The immature spine in type-1 neurofibromatosis

A Nationwide Study Characterizing the Risk and Outcome Profiles of Multilevel Fusion Procedures in Neuromuscular Scoliosis Patients with Neurofibromatosis Type 1

BACKGROUND

Spine abnormalities are a common manifestation of Neurofibromatosis Type 1 (NF1); however, the outcomes of surgical treatment for NF1-associated spinal deformity are not well explored. The purpose of this study was to investigate the outcome and risk profiles of multilevel fusion surgery for NF1 patients.

METHODS

The National Inpatient Sample was queried for NF1 and non-NF1 patient populations with neuromuscular scoliosis who underwent multilevel fusion surgery involving eight or more vertebral levels between 2004 and 2017. Multivariate regression modeling was used to explore the relationship between perioperative variables and pertinent outcomes.

RESULTS

Of the 55,485 patients with scoliosis, 533 patients (0.96%) had NF1. Patients with NF1 were more likely to have comorbid solid tumors (P < 0.0001), clinical depression (P < 0.0001), peripheral vascular disease (P < 0.0001), and hypertension (P < 0.001). Following surgery, NF1 patients had a higher incidence of hydrocephalus (0.6% vs. 1.9% P = 0.002), seizures (4.9% vs. 5.7% P = 0.006), and accidental vessel laceration (0.3% vs.1.9% P = 0.011). Although there were no differences in overall complication rates or in-hospital mortality, multivariate regression revealed NF1 patients had an increased probability of pulmonary (OR 0.5, 95%CI 0.3-0.8, P = 0.004) complications. There were no significant differences in utilization, including nonhome discharge or extended hospitalization; however, patients with NF1 had higher total hospital charges (mean -$18739, SE 3384, P < 0.0001).

CONCLUSIONS

These findings indicate that NF1 is associated with certain complications following multilevel fusion surgery but does not appear to be associated with differences in quality or cost outcomes. These results provide some guidance to surgeons and other healthcare professionals in their perioperative decision making by raising awareness about risk factors for NF1 patients undergoing multilevel fusion surgery. We intend for this study to set the national baseline for complications after multilevel fusion in the NF1 population.

How to select the lowest instrumented vertebra in NF-1 non-dystrophic scoliosis

PURPOSE

To investigate lowest instrumented vertebra (LIV) selection strategy for neurofibromatosis type 1 (NF-1) non-dystrophic scoliosis.

METHODS

Consecutive eligible subjects with NF-1 non-dystrophic scoliosis were included. All patients were followed up at least for 24 months. Enrolled patients with LIV in stable vertebra were divided into stable vertebra group (SV group), and the other patients with LIV above the stable vertebra were divided into above stable vertebra group (ASV group). Demographic data, operative data, preoperative and postoperative radiographic data, and clinical outcome were collected and analyzed.

RESULTS

There were 14 patients in SV group (ten males and four females, mean age 13.9 ± 4.1 years) and 14 patients in ASV group (nine males and five females, mean age 12.9 ± 3.5 years). The mean follow-up period was 31.7 ± 17.4 months for patients in SV group and 33.6 ± 17.4 months for patients in ASV group, respectively. No significant differences were found in demographic data between two groups. The coronal Cobb angle, C7-CSVL, AVT, LIVDA, LIV tilt and SRS-22 questionnaire outcome significantly improved at the final follow-up in both groups. However, significantly higher loss of correction rate and increasement of LIVDA were found in ASV group. Two patients (14.3%) in ASV group but none in SV group suffered adding-on phenomenon.

CONCLUSIONS

Although patients in both SV and ASV groups obtained improved therapeutic efficacy at final follow-up, the radiographic and clinical outcome seemed more likely to deteriorate in ASV group after surgery. The stable vertebra should be recommended as LIV for NF-1 non-dystrophic scoliosis.

Phenotyping spinal abnormalities in patients with Neurofibromatosis type 1 using whole-body MRI

Neurofibromatosis Type 1 (NF1) has been reported to be associated with a variety of spinal abnormalities. The purpose of this study was to quantify the prevalence of spinal abnormalities in a collective of NF1 patients that is representative for the general NF1 population, to associate the co-appearance of spinal abnormalities with both NF1 and clinical symptoms and to investigate if different mutations of the NF1 gene affect the prevalence of these abnormalities. Retrospectively, 275 patients with NF1 and an age- and sex-matched collective of 262 patients were analyzed. The prevalence of spinal abnormalities was recorded. Mutational analysis of the NF1 gene was obtained in 235 NF1 patients. Associations between spinal abnormalities, clinical symptoms and genotype were investigated by binary logistic regression analysis. Prevalence of all spinal abnormalities was higher in NF1 patients than in the control group. Six characteristics of spinal abnormalities were significantly associated with NF1 (all p < 0.05). An influence of scalloping on scoliosis (OR 3.01; p = 0.002); of meningoceles (OR 7.63) and neuroforaminal tumors (OR 2.96) on scalloping, and of dural ectasia on neuroforaminal tumors (OR 1.93) was identified. Backpain and loss of motor function were associated with neuroforaminal tumors, spinal tumors and scalloping of vertebral bodies (all p < 0.05). Specific mutations of the NF1 gene were not relevantly associated with the development of spinal abnormalities. These findings can aid clinicians to improve clinical care of NF1 patients by creating awareness for co-appearences of specific spinal abnormalities and associated symptoms.

Classification of neurofibromatosis-related dystrophic or nondystrophic scoliosis based on image features using Bilateral CNN

PURPOSE

We developed a system that can automatically classify cases of scoliosis secondary to neurofibromatosis type 1 (NF1-S) using deep learning algorithms (DLAs) and improve the accuracy and effectiveness of classification, thereby assisting surgeons with the auxiliary diagnosis.

METHODS

Comprehensive experiments in NF1 classification were performed based on a dataset consisting 211 NF1-S (131 dystrophic and 80 nondystrophic NF1-S) patients. Additionally, 100 congenital scoliosis (CS), 100 adolescent idiopathic scoliosis (AIS) patients, and 114 normal controls were used for experiments in primary classification. For identification of NF1-S with nondystrophic or dystrophic curves, we devised a novel network (i.e., Bilateral convolutional neural network [CNN]) utilizing a bilinear-like operation to discover the similar interest features between whole spine AP and lateral x-ray images. The performance of Bilateral CNN was compared with spine surgeons, conventional DLAs (i.e., VGG-16, ResNet-50, and Bilinear CNN [BCNN]), recently proposed DLAs (i.e., ShuffleNet, MobileNet, and EfficientNet), and Two-path BCNN which was the extension of BCNN using AP and lateral x-ray images as inputs.

RESULTS

In NF1 classification, our proposed Bilateral CNN with 80.36% accuracy outperformed the other seven DLAs ranging from 61.90% to 76.19% with fivefold cross-validation. It also outperformed the spine surgeons (with an average accuracy of 77.5% for the senior surgeons and 65.0% for the junior surgeons). Our method is highly generalizable due to the proposed methodology and data augmentation. Furthermore, the heatmaps extracted by Bilateral CNN showed curve pattern and morphology of ribs and vertebrae contributing most to the classification results. In primary classification, our proposed method with an accuracy of 87.92% also outperformed all the other methods with varied accuracies between 52.58% and 83.35% with fivefold cross-validation.

CONCLUSIONS

The proposed Bilateral CNN can automatically capture representative features for classifying NF1-S utilizing AP and lateral x-ray images, leading to a relatively good performance. Moreover, the proposed method can identify other spine deformities for auxiliary diagnosis.

Management of Proximal Thoracic Kyphoscoliosis with Early Myelopathy in a Young Adult with Neurofibromatosis Type 1: A Case Report and Review of Literature

INTRODUCTION

Neurofibromatosis (NF) 1 is associated with skeletal deformities. Scoliosis is seen in about 10-64% of NF-1 patients. NF-1 may be associated with dystrophic or non-dystrophic type of curve. There are technical difficulties in treating large dystrophic curve with proximal thoracic kyphoscoliosis in NF-1. This case report and subsequent review of literature attempts to provide a line of management for such difficult lesions.

MATERIALS AND METHODS

We present a case of 22-year-old male with NF-1 who came to us with gradually progressive upper back deformity and signs of early myelopathy for 2-3 months. The patient had a 100° proximal thoracic kyphosis and 100° scoliosis with no neurological deficit and brisk reflexes. A single stage posterior fixation with three column osteotomy at the apex of the curve was performed.

RESULTS

The kyphosis was corrected to 65° from 100, the scoliosis was corrected to 60° from 100. Clinically, the hump in the upper back was visibly reduced. At 1-year follow-up, the patient remained asymptomatic with no loss of correction and implant breakage on X-ray.

CONCLUSION

Large dystrophic proximal thoracic kyphoscoliosis is a difficult lesion to treat and can be managed with an all posterior approach, achieving good cosmetic and neurological outcomes, as demonstrated by this case.

Morphological Differences Between the Pedicles in Nondystrophic Scoliosis Secondary to Neurofibromatosis Type 1 and Those in Adolescent Idiopathic Scoliosis

OBJECTIVE

To compare the pedicle morphology of nondystrophic scoliosis secondary to neurofibromatosis type 1 (ND-NF1) scoliosis secondary to neurofibromatosis type 1 (NF1-S) and adolescent idiopathic scoliosis (AIS) using computed tomography (CT) in a consistent classification system.

METHODS

The transverse pedicle widths of cancellous and cortical channels were measured using preoperative spinal CT images (T1-L5) and then classified as having type A-E pedicles; type B, C, D, and E pedicles were regarded as abnormal. A subset of these patients, a postoperative CT was performed to evaluate the accuracy of pedicle screw placement. According to the perforation of the medial or lateral pedicle walls by the pedicle screw, the placement of screw was classified by a grade ranging from 0 to 3, and grades 2 and 3 were regarded as misplacement.

RESULTS

In total, 3230 pedicles were measured and classified, and the incidence rate of abnormal pedicles in the ND-NF1 group was significantly greater than that of the AIS group (65.9% vs. 61.4%, P = 0.03). The misplacement rate in the ND-NF1 group was significantly greater than that in the AIS group (12.2% vs. 7.4%; P = 0.01), and in terms of the corresponding 1100 pedicles, the incidence rate of abnormal pedicles in the ND-NF1 group was higher than that in the AIS group (71.7% vs. 64.9%; P = 0.02).

CONCLUSIONS

The incidence rate of abnormal pedicles in patients with ND-NF1 is significantly greater than that of patients with AIS, and it may the reason for the higher misplacement rate of pedicle screws in patients with ND-NF1.

Grade V Thoracic Spondylolisthesis in Neurofibromatosis Type 1: Case Report and Literature Review

BACKGROUND

Grade V thoracic spondylolisthesis secondary to neurofibromatosis type 1 (NF-1), especially combined with vertebral fusion, is rare. We reported a case of a 26-year-old female diagnosed with grade V T2spondylolisthesis and T2-T5 autofusion secondary to NF-1, which caused severe kyphotic deformity and neurologic deficits, and she was treated with posterior decompression, internal fixation, and fusion.

CASE DESCRIPTION

The right-handed patient admitted to the clinic due to weakness of her legs. An eye examination documented a sign of Lisch nodules in the iris. Café-au-lait macules, dermal neurofibroma of multiple forms, and rubbery bumps of varying sizes could be observed on her skin. Paresis with muscle strength of 2/5 in both lower extremities with increased muscle tone and decreased muscle mass could be observed. Radiographic results indicated grade V thoracic spondylolisthesis with vertebral fusion from T2-T5 level. To alleviate neurologic dysfunction, posterior decompression, internal fixation, and fusion were performed. She reported marked improvement in lower limb motor and sensory functions during the follow-up, and her muscle strength recovered to 5/5.

CONCLUSIONS

Grade V thoracic spondylolisthesis combined with vertebral fusion on T2-T5 level in NF-1 is rare. Early surgical intervention of posterior spinal decompression with internal fixation and fusion yielded satisfactory clinical outcomes.

Management of spinal deformities and tibial pseudarthrosis in children with neurofibromatosis type 1 (NF-1)

The skeletal system is affected in up to 60% of patients with neurofibromatosis type 1. The most commonly observed entities are spinal deformities and tibial dysplasia. Early recognition of radiologic osseous dystrophy signs is of utmost importance because worsening of the deformities without treatment is commonly observed and surgical intervention is often necessary. Due to the relative rarity and the heterogenic presentation of the disease, evidence regarding the best surgical strategy is still lacking.

PURPOSE

To report our experience with the treatment of skeletal manifestations in pediatric patients with (neurofibromatosis type 1) NF-1 and to present the results with our treatment protocols.

MATERIALS AND METHODS

This is a retrospective, single expert center study on children with spinal deformities and tibial dysplasia associated with NF-1 treated between 2006 and 2020 in a tertiary referral institution.

RESULTS

Spinal deformity: Thirty-three patients (n = 33) were included. Mean age at index surgery was 9.8 years. In 30 patients (91%), the deformity was localized in the thoracic and/or lumbar spine, and in 3 patients (9%), there was isolated involvement of the cervical spine. Eleven patients (33%) received definitive spinal fusion as an index procedure and 22 (67%) were treated by means of "growth-preserving" spinal surgery. Halo-gravity traction before index surgery was applied in 11 patients (33%). Progression of deformity was stopped in all patients and a mean curve correction of 60% (range 23-98%) was achieved. Mechanical problems with instrumentation requiring revision surgery were observed in 55% of the patients treated by growth-preserving techniques and in none of the patients treated by definitive fusion. One patient (3%) developed a late incomplete paraplegia due to a progressive kyphotic deformity. Tibial dysplasia: The study group comprised of 14 patients. In 5 of them (36%) pathological fractures were present on initial presentation. In the remaining 9 patients (64%), anterior tibial bowing without fracture was observed initially. Four of them (n = 4, 28%) subsequently developed a pathologic fracture despite brace treatment. Surgical treatment was indicated in 89% of the children with pathological fractures. This involved resection of the pseudarthrosis, autologous bone grafting, and intramedullary nailing combined with external fixation in some of the cases. In 50% of the patients, bone morphogenic protein was used "off-label" in order to promote union. Healing of the pseudarthrosis was achieved in all of the cases and occurred between 5 to 13 months after the index surgical intervention. Four of the patients treated surgically needed more than one surgical intervention in order to achieve union; one patient had a re-fracture. All patients had a good functional result at last follow-up.

CONCLUSION

Early surgical intervention is recommended for the treatment dystrophic spinal deformity in children with NF-1. Good and sustainable curve correction without relevant thoracic growth inhibition can be achieved with growth-preserving techniques alone or in combination with short spinal fusion at the apex of the curve. Preoperative halo-gravity traction is a safe and very effective tool for the correction of severe and rigid deformity in order to avoid neurologic injury. Fracture union in tibial dysplasia with satisfactory functional results can be obtained in over 80% of the children by means of surgical resection of the pseudarthrosis, intramedullary nailing, and bone grafting. Wearing a brace until skeletal maturity is achieved is mandatory in order to minimize the risk of re-fracture.

[Etiology and significance of growth disturbances of the spine]

BACKGROUND

The majority of growth disturbances of the spine are acquired and their etiology is still unknown. Both scolioses and sagittal profile disorders are most commonly of idiopathic origin.

ETIOLOGY

The etiology is multifactorial and besides genetic, hormonal and mechanical factors also metabolic components seem to be involved. The risk of progression of an existing deformity is particularly high during the pubertal growth spurt. Accordingly, regular clinical and radiological controls should be carried out in this vulnerable period. Recently, spinal deformities have been classified according to the time of diagnosis rather than according to their etiology, considering the increasing knowledge about the correlation between spinal and thoracic growth and the associated maturation of the lungs. Therefore, the term "early onset scoliosis" considers all deformities of the spine diagnosed before the age of 10 years.

TREATMENT

In the case of failure of conservative treatment options, which have to be applied for as long as possible, definitive spinal fusion surgery should be delayed by the use of growth-sparing surgical techniques, aiming to achieve as normal pulmonary function as possible.

Treatment of early-onset scoliosis with growing rods in patients with neurofibromatosis-1

This study aimed at verifying the efficacy of growing rod treatment in patients affected by neurofibromatosis with early-onset scoliosis. The authors present a retrospective case study of seven children treated between 2001 and 2017. Mean age at initial surgery was 7.2 years. Mean Cobb angle was 82.7°. Lengthening was performed once a year. Mean Cobb angle at last follow-up was 50.1°. Mean spinal growth was 13.6 mm/year, with regular gain during lengthening procedures. Mean follow-up period was 7 years after the first surgery. Three patients underwent final fusion. Complications were one proximal junctional kyphosis, nine rod breakages, and one hook dislocation.

National Trends in Spinal Fusion Surgery for Neurofibromatosis

STUDY DESIGN

Analysis of a national database.

OBJECTIVE

To analyze trends in spinal fusion surgery for neurofibromatosis type I (NF-1) patients and to compare the surgical approaches.

SUMMARY OF BACKGROUND DATA

The preferred surgical approach for fusion treatment of spinal deformity in NF is not well established.

METHODS

We identified 548 patients with a diagnosis of NF-1 who had received spinal fusion surgery between 2003 and 2014. We compared posterior spinal fusion (PSF), anterior-posterior spinal fusion (APSF), and anterior spinal fusion with respect to patient demographics, institutional characteristics, in-hospital complications, and hospitalization lengths and costs. Significance was set at a value of p less than .05.

RESULTS

The number of spinal fusions for NF-1 significantly increased (p = .02) over the study period. The rate of PSF surgeries increased 2.9-fold, whereas the rate of APSF surgeries decreased 2.2-fold. There was also a significant association between the location of the fusion and surgical approach (p<.01), with 66% of ASF cases being cervical spine cases. Compared with patients undergoing PSF and ASF, patients undergoing APSF were significantly younger (p<.01) and had significantly higher hospitalization lengths and costs (p<.01). APSF costs were $180,714 as compared to $144,027 for PSF and $105,312 for ASF.

CONCLUSIONS

There have been significant increases in the rate of spinal fusion surgeries for NF-1 patients. Surgical treatment has shifted over the years and is dependent on the location of the deformity. Patients undergoing APSF are significantly younger.

LEVEL OF EVIDENCE

Level III.

Thoracic compression myelopathy due to the progression of dystrophic scoliosis, the presence of a paraspinal tumor, and high and excessive amplitude movement of the shoulder

The authors present a case of 45-year-old man with neurofibromatosis type 1 (NF-1) and thoracic scoliosis, previously undergoing fusion surgery, who developed myelopathy. This patient further complained of lightning pain when he extended and horizontally abducted the convex-side shoulder. Radiological examination revealed the progression of dystrophic scoliosis with opened spinal canals and the presence of a neurofibroma behind the spinal cord at the apical levels. Delayed development of spinal instability can occur due to dystrophy even postoperatively in patients with NF-1. After tumor resection, he had rapid recovery from myelopathy and no recurrence of radiating pain despite shoulder movement. These findings provide a speculation that high, intense amplitude movement of the shoulder toward the spinal canal causes the impingement on the neurofibroma, resulting in indirect compression of the exposed spinal cord. This is the first report describing thoracic compression myelopathy associated with paraspinal displacement of the scapula.

Surgical Treatment of Dystrophic Spinal Curves Caused by Neurofibromatosis Type 1: A Retrospective Study of 26 Patients

Dystrophic scoliosis in neurofibromatosis type 1 (NF-1) is difficult to treat. The purpose of this study was to review the clinical and radiological outcome of surgical treatment of dystrophic spinal curves in NF-1, for analyzing its efficacy, safety, and possible complications.This retrospective study consisted of 26 NF-1 patients with spinal deformities treated between 2003 and 2012 in our department. Preoperative X-ray, 3D-CT, and MRI were performed to evaluate the deformities of dystrophic scoliosis accurately. All patients were treated with posterior instrumented fusion alone using screws and hooks. According to the anatomical development situation of each patient's pedicles and the transverse processes, we chose different fixations and different fixed segments. The clinical and radiological outcomes of surgical correction were evaluated postoperatively.The average preoperative kyphosis was 43° (range 15-86°). The postoperative kyphosis had an average of 20° (range 10-39°) yielding 53% correction. At final follow-up, there was an average of 4.6% correction loss. The preoperative scoliosis Cobb angle had an average of 47° (range 35-96°). The postoperative scoliosis Cobb angle had an average of 21° (range 10-37°) yielding 55% correction. At final follow-up, there was an average of 6.6% correction loss. The apical vertebral body rotation was corrected by an average of 48%. At final follow-up, the score of the SRS-30 questionnaire ranged from 97 to 135 with an average of 109.In conclusion, the deformities of dystrophic scoliosis can be accurately determine through preoperative radiolographic evaluation, which plays an important role in guiding the correction of scoliosis program development. The results of this study demonstrate that satisfactory therapeutic effects can be achieved in the dystrophic scoliosis patients by preoperative meticulous surgical plans, intraoperative careful manipulation, and hybrid instrumentation.

Dystrophic spinal deformities in a neurofibromatosis type 1 murine model

Despite the high prevalence and significant morbidity of spinal anomalies in neurofibromatosis type 1 (NF1), the pathogenesis of these defects remains largely unknown. Here, we present two murine models: Nf1^flox/−;PeriCre and Nf1^flox/−;Col.2.3Cre mice, which recapitulate spinal deformities seen in the human disease. Dynamic histomorphometry and microtomographic studies show recalcitrant bone remodeling and distorted bone microarchitecture within the vertebral spine of Nf1^flox/−;PeriCre and Nf1^flox/−;Col2.3Cre mice, with analogous histological features present in a human patient with dystrophic scoliosis. Intriguingly, 36–60% of Nf1^flox/−;PeriCre and Nf1^flox/−;Col2.3Cre mice exhibit segmental vertebral fusion anomalies with boney obliteration of the intervertebral disc (IVD). While analogous findings have not yet been reported in the NF1 patient population, we herein present two case reports of IVD defects and interarticular vertebral fusion in patients with NF1. Collectively, these data provide novel insights regarding the pathophysiology of dystrophic spinal anomalies in NF1, and provide impetus for future radiographic analyses of larger patient cohorts to determine whether IVD and vertebral fusion defects may have been previously overlooked or underreported in the NF1 patient population.

CARM1 regulates astroglial lineage through transcriptional regulation of Nanog and posttranscriptional regulation by miR92a

Coactivator-associated arginine methyltransferase (CARM1/PRMT4)-mediated transcriptional coactivation and arginine methylation is known to regulate various tissue-specific differentiation events. Although CARM1 is expressed in the neural crest region in early development, coinciding with early neuronal progenitor specification, the role of CARM1 in any neuronal developmental pathways has been unexplored. Using a specific small-molecule inhibitor of CARM1-mediated H3R17 methylation in human embryonic stem cell line, we find that H3R17 methylation contributes to the maintenance of the astroglial cell population. A network of regulation was observed on the miR92a promoter by which H3R17-responsive Nanog bound to the miR92a promoter decreased upon inhibition, resulting in an abnormal gene expression program influencing the glial lineage. This was also true in zebrafish, in which, with the help of CARM1 inhibitor and CARM1 morpholinos, we show that inhibition of H3R17 methylation results in defective glial cell morphology and a sensory defect in a subpopulation. A gain-of-function strategy in which mCARM1 was introduced in the morpholino-treated embryos exhibited recovery of the sensory defect phenotype. This study thus establishes the functional cooperation between arginine methylation and microRNA expression in the neuronal developmental process, with potential implications in sensory development pathways.

Posterior-only spinal fusion without rib head resection for treating type I neurofibromatosis with intra-canal rib head dislocation

OBJECTIVES

Patients with Type I neurofibromatosis scoliosis with intra-canal rib head protrusion are extremely rare. Current knowledge regarding the diagnosis and treatment for this situation are insufficient. The purpose of this study is to share our experience in the diagnosis and surgical treatments for such unique deformities.

METHODS

Six patients with Type I neurofibromatosis scoliosis with rib head dislocation into the spinal canal were diagnosed at our institution. Posterior instrumentation and spinal fusion without intra-canal rib head resection via a posterior-only approach was performed for deformity correction and rib head extraction. The efficacy and outcomes of the surgery were evaluated by measurements before, immediately and 24 months after the surgery using the following parameters: coronal spinal Cobb angle, apex rotation and kyphosis of the spine and the intra-canal rib head position. Post-operative complications, surgery time and blood loss were also evaluated.

RESULTS

Patients were followed up for at least 24 months post-operatively. The three dimensional spinal deformity was significantly improved and the intra-canal rib head was significantly extracted from the canal immediately after the surgery. At follow-up 24 months after surgery, solid fusions were achieved along the fusion segments, and the deformity corrections and rib head positions were well maintained. There were no surgery-related complications any time after the surgery.

CONCLUSIONS

Systematic examinations are needed to identify patients with Type I neurofibromatosis scoliosis with rib head dislocation into the canal who can be treated by posterior-only spinal fusion without rib head resection.

Osseous erosion by herniated nucleus pulposus mimicking intraspinal tumor: a case report

Erosion of spinal osseous structure, so-called scalloping, has been rarely reported associated with herniated nucleus pulposus (HNP). We report a rare case of HNP causing erosion of the spinal osseous structure (including lamina). The patient was an 81-year-old woman with 3-year history of low-back pain and left leg radiating pain. Muscle weakness of the left leg was also apparent. Computed tomography following myelography showed severe compression of the dural sac at the level of L3–L4; furthermore, erosion of the lamina, pedicle, and vertebral body was noted, indicating that the space-occupying mass was most probably a tumorous lesion. The mass also showed calcification inside. During the surgery, the mass was confirmed to be an HNP with calcification. Following resection, the pain disappeared. Surgeons should be aware of the possibility of scalloping of the vertebrae caused by HNP mimicking a tumorous lesion.

Osteoclasts in neurofibromatosis type 1 display enhanced resorption capacity, aberrant morphology, and resistance to serum deprivation

Neurofibromatosis 1 syndrome (NF1) presents with skeletal involvement suggesting that altered bone dynamics is associated with NF1. Histological analysis of three cases of NF1-related pseudarthrosis revealed numerous osteoclasts in contact with adjacent bone, and within the pseudarthrosis tissue itself. These findings prompted us to evaluate the differentiation and resorption capacity of NF1-osteoclast like cells (OLCs) in vitro. Osteoclast progenitors were isolated from peripheral blood of 17 patients with NF1 and allowed to differentiate into OLCs on bone slices. The following differences were found between NF1 and control samples: samples from NF1 patients resulted in a higher number of resorbing OLCs; NF1 OLCs were larger in size; their nuclei were more numerous; actin rings were more frequent; and the resorption pits in NF1 samples were more numerous and larger. Bone resorption markers revealed that the resorption activity in NF1 OLC cultures was approximately two times higher than in controls. Following deprivation from serum, the number of NF1 OLCs remained essentially the same during 24h, whereas the number of control OLCs was dramatically reduced during the same time. Three patients had NF1-related lytic bone lesions, and their in vitro results differed from those of other patients. Our results demonstrate that OLCs derived from blood of patients with NF1 display elevated resorption activity under conditions isolated from microenvironment operative in vivo. Thus, increased osteoclast activity may be a phenotypic property of the NF1 syndrome, and at least in part explain selected skeletal findings in NF1, such as osteoporosis/osteopenia.

Reconstruction of skull base defects in sphenoid wing dysplasia associated with neurofibromatosis I with titanium mesh

Sphenoid wing dysplasia occurs in 3-7% of patients with neurofibromatosis type 1 (NF1). The typical radiological features are partial or complete absence of the greater wing of the sphenoid. This condition is slowly progressive and may result in temporal lobe herniation into the orbital cavity, producing pulsating exophthalmos and gross facial deformity. Thus, reconstruction of the orbit is important for both cosmetic and functional reasons. Traditional surgical treatment of sphenoid dysplasia involves split bone grafting and repair of the anterior skull base defect. However, several reports have demonstrated complications of graft resorption and recurrence of proptosis and pulsating exopthalmos. In this case series, we present two patients suffering from pulsating exophthalmos due to sphenoid dysplasia. Radiological and MRI studies demonstrated orbital enlargement and complete absence of the greater wing of the sphenoid. Surgical management of these patients involved dural defect repair, and the use of titanium mesh in conjunction with bone graft to act as a barrier between the orbit and the middle cranial fossa. The mesh was fixed by fine screws. Proptosis improved markedly post-operatively and resolved within a few weeks. Ocular pulsation subsided and remained quiescent with at least 1-year follow-up.

Local low-dose lovastatin delivery improves the bone-healing defect caused by Nf1 loss of function in osteoblasts

Postfracture tibial nonunion (pseudoarthrosis) leads to lifelong disability in patients with neurofibromatosis type I (NF1), a disorder caused by mutations in the NF1 gene. To determine the contribution of NF1 in bone healing, we assessed bone healing in the Nf1(ob) (-/-) conditional mouse model lacking Nf1 specifically in osteoblasts. A closed distal tibia fracture protocol and a longitudinal study design were used. During the 21- to 28-day postfracture period, callus volume, as expected, decreased in wild-type but not in Nf1(ob) (-/-) mice, suggesting delayed healing. At these two time points, bone volume (BV/TV) and volumetric bone mineral density (vBMD) measured by 3D micro-computed tomography were decreased in Nf1(ob) (-/-) callus-bridging cortices and trabecular compartments compared with wild-type controls. Histomorphometric analyses revealed the presence of cartilaginous remnants, a high amount of osteoid, and increased osteoclast surfaces in Nf1(ob) (-/-) calluses 21 days after fracture, which was accompanied by increased expression of osteopontin, Rankl, and Tgfbeta. Callus strength measured by three-point bending 28 days after fracture was reduced in Nf1(ob) (-/-) versus wild-type calluses. Importantly, from a clinical point of view, this defect of callus maturation and strength could be ameliorated by local delivery of low-dose lovastatin microparticles, which successfully decreased osteoid volume and cartilaginous remnant number and increased callus BV/TV and strength in mutant mice. These results thus indicate that the dysfunctions caused by loss of Nf1 in osteoblasts impair callus maturation and weaken callus mechanical properties and suggest that local delivery of low-dose lovastatin may improve bone healing in NF1 patients.

Corpectomy and circumferential spinal fusion in dystrophic neurofibromatous curves

PURPOSE

Spinal deformity in neurofibromatosis, when associated with dystrophic change, is a major treatment challenge. Early anterior and posterior spinal fusion is the accepted treatment plan for severe progressive kyphoscoliosis. Resection of the vertebral body as an additional step in correction and fusion has not been previously investigated. Information on the functional status of the neurofibromatous curves is also scarce in the literature. The purpose of this study is to report an experience with corpectomy and circumferential fusion in dystrophic spines of neurofibromatosis.

METHODS

Among 16 patients with dystrophic spinal curves, nine cases who had undergone anterior and posterior fusion with 6.7 years (range 2-11.9) average follow-up were evaluated clinically, radiographically, and functionally (SRS-22).

RESULTS

Nine cases with a mean age of 11.8 years (range 7.8-17) at surgery consisted of seven kyphoscoliotic patients, who had received one or two levels of cord decompression and corpectomy, and two cases of scoliosis with hypokyphosis. Surgery improved the mean preoperative scoliosis of 87 (range 60-110) and local kyphosis of 69.3° (range 50-100) to 49 (range 15-85) and 49° (range 35-70), respectively. Loss of correction of 5° in the scoliosis and 13° in the kyphosis angles was observed in the final follow-up. One surgery resulted in an immediate postoperative mortality. Fusion was achieved in all cases. The average SRS-22 score of 4.1 (range 3-4.6) was obtained.

CONCLUSIONS

Simultaneous anterior and posterior fusion with corpectomy for dystrophic neurofibromatous spinal deformities is associated with a high fusion rate, good correction, and also good functional outcome.

Surgical correction of severe dystrophic neurofibromatosis scoliosis: an experience of 32 cases

The surgical management of severe rigid dystrophic neurofibromatosis curves is a demanding procedure with uncertain results. Several difficulties are present in such patients including a poor bone stock, sharp angulation of these dystrophic curves and dural thinning or ectasia. The aim of this work was to review the clinical and radiographic outcomes of three-dimensional correction of severe rigid neurofibromatosis curves analyzing its efficacy, safety and possible complications. Thirty-two patients were followed up for an average of 6.5 years (range 3-9 years). The average age at surgery was 14 years (range 11-19 years). All patients had typical dystrophic curves, and the apex of the deformity was thoracic (n = 13), thoracolumbar (n = 14) and lumbar (n = 5). All patients had a two-staged procedure; an anterior release followed latter by posterior hybrid instrumentation augmented by sublaminar wires. Two wires were usually placed immediately below the proximal anchor, and several sublaminar wires were always passed at the apex of the deformity. There were a total of 142 wires with an average of 6.5 wires/patient (range 5-8 wires). The mean preoperative Cobb angle of the scoliotic curve was 102.2 degrees (range 71 degrees-114 degrees) corrected to an average of 39 degrees (range 16 degrees-49 degrees), and the loss of correction had an average of 4 degrees. The mean preoperative sagittal plane deformity was 49 degrees corrected by an average of 61%, and rotation was corrected by an average of 34%. There were no dural tears during passage of the sublaminar wires, no implant-related complications and no permanent neurologic deficits. The use of extensive and vigorous anterior release with posterior hybrid instrumentation has proved useful and effective in the treatment of these severe deformities; sublaminar wires allow safe gradual correction and even distribution of forces over multiple anchor points improving the correction achieved and decreasing implant-related complications.

Rib head protrusion into the central canal in type 1 neurofibromatosis

BACKGROUND

Intraspinal rib head dislocation is an important but under-recognized consequence of dystrophic scoliosis in patients with neurofibromatosis 1 (NF1).

OBJECTIVE

To present clinical and imaging findings of intraspinal rib head dislocation in NF1.

MATERIALS AND METHODS

We retrospectively reviewed clinical presentation, imaging, operative reports and post-operative courses in four NF1 patients with intraspinal rib head dislocation and dystrophic scoliosis. We also reviewed 17 cases from the English literature.

RESULTS

In each of our four cases of intraspinal rib head dislocation, a single rib head was dislocated on the convex apex of the curve, most often in the mid- to lower thoracic region. Cord compression occurred in half of these patients. Analysis of the literature yielded similar findings. Only three cases in the literature demonstrates the MRI appearance of this entity; most employ CT. All of our cases include both MRI and CT; we review the subtle findings on MRI.

CONCLUSION

Although intraspinal rib head dislocation is readily apparent on CT, sometimes MRI is the only cross-sectional imaging performed. It is essential that radiologists become familiar with this entity, as subtle findings have significant implications for surgical management.

Recent insights into bone development, homeostasis, and repair in type 1 neurofibromatosis (NF1)

Neurofibromatosis type 1 (NF1) is one of the most common single gene syndromes and is typified by a range of characteristic but variably penetrant manifestations. The orthopaedic manifestations of congenital pseudarthrosis of the tibia (CPT) and scoliosis, along with other skeletal defects including sphenoid wing dysplasia, rib penciling, and gracile bones have been classically associated with NF1. Added to this, several recent studies have reported a high prevalence of osteoporosis or osteopenia in NF1 cohorts. Clues to the underlying molecular and cellular deficiencies that cause these bony defects can be gleaned from genetically modified mouse models of Nf1 gene deficiency. These studies suggest that a variety of different cell lineages may be adversely affected by Nf1 haploinsufficiency or by double inactivation of the Nf1 gene. Osteoblasts, osteoclasts, chondrocytes, fibroblasts, and vascular endothelial cells all express the Nf1 gene product, neurofibromin, and may be functionally compromised when levels are decreased or absent. This paper reviews the current literature on NF1 bone development, homeostatic regulation, and repair, and highlights some emerging themes that may have relevance for managing orthopaedic disorders that can arise in individuals with NF1.

Scoliosis associated with neurofibromatosis

Neurofibromatosis type 1 (NF-1) is a multisystemic disease. It may manifest as abnormalities of the nervous tissue, bones, soft tissue, and skin. The manifestations of NF-1 vary from person to person and range from subclinical to severe. Individuals who carry the gene eventually exhibit some clinical feature of the disease. The penetrance for NF-1 nears 100% during adulthood. Skeletal abnormalities are common in NF-1, with most patients presenting with some type of bony dysplasia. The orthopedic complications usually appear early. They include spinal deformities, such as scoliosis or kyphosis, congenital tibial dysplasia with bowing and pseudarthrosis of the tibia, forearm, other bones, as well as overgrowth phenomenon of an extremity, and soft tissue tumors.