Current Aspects on the Pathophysiology of Bone Metabolic Defects during Progression of Scoliosis in Neurofibromatosis Type 1

Clinical features and surgical treatments of scoliosis in neurofibromatosis type 1: a systemic review and meta-analysis

BACKGROUND

Neurofibromatosis type 1 (NF 1) is an autosomal-dominant tumor predisposition genetic disease affecting approximately 1 in 3000 live births. The condition could present various manifestations ranging from skin abnormalities to neurological tumors. The musculoskeletal system could also be frequently affected, and scoliosis is the most common orthopedic manifestation. Characterized by the early-onset and rapid progression tendency, NF 1-related dystrophic scoliosis presented discrepancies from idiopathic scoliosis in terms of natural history, clinical features, and management outcomes and thus required special attention. In the current study, the authors conducted a systemic review to outline the body of evidence of the natural history, clinical characteristics, surgical outcomes, and surgical complications of NF 1-induced scoliosis, aiming to provide an elucidative insight into this condition.

METHOD

Systemic review and meta-analysis were conducted according to the latest Preferred Reporting Items for Systematic Reviews Meta-Analyses (PRISMA) guidelines. The search was performed in Medline, Embase, and Web of Science Core Collection up to December 27, 2022, using related keywords. Clinical features such as frequencies, segmental involvement, and hereditary information were summarized and described qualitatively. Meta-analysis was conducted using R software and the 'meta' package to yield an overall outcome of efficacy and safety of surgical management, precisely, spinal fusion procedure and growing rods procedure. Corrective rate of Cobb angle, sagittal kyphosis angle, and T1-S1 length post-operative and at the last follow-up was used to evaluate the efficacy, and the occurrence of surgery-related complications was used to evaluate the safety.

RESULT

A total of 37 articles involving 1023 patients were included. Approximately 26.6% of the NF 1 patients would present with scoliosis. Patients tend to develop scoliosis at an earlier age. The thoracic part turned out to be the most affected segment. No obvious correlation between scoliosis and genotype or hereditary type was observed. Both spinal fusion and growing rod surgery have shown acceptable treatment outcomes, with spinal fusion demonstrating better performance in terms of effectiveness and safety. The growing rods technique seemed to allow a better lengthening of the spine. The mainstay post-operative complications were implant-related complications but could be managed with limited revision surgery. Severe neurological deficits were rarely reported.

CONCLUSION

Scoliosis, especially the subtype characterized by dystrophic bony changes, is a significant orthopedic manifestation of NF1. It has an early onset, a tendency to persistently and rapidly progress, and is challenging to deal with. The current review outlines the available evidence from the perspective of natural history, clinical features, and the treatment efficacy and safety of the mainstay surgical options. Patients with NF1 scoliosis will benefit from a better understanding of the disease and evidence based treatment strategies.

Pathogenesis and treatment of a giant occipital bone defect with meningoencephalocele in an NF1 child: case report and review of the literature

Autosomal dominantly inherited neurofibromatosis type I (NF1) is a systemic disorder caused by a mutation of a gene on chromosome 17q11.2 and characterized by multiple café-au-lait spots, lentiginous macules, Lisch nodules of the iris, and tumors of the nervous system. Bony manifestations such as scoliosis, dysplasia of the greater sphenoidal wing, tibial pseudoarthrosis, short stature, and macrocephaly have been reported in approximately 50% of patients. However, calvarial bone defects are rare. After screening 324 articles, 23 cases (12 adult and 11 pediatric patients) of occipital bone defects in NF1 patients were selected. All patients had a single/multiple bone defect over the lambdoid suture. Adjacent benign plexiform neurofibromas were observed in 14 patients (60.8%, 7 adults and 7 children); one adult patient was diagnosed with neurofibrosarcoma. Meningoencephalocele over the occipital defect was noted in 8 cases (34.78%, all adults). Cranioplasty was performed in only 17.39% of patients. Histologic examination was performed in 7 of the 15 patients with associated neurofibromas/neurofibrosarcomas. Biopsy of the bone margins surrounding the defect was performed in only one case. Pathologic examination of the herniated parieto-occipital or cerebellar tissue was not performed in any of the patients studied. We report the case of a 9-year-old girl with NF1 and a significant occipital bone defect and performed a systematic review of the relevant literature to highlight the challenges in treating this condition and to investigate the underlying mechanisms contributing to bone defects or dysplasia in NF1.

Icariin Promotes Osteogenic Differentiation in a Cell Model with NF1 Gene Knockout by Activating the cAMP/PKA/CREB Pathway

Neurofibromatosis type 1 is a rare autosomal dominant genetic disorder, with up to 50% of patients clinically displaying skeletal defects. Currently, the pathogenesis of bone disorders in NF1 patients is unclear, and there are no effective preventive and treatment measures. In this study, we found that knockout of the NF1 gene reduced cAMP levels and osteogenic differentiation in an osteoblast model, and icariin activated the cAMP/PKA/CREB pathway to promote osteoblast differentiation of the NF1 gene knockout cell model by increasing intracellular cAMP levels. The PKA selective inhibitor H89 significantly impaired the stimulatory effect of icariin on osteogenesis in the NF1 cell model. In this study, an osteoblast model of NF1 was successfully constructed, and icariin was applied to the cell model for the first time. The results will help to elucidate the molecular mechanism of NF1 bone disease and provide new ideas for the clinical prevention and treatment of NF1 bone disease and drug development in the future.

Low Bone Mass and Recurrent Fractures in Neurofibromatosis With Concomitant Hemoglobin SC Disease

Bone disease and bone loss are common features in certain monogenic diseases such as RASopathies, including neurofibromatosis (NF). Similarly, bone complications are frequent in hemoglobinopathies, another group of Mendelian diseases. This paper reports a young patient with both NF and hemoglobin SC (HbSC) diseases who had multiple vertebral fractures with osteopenia. We also discuss the cellular and pathophysiological mechanisms underlying both diseases and the factors responsible for bone pain and low bone mass in NF and hemoglobinopathies such as HbSC. This case emphasizes the importance of careful evaluation and management of osteoporosis in patients with HbSC and NF1, as both are relatively common monogenic diseases in certain communities.

[Neurofibromatosis type 1 : From diagnosis to follow-up]

BACKGROUND

Neurofibromatosis type 1 (NF1) is a tumor predisposition syndrome and is one of the most common genetic diseases. It is therefore a condition encountered by radiologists in clinical routine. Since the variability of the clinical expression is very high and several organ systems are affected, we present a standardized diagnostic approach in this article.

METHODS

Evaluation of the literature on neurofibromatosis type 1 in the context of radiological examination methods.

RESULTS

In addition to the frequently known changes in the central and peripheral nervous system such as optic gliomas and plexiform neurofibromas, lesions from the orthopedic spectrum and vascular changes must also be included in the radiological diagnosis.

CONCLUSIONS

Due to the diversity of the clinical picture of NF1, it is reasonable to define an examination strategy which takes into account the needs of radiological routine and also reliably detects the most frequent and prognostically significant pathologies accompanying this disease. In this article, the current recommendations for diagnosis of neurofibromatosis-associated tumors and skeletal changes are summarized, and examination protocols and time intervals are suggested.