Neurofibromatosis and the spine
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This document discusses neurofibromatosis and its effects on the spine. Neurofibromatosis is a genetic disorder that can cause tumors to grow along nerves. There are four main types, with neurofibromatosis type 1 being the most common. Spinal deformities are a frequent complication, with scoliosis occurring in 10-20% of NF1 patients. Scoliosis can be classified as dystrophic or non-dystrophic based on x-ray and MRI findings. Treatment depends on the type and severity of the curve and may involve observation, bracing, surgery, or a combination. Post-operative immobilization is recommended to allow for fusion. Complications can include pseudoarthrosis, paraplegia
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Neurofibromatosis and the spine
- 1. Neurofibromatosis and the spine Shekar Roopan Spinal Unit King Dinuzulu Hospital Complex
- 2. Introduction • Multisystem disease affecting all three germ lines (neuroectoderm, mesoderm and endoderm) • Four varieties exist • Neurofibromatosis 1 (NF1) the most common
- 3. History • 1847 - Virchow • 1882 - von Recklinghausen • The elephant man - Joseph Carey Merrick
- 4. Classification • Neurofibromatosis 1 - Peripheral neurofibromatosis • Neurofibromatosis 2 - Central neurofibromatosis • Segmental neurofibromatosis • Schwannomatosis
- 5. Epidemiology and genetics • Autosomal dominant • 50% of cases spontaneous mutations • Gene located on long arm of chromosome 17 (NF1) • Prevalence 1:4000 • First peak - 5-10 years • Second peak - 36-50 years (75% of clinical problems due to malignancy)
- 6. Diagnostic Criteria 1. ≥6 cafe-au-lait spots (>5mm prepubertal, >15mm post pubertal) 2. ≥2 neurofibromas/≥1 plexiform neurofibroma 3. Axillary/inguinal freckling 4. Optic glioma 5. ≥2 Lisch nodules 6. Osseous lesion (sphenoid dysplasia/long bone cortex thinning) 7. NF1 in first degree relative Consensus development conference of the National Institute of Health; 1987
- 7. Cafe-au-lait spots • 90% of patients • Melanotic in origin • Found in skin areas not exposed to the sun • Under 5 years, 2 cafe au lait spots are common and normal Whitehouse D; Diagnostic value of cafe-au-lait spot in children; Arch Dis Child;1966
- 8. Neurofibromas • Fibroma molluscum - small neurofibroma in the subcutis • Plexiform neurofibroma - “bag of worms” feeling
- 9. Axillary and inguinal freckling • diffuse, small hyper pigmented spots (2-3mm diameter) • 40% patients - axillary freckling
- 10. Optic Glioma • Account for 2-5% of all brain tumours in childhood • 70% of cases are in NF1
- 11. Lisch Nodules • slightly raised, well circumscribed hamartomas on the iris • Present in 90% of patients >6 years • Specific to NF1
- 12. Skeletal associations • Generalised - osteoporosis, osteomalacia, short stature, macrocephaly • Focal - spinal deformities, long bone and sphenoid wing dysplasias, chest wall and dental abnormalities, cystic osseous lesions
- 13. Other associations • Cardiovascular - pulmonary stenosis, hypertension • Renal • renal artery stenosis - 2% NF1 patients • phaeochromocytoma - 2% NF1 patients
- 14. Spinal deformities • Cause remains unknown • Aetiological theories: • infiltration of bone by localised neurofibromas, metabolic bone deficiency, osteomalacia, endocrine disturbance and mesodermal dysplasia - inconclusive
- 15. Cervical spine • Rarely reported in literature • Presentation: asymptomatic, pain, deformity, neck mass, neurological deficit, atlanto-axial dislocations • Kyphosis is the most common abnormality • All NF1 patients require x-ray c-spine before a general anaesthetic/skull traction Neurofibromatosis of the cervical spine; JB Craig, S Govender; JBJS Br; 1992
- 16. Thoracolumbar spine • Scoliosis: • Dystrophic • Non dystrophic • Kyphoscoliosis • Lordoscoliosis • Spondylolisthesis
- 17. Scoliosis • Commonest spinal deformity in NF1 (10-20%) • Cause of deformity unknown - ?secondary to osteomalacia, localised neurofibromatous tumour eroding bone, endocrine disturbances and/or mesodermal dysplasia • Dystrophic/non dystrophic
- 18. Non dystrophic scoliosis • Commonest spinal deformity • Involves 8-10 spinal segments • Usually convex to the right • Similar to idiopathic scoliosis
- 19. Dystrophic scoliosis • Less common • Usually short segment, sharply angulated curve • 3 or more dystrophic features on x-ray • The more severe the dystrophic changes the greater the chance the curve will deteriorate
- 20. Dystrophic features • rib pencilling
- 21. Dystrophic features • posterior vertebral scalloping
- 22. Dystrophic features • vertebral rotation • widening of intervertebral foramina • lateral vertebral scalloping
- 23. Dural ectasia • Circumferential dilation of dural sac • Contains CSF and brownish proteinaceous material • Due to abnormal pressure phenomenon • Expanding dura erodes surrounding bony structures, widening the spinal canal and may destabilise the vertebral elements • MRI for all dystrophic curves prior to surgery
- 24. Modulation • Transformation of non dystrophic curve to dystrophic or addition of further dystrophic features to a dystrophic curve • MRI studies have questioned the theory of modulation Tsirikos et al; Assessment of vertebral scalloping in NF1 with plain radiography and MRI • Characterisation of curve as dystrophic or not should be based on x-ray and MRI AH Crawford et al; Spine deformity preview issue; Sept 2012
- 25. Kyphoscoliosis • Curve of 50 degrees or more in sagittal plane with any degree of coronal deformity • Can present with paraplegia (spinal cord elongation, rib protrusion into canal and intraspinal tumours) • Flexibility of curve needs to be assessed
- 26. Lordoscoliosis • Not common • Causes respiratory compromise and mitral valve prolapse
- 27. Spondylolisthesis • Rare • Usually associated with pathologic elongation of pedicles and pars interarticularis by lumbosacral foramina neurofibromas or dural ectasia with meningoceles • Combined anterior and posterior fusion • Postoperative immobilisation until fusion is solid
- 28. Approach • History - establish diagnosis of NF1 • Examination - define deformity, ascertain level and assess flexibility; neurological deficit; exclude cardiovascular and renal involvement; exclude pulmonary compromise • Investigations • Bloods - FBC, U&E, urinary catecholamines, PFT, Crossmatch • X-rays, CT, MRI - Dystrophic/Non dystrophic, curve magnitude, intraspinal lesions/changes; c-spine
- 29. Scoliosis Non-Dystrophic Curve <25 Observe 25-40 Brace 40-60 PSF >60 ASF+PSF AH Crawford; Neurofibromatosis: etiology, commonly encountered spinal deformities, common complications; Spine deformity preview issue; 2012
- 30. Scoliosis Dystrophic Curve <20 Observe 20-40 PSF >40 ASF+PSF >90 AR+CFT +PSF AH Crawford; Neurofibromatosis: etiology, commonly encountered spinal deformities, common complications; Spine deformity preview issue; 2012
- 31. Kyphosis Neurology No Yes Curve 50-70 ASF+PSF Pre-op CFT >70 AR+CFT +PSF Flexible Yes No ASF+PSF AR+CFT +PSF AH Crawford; Neurofibromatosis: etiology, commonly encountered spinal deformities, common complications; Spine deformity preview issue; 2012
- 32. Postoperative • Immobilsation postoperatively • Fusion mass assessed at 6 months by CT scan
- 33. Complications • Pseudoarthrosis • Crawford - 15% incidence • Sirois and Drennan - 38% incidence • Prevention - decortication, abundant autogenous bone grafting, segmental instrumentation, meticulous resection of pathologic soft tissue, orthotic immobilisation until fusion mass seen on CT, ?rhBMP-2
- 34. Complications • Paraplegia: • cord compression secondary to spinal deformity, rib penetration, intraspinal tumours • Younger patients - usually spinal deformity • Older patients - usually tumours
- 35. Complications • Rib protrusion • Usually occurs on convex of curve • Important surgical consideration for correction • Ostectomy of 2.5-5cm of protruding rib indicated at posterior fusion
- 36. Complications • Bleeding • Dural leaks
- 37. Conclusion • Scoliosis most common spinal deformity in NF1 • Multidisciplinary treatment strategy is needed • Management depends on recognition of non-dystrophic or dystrophic curves • Post operative immobilisation is always recommended
- 38. Thank You References • Orthopaedic complications of von Recklinghausen's disease in children. A.H Crawford. Current Orthopaedics 01/1996 • Neurofibromatosis: Etiology, Commonly Encountered Spinal Deformities, Common Complications and Pitfalls of Surgical Treatment; A.H. Crawford et al. / Spine Deformity Preview Issue (September 2012) • Spinal deformity in neurofibromatosis type-1: diagnosis and treatment; Athanasios I. Tsirikos; Eur Spine J. Jun 2005
Notes de l'éditeur
- NF is a multisystem disease that affects the neuroectodermal, mesodermal and endodermal germ lines. There are four varieties that exist with the commonest being type 1
- Historically NF1 was first reported by german pathologist Virchow but it was his student von Recklinghausen who described the histology of NF1 which was initially named after him. NF1 was popularised by the Elephant man in London in 1880 but recently it is thought that the elephant man had proteus disease
- NF is classified into 4 types. NF1 being the peripheral type is the focus of this presentation. NF 2 is the central type which is associated with vestibular schwannomas and multiple spinal schwannomas. Segemental NF has features of NF1 involving a single body segment and schwannomatosis being the last type
- NF1 is an autosomal dominate condition with the gene being located on long arm of chromosome 17. The gene product neurofibromin acts as a tumour suppressor gene. 50% of cases are due to new mutations. The prevalence of nf1 being 1 in 4000 with 2 peaks of presentation, the first peak at 5-10 years and second at 36-50 yrs
- The diagnostic criteria for NF 1 were described in 1987 at the consensus development conference of the National institute of healt. NF1 is diagnosed with 2 or more of the following: 6 or more cafe au lait spots measuring more than 15mm in adults; 2 or more neurfibromas or 1 plexiform neurofibroma; axillary and inguinal freckling; optic gliomas, 2 or more lisch nodules; osseous lesions or a first degree relative with NF1
- cafe au lait spots are present in 90% of patients with NF1. The pigmentation is melanotic in origin and found in areas not exposed to the sun. It is important to note that up to 2 spots is a normal and common finding in children under 5
- Neurofibromas are mixed cell tumours enriched with schwann cells which can present as fibroma molluscum or a plexiform neurofibroma
- Freckling is present in 40% of patients with NF1. Its important to note that freckling and occasional dermal neurofibroma may be the only physical findings in parents of a child who shows other criteria for diagnosis
- Optic gliomas account for 2-5% of all brain tumours and 70% of the cases are found in NF1 patients
- Lisch nodules are slightly raised well circumscribed hamartomas in the iris and are present in over 90% of patients over 6 years. The lesion is specific to NF1
- The skeletal associations with NF1 can categorised into generalised or focal. The generalised associations include osteoporosis, osteomalacia, short stature and macrocephaly. Focal associations include spinal deformities, long bone and sepnoid wing dysplasias, chest wall and dental abnormalities
- Since NF affects all three germ lines other important associations to consider especially in patients for operative management include pulmonary stenosis and hypertension. Renal artery stenosis and phaechromoctoma has been quoted as being present in 2% of NF1 patients
- The cause of spinal deformities are unknown several etiological theories have been described but they are inconclusive.
- Cervical spine deformities are rarely reported in literature. The presentation varies from asymptomatic to symptoms like pain which is the commonest presentation, deformity, neck mass, neurological deficit atlanto axial dislocations. Kyphosis is the most common abnormality in the cervical spine. All patients with NF1 require a c spine x-ray before a general anaesthetic or skull traction
- In the throacolumbar spine deformities include a scoliosis, khyphscoliosis, lordoscoliosis and spondylolisthesis
- Scoliosis is the commonest spinal deformity in NF1. The cause of the scoliosis is unknown as mentioned earlier. The scoliosis can be classified in dystrophic or non dystrophic curves
- Non dystrophic curves are the commonest. It usually involves 8-10 spinal segments and is usually convex to the right but not always. The presentation is similar to idiopathic scoliosis
- The dystrophic curve is less common than non dystrophic but has a higher chance of progression. It usually involves a short segment with a sharply angulated curve. It is diagnosed with the presence of 3 or more dystrophic features on x-ray
- The dystrophic features include Rib pencilling were the rib is smaller than the narrowest part of the second rib
- posterior vertebral scalloping
- vertebral rotation; widening of intervertebral foramina and lateral vertebral scalloping
- Dural ectasia is characteristic of NF1. Its is an expansion of the thecal sac due to abnormal pressure phenomenon at the expense of bony and ligamentous structures. This may result in posterior vertebral scalloping and lateral thoracic meningocele formation often causing destabilisation of the vertebrae leading to subluxation or dislocation. MRI is required in all dystrophic curves prior to surgery as the intraspinal elements may compromise the cord when instrumentation and stabilisation attempted or may cause erosive changes in the bone preventing primary fusion.
- Modulation refers to the transformation of a non dystrophic curve to dystrophic or addition of dystrophic features to a dystrophic curve. Recent MRI studies have questioned modulation stating that curves labelled as non dystrophic on x-ray may have dystrophic features on MRI hence Crawford has suggested using x-ray and MRI to assess curves.
- Non dystrophic curves are managed based on curve measurement: 20-25 degress - observe 25-40 degrees - bracing 40-60 degrees - posterior spinal fusion with instrumentation >60 degrees - anterior disc excision and fusion with autologous bone graft followed by posterior spinal fusion, instrumentation and autogenous iliac crest graft
- Dystrophic curve: Bracing not recommended in dystrophic curves <20 degrees - observed at 6 month intervals for progression 20-40 degress - posterior spinal fusion from neutral vertebra cephalad to the curve to the neutral vertebra caudal to the curve >40 degrees - anterior disectomy and intervertebral fusion followed by posterior fusion Rigid curves >90 - anterior release, nasojejunal alimentation and craniofemoral traction followed by posterior spinal fusion Postoperatively orthotic immobilisation until fusion mass obtained as seen on CT or MRI at 6 months
- Kyphoscolisos is a curve of 50 degrees or more in the saggital plane with any degree of coronal deformity. These patients can present with paraplegia due to elongation of the cord with the kyphosis but rib protrusion and intraspinal tumours need to be excluded. The flexibility also needs to be assessed for management purposes.
- All patients with khysphoscoliosis require anterior and posterior fusion. Flexible curves can be performed at the same anaesthesia. Severe and rigid curves should be done as a staged procedure with anterior release and intervertebral body fusion followed by craniofemoral traction for 7-10 days and then posterior fusion is performed.
- Lordoscoliosis has not been frequently reported. It does however predispose to significant respiratory compromise and mitral valve prolapse
- Spondylolisthesis is rare but when present is usually associated with pathologic elongation of pedicles and pars interarticularis by lumbosacral foramina neurofibromas or dural ectasia with meningoceles. Surgical management requires a combined anterior and posterior fusion with postoperative immobilisation
- The approach to a NF patient with spinal deformity starts with the history followed by examination. The things that need to be determined are the type of deformity, its flexibility and associated neurology. The cardiovascular, respiratory and renal systems need to be examined to assess for hypertension, pulmonary stenosis and renal artery stenosis. as mentioned earlier. Investigations need to be performed to stage the patient as a host and to determine if the curve is dystrophic or not, the curve magnitude and to assess for intraspinal lesions which may affect surgical management.
- If a non dystrophic scoliosis is present management depends on the curve magnitude. If <25 degrees it is observed at 6 month intervals. Between 25-40 degrees and skeletally immature bracing is considered. Curves between 40-60 degrees require posterior fusion and more than 60 degrees combined anterior and posterior fusions
- Dystrophic curves that are <20 degrees are observed at 6 month intervals. Between 20 and 40 posterior stabilisation is performed, greater than 40 degrees anterior and posterior stabilisation is performed and >90 degrees anterior release with craniofemoral traction and nasojegunal tube alimentation followed by posterior stabilisation is recommended.
- Management when there is a kyphosis of greater than 50 degrees present depends on if there is neurology is present. If there is no neurology is present the deformity is managed according to the magnitude of the curve. If neurology is present with a flexible curve preoperative craniofemoral traction is done followed by anterior and posterior fusions. If the curve is rigid anterior release with craniofemoral traction is done followed by posterior stabilisation
- Postoperatively all patients must be immobilised for at least 6 months when a CT can be performed to assess the fusion mass
- In terms of complications Pseudoarthrosis has been reported ranging from 15-38%. This can be reduced by decortication with abundant bone grafting; meticulous pathologic soft tissue resection and maintaining immobilisation post operatively until fusion mass is seen on CT. Recombinant human bone morphogenic protein 2 has been used off label but recent reports show malignant transformation of neurofibroma after application
- Other complications include paraplegia which can be secondary to deformity, rib penetration or intraspinous tumours. Younger patients usually have paraplegia due to spinal deformity while in older patients it is usually due to tumour
- Rib protrusion usually occurs on convex of the curve. It is an important consideration since correction of deformity will cause the cord to impinge on the rib head. If the rib head is protruding an ostectomy of 2.5-5cm can be performed at the time of posterior fusion.
- Bleeding from the plexiform venous channels and dural leaks are also other possible complications.
- In conclusion scoliosis is the most common spinal deformity in NF1. It requires a multidisciplinary treatment strategy. Management depends on if the curve is dystrophic or not and post operative immobilisation is always recommended