Associations of osseous abnormalities in Neurofibromatosis 1

Mandibular symmetry on posterior-anterior cephalograms of neurofibromatosis type 1 patients with facial plexiform neurofibroma

Introduction

Neurofibromatosis type 1 (NF1) is an is an autosomal dominant heritable tumor predisposition syndrome.. Peripheral nerve sheath tumors (PNST) are a hallmark of NF1. Plexiform neurofibromas (PNF) are neoplasms that are characteristic of NF1, often causing disfiguring effects (e.g., on the face), and are considered precancerous lesions. Previous studies have shown that facial PNF (FPNF) have an impact on the shape of facial bones. This study examines deviations of mandibular symmetry from cephalometric reference planes considering the topography of FPNF.

Material and methods

The posterior-anterior (PA) cephalograms of 168 patients with NF1 were examined. We compared three groups: patients with FPNF (n=74), with disseminated cutaneous neurofibroma (DNF (n=94)), and control subjects without NF1 (n=23). The PNF group was subtyped with respect to facial PNST type and location. Typical mandibular cephalometric reference points were determined (condyle, antegonion, and menton).

Results

The skeletal measurement points of the mandible in FPNF patients often differ significantly from those of the DNF group. It has been proven that typical asymmetries of the median-sagittal measurement points are indicators of PNF. Differences within the trigeminal tumor spread patterns are indicated in the measured values. A local tumor effect (PNF) on the relation of the measurement points to the reference planes is made plausible by the study results. The investigations prove that tumor type (FPNF) and the number of FPNF affected branches of the trigeminal nerve may correlate with significant deviations of mandible from symmetry on PA projections.

Conclusion

The presented study shows that characteristic patterns of mandibular deformity can be measured on standardized radiographs in NF1 patients with FPNF. Mandibular deformities imaged on standardized radiographs may be initial indicators of a previously unrecognized NF1. Tumor-associated alterations of the mandible should be considered in the classification systems of pathognomonic, diagnostically pioneering osseous findings in NF1. The radiological findings provide clues for planning mandibular osteotomies in NF1 patients, especially for assessing facial regions typically highly vascularized by tumor spread. Furthermore, the radiological findings are an indication of a tumor potentially invading and destroying adjacent masticatory and mimic muscle, findings that may have an influence on surgical measures (function, aesthetics, and wound healing).

Lateral orbital wall anomaly in a patient with thyroid eye disease

An isolated defect in the lateral orbital wall is an uncommon occurrence, although cases of orbital floor, roof, and medial wall spontaneous dehiscence have been described in the literature. Here, we describe a lateral orbital wall defect in a patient with thyroid eye disease - which may be related to bony remodeling or may represent a rare congenital anomaly. Computed tomography (CT) prior to decompression surgery revealed a defect in the left lateral orbital wall. At the time of orbital decompression, prolapse of buccal fat into the orbit was noted once the subperiosteal plane was entered along the lateral orbital wall in the area of this bony defect. Literature review revealed only a few previous reports of lateral wall abnormalities, including two involving the inferior orbital fissure; one other case was associated with Down syndrome, and other reports consist of sphenoid hypoplasia associated with neurofibromatosis.

Bone deformities in patients with neurofibromatosis type 1: Single-center experience

BACKGROUND

Neurofibromatosis type 1 (NF-1) is the most common neurocutaneous syndrome with an autosomal dominant inheritance. However, half of the cases are de novo mutations. Involvement of bone, skin (cafe au lait macules), as well as ocular and tumoral formations is also associated with NF-1. Here, we present our case series of patients with bone deformities.

METHODS

The medical files of patients with NF-1 who were followed up by the same doctor in the pediatric neurology outpatient clinic over 2 years were retrospectively analyzed.

RESULTS

Overall, 19 girls and 13 boys were diagnosed with NF-1. Of these 32 patients, 12 (nine girls, three boys) were found to have bone pathologies. The average age was of these patients with bone pathology was 7.5 and 9.5 years. Scoliosis, bowing, short stature, and long bone cysts were found in descending order of frequency. Severe adhesions in the hands and feet as well as phalangeal hypoplasia were noted in one patient.

CONCLUSION

NF-1 requires a multidisciplinary approach. Routine follow-up is very important as it is known that deformities that affect different systems may appear or increase with age. Severe hand and foot anomalies seen in one of our patients did not seem to be associated with NF-1.

RASopathies: The musculoskeletal consequences and their etiology and pathogenesis

The RASopathies comprise an ever-growing number of clinical syndromes resulting from germline mutations in components of the RAS/MAPK signaling pathway. While multiple organs and tissues may be affected by these mutations, this review will focus on how these mutations specifically impact the musculoskeletal system. Herein, we review the genetics and musculoskeletal phenotypes of these syndromes in humans. We discuss how mutations in the RASopathy syndromes have been studied in translational mouse models. Finally, we discuss how signaling molecules within the RAS/MAPK pathway are involved in normal and abnormal bone biology in the context of osteoblasts, osteoclasts and chondrocytes.

Intra-articular hip neurofibromas in von Recklinghausen's disease

Neurofibromatosis is a genetic disorder with osteo-articular manifestations. The intra-articular location of neurofibroma is scarce.

Understanding the Biological Activities of Vitamin D in Type 1 Neurofibromatosis: New Insights into Disease Pathogenesis and Therapeutic Design

Vitamin D is a fat-soluble steroid hormone playing a pivotal role in calcium and phosphate homeostasis as well as in bone health. Vitamin D levels are not exclusively dependent on food intake. Indeed, the endogenous production-occurring in the skin and dependent on sun exposure-contributes to the majority amount of vitamin D present in the body. Since vitamin D receptors (VDRs) are ubiquitous and drive the expression of hundreds of genes, the interest in vitamin D has tremendously grown and its role in different diseases has been extensively studied. Several investigations indicated that vitamin D action extends far beyond bone health and calcium metabolism, showing broad effects on a variety of critical illnesses, including cancer, infections, cardiovascular and autoimmune diseases. Epidemiological studies indicated that low circulating vitamin D levels inversely correlate with cutaneous manifestations and bone abnormalities, clinical hallmarks of neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant tumour predisposition syndrome causing significant pain and morbidity, for which limited treatment options are available. In this context, vitamin D or its analogues have been used to treat both skin and bone lesions in NF1 patients, alone or combined with other therapeutic agents. Here we provide an overview of vitamin D, its characteristic nutritional properties relevant for health benefits and its role in NF1 disorder. We focus on preclinical and clinical studies that demonstrated the clinical correlation between vitamin D status and NF1 disease, thus providing important insights into disease pathogenesis and new opportunities for targeted therapy.

Bone tissue and mineral metabolism in hereditary endocrine tumors: clinical manifestations and genetic bases

Inherited endocrine tumors are neoplasms of endocrine cells, transmitted via autosomal dominant germinal mutations. They present in two different forms: non-syndromic (patient has a single affected endocrine organ during his/her lifetime) or syndromic forms (multiple tumors in endocrine and non-endocrine organs during his/her lifetime).In addition to their common tumoral manifestations, many of these diseases present clinical affection of bone tissues and/or mineral metabolism, both as secondary complications of primary tumors and as primary defects due to genetic mutation. To date, few studies have documented these bone complications, and there are no systematic reviews in this area.We present a revision of medical literature about skeletal and mineral metabolism affections in inherited endocrine tumor syndromes, and studies, in cells and animal models, investigating the direct role of some genes, whose mutations are responsible for the development of endocrine tumors, in the regulation of bone and mineral metabolism.

Clinical, radiological features and surgical strategies for 23 NF1 patients with intraorbital meningoencephalocele

Intraorbital meningoencephalocele is a rare manifestation of neurofibromatosis type 1 (NF1) caused by secondary changes in sphenoid dysplasia, and it seriously affects patients' vision and facial appearance. We retrospectively analyzed the clinical data of 23 patients with NF1 and intraorbital meningoencephalocele, summarized the surgical strategies employed, and evaluated their clinical efficacy in order to better understand its management in clinical practice, establish a reasonable surgical strategy, and assess prognosis. Before surgery, 22 patients had unilateral pulsatile exophthalmos, 18 patients had significant visual impairment, and 13 patients had ptosis associated with an orbital plexiform neurofibroma (PNF). All 23 patients underwent microsurgical craniotomy with skull base reconstruction using a soft titanium mesh. One month after surgery, the degree of exophthalmos in the 22 (95.65%) patients was significantly reduced compared with before surgery (P < 0.001), and ocular pulsation had subsided. The visual acuity did not decrease significantly (P = 0.298) compared with before surgery. Eleven (47.83%) patients received phase-II eyelid PNF resection and/or oculoplastic surgery, and the degree of ptosis was significantly reduced (P < 0.001). There was no recurrence of pulsatile exophthalmos, displacement of titanium mesh, decreased visual acuity, or increased degree of ptosis noted during follow-up. The best strategy is to reconstruct the skull base under microscopy to relieve pulsating exophthalmos and preserve existing visual function. In cases of ptosis caused by an eyelid PNF, surgical resection should be performed as soon as possible to remove the tumor, and/or oculoplastic surgery should be performed to improve the cosmetic outcome.

Height Growth Impairment in Children With Neurofibromatosis Type 1 Is Characterized by Decreased Pubertal Growth Velocity in Both Sexes

Previous studies have suggested that children with neurofibromatosis type 1 are shorter than their unaffected counterparts as an effect of a germline NF1 gene mutation. The pathophysiology of this effect is still uncertain. The purpose of this study was to characterize longitudinal growth in children with neurofibromatosis type 1 in order to assess growth velocity and its influence on stature. Longitudinal height data were collected for 188 patients with a confirmed clinical diagnosis of neurofibromatosis type 1. Children with neurofibromatosis type 1 had population mean heights statistically different from the general population, with a reduced peak height velocity during pubertal growth. In addition, there were no significant differences in the timing of peak height velocity during puberty between the general population and those with neurofibromatosis type 1. These data demonstrate that short stature in neurofibromatosis type 1 is due in part to subnormal height acquisition during puberty.

A combination of skeletal deformations of the dorsal mandible and temporomandibular region detected in orthopantomograms of patients with neurofibromatosis type 1 indicates an associated ipsilateral plexiform neurofibroma

PURPOSE

Neurofibromatosis type 1 (NF1) is a tumour suppressor syndrome and also a bone disease. In the craniofacial region, local skeletal deformities have been recorded in patients with NF1. Obvious syndrome-related alterations of the jaws are particularly conspicuous in the mandible. Here we aimed to analyse the mandibular alterations of NF1-affected individuals from orthopantomograms (OPGs).

MATERIALS AND METHODS

This study analyses 358 OPGs of 358 patients (mean age, 34.63 years; range, 12.57-69.13 years). The OPGs of 179 patients of Caucasian origin with NF1 were investigated (mean age, 34.84 years; range, 12.83-68.89 years; 44.13% male, 55.86% female). The radiographic findings were compared to those obtained from OPGs of sex- and age-matched controls.

RESULTS

Characteristic deformations of the bone regions of interest occur in NF1 patients, especially in patients with plexiform neurofibroma of trigeminal nerve. These findings are always one-sided. The co-occurrence of several skeletal deformations can be expected with very high probability in this patient group.

CONCLUSION

The radiological sign of the unilateral deformed mandible should be included in the diagnostic criteria for NF1. In addition to the diagnostic value in this syndrome, these findings are important for avoiding surgical complications in planned interventions in this region.

Neuroimaging findings of extensive sphenoethmoidal dysplasia in NF1

Whereas isolated sphenoid wing dysplasia (SWD) is a well-known clinical feature in neurofibromatosis 1 (NF1), extensive cranial defects involving multiple bones have been rarely reported in this disorder. In this report, we describe the clinical course of a 20-year-old male with NF1 and an extensive cranial bone dysplasia. The large sphenoethmoidal defect was associated with transethmoidal and orbital cephalocele as well as inferolateral herniation of the frontal lobe. In spite of the large defect, the individual did not have any symptoms or complications resulting from the osteopathy. We review the current knowledge of the pathogenesis and management of cranial bone dysplasia in NF1.

Peripheral nerve sheath tumors of the upper extremity and hand in patients with neurofibromatosis type 1: topography of tumors and evaluation of surgical treatment in 62 patients

Objective: Neurofibromatosis type 1 (NF1) is an autosomal dominant tumor predisposition syndrome with a tendency to develop peripheral nerve sheath tumors (PNST). Plexiform neurofibromas (PNF) are detected in a high proportion of affected patients. The tumors can lead to severe disfigurement and are classified as precancerous. This study examines the surgical procedures that have been performed on large PNST of the upper limb and hand, and investigates whether a specific distribution pattern of the tumors can be detected in surgically treated cases.

Methods: Surgical procedures on the upper extremity and hand performed on patients with NF1 were evaluated at an interval of 25 years (1992–2016). Topography of the tumors was classified according to dermatomes. The number of interventions per patient, duration of operations, and complications of the interventions were registered. An overview of the surgical treatment of PNST of the upper limb and hand was obtained from the literature, with special consideration of the genetic background of treated tumors.

Results: One hundred and sixty-three surgical interventions on the upper limb and hand were performed in 62 patients with NF1 for the treatment of large PNST, predominantly PNF (age: mean value: 27.33 years, male: 33, female: 29; right side: 25, left side: 26, bilateral: 7). Surgical procedures lasted an average of 72.47 minutes. In approximately half of the patients, one surgical procedure was sufficient. Duration of stay in hospital was on average 7–11 days. Neurological complications were rarely noted and occurred only temporarily. There were no dermatomes affected by PNF with particular frequency. However, some dermatomes were more often simultaneously affected by a PNF at the same time as others.

Conclusion: Although the distribution pattern shows some accumulation of tumor localization, tumors are distributed evenly and show very variable size and extent in individual cases. Surgical treatment of PNF of the upper limb and hand helps alleviate the physical discomfort that these patients have from their disfiguring disease. Repeated interventions are necessary relatively often in order to adapt the tumorous region to the outline of the limb and to improve its function.

Altered cerebrospinal fluid dynamics in neurofibromatosis type l: severe arachnoid thickening in patients with neurofibromatosis type 1 may cause abnormal CSF dynamic

INTRODUCTION

The object of this study is to understand abnormal dynamic of cerebrospinal fluid (CSF) in patients with neurofibromatosis type 1 (NF1), which may cause temporal lobe herniation and bulging of temporal fossa.

METHODS

Four patients, three females and one male, with NF1 were studied retrospectively. They presented with a similar craniofacial deformity, which consisted of pulsatile exophthalmos, an enlarged bony orbit, dysplasia of the sphenoid wing with the presence of a herniation of the temporal lobe into the orbit, and a bulging temporal fossa.

RESULTS AND DISCUSSION

Surgical exploration demonstrated abnormally thickened arachnoid membrane in one case. Protruding temporal lobe, which was one of the main symptoms in NF1 patients, could be stopped by control of intracranial pressure (ICP) via programmable ventriculoperitoneal shunt (VPS) or extra ventricle drainage implantation. The dense fibrosis of the arachnoid membrane and consequent altered hemispheric CSF dynamics may cause symptoms including pulsatile exophthalmos and consequent worsening of vision, prolapse of the temporal lobe, and enlargement of the temporal fossa. This finding may not present with general features of hydrocephalus, so that delays in diagnosis often result.

CONCLUSION

For the NF1 patients with cranio-orbito-temporal deformities, prior to any surgical reconstruction, control of increased ICP (IICP) should be primarily considered.

Sella turcica measurements on lateral cephalograms of patients with neurofibromatosis type 1

The aim of this study was to measure line segments and areas of sella turcica on lateral cephalograms with respect to the clinical diagnosis of facial phenotype of patients with neurofibromatosis type 1 (NF1). Special attention was given to correlate the measured values with certain tumour types that are typical for this disease.

Material and methods: Lateral cephalograms of 194 individuals were investigated. Patients with NF1 were further divided according to the detection and topography of facial plexiform neurofibromas (PNF) taking into account the distribution pattern of the trigeminal nerve. All patients with PNF showed unilateral tumour localisation. Patients without any facial PNF constituted a separate group. Healthy volunteers with ideal occlusion and no history of any intervention in the maxillofacial region served as a control group. The following items were determined on the radiographs: sella entrance, sella width, sella depths, sella diagonal, and sella area.

Results: Patients with PNF of the first and second trigeminal nerve branch or affected in all branches showed highly statistically significant enlarged sella tucica measurement values. On the other hand, patients with PNF restricted to one branch only or simultaneously in the second and third branches showed measurement values that were not different to those obtained in NF1 patients devoid of facial PNF. The latter group also showed no difference of sella turcica parameters obtained in the control group.

Conclusion: This study provides evidence for the association of a certain NF1 phenotype with distinct skeletal alterations of the skull base, shown here using the example of the representation of the sella turcica in the lateral radiograph. These findings are also relevant in the discussion of NF1 as a disease of bones and in the assessment of brain development in NF1. Both items are discussed in relationship to a facial plexiform neurofibroma. Furthermore, the knowledge of this association of findings provides the clinician with relevant information in the planning of skull base procedures in these patients.

Occlusal traits in children with neurofibromatosis type 1

OBJECTIVES

Literature is poor of data about the occlusion in children affected by neurofibromatosis type 1 (NF1). This case-control study investigated the occlusal traits in a group of children with NF1.

SETTING AND SAMPLE POPULATION

A hundred and fifteen children with NF1 were enrolled; non-NF1 controls were sequentially selected among subjects referred to the Pediatric Dentistry Department.

MATERIAL AND METHODS

All patients underwent a clinical dental examination and a panoramic radiography. The following orthodontic variables were considered: molar relationship, overjet, overbite, cross-bite, scissor bite, and crowding/spacing.

RESULTS

Class III molar relationship resulted significantly (p = 0.01) more common in children with NF1 than in the control group as well as the unilateral posterior cross-bite (p = 0.0017). Forty-three children with NF1 (37.3%) showed radiographic abnormalities; in one case, a plexiform neurofibroma was detected.

CONCLUSIONS

An early orthodontic evaluation might be planned in the management of children with NF1 to prevent or decrease the need for extensive orthodontic interventions.

Cephalometry in adults and children with neurofibromatosis type 1: Implications for the pathogenesis of sphenoid wing dysplasia and the "NF1 facies"

BACKGROUND

Neurofibromatosis type 1 (NF1) is a common, autosomal dominant tumor-predisposition disorder that arises secondary to mutations in the tumor suppressor gene NF1. Cephalometry is an inexpensive, readily available and non-invasive technique that is under-utilized in studying the NF1 craniofacial phenotype. An analysis of NF1 cephalometry was first published by Heervä et al. in 2011. We expand here on that first investigation with a larger cohort of adult and pediatric patients affected with NF1 and sought objective insight into the NF1 facies, said to feature hypertelorism and a broad nasal base, from cephalometric analysis.

METHODS

We obtained cephalograms from 101 patients with NF1 (78 adults and 23 children) from two NF1 protocols at the National Institutes of Health. Each subject had an age-, gender- and ethnicity-matched control. We used Dolphin software to make the cephalometric measurements. We assessed the normality of differences between paired samples using the Shapiro-Wilk test and evaluated the significance of mean differences using paired t-tests and adjusted for multiple testing. We explored the relationship between the cephalometric measurements and height, head circumference and interpupillary distance.

RESULTS

In this dataset of American whites with NF1, we confirmed in a modestly larger sample many of the findings found by Heerva et al. in an NF1 Finnish cohort. We found a shorter maxilla, mandible, cranial base, (especially anteriorly, p = 0.0001) and diminished facial height in adults, but not children, with NF1. Only one adult exhibited hypertelorism.

CONCLUSIONS

The cephalometric differences in adults arise in part from cranial base shortening and thus result in a shorter face, mid-face hypoplasia, reduced facial projection, smaller jaw, and increased braincase globularity. In addition, we suggest that NF1 sphenoid bone shortening, a common event, is consistent with an intrinsic NF1 bone cell defect, which renders the bone more vulnerable to a random "second hit" in NF1, leading to sphenoid wing dysplasia, a rare event.

Proliferation and arrest: the genetics of orbital disorders

PURPOSE OF REVIEW

Oculoplastic genetic diseases can be divided into eyelid, lacrimal, and orbital disorders. The purpose of this review is to develop a rational approach to the categorization of genetic diseases that affect the orbit and review the most recent developments.

RECENT FINDINGS

Genetic disorders that affect the orbit can simply be divided into whether they cause proliferation or arrest of orbital structures. Proliferative conditions include vascular, neural, bony, mesenchymal, and lymphoid. Conditions that cause arrest can be subcategorized into whether they cause soft tissue or bony arrest of development. The genetics of many of these conditions have been elucidated and novel treatments, based on the molecular defects, have been utilized with some success.

SUMMARY

Molecular advances may result in substitution of a molecular categorization scheme for the one proposed in this manuscript. Delineation of the underlying molecular causes of these disorders will result in earlier, less invasive procedures than those that are currently employed.

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.

Orbital reconstruction for pulsatile exophthalmos secondary to sphenoid wing dysplasia

Sphenoid wing dysplasia or absence of the greater sphenoid wing is a rare condition that is considered pathopneumonic for neurofibromatosis type 1 (NF1). It occurs in 4% to 11% of NF1 patients, and its precise cause is unclear. Some cases appear to be congenital, while others have demonstrated it to be a progressive degeneration of the orbital wall. In about half of cases, associated adjacent neurofibromas are described. Consistently, however, the clinical sequelae is herniation of the temporal lobe into the orbit, causing progressive proptosis and pulsatile exophthalmos. Reconstruction of the orbit has traditionally been with bone grafts, but due to problems with bone resorption and recurrence, titanium plates in conjunction with bone grafts have been reported. We present a case of a 6-year-old male patient who was first diagnosed with NF1 and associated absence of the greater sphenoid wing at the age of 2. Four years later, he was referred for reconstruction after the development of pulsatile exophthalmos. Surgical management included dissection of the dura of the temporal lobe off of the periorbita and skull base reconstruction with a combination of radial-shaped titanium mesh and split calvarial bone grafts. Postoperatively, there was near immediate resolution of the pulsatile exophthalmos, and follow-up at 1 year showed no recurrence.

Bilateral and Symmetrical Anteromedial Bowing of the Lower Limbs in a Patient with Neurofibromatosis Type-I

An 8-year-old girl was referred to our department because of generalized bowing of long bones (radii, ulnae, and femora) and significant bilateral and symmetrical posteromedial bowing of the tibiae and fibulae. The femora were laterally bowed whereas the tibiae and fibulae showed posteromedial bowing between the middle and distal thirds of the tibia with posterior cortical thickening effectively causing the development of bilateral congenital anterolateral bowing of the tibiae and fibulae. We referred to closing-wedge osteotomy of the left tibia along with fibular osteotomy in order to realign the deformity. Due to the delayed appearance of skin stigmata in her early life, the diagnosis of neurofibromatosis was ruled out. At the age of 9 years, café-au-lait spots and axillary freckling were apparent. Genetic tests confirmed von Recklinghausen disease (neurofibromatosis type-I (NF1)) (gene has been localised to 17q22). Interestingly, bilateral and symmetrical anteromedial bowing of the tibiae and fibulae has not been described in patients with NF-I.

Neurofibromatosis type 1: a multidisciplinary approach to care

Neurofibromatosis type 1 is a relatively common inherited disorder. Patients have a high predisposition to develop both benign and malignant tumours. Although many manifestations of neurofibromatosis type 1 affect the nervous system, other organs and tissues can also be affected. Because of the varying features and clinical heterogeneity inherent to this disorder, patients can present to different medical and surgical specialists and, therefore, the association of clinical symptoms with neurofibromatosis type 1 might not be appreciated. Thus, for prompt diagnosis and to provide optimum care for patients with neurofibromatosis type 1, clinicians must be aware of the diverse clinical features of this disorder. We advocate a multidisciplinary approach to care, entailing a dedicated team of specialists throughout the lifetime of the patient. As our understanding of this disorder deepens through basic laboratory and clinical investigations, swift implementation of new effective treatments becomes feasible.

Calvarial defects and skeletal dysplasia in patients with neurofibromatosis Type 1

OBJECT

Skull defects, including sphenoid dysplasia and calvarial defects, are rare but distinct findings in patients with neurofibromatosis Type 1 (NF1). The underlying pathophysiology is unclear. The goal of this study was to identify the clinical characteristics and natural history of skull defects in patients with NF1.

METHODS

An electronic search engine of medical records was used to identify patients with NF1 and bony skull anomalies. All clinical, radiographic, pathology, and operative reports were reviewed. The relationship between bony anomalies and significant clinical associations was evaluated. This study received institutional review board approval.

RESULTS

Twenty-one patients were identified. The mean age at NF1 diagnosis was 4.2 years. The mean age at skull defect diagnosis was 8.8 years (9.7 years in the sphenoid wing dysplasia group and 11.9 years in the calvarial defect group). Sphenoid dysplasia was associated with a plexiform neurofibroma or dural ectasia in 73.3% and 80.0% of cases, respectively. Calvarial defects were associated with a plexiform neurofibroma or dural ectasia in 66.7% and 33.3% of patients, respectively. An absence of either an associated neurofibroma or ectasia was not noted in any patient with sphenoid wing dysplasia or 25.0% of those with calvarial defects. In 6 patients, both types of skull defects presented simultaneously. Serial imaging studies were obtained for a mean follow-up time of 7.5 years (range 0.4-20.0 years). Of these patients with serial imaging, radiographic progression was found in 60% of cases of calvarial defects and 56% of cases of sphenoid wing dysplasia. Two patients underwent surgical repair of a skull defect, and both required repeat procedures.

CONCLUSIONS

The majority of skull defects in patients with NF1 were associated with an adjacent structural lesion, such as a plexiform neurofibroma or dural ectasia. This findings from this cohort also support the concept of progression in defect size in more than half of the patients. Potential mechanisms by which these secondary lesions contribute to pathogenesis of the bony defect may include changes in the bony microenvironment. A better understanding of the pathophysiology of skull defects will help guide detection, improve treatment and outcome, and may contribute to the understanding of the pathogenesis of bony lesions in NF1.

Evaluation of tibial osteopathy occurrence in neurofibromatosis type 1 Italian patients

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant disorder characterized by high penetrance, widely variable expressivity and occurrence of specific skeletal changes such as tibial osteopathy (TO). We collected data on patients referred to the Italian Neurofibromatosis Study Group in order to compare clinical features between 49 NF1 patients with TO, and 98 age-matched NF1 patients without TO, and to determine whether the presence of TO is associated with a different risk of developing the typical NF1 complications. We assessed both groups for: age at diagnosis of NF1, gender distribution, family history, gender inheritance, presence of scoliosis, sphenoid wing osteopathy, other skeletal abnormalities, macrocrania, hydrocephalus, plexiform neurofibromas, tumors, optic pathway gliomas, T2H (high-signal intensity areas on T2 weighted brain MRI), epilepsy, headache, mental retardation, cardiovascular malformations, and Noonan phenotype. Patients of both groups were subdivided by gender and re-evaluated for these items. Statistical comparison was carried out between the two groups of patients for each feature. We collected data on type of treatment and on the clinical conditions of NF1-TO patients after follow-up. Patient's age at NF1 diagnosis was significantly younger in NF1-TO subjects compared with NF1 subjects without TO, and the incidence of T2H was significantly reduced in NF1-TO males compared with NF1 males without TO. The presence of TO does not imply that there is an increased risk of developing typical complications of NF1 (e.g., optic pathway glioma, plexiform neurofibroma, etc.), however, it does allow us to make an earlier diagnosis of NF1.

Deterioration of fracture healing in the mouse model of NF1 long bone dysplasia

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disease resulting from inactivating mutations in the gene encoding the protein neurofibromin. NF1 manifests as a heritable susceptibility to tumours of neural tissue mainly located in the skin (neurofibromas) and pigmented skin lesions. Besides these more common clinical manifestations, many NF1 patients (50%) have abnormalities of the skeleton. Long bones are often affected (usually the tibia) and the clinical signs range from bowing to spontaneous fractures and non-unions. Here we present the analysis of bone fracture healing in the Nf1(Prx1)-knock-out mouse, a model of NF1 long bone dysplasia. In line with previously reported cortical bone injury results, fracture healing was impaired in Nf1(Prx1) mice. We showed that the defective fracture healing in Nf1(Prx1) mice is characterized by diminished cartilaginous callus formation and a thickening of the periosteal bone. These changes are paralleled by fibrous tissue accumulation within the fracture site. We identify a population of fibrous tissue cells within the Nf1 deficient fracture as alpha-smooth muscle actin positive myofibroblasts. Additionally, histological and in-situ hybridization analysis reveal a direct contact of the fracture site with muscle fascia, suggesting a possible involvement of muscle derived cells in the fracture deterioration.

Primary osteopathy of vertebrae in a neurofibromatosis type 1 murine model

Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder caused by mutation of the NF1 tumor suppressor gene. Spinal deformities are common skeletal manifestations in patients with NF1. To date, the mechanism of vertebral abnormalities remains unclear because of the lack of appropriate animal models for the skeletal manifestations of NF1. In the present study, we report a novel murine NF1 model, Nf1(flox/-);Col2.3Cre(+) mice. These mice display short vertebral segments. In addition, a significant reduction in cortical and trabecular bone mass of the vertebrae was observed in Nf1(flox/-);Col2.3Cre(+) mice as measured by dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT). Peak stress and peak load were also significantly reduced in Nf1(flox/-);Col2.3Cre(+) mice as compared to controls. Furthermore, the lumbar vertebrae showed enlargement of the inter-vertebral canal, a characteristic feature of lumbar vertebrae in NF1 patients. Finally, histologic analysis demonstrated increased numbers of osteoclasts and decreased numbers of osteoblasts in the vertebrae of Nf1(flox/-);Col2.3Cre(+) mice in comparison to controls. In summary, Nf1(flox/-);Col2.3Cre(+) mice demonstrate multiple structural and functional abnormalities in the lumbar vertebrae which recapitulate the dystrophic vertebral changes in NF1 patients. This novel murine model provides a platform to understand the cellular and molecular mechanisms underlying the pathogenesis of spinal deficits in NF1 patients.

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.

Skeletal abnormalities in neurofibromatosis type 1: approaches to therapeutic options

The skeleton is frequently affected in individuals with neurofibromatosis type 1, and some of these bone manifestations can result in significant morbidity. The natural history and pathogenesis of the skeletal abnormalities of this disorder are poorly understood and consequently therapeutic options for these manifestations are currently limited. The Children's Tumor Foundation convened an International Neurofibromatosis Type 1 Bone Abnormalities Consortium to address future directions for clinical trials in skeletal abnormalities associated with this disorder. This report reviews the clinical skeletal manifestations and available preclinical mouse models and summarizes key issues that present barriers to optimal clinical management of skeletal abnormalities in neurofibromatosis type 1. These concepts should help advance optimal clinical management of the skeletal abnormalities in this disease and address major difficulties encountered for the design of clinical trials.

Neurofibromatosis type 1 revisited

Neurofibromatosis type 1 (NF1) is an autosomal dominant condition with a worldwide incidence of approximately 1 per 2500 to 3000 individuals. Caused by a germ-line-inactivating mutation in the NF1 gene on chromosome 17, the disease is associated with increased morbidity and mortality. In the past several years, significant progress has been made in standardizing management of the major clinical features of neurofibromatosis type 1. Moreover, improved understanding of how the neurofibromatosis type 1 protein, neurofibromin, regulates cell growth recently provided insight into the pathogenesis of the disease and has led to the development of new therapies. In this review, we describe the clinical manifestations, recent molecular and genetic findings, and current and developing therapies for managing clinical problems associated with neurofibromatosis type 1.