Surgical Correction of Severe Dystrophic Cervical Kyphosis With Intraoperative Motor-Evoked Potential Changes in a Pediatric Patient With Neurofibromatosis Type 1

Discussion

Dystrophic cervical kyphosis is a rare but potentially devastating spinal manifestation of NF-1. Although spinal deformities are relatively common in patients with NF-1, severe dystrophic deformity involving the cervical spine is uncommon, and the available literature remains limited.1–5,8–11 Dystrophic changes, including vertebral wedging and scalloping, enlargement of the neural foramina, and thinning or dysplasia of the pedicles and posterior elements, may lead to rapid progression of kyphosis, instability, and neurological compromise.3–5,8–11 These characteristics are particularly concerning in young children, in whom progression of the deformity may continue during growth.4,10

Management of severe dystrophic cervical kyphosis in NF-1 remains challenging. Conservative treatment, including bracing, is generally ineffective for progressive dystrophic deformities, and surgical stabilization is often required when severe or progressive kyphosis or neurological impairment is present.4,5,8–11 However, poor bone quality, dysplastic vertebrae, deficient posterior elements, severe deformity, and associated neurofibromas can complicate instrumentation and achievement of solid fusion.3–11 Furthermore, pseudarthrosis, loss of correction, progression of vertebral dysplasia, instrumentation failure, and neurological complications remain important concerns after surgical treatment.5,8–11

The optimal surgical approach remains controversial. Combined anterior and posterior fusion has traditionally been advocated for severe dystrophic cervical kyphosis because it can provide circumferential stability and promote solid fusion.5–11 Helenius et al reported 22 children with NF-1-associated cervical kyphosis and found significantly greater correction following combined anteroposterior surgery than following posterior-only fusion (83% vs 58%).10 However, complications occurred in 13 of the 22 patients, including 5 new neurological deficits, and 9 patients required revision surgery.10 Lin et al compared anterior-only, posterior-only, and anteroposterior approaches in 81 patients and reported that the anteroposterior approach provided the greatest correction of dystrophic cervical kyphosis and sagittal alignment.9 More recently, a systematic review of 124 patients found that combined anterior-posterior surgery generally achieved greater deformity correction than single-approach procedures, although the combined approach was associated with greater surgical risk.11 Therefore, the surgical strategy should be individualized according to the severity and rigidity of the deformity, the extent of dystrophic changes, neurological status, and the location of associated neurofibromas.

Achieving reliable spinal fusion is another major challenge in NF-1-associated dystrophic cervical kyphosis. Fibular grafting has been used to provide structural anterior support in severe deformities.6–8 Kumagai et al reported 2 patients treated with anterior fusion using vascularized fibular grafts with favorable long-term outcomes,6 while Kakuta et al described circumferential fusion using an autologous vascularized free fibula for severe NF-1-associated cervical kyphosis.7 Kawabata et al also reported surgical correction of severe cervical kyphosis using combined reconstruction.8 In the present patient, anterior fusion from C3 to C7 using an autologous fibular graft following posterior instrumentation resulted in correction of the kyphosis from 87° to 26°, and solid bony fusion was confirmed 8 months postoperatively.

Intraoperative neuromonitoring was particularly important in the present case. Although MEP signals remained stable during cervical motion under general anesthesia and skull traction, a significant decrease in MEPs in both the upper and lower extremities occurred following final posterior fixation. Removal of the C3 and C4 lateral mass screws and decompression from C2 to C5 resulted in recovery of the MEP signals. This event suggests that even when preoperative traction and intraoperative positioning are neurologically tolerated, correction and instrumentation of a severely dystrophic cervical spine may produce acute spinal cord compromise. Given the substantial risk of neurological complications reported in previous surgical series,5,8–11 intraoperative MEP monitoring can serve not only as a means of detecting neurological injury but also as a real-time guide for modifying the surgical strategy before irreversible neurological damage occurs.

NF-1 further complicates long-term management because of the presence and potential progression of plexiform neurofibromas.12–16 Surgical resection may be difficult or impossible depending on the location and extent of the tumor.12,13 In the present patient, unresectable plexiform neurofibromas were present at the bilateral brachial plexus and thoracic apex. Selumetinib, a MEK inhibitor, has demonstrated efficacy in children with symptomatic, inoperable NF-1-associated plexiform neurofibromas.17,18 Following confirmation of spinal fusion, selumetinib therapy was initiated and resulted in tumor reduction. Long-term multidisciplinary follow-up is therefore important not only for maintenance of spinal alignment and fusion but also for management of the underlying manifestations of NF-1.

This case illustrates that severe dystrophic cervical kyphosis in a young child with NF-1 requires an individualized and multidisciplinary treatment strategy. Combined anterior and posterior stabilization can provide substantial deformity correction and solid fusion, but the high neurological risk associated with correction of a severely dystrophic cervical spine should be recognized. In particular, the reversible intraoperative MEP deterioration observed in this patient highlights the value of continuous neuromonitoring and immediate modification of the surgical procedure when neurological compromise is detected.