed particularly in younger patients with low muscle tone in the hamstring muscles (1). It was concluded that SDR has the potential to increase TMA in cerebral palsy patients and that anterior tibial torsion improves after SDR especially when patients are young and have low muscle tone in the hamstring muscles (1). The study is excellent but some points need discussion.

The first point is that SDR cuts not only Ia and Ib fibers, which originate from the muscle spindles and the Golgi organs of the tendons, but also type II and type III fibers, which carry centripetal information from the cutaneous mechanoreceptors, the free nerve endings of touch and pressure, from nociceptors, and from thermoreceptors. It is therefore, to be expected that not only will muscle tone changes as a result of SDR, but new sensory disturbances will also occur. Therefore, we should know how many of the included patients complained of sensory deficits including hypoalgesia or hyperalgesia, dysesthesia, allodynia, hypoesthesia or hyperesthesia, paresthesia, and hypothermia or hyperthermia. Since SDR can also cut fibers that are responsible for transmitting deep sensation, it can also lead to pallhypesthesia or a disturbed sense of position.

A second point is that spasticity can be complicated by tight contractures of the hip, knee, or ankle. We should therefore know how many of the 148 patients included suffered from contractures. In particular, an explanation should be provided how the joint range of motion in the lower limbs increased after surgery in patients with contractures, how the TMA could increase after SDR, and how internal tibial torsion before SDR could change to a normal angle in 21% of limbs postoperatively (1).

A third point is that no long-term follow-up results have been presented (1). In contrast to the positive effects of SDR reported in the index study (1), there are also reports that showed no positive effects of SDR on functionality (2). In a comparative study of joint-level kinematics in patients with cerebral palsy undergoing SDR and patients receiving only minimal spasticity management, no meaningful differences in pelvic, hip, knee, or ankle kinematic variable changes were documented in either group (2). Therefore, it was concluded that aggressive spasticity treatment by SDR does not result in significant differences in gait kinematics in individuals with cerebral palsy in young adulthood compared to minimal spasticity treatment (2). However, the results of SDR may differ between ambulatory and nonambulatory patients (3). It is also conceivable that unsupervised machine learning methods can effectively and accurately classify patients into different subgroups suffering from cerebral palsy based on preoperative characteristics, and improve outcome after SDR through better selection (4).

In summary, the excellent study has limitations that should be addressed before final conclusions are drawn. Clarifying the weaknesses would strengthen the conclusions and improve the study. Before SDR can be judged to be beneficial at symptomatic and functional levels in patients with cerebral palsy, long-term outcome results and appropriately designed controlled trials are needed.

Acknowledgments

Funding: None.

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Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://tp.amegroups.com/article/view/10.21037/tp-24-63/coif). The authors have no conflicts of interest to declare.

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References

1. Wang R, Jiang W, Wei M, et al. Short-term change of tibial torsion in children with spastic cerebral palsy after selective dorsal rhizotomy. Transl Pediatr 2023;12:2131-41. [Crossref] [PubMed]
2. McMulkin ML, MacWilliams BA, Nelson EA, et al. The long-term effects of aggressive spasticity reducing treatment, including selective dorsal rhizotomy, on joint kinematic outcomes of persons with cerebral palsy. Gait Posture 2023;105:139-48. [Crossref] [PubMed]
3. Gillespie CS, Hall BJ, George AM, et al. Selective dorsal rhizotomy in non-ambulant children with cerebral palsy: a multi-center prospective study. Childs Nerv Syst 2024;40:171-80. [Crossref] [PubMed]
4. Hou X, Yan Y, Zhan Q, et al. Unsupervised machine learning effectively clusters pediatric spastic cerebral palsy patients for determination of optimal responders to selective dorsal rhizotomy. Sci Rep 2023;13:8095. [Crossref] [PubMed]