|Year : 2020 | Volume
| Issue : 2 | Page : 49-56
Spinal deformities in neurofibromatosis 1
Suresh S Pillai1, PA Ramsheela2
1 Sr Consultant Spine Surgeon, BMH Spine Centre, Baby Memorial Hospital, Calicut, Kerala, India
2 Resident in Spine Surgery, BMH Spine Centre, Baby Memorial Hospital, Calicut, Kerala, India
|Date of Submission||13-Dec-2020|
|Date of Acceptance||24-Dec-2020|
|Date of Web Publication||08-Mar-2021|
Suresh S Pillai
Sr Consultant spine surgeon, BMH Spine centre, Baby memorial hospital, Calicut, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Pillai SS, Ramsheela P A. Spinal deformities in neurofibromatosis 1. J Orthop Assoc South Indian States 2020;17:49-56
| Introduction|| |
Neurofibromatosis (NF) is a spectrum of genetic disorders with a range of clinical manifestations, involving skin, nervous tissue, bones, and soft tissues. Neurofibromatosis type I (peripheral, Von Recklinghausen disease), neurofibromatosis type (central NF-2), segmental neurofibromatosis2, schwannomatosis. NF-1 is an autosomal dominant disorder with nearly 100% penetrance. It is the most common single-gene disorder in humans. The responsible gene was localized to chromosome 17 (17q11.2). Approximately 50% of NF-1 is the new mutation. NF-1 clinically manifests when neurofibroma, a Ras-specific GTPase activator, is absent. One domain of neurofibroma downregulates P21-Ras, a cell growth promoter. The active Ras is guanosine triphosphate (GTP) bound neurofibroma is Ras-specific GTPase activator acting as a tumor suppressor. In NF-2, there are bilateral schwannomas of the vestibular portion of the eighth cranial nerve, which is absent in NF-1. Spinal deformity is the most common orthopedic manifestation of NF-1. Pseudoarthrosis of tibia, overgrowth phenomenon of the extremities, soft tissue tumors, dural ectasia, meningoceles, dumbbell tumors, and abnormal dilated vascular channels also occur in NF-1. NF-2 and other forms of NF do not have direct bone involvement.
The diagnosis of NF-1 is based on any two or more of the criteria that put forward by the consensus development conference on NF at NIH.
- Six or more café-au-lait spots, 5 mm diameter in prepubertal people and 15 mm diameter in postpubertal people
- Two or more neurofibroma of any type or one plexiform neurofibroma
- Axillary or inguinal freckling
- Optic nerve glioma
- Two or more iris Lisch nodules (iris hamartoma)
- A distinctive bone lesion, sphenoid wing hypoplasia, thinning of long bone cortex with or without pseudoarthrosis
- A first-degree relative who has NF-1 by the above criteria.
Comprehensive genetic testing by direct sequencing offers 95% sensitivity for diagnosis, but this does not predict the clinical manifestation, severity, or complications of the condition. Even then, each person who carries the gene will show some features of the condition. The clinical manifestations of NF-1 peak at two stages of life: 5–10 years and 36–50 years of life. The second peak is associated with malignant neoplasms in 75% of cases.
| Spinal Deformities in Neurofibromatosis 1|| |
Spinal deformity is the most common osseous defect associated with NF-1. The true prevalence of NF-1 is unknown, but the reported prevalence with various literature ranges from 10% to 77% with different authors. Scoliotic curves in NF-1 may be classified as dystrophic and nondystrophic. Nondystrophic curves behave more or less like idiopathic scoliosis and may be treated like idiopathic scoliosis, but the possibility of an idiopathic looking curve to turn into dystrophic curves with severe progression in the long run is very much on cards. This is called modulation., Modulation is the character of a deformity, which changes over time to more aggressive forms and is unique to NF-1. The dystrophic curves are usually short segmented (involving 4–6 vertebrae), sharply angulated and located in the upper thoracic spine. Scalloping of the vertebral borders, widened neural foraminae, severe rotation of the apical vertebrae, widening of the spinal canal, hypoplastic or absent pedicles, paraspinal masses, spindling of the ribs and transverse process, and rotation of the ribs are other dystrophic features. The exact etiology of these dystrophic changes is not well understood. Endocrine changes, primary mesodermal defects, and direct infiltration of NF tissue are some of the reasons that put forward. The erosive and destructive effects of the adjacent soft tissue need special attention.
Patients with NF-1 should be properly evaluated for any neurological deficit and should be imaged to see the entire spine. Computed tomography (CT) myelo and/or magnetic resonance imaging (MRI) should be used for this. It is mandatory before any spinal surgery in these patients, especially so when a severe deformity is addressed. Some of them may have erosive changes in the skull. Hence, X-ray of the skull is a must before application of skull traction or halo in these patients. It is ideal to have radiograph before putting any implants in the femur or tibia or any bone in NF-1 patients.
| Cervical Spine Deformity in Neurofibromatosis 1|| |
This may range from severe kyphosis to atlantoaxial dislocation, spondyloptosis of subaxial cervical spine, severe kyphosis, scoliosis, anterior meningocele, plexiform neurofibroma, and dumbbell tumors of the nerve roots. A cervical kyphosis is the most common deformity in NF-1. It is also possible after cervical laminectomy without fusion. Hence, it is mandatory to instrument and fuse the cervical spine whenever the posterior tension band is breached. In severe cervical kyphosis which are rigid and more than 50-700 require anterior and posterior release and instrumented fusion at the earliest possible date. Translational malalignment also requires anterior and posterior surgery. A surgeon should evaluate the patient preoperatively for thinned out and narrow pedicles, malformed facets, widened and eroded neural foraminae, and increased bleeding from the dystrophic bone and abnormal vascular channels.
A 14-year-old boy presented with numbness of his fingers. His father had multiple neurofibromas all over the body. This boy had multiple cafe-au-lait spots and cervical kyphosis. [Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5],[Figure 6],[Figure 7],[Figure 8]
Upon evaluation with MRI, there was severe compression of the cervical cord at D6. The cervical spine was severely kyphotic.
Hence, an anterior and posterior fusion was planned. C6 corpectomy interbody fusion between C5 and C7 with mesh cage and graft, C4–5 discectomy and fusion with iliac crest bone graft, and anterior stabilization from C4 to C7 were done with a cervical spine locking plate and screws under neuromonitoring.
Under the same anesthesia in the prone position, a posterior fusion was done from C4 to C7 with lateral mass screws, rods, and autogenous iliac crest graft. Intraoperatively, C5–6 and C6–7 facets were dysplastic and poorly formed.
A 44-year-old woman with multiple NF (NF1) presented with difficulty in walking. She was wheelchair bound at presentation with weakness of both upper and lower limbs. Upon evaluation, MRI showed diffuse neurofibromas all over the body. [Figure 9],[Figure 10],[Figure 11],[Figure 12]
|Figure 12: Intraoperative picture showing dural closure after tumor removal and instrumentation|
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Furthermore, there were multiple intradural tumors in the cervical spine.
Among the three tumors, one was a dumbbell tumor causing compression of the spinal cord. In view of the deteriorating neurology, the patient was taken up for surgery. The dura was opened and the tumors removed.
The dumbbell component was also removed, the dura repaired, and the cervical spine instrumented and fused posterolaterally with nibbled bone chips.
The patient improved following surgery. She started walking 3 weeks after surgery. She was warned about the possibility of recurrence of the tumor. In these cases, it is not practical to remove all the tumors in the body.
A 34-year-old male patient with severe kyphoscoliosis and plexiform NF wanted to get his deformity corrected before he gets married. [Figure 13]
|Figure 13: Figure showing plexiform neurofibroma and severe kyphoscoliosis|
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Due to severe exertional dyspnea and severe abnormality in the pulmonary function test deferred him by anesthetist from undergoing a major procedure.
| Thoracic and lumbar deformities|| |
Thoracic and lumbar scoliosis and kyphosis increase at an average of 8°/year 11.2°/year, respectively. Hyperkyphosis and short curves tend to increase despite solid anterior and posterior fusion.
Nondystrophic scoliotic curves may be managed similar to idiopathic curves. The chances of pseudoarthrosis and “modulation which can occur in the later years warrants close follow-up and postoperative bracing of these patients.” Dystrophic scoliosis always progresses. Hence, treatment should be initiated before the curve becomes a grotesque deformity. Early fusion is the best method. Evaluate these patients thoroughly before surgery to avoid any surprises and prevent intraoperative complications. Fusion of the curve in young individuals stunts the growth minimally, as the curve is short and involves only a few vertebrae to affect the growth potential. The chance of progression persists in dystrophic curves even after solid anterior and posterior fusion.
Spinal fusion is recommended for curves between 20° and 40° with progressive curves. If dural ectasia or tumors adjacent to the spine are identified, anterior and posterior fusion must be performed even if the curve is moderate. The fusion should extend from one neutral vertebra to the other neutral vertebra spanning the entire curve. The dystrophic vertebrae are severely osteoporotic making them vulnerable for screw pull out. Insertion of sublaminar wires in cases of dural ectasia is also fraught with complications quite often. Possibility of pseudoarthrosis is also very high in dystrophic curves. Hence, the use of Bone Morphogenic Protein (BMP) and other osteoinductive agents is also recommended to achieve good fusion in these patients.
Dystrophic curves more than 60° may be treated by preoperative halo vest traction for an average of 3 weeks. In some cases, the anterior fusion should extend the entire structural area of the curve. Tibial or fibular strut graft should be used whenever possible. The fusion bed should be prepared properly without any soft tissue, and less grafts should be placed with proper bone-to-bone contact. It is neither necessary nor practical to secure all the soft tissue tumors in the body. If there is cord compression anteriorly, it should be addressed anteriorly. A laminectomy for anterior compression of the cord in severe kyphoscoliosis is absolutely contraindicated.
A young girl with NF-1 presented with difficulty in walking. She gave a history of anterior and posterior spinal surgery around 10 years back at another center for a kyphotic deformity in the thoracolumbar area. [Figure 14],[Figure 15],[Figure 16],[Figure 17],[Figure 18],[Figure 19],[Figure 20],[Figure 21],[Figure 22],[Figure 23]
|Figure 14: Clinical picture showing severe kyphosis of the thoracolumbar spine|
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|Figure 17: Magnetic resonance imaging of the spine showing the cord draped over the deformity|
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|Figure 19: Intraoperative picture showing posterior instrumentation and fusion|
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The deformity has become grotesque, with clonus and spastic paraparesis. Her neurological status and worsening deformity made it imperative for her to undergo surgery again. She was evaluated with X-ray [Figure 15], CT scan [Figure 16], and MRI [Figure 17]. The X-ray showed previously inadequate posterior fixation with a single clamp with evidence of anterior fusion and posterior decompression.
The patient was planned for a posterior vertebral column resection.
The spine instrumented three levels above and below. There was severe adhesion of the dura and nerve roots from the posterior surgery. Hence, a posterior vertebral column resection could not be done at that time. Iliac crest bone graft and rib graft were used for fusion. The amount of graft was insufficient for a good union for this case of NF, which is prone for pseudoarthrosis. Hence, bone graft substitute G-bone was also used.
Postoperatively, the patient started walking normally. Postoperative radiographs showed good position of the screws. The patient was warned for a second procedure at a later date if she deteriorated.
Nine months after the surgery, she developed difficulty in walking again. This time, through a thoracoabdominal approach (through the opposite side of the previous anterior surgery in her childhood), the spine was fused anteriorly with a fibular strut graft.
The apex of the curve was fused with cancellous bone graft from the iliac crest. Postoperatively, the patient went on to do well.
Her fusion is maintained, and she is symptom free for the last 11 years.
A 14-year-old girl with NF-1 presented with kyphoscoliosis of the thoracolumbar spine. Upon evaluation, she had posterior quadrant vertebra at D12. [Figure 24],[Figure 25],[Figure 26],[Figure 27],[Figure 28],[Figure 29]
|Figure 24: Clinical picture and X-ray showing posterior quadrant vertebra with kyphoscoliosis|
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|Figure 25: Clinical picture and X-ray showing posterior quadrant vertebra with kyphoscoliosis|
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She underwent simultaneous anterior and posterior surgery. Anteriorly, through a thoracoabdominal approach, the posterior quadrant vertebra was partly resected along with the intervening soft tissues and discs for an anterior fusion between D11 and L1 with iliac crest bone graft.
Posteriorly, she was instrumented two levels above and below with pedicle screws and fused with autogenous rib and iliac crest graft.
The patient has been followed up for 10 years with good results (she is married, blessed with a baby, and leads a normal family life).
“Dural ectasia” is a circumferential dilatation of the dural sac from unknown etiology. The dura is expanded, thin, friable, and contains brownish material in the CSF. This expansion of the dura erodes the vertebrae. Hence, the treating surgeon should be wary of the potential complications possible. Meningoceles may occur anteriorly, laterally through the neural foramen, or posteriorly through the space between the laminae. The spine should be preoperatively thoroughly evaluated to prevent unexpected complications.
Dumbbell tumors constrict the tumor by narrow intervertebral foramen or through the interlaminar space of the vertebrae. Further, significant bleeding is possible during spinal surgery because of plexiform venous abnormalities and increased vascularity or neurofibromatous tissue.
| Conclusion|| |
The potentially dangerous situation while dealing with severe spinal deformities in NF-1 patients is putting implants in these dystrophic vertebrae. Hence, all types of implants should be there in ones' armamentarium intraoperatively. Potential lesions should be addressed then and there.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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