Neurofibromatosis Etiology, Commonly Encountered Spinal Deformities and Surgical Treatment

Spine Deformity Preview Issue (September 2012) 85e94www.spine-deformity.org

Neurofibromatosis: Etiology, Commonly Encountered SpinalDeformities, Common Complications and Pitfalls of Surgical TreatmentAlvin H. Crawford, MD, FACSa,*, Marios G. Lykissas, MD, PhDa, Elizabeth K. Schorry, MDb,

Sean Gaines, MDa, Viral Jain, MDa, Tiziani Greggi, MDc, David Viskochil, MDd

aDivision of Orthopaedic Surgery, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, MLC 2017, Cincinnati, OH 45229, USAbDivision of Human Genetics, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, MLC 4006, Cincinnati, OH 45229, USA

cSpine Surgery Division, Rizzoli Orthopaedic Institute, 1 Via GC Pupilli, Bolognia 40136, ItalydShriners Hospitals for Children Salt Lake City, Fairfax Road at Virginia Street, Salt Lake City, UT 84103, USA

Abstract

Neurofibromatosis 1 (NF-1) is a multisystemic, autosomal dominant genetic disorder. Skeletal complications usually present early in lifeand can be attributed to abnormalities of bone growth, remodeling, and repair, or can be secondary to nearby soft-tissue abnormalitiescomplicating NF-1. Skeletal complications can be categorized as generalized or focal manifestations. The incidence of spinal deformities inassociation with NF-1 varies from 2% to 36%, with scoliosis being the most common. Both heritable and nonheritable factors contribute tothe pathogenesis of spinal deformities in NF-1 patients. Traditionally, the spinal deformities are classified into dystrophic or nondystrophic.The pathophysiology of dystrophic curves is still uncertain, but may require a nonhereditary event, such as an adjacent tumor or a second hitevent in local bone cells, leading to the underlying dysplasia. Dystrophic curves may result in scoliosis, kyphosis, or frequently, kypho-scoliosis. The goal of surgical management is to arrest the progression of deformity instead of achieving complete correction. The currentstate-of-the-art treatment for significant deformity is combined anterior and posterior spinal arthrodesis. Postoperative orthotic immobi-lization is almost always recommended in an effort to prevent pseudoarthrosis. The orthosis should be maintained until a fusion mass isobtained. Assessment of the fusion mass by computed tomography (CT) or magnetic resonance imaging (MRI) should be performed. Majorcomplications, such as paraplegia, pseudoarthrosis, intraoperative hemorrhage, and postoperative progression of the deformity may occur.In an attempt to eliminate complications and achieve the best results, a multidisciplinary treatment strategy is needed. The intent of thisarticle is to present the spinal deformities that are most commonly associated with NF-1, to identify the underlying biology of spinaldeformities based on the most recent literature, and to address the common complications and pitfalls of their surgical management.� 2012 Scoliosis Research Society.

Keywords: Neurofibromatosis; Spinal deformity; Scoliosis; Kyphosis; Spinal fusion

Introduction

Neurofibromatosis is a multisystemic, autosomal domi-nant genetic disorder defined as a spectrum of multifaceteddiseases involving neuroectoderm, mesoderm, and endo-derm. The primary pathologic process involves activationof the Ras pathway; however, the etiology of many of thenontumor features is still unclear. The clinical features ofthe most common form of the disease, neurofibromatosis

Author disclosures: AHC (none); MGL (none); EKS (none); SG (none);

VJ (none); TG (none); DV (none).

*Corresponding author. Division of Orthopaedic Surgery, Cincinnati

Children’s Hospital Medical Center, 3333 Burnet Avenue, MLC 2017, Cin-

cinnati, OH 45229, USA. Tel.: (513) 636-8932; fax: (513) 636-3928.

E-mail address: [email protected] (A.H. Crawford).

2212-134X/$ - see front matter � 2012 Scoliosis Research Society.

http://dx.doi.org/10.1016/j.jspd.2012.04.004

type 1 (NF-1), were reported in several family members byGerman pathologist Virchow in 1847 [1], but it was hisstudent von Recklinghausen who, 35 years later, describedthe histologic features of the syndrome that often bears hisname [2].

NF-1 is characterized by extreme variability of expres-sion, with manifestations ranging from mild cutaneouslesions to severe life-threatening complications. Skeletalcomplications usually present early in life and can beattributed to abnormalities of bone growth, remodeling, andrepair, or can be secondary to nearby soft-tissue abnor-malities complicating NF-1. Skeletal complications can becategorized as generalized or focal manifestations [3].Generalized skeletal abnormalities include osteoporosis,osteopenia, osteomalacia, shortness of stature, and

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86 A.H. Crawford et al. / Spine Deformity Preview Issue (September 2012) 85e94

macrocephaly. Focal abnormalities of the skeleton are lesscommon than generalized abnormalities, but may causesignificant morbidity. Focal manifestations include spinaldeformities, dysplasia of the tibia and other long bones,sphenoid wing dysplasia, chest wall deformities (pectusexcavatum), dental abnormalities, periapical cementaldysplasia, and cystic osseous lesions. The effect of gener-alized abnormalities in the occurrence or progression offocal skeletal manifestations remains elusive.

The incidence of spinal deformities in association withNF-1 varies from 2% to 36%, with scoliosis being the mostcommon musculoskeletal manifestation of NF-1 [4,5]. Theintent of this article is to present the spinal deformities thatare most commonly associated with NF-1, to identify theunderlying biology of spinal deformities based on the mostrecent literature, and to address the common complicationsand pitfalls of their surgical management.

Classification

Neurofibromatosis 1

Neurofibromatosis 1 (NF-1), or peripheral neurofibro-matosis, is a common autosomal dominant single-genedisorder with an estimated prevalence of 1 in 3,000 [6]. Itis the most common form of neurofibromatosis and the onemost likely to be encountered by the orthopedist. It ispredicted to affect over 2 million people worldwide in allracial and ethnic groups. The NF-1 gene is large in size, inthe range of 350,000 base pairs with 59 exons, and its locuswas discovered on chromosome 17q11.2. The diagnosis ofNF-1 is established when at least 2 of the most commonlypresenting features of the disease, as defined by the 1987Consensus Development Conference of the National Insti-tutes of Health, are present (Table) [7].

Neurofibromatosis 2

Neurofibromatosis 2 (NF-2), or central neurofibroma-tosis, has an estimated incidence of 1 in 33,000 individualsand is associated with bilateral vestibular schwannomas and

Table

Diagnostic criteria for neurofibromatosis 1 as defined by the 1987

Consensus Development Conference of the National Institutes of

Health [7].

1 Six or more caf�e au lait macules more than 5 mm in greatest

diameter in prepubertal individuals and more than 15 mm in

postpubertal individuals

2 Two or more neurofibromas of any type or more than one

plexiform neurofibroma

3 Freckling in the axillary or inguinal regions

4 Two or more Lisch nodules (iris hamartomas)

5 Optic glioma

6 A distinctive osseous lesion, such as sphenoid dysplasia or

thinning of long bone cortex, with or without pseudoarthrosis

7 A first degree relative (parent, sibling, or offspring) with

neurofibromatosis 1 by the above criteria

multiple spinal shwannomas. NF-1 and NF-2 are geneti-cally distinct disorders with different gene loci, despite thesimilarity of their names.

Segmental neurofibromatosis

Segmental neurofibromatosis is characterized byfeatures of NF-1, but involving a single body segment.Typically, only a single segment of the body (such as leftupper extremity) is affected with caf�e-au-lait spots andfreckling, and lesions usually do not cross the bodymidline.

Legius syndrome

Legius syndrome can present with multiple caf�e-au-laitspots, freckling, macrocephaly, and mild learning disabili-ties, but does not present with any of the benign ormalignant tumors associated with NF-1.

Schwannomatosis

Schwannomatosis is a distinct form of neurofibromatosis,which typically involves multiple schwannomas throughoutthe body but without the vestibular schwannomas typicalof NF-2. The familial schwannomatosis is due to mutationsin the INI1 gene, linked to NF-2 on chromosome 22.

Spinal Deformities

Etiology

The cause of spinal deformity remains unknown. Severaltheories including metabolic bone deficiency, osteomalacia,endocrine disturbance, and mesodermal dysplasia have beenproposed and are, at best, inconclusive. The dystrophicchanges may be attributed to intrinsic factors or may beassociated with anomalies of the spinal canal secondary toabnormalities of the spinal cord dura mater (dural ectasia).

Pressure erosive effects of dural ectasia and paravertebraltumors have been frequently found adjacent to and approx-imated to the deformities, initiating instability and subse-quent deformity. Dural ectasia, a disorder unique to certainconditions, is an expansion or dilatation of the dural sac andit is thought to arise from increased hydrostatic pressure,which progressively expands the dural sac. A current alter-native hypothesis is mesodermal dysplasia [8].

Scalloping was initially thought to represent the result oferosive pressure or direct infiltration of the vertebra byadjacent neurofibroma [9-14]. Another proposed cause is aneurofibroma-derived, locally active biochemical substanceor hormone that triggers dystrophic features in the adjacentvertebra [9]. The altered response of the vertebral bonein NF-1 to a paraspinal tumor has been hypothesized.Some authors suggest an interactive pathophysiologicalmechanism between a genetically compromised bone anda neuroectodermal derivative, such as a contiguous neuro-fibroma or an abnormal meningeal sheath [9,11].

Fig. 1. (A) Eleven-year-old boy with NF-1 and severe cervical kyphosis with spinal cord compression at the level C3eC4 (A). (B) Multiple cervical para-

spinal neurofibromas are identified on magnetic resonance imaging scan.

87A.H. Crawford et al. / Spine Deformity Preview Issue (September 2012) 85e94

A recent study of 10 monozygotic twins with NF-1demonstrated mixed concordance and discordance for pres-ence of scoliosis [15]. The affected twin pairs were discor-dant for presence of dystrophic features, degree of curvature,and need for surgery. This finding suggests that both heri-table and nonheritable factors contribute to the pathogenesisof spinal deformities in patients with NF-1. Dystrophiccurves most likely require a nonhereditary event, such as anadjacent tumor or dural ectasia, or a second hit event in localbone cells leading to the underlying dysplasia.

Commonly encountered spinal deformities

Cervical spineThe dysplastic features are more commonly associated

with deformities of the cervical spine compared with otherregions of the spine. Most of the patients with spinal defor-mities are asymptomatic. When symptoms are present, neckpain is the most common presenting concern. In more severecases, neurologic deficits, including nerve root compromiseand complete or incomplete spinal cord compromise, mayoccur. However, clinical consequences of cervical spinedeformities are less marked than in other areas of the spinebecause the cord versus canal diameter is less critical.

Anteroposterior and lateral Radiographs of the cervicalspine should be obtained in all NF-1 patients who: 1) areplaced in halo traction; 2) undergo surgery; 3) requireendotracheal intubation; 4) present with neck tumors; 5)complain of neck pain; or 6) present with symptoms indi-cating intra- or extraspinal neurofibromas, such as torti-collis or dysphagia. If there is any suspicion of instability,computed tomography (CT) and/or flexion-extensionmagnetic resonance imaging (MRI) are indicated. Erosivedefects of the skull may be present in some patients withNF-1. Thus, plain Radiographs of the skull before appli-cation of halo or Gardner-Wells tong traction pins are

strongly recommended. A CT scan of the scull may beordered if plain Radiographs are difficult to interpret.

The most commonly encountered cervical spine defor-mity is kyphosis (Fig. 1). It may be associated with atlan-toaxial instability. Progressive kyphosis is more commonthan nonprogressive kyphosis. The most common scenariois kyphosis secondary to tumor excision surgery withresection of the laminae and posterior elements withoutstabilization. Therefore, we recommend stabilization of thespinal column at the same time of surgical removal oftumors from the spinal canal.

In cases of progressive kyphosis of the cervical spine withinstability, posterior spinal fusion is recommended. If thedeformity is flexible, preoperative halo traction is indicated.For rigid deformities, anterior release followed by halotraction and posterior fusion is the treatment of choice. Incases of previous laminectomy, anterior release and fusionusing an autologous fibula followed by posterior fusion withautologous iliac bone graft and instrumentation is needed.The level of instability often requires an occipitocervicalfusion. Internal fixationwith pedicle and lateralmass screws ispreferred for posterior instrumentation. Sublaminar wirefixationmaybedifficult secondary todural ectasia andosseousfragility. For anterior fixation, we currently use bioabsorbableplates in young children. Even with rigid plate fixation, post-operative halo immobilization is recommended until a fusionmass with trabecular pattern is seen on cervical CT.

Thoracolumbar spineScoliosis. Coronal plane deformity of the thoracic and/orlumbar spine can present either with dystrophic features orin a pattern that is clinically indistinguishable from anidiopathic curve. Traditionally, the term dystrophic scoli-osis is used to describe thoracic and/or lumbar curves thathave, at the time of diagnosis, more than 3 dystrophicfeatures, as identified on plain radiographs. Dystrophic

Fig. 2. Seven-year-old female patient with NF-1 and severe cervicothoracic scoliosis, significant tumor burden around the thoracic spine and spinal cord

compression with myelomalacia on imaging, and weakness in the lower extremities (A, B, C, D). Preoperatively, halo traction was applied. The patient under-

went C6eT4 bilateral laminectomy for decompression of spinal cord followed by C4eT12 cervicothoracic posterior fusion with instrumentation and allo-

graft (E, F, G, H).


features include rib penciling (the rib being smaller indiameter than the 2nd rib), vertebral rotation, posteriorvertebral scalloping, vertebral wedging, spindling of thetransverse process, anterior vertebral scalloping, widenedintervertebral foramina, enlarged intervertebral foramina,and lateral vertebral scalloping. The concept of modulationrefers to the ability of a spinal deformity to transform byacquiring various dystrophic features. This condition hasbeen described only in patients with NF-1. Modulation canresult either in transformation of a nondystrophic curve todystrophic, or an addition of further dystrophic features toa curve already diagnosed as dystrophic.

More recent MRI studies have questioned the theory ofmodulation [16]. Patients with radiographically labelednondystrophic curves have been found to have significantdysplastic changes on MRI. Considering the higher sensi-tivity of MRI in identifying dystrophic features comparedwith X-rays films, we recommend characterization of thecurve as dystrophic or not based on findings from both MRIand X-ray films.

Nondystrophic scoliosis. Nondystrophic scoliosis repre-sents the most common spinal deformity in patients withNF-1. Clinical and radiographic findings, treatment, andcomplications are similar to those described for idiopathicscoliosis [17]. Observation is indicated for patients withnondystrophic curves measuring 20� to 25�. If the patient isskeletally immature and presents with a curve between 25�

and 40�, bracing or growing rod is to be considered. If thedeformity exceeds 40�, it should be treated with posteriorspinal fusion with instrumentation (Fig. 2). For curvesexceeding 55� to 60�, the treatment is anterior disc excisionand fusion with autologous bone graft of the area ofcurvature followed by posterior spinal fusion of all articularfacets, segmental spinal instrumentation, and autogenousiliac crest bone graft [18]. Postoperative orthosis andassessment of the fusion mass by CT or MRI at 6 monthsafter surgery are highly recommended (Fig. 3).

Dystrophic Scoliosis. Although less common than non-dystrophic curves, dystrophic curves represent a challenge

Fig. 3. Postoperative coronal computed tomography of a 14-year-old

male patient with dystrophic curve of the thoracic spine. A solid fusion

mass is noted at 6 months after his instrumented posterior spinal fusion

from T3eT12.


for the spine surgeon. They are characterized by rapidcourse of progression, a tendency to progress to a severedeformity, and a higher rate of pseudoarthrosis aftersurgery. A dystrophic curve is defined as any curvature with3 or more dystrophic features. The classic dystrophicdeformity is a short segmented and sharply angulated curvethat usually involves less than 6 spinal segments in theupper thoracic spine. Apical vertebral rotation can becomeso severe that it rotates out of the support axis [19]. Onplain radiographs, this may be interpreted as a congenitaldeformity. The patient may present with scoliosis,kyphosis, or frequently, with kyphoscoliosis.

Almost all authors agree on an early and aggressiveapproach to dystrophic curves [19,20]. This discussion willnot include early onset spinal deformities in children under9 years old. Bracing has not been effective and is not rec-ommended in any dystrophic deformity. Dystrophic curvesless than 20� should be observed for progression at 6-monthintervals. For patients with deformity between 20� and 40�

in the coronal plane, a posterior spinal fusion from theneutral vertebra cephalad to the curve to the neutral vertebracaudal to the curve and segmental spinal instrumentationwith pedicle screws, if possible, is performed [21,22]. Theuse of autogenous iliac crest graft is highly recommended tominimize the occurrence of pseudoarthrosis and recurrenceof the deformity. Trunkal height loss is not significantbecause the curve is usually short with poor growth poten-tial in the involved vertebrae. Dystrophic curves exceeding40� in the coronal plane or associated with kyphosis greaterthan 50� should be treated with anterior discectomy and

intervertebral fusion, followed by posterior fusion andstabilization with segmental instrumentation [22]. For rigidcurves greater than 90�, we recommend anterior release,nasojejunal tube alimentation, and craniofemoral tractionfollowed by posterior spinal fusion. If the curve exceeds100� in any plane, anterior and posterior release, nasojeju-nal tube alimentation, and craniofemoral traction followedby posterior spinal fusion is our treatment of choice. Thegoal of surgical management is to arrest the progression ofdeformity instead of achieving complete correction [20].We always recommend postoperative orthotic immobiliza-tion in an effort to prevent pseudoarthrosis. The orthosisshould be maintained until a fusion mass is obtained.Assessment of the fusion mass by CT or MRI at 6 monthsafter surgery is recommended.

Kyphoscoliosis. Kyphoscoliosis is distinguished by a curveof 50� or more in the sagittal plane associated with anydegree of coronal deformity (Fig. 4). Paraplegia is a notinfrequent complication in patients with NF-1 and kypho-scoliosis. This can be explained by elongation of the spinalcanal and deformation of the spinal cord after increasedspinal flexion, as in case of kyphosis [23]. This, in turn, willlead to excessive tension of the spinal cord parenchyma andsubsequent neurologic impairment. Dural ectasia and spinalcanal expansion is felt to be protective of the spinal cord insevere curves. In all NF-1 patients with paraplegia, ribprotrusion into the spinal canal and intraspinal tumorsshould be ruled out with an MRI. Imaging evaluation ofkyphoscoliosis also includes a hyperextension cross tablelateral view with the patient lying over a bolster to accessthe flexibility of the curvature. The vertebral bodies at theapex are frequently so deformed that it may be impossibleto identify them on plain Radiographs. In such cases, a 3-dimensional CT scan can be very helpful in surgicalplanning.

All patients with NF-1 and associated kyphoscoliosisrequire both anterior and posterior fusion [22]. Even ifa combined approach is performed, a bona fide fusion is notalways achievable, making repeat operative proceduresoccasionally necessary. With flexible curves, these proce-dures can be performed during the same anesthesia, unlessthere is a medical contraindication. If the deformity issevere and rigid, we recommend a staged procedure toobtain better correction. Anterior release and intervertebralbody fusion is followed by craniofemoral traction of 7 to 10days, during which the patient should be observed carefullywith repeated neurologic examinations. Then, posteriorinstrumented fusion is performed. Assessment of the fusionmass by CT at 6 months postoperatively is recommended. Ifpseudoarthrosis is noted, augmentation of the fusion massis indicated. Vertebral column resection is an option insome of these cases.

Lordoscoliosis. Lordoscoliosis has not been as frequentlyreported in patients with NF-1 as kyphoscoliosis is (Fig. 5).

Fig. 4. (A, B, C) Male patient with NF-1, progressive kyphoscoliosis, and congenital heart disease. (D, E) At age 17 years, he underwent posterior spinal

fusion with instrumentation from T1eL2.


However, lordosis of the thoracic spine may predispose tosignificant respiratory compromise and mitral valveprolapse. Anterior release and intervertebral fusion fol-lowed by posterior instrumented fusion is considered themost reliable surgical option to achieve correction ofdystrophic lordoscoliosis. Sublaminar wires, pediclescrews, or rod-multiple hook constructs can be used.

Spondylolisthesis. Spondylolisthesis in patients with NF-1is rare [14]. It is characterized by pathologic forwardprogression of the anterior elements of the spinal column.Spondylolisthesis in patients with NF-1 is most often

associated with pathologic elongation and thinning of thepedicles or pars interarticularis by lumbosacral foraminalneurofibromas or dural ectasia with meningoceles. Thevertebral bodies may also be small and dystrophic. MRIand/or CT scans are absolutely necessary for preoperativeevaluation. Fusion may also be delayed because of theforward traction effect of the vertebral bodies and the slowhealing and remodeling of bone for patients with NF-1. Werecommend a combined anterior and posterior fusion fromL4 to sacrum using intervertebral body grafting andlumbosacral instrumentation. Postoperative immobilizationis indicated until the fusion is absolutely solid.

Fig. 5. Clinical (A, B) and radiographic (C, D, E) presentation of a 9-year-old female patient with NF-1, lordoscoliosis of the thoracic spine and significant

tracheobronchial tumor load. (F, G) She was treated with a posterior spinal fusion and instrumentation with a hybrid construct extending from T1eL1.


Complications and Pitfalls of Surgical treatment

Pseudoarthrosis

The incidence of pseudoarthrosis after an attempt atspinal fusion in NF-1 patients with dystrophic or non-dystrophic spinal deformities is higher than in patients withidiopathic scoliosis. Crawford reported a 15% incidence ofpseudoarthrosis [22]. Sirois and Drennan reported a 38%incidence of pseudoarthrosis and an average of 1.7

procedures to achieve solid fusion [24]. Parisini et al.conducted a retrospective evaluation of surgical outcomesin NF-1 patients with severe progressive scoliosis in thepediatric age group [20]. Twenty-three consecutive patientswere surgically treated over 15 years. Patients were dividedinto 2 groups according to the surgical procedure adopted.Fusion failure was observed in 47% of patients whounderwent posterior fusion alone and in 33% of patientswho underwent preplanned circumferential fusion.

Fig. 6. Treatment algorithm in patients with neurofibromatosis 1 (NF-1) and spinal deformity.


Decortication, abundant autogenous bone grafting, andsegmental instrumentation are necessary to minimize theoccurrence of pseudoarthrosis. Pedicle screw fixation is thetreatment of choice if pedicles are adequate. Hooks and/orsublaminar wires should be available. During anterior dis-kectomy and release, meticulous resection of all the patho-logic soft tissue is of paramount importance. Any graftmaterial that is surrounded by abnormal soft tissue tends toresorb in the midportion. Even if rigid fixation has beenachieved using modern instrumentation, orthotic immobili-zation is recommended until a fusion mass with trabecularpattern is seen in CT scan performed 6 months after surgery.Re-exploration and graft augmentation is indicated for failedfusions. Most recently, recombinant human bone morphoge-netic protein-2 (rhBMP-2) has been used off label to achievea definitive fusion. A recent report of malignant trans-formation of a neurofibroma to sarcoma after application ofrhBMP-2 has been published [25]. Although there does notappear to be a clear association, the potential for stimulationof malignant degeneration of a benign plexiform neurofi-broma gives one concern.

Paraplegia

A neurologic deficit in a patient with NF-1 can be due tospinal cord compression secondary to spinal deformity, ribpenetration into the spinal canal, or intraspinal tumors,including neurofibromata, schwannoma or other tumors of

neuroectodermal origin. Paraplegia in young patients isusually caused by spinal deformity, whereas in olderpatients it is usually caused by tumors. Neurologicimpairment is more common in patients with NF-1 andkyphosis. Patients with paraplegia associated with spinalcurvatures and without significant kyphosis should beassumed to have intraspinal lesions until proven otherwise.In any case, the cause should be accurately defined with anMRI of the spine.

Rib protrusion

Clinical presentation of intraspinal rib displacementvaries with the majority of patients being asymptomatic[26]. A painful rib hump has been described as a warningsign of rib dislocation [27]. More severe cases may result inparaplegia secondary to spinal cord impingement. Ribprotrusion occurs at the convex side of the apex and usuallyinvolves a single middle to lower rib. In contrast, the spinalcord in the canal usually displaces towards the concaveside. When rib dislocation is present and not addressedbefore surgery, correcting the deformity may cause the cordto be centralized in the canal and impinged by the rib headon the convex side.

Rib head dislocation into the spinal canal should beruled out before any attempt for surgical correction of thespinal deformity because correction may result in spinalcord impingement by the unrecognized dislocated rib head.


Imaging with CT is indicated to accurately demonstratebone pathology. When rib protrusion is identified beforesurgery, ostectomy of 2.5 to 5 cm of the protruding rib isindicated at the time of posterior fusion.

Vertebral column dislocation

Extensive osseous erosion secondary to dural ectasiamay result in subluxation or dislocation of the spine withlittle radiographic or clinical warning. This diagnosisshould be considered in any patient with NF-1 whocomplains of pain in the neck or back. Rotational disloca-tion of the spine in patients with NF-1 is a rare complica-tion first described by Duval-Beaupere and Dubousset in1972 [28]. It usually involves the thoracic spine and resultsin progressive spinal deformity with or without neurologicdeficit.

Atlantoaxial instability has been attributed to laxity ofcapsular and ligamentous structures. Posterior spinalfusion is recommended in patients with cervical spineinstability. The level of instability often requires an occi-pitocervical fusion. Even when using instrumentation,a halo orthosis is recommended to stabilize the occipito-cervicothoracic area until fusion takes place. The screeningfor instability is only carried out in patients who haveundergone surgical decompression without fusion. Patientsnot treated with surgery are screened annually with a plainRadiograph.

Intraoperative complications

Bleeding during spine deformity surgery as well aspostoperative hemorrhage and hematoma formation are notuncommon in patients with NF-1, especially if an anteriorapproach was used. Meticulous hemostasis using bipolarcoagulation and hemostatic agents, ie, thrombin, hemo-static matrix (Floseal, Baxter, USA), must be carried outduring surgery. The senior author recommends a putty ofGelfoam (Baxter, USA), microfibrillar collagen hemostat(Avitene, Davol Inc., USA) and thrombin (human powder)to be available. Hemovac drainage is recommended in allpatients with NF-1 undergoing spine surgery.

Progression

Progression of the deformity may be noticed after solidspinal arthrodesis. Thus, close follow-up is needed evenafter successful spinal fusion. In patients who are skeletallyimmature, anterior spinal fusion in conjunction withposterior surgery is required to prevent the occurrence ofcrankshaft phenomenon, which is produced by continuingunbalanced anterior vertebral growth.

Pulmonary compromise

Lordoscoliosis predisposes to significant decrease inpulmonary function and mitral valve prolapse. Anterior

surgery may result in pulmonary problems, includingatelectasis, pneumonia, and hemothorax. Pulmonarysymptoms, including cough and dyspnea, have been asso-ciated with massive intrathoracic meningoceles.

Gastrointestinal problems

Ileus and nutritional problems are not infrequent whena staged anterior and posterior spine surgery is performedand while the patient is kept in craniofemoral traction.Therefore, we recommend nasojejunal tube placement andhyperalimentation for all patients who undergo stagedanterior and posterior surgery.

Other

Additional complications after surgical treatment ofspinal deformities in patients with NF-1 include duralleaks, urinary track infection, and thrombophlebitis.

Conclusion

Scoliosis is the most common osseous manifestation ofNF-1 (Fig. 6). It is important to recognize the dystrophiccurve and to distinguish it from the nondystrophic curve.Dystrophic curves may result in scoliosis, kyphosis, orfrequently, kyphoscoliosis. Bracing is not effective in themanagement of dystrophic curves, and an aggressiveapproach to management is recommended. The currentstate-of-the-art treatment for significant deformity iscombined anterior and posterior spinal arthrodesis. Post-operative orthotic immobilization is almost always recom-mended in an effort to prevent pseudoarthrosis. Majorcomplications, such as paraplegia, pseudoarthrosis, intra-operative hemorrhage, and postoperative progression of thedeformity may occur. In an attempt to eliminate compli-cations and achieve the best results, a multidisciplinarytreatment strategy is needed.

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Neurofibromatosis Etiology, Commonly Encountered Spinal Deformities and Surgical Treatment

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