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Chapter Summary
• Context: Neurofibromatosis type 1 (NF1) is a multisystem genetic disorder affecting the skin, nervous system, and musculoskeletal apparatus. Among its orthopaedic manifestations, spinal deformity occupies a central role and can exhibit a clinical course strikingly different from idiopathic scoliosis. The decisive prognostic element is the presence or absence of dystrophic vertebral changes. Non-dystrophic curves generally behave like adolescent idiopathic scoliosis, whereas dystrophic curves are typically short, sharply angulated, early-onset, and prone to rapid progression with associated kyphosis, vertebral scalloping, dural ectasia, rib penciling, paravertebral plexiform neurofibromas, and profound spinal instability. Cervical spine abnormalities may also coexist and remain clinically silent. The primary clinical challenge is to recognize the aggressive dystrophic pattern early, thoroughly investigate the entire neuraxis, and construct a robust reconstruction capable of controlling deformity despite dysplastic bone quality, high pseudarthrosis rates, osteolysis, and instrumentation failure risks.
• Chapter Objective: To present the clinical, genetic, and radiographic characteristics of spinal deformity in NF1. The reader will understand its genetic basis, differentiate dystrophic from non-dystrophic curves, identify pathognomonic radiographic features associated with progression, recognize when to investigate the cervical spine and neuraxis, and master the principles guiding observation, bracing, traction, and complex spinal fusion, including complication management and long-term follow-up protocols.
• NF1 and spinal manifestationsNF1 displays marked phenotypic variability. Café-au-lait macules, neurofibromas, Lisch nodules, skeletal dysplasia, and positive family history form the core diagnostic criteria reviewed in the chapter. The disease is also associated with plexiform neurofibromas and malignant peripheral nerve sheath tumors, whose paraspinal presence directly alters vertebral bony anatomy and complicates surgical planning.
• Dystrophic versus non-dystrophic curvesThis distinction represents the central axis of clinical management. Non-dystrophic curves are more common and tend to follow a natural history similar to adolescent idiopathic scoliosis. They may be observed or braced in select immature patients, although vigilant monitoring for dystrophic modulation (conversion to a dystrophic phenotype) is mandatory. Dystrophic curves exhibit rapid, unrelenting progression. Classic dystrophic signs include rib penciling, severe vertebral body wedging and scalloping, enlarged intervertebral foramina, interpedicular widening, and thinned pedicles related to dural ectasia. Dystrophic curves are typically short-segmented, acute, sharply angulated, and present early in childhood. Associated angular kyphosis dramatically elevates neurological risk.
• Cervical spine and neuraxis surveillanceThe cervical spine requires targeted clinical and radiographic evaluation, as dystrophic changes and neurofibromas can remain clinically subtle. Torticollis, dysphagia, progressive motor weakness, or hyperreflexia should heighten suspicion. In all dystrophic, atypical, or neurologically involved curves, the chapter mandates comprehensive whole-spine MRI. MRI identifies intraspinal neurofibromas, dural ectasia, cord compression, syringomyelia, and altered vascular anatomy. Case 1 and Figure 1 illustrate the critical intersection of cervical dystrophic deformity, neural deficit, and multiplanar spinal realignment.
• Principles of surgical managementCurve behavior dictates intervention. In non-dystrophic curves, standard idiopathic treatment algorithms apply. In dystrophic curves, orthotic treatment is notoriously ineffective, and early surgical fusion is indicated upon documented progression. The presence of rigid kyphosis, extensive bone loss, plexiform lesions, and dural ectasia necessitates complex reconstructions. The historical role of circumferential anterior-posterior fusion is contrasted with modern multi-anchor posterior segmental pedicle screw constructs; however, the authors emphasize that the biological risk of nonunion remains substantial. Preoperative halo-gravity traction is valuable in rigid deformities. In severe cases, cord decompression combined with 3D structural reconstruction is required (Figures 2–6).
• Complications and long-term surveillancePseudarthrosis, osteolysis, implant loosening, loss of correction, and late distal adding-on are prevalent complications in NF1. Even after a successful index reconstruction, the chapter emphasizes prolonged clinical and radiographic vigilance and proactive family counseling regarding potential revision surgeries.
• Clinical Application: In clinical practice, the first step when evaluating a patient with NF1 and scoliosis is determining whether dystrophic vertebral features are present. This distinction fundamentally alters natural history expectations and follow-up frequency. A non-dystrophic curve can be monitored according to standard AIS guidelines, while a short, sharply angulated, kyphoscoliotic curve with scalloping must be treated as high-risk. Evaluation cannot stop at the thoracolumbar curve: the cervical spine must be systematically screened even without dramatic neck symptoms. In dystrophic patterns or any neurological abnormality, full-neuraxis MRI is mandatory. 3D CT mapping clarifies dysplastic pedicle channels and guide screw purchase (Figure 4). Surgical planning must anticipate poor bone stock, expansive dural ectasia, dilated foramina, and friable plexiform neurofibromas. The fusion construct must be biologically robust (abundant autograft/allograft) to overcome impaired osteogenesis. Postoperative management also differs from AIS: initial solid-appearing correction does not guarantee cure, as late osteolysis, crankshafting, adding-on, and pseudarthrosis can occur years later, mandating long-term clinical surveillance.
