Cranial MR imaging in neurofibromatosis

The RASopathies: Biology, genetics and therapeutic options

The RASopathies are a group of genetic diseases in which the Ras/MAPK signaling pathway is inappropriately activated as a result of mutations in genes encoding proteins within this pathway. As their causative mutations have been identified, this group of diseases has expanded to include neurofibromatosis type 1 (NF1), Legius syndrome, Noonan syndrome, CBL syndrome, Noonan syndrome-like disorder with loose anagen hair, Noonan syndrome with multiple lentigines, Costello syndrome, cardiofaciocutaneous syndrome, gingival fibromatosis and capillary malformation-arteriovenous malformation syndrome. Many of these genetic disorders share clinical features in common such as abnormal facies, short stature, varying degrees of cognitive impairment, cardiovascular abnormalities, skeletal abnormalities and a predisposition to develop benign and malignant neoplasms. Others are more dissimilar, even though their mutations are in the same gene that is mutated in a different RASopathy. Here, we describe the clinical features of each RASopathy and contrast them with the other RASopathies. We discuss the genetics of these disorders, including the causative mutations for each RASopathy, the impact that these mutations have on the function of an individual protein and how this dysregulates the Ras/MAPK signaling pathway. As several of these individual disorders are genetically heterogeneous, we also consider the different genes that can be mutated to produce disease with the same phenotype. We also discuss how our growing understanding of dysregulated Ras/MAPK signaling had led to the development of new therapeutic agents and what work will be critically important in the future to improve the lives of patients with RASopathies.

Glioma-Induced Seizure in a Neurofibromatosis Type 1 Patient: A Case Report

Neurofibromatosis type 1 (NF-1), also known as Von Recklinghausen's disease, is an autosomal-dominant disease that is characterized by high-frequency mutations leading to multiple benign tumors called neurofibromas and café au lait spots on the skin. Although NF-1 mainly affects the nervous system, it can have multisystem involvement as well, associated with the cardiovascular, orthopedic, gastrointestinal, and dermatologic systems. Psychiatric complications like anxiety, dysthymia, and depression have also been reported in patients with NF-1. The prevalence of this disorder is one in 3,000 births. NF-1 patients have a higher prevalence of seizures compared to the general population.

A 20-year-old male with a diagnosis of NF-1 at the age of three months presented to the emergency room (ER) of a local hospital for the evaluation of an unwitnessed seizure characterized by loss of consciousness and bladder control. MRI of the brain without contrast revealed hyperintensities in the mesial temporal lobe bilaterally, with a hyperintense FLAIR lesion in the splenium of the corpus callosum. The patient exhibited sudden aggression and combativeness while in the ER and also experienced a second seizure, which prompted immediate intubation. A second MRI with contrast confirmed the presence of the lesion. The patient also underwent electroencephalogram (EEG) monitoring later during his hospital stay, the results of which were unremarkable.

This case report discusses an adult male with NF-1 and a tumor of the splenium of the corpus callosum. The displayed imaging suggested a possible etiology for high seizure frequency in patients with NF-1 compared to the general population.

Gadolinium-based contrast agents in neurofibromatosis type 1 (Review)

Gadolinium (symbol Gd) is the chemical element with atomic number 64 and is aductile rare-earth metal, and +3 is its most frequent oxidation state. Gadolinium has an ionic radius of 0.99 Å and is nearly identical to the one of Ca²⁺. Gd³⁺ and Ca²⁺ can become toxic to biological systems if complete. It slowly reacts with atmospheric oxygen to form a black coating and in nature it is usually found only in an oxidized form. Gadolinium usually has impurities similar to those of other rare-earth metals, when separated, because of their similar chemical properties. Neurofibromatosis type 1 (NF1) or von Recklinghausen's disease is an autosomal dominant disorder of tissues of ectodermal origin, accounting for over 90% of neurofibromatosis cases. Diagnosis is primarily clinical and the central nervous system is commonly involved. The screening of the brain with magnetic resonance (MR) imaging is utilised to evaluate the patients with neurofibromatosis type 1 and as an aid in the diagnosis of asymptomatic patients when clinical criteria are not met.

Genetics of Colloid Cyst in Monozygotic Twins: Case Report and Review of Literature

BACKGROUND

Colloid cysts are rare developmental lesions, accounting for approximately 1% of intracranial tumors. Often, these benign lesions are asymptomatic, but they are associated with significant mortality as a result of acute hydrocephalus. This mortality in patients with vague or no symptoms dictates a need for better understanding of the etiology of colloid cysts to expedite diagnosis and management. We present a case of monozygotic twins with colloid cysts to propose a genetic etiology for colloid cyst.

CASE DESCRIPTION

Previously healthy male monozygotic twins presented 4 years apart with headache secondary to hydrocephalus as a result of colloid cysts. Both patients underwent multiple surgeries and were doing well at last follow-up.

CONCLUSIONS

The present case adds to a body of literature of familial colloid cysts, suggesting higher concordance in monozygotic compared with dizygotic twins. This may be due to high genetic load, shared intrauterine environment, epigenetic changes, or genetic mutation. This literature review suggests that given high morbidity and mortality of colloid cysts, screening may be beneficial. Even in the absence of a single, definitive genetic etiology, we recommend consideration of genetic screening or, at a minimum, screening with neuroimaging for monozygotic twins in cases where 1 twin is diagnosed with colloid cyst.

Recent Advances in the Diagnosis and Pathogenesis of Neurofibromatosis Type 1 (NF1)-associated Peripheral Nervous System Neoplasms

The diagnosis of a neurofibroma or a malignant peripheral nerve sheath tumor (MPNST) often raises the question of whether the patient has the genetic disorder neurofibromatosis type 1 (NF1) as well as how this will impact the patient's outcome, what their risk is for developing additional neoplasms and whether treatment options differ for NF1-associated and sporadic peripheral nerve sheath tumors. Establishing a diagnosis of NF1 is challenging as this disorder has numerous neoplastic and non-neoplastic manifestations which are variably present in individual patients. Further, other genetic diseases affecting the Ras signaling cascade (RASopathies) mimic many of the clinical features of NF1. Here, we review the clinical manifestations of NF1 and compare and contrast them with those of the RASopathies. We also consider current approaches to genetic testing for germline NF1 mutations. We then focus on NF1-associated neurofibromas, considering first the complicated clinical behavior and pathology of these neoplasms and then discussing our current understanding of the genomic abnormalities that drive their pathogenesis, including the mutations encountered in atypical neurofibromas. As several neurofibroma subtypes are capable of undergoing malignant transformation to become MPNSTs, we compare and contrast patient outcomes in sporadic, NF1-associated and radiation-induced MPNSTs, and review the challenging pathology of these lesions. The mutations involved in neurofibroma-MPNST progression, including the recent identification of mutations affecting epigenetic regulators, are then considered. Finally, we explore how our current understanding of neurofibroma and MPNST pathogenesis is informing the design of new therapies for these neoplasms.

Medullary unidentified bright objects in Neurofibromatosis type 1: a case series

Background

In Neurofibromatosis type 1, cerebral Unidentified Bright Objects are a well-known benign entity that has been extensively reported in the literature. In our case series, we wish to focus on a further possible location of such lesions, the spinal cord, which we have defined as medullary Unidentified Bright Objects. These have been, to our knowledge, scarcely described in previous works.

Case presentation

We report the cases of 7 patients with medullary Unidentified Bright Objects in Neurofibromatosis type 1 that we have followed for up to 9 years in our Regional Referral Center for Neurofibromatosis. In all of our patients, these lesions were completely asymptomatic and reported on Magnetic Resonance exams the patients underwent for other clinical indications.

Conclusions

The aim of our work is to increase awareness of the possibility of medullary Unidentified Bright Objects in Neurofibromatosis type 1 patients, which can simulate neoplastic lesions, suggesting a more conservative approach in these cases.

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.

MR Imaging of Spinal Neurofibromatosis

The MR findings in 7 patients with neurofibromatosis involving the spine were evaluated. Six patients had paraspinal tumors at multiple levels. In 4 they were bilateral. Five patients had multiple intraspinal lesions, frequently with growth through the neural foramen. In one patient paraspinal tumors were found in the lumbar sacral plexus and in another bony dysplasia and meningoceles but no tumors were disclosed. In 2 patients the lesions were associated with bilateral acoustic neuromas and multiple intracranial meningeomas. In one of these a spinal meningeoma with signal characteristics close to spinal cord was found. The other tumors had a signal that was equal to or slightly lower than the spinal cord and slightly higher than muscle on T1-weighted images. On T2-weighted images the tumors had a markedly increased signal compared to surrounding tissue. In 3 patients with tumors larger than 4 cm the signal intensity was inhomogeneous with decreased signal in the center on T2-weighted images, indicating the presence of increased fibrous tissue. Gadolinium-DTPA was given to one patient with marked increase in intensity of small tumors on T1-weighted images. The study shows that MR imaging is the modality of choice for evaluating most aspects of spinal and paraspinal neurofibromatosis.

Is magnetic resonance spectroscopy capable of detecting metabolic abnormalities in neurofibromatosis type 1 that are not revealed in brain parenchyma of normal appearance?

BACKGROUND

Results of magnetic resonance spectroscopy studies in normal-appearing brain and in non-neoplastic brain lesions in individuals with neurofibromatosis type 1 (NF1) have been discrepant.

OBJECTIVE

We used magnetic resonance spectroscopy to analyze the metabolic patterns in the basal ganglia of patients with NF1 and examine their correlation with focal hyperintense lesions in T2-weighted images (T2-weighted hyperintensities).

METHODS

We used magnetic resonance spectroscopy data of 42 individuals with NF1 (18 with and 24 without T2- weighted hyperintensities) and 25 controls matched for gender and age. A single-voxel technique was employed by manually placing a region of interest with a uniform size over a predetermined anatomical region including the globus pallidum and putamen (capsulolenticular region). We further analyzed the ratios of choline/creatine, N-acetyl aspartate (NAA)/creatine, and myoinositol/creatine metabolites and the occurrence of T2-weighted hyperintensities in these regions in individuals with NF1.

RESULTS

There was a significant difference between the NF1 and control groups with regard to the mean values of myoinositol/creatine and choline/creatine, with higher metabolite values observed in the NF1 group (P < 0.001). Only the myoinositol/creatine ratio was able to discriminate between NF1 subgroups with and without T2-weighted hyperintensities. For the NAA/creatine ratio, there was no significant difference between the NF1 and the control groups.

CONCLUSION

Magnetic resonance spectroscopy allows the characterization of tissue abnormalities not demonstrable in the structural images of individuals with NF1 through choline and myoinositol metabolite analysis. Yet the preserved NAA values argue against demyelination and axonal degeneration occurring in the region, suggesting instead a functional neuronal stability. Taken in association with the findings of lack of clinical manifestations and the known transient nature of T2-weighted hyperintensities in NF1 as demonstrated by other studies, our results support the current histopathologically driven hypothesis that such T2-weighted hyperintensities may be related to intramyelinic edema.

Characterizing the microstructural basis of "unidentified bright objects" in neurofibromatosis type 1: A combined in vivo multicomponent T2 relaxation and multi-shell diffusion MRI analysis

Introduction

The histopathological basis of “unidentified bright objects” (UBOs) (hyperintense regions seen on T2-weighted magnetic resonance (MR) brain scans in neurofibromatosis-1 (NF1)) remains unclear. New in vivo MRI-based techniques (multi-exponential T2 relaxation (MET2) and diffusion MR imaging (dMRI)) provide measures relating to microstructural change. We combined these methods and present previously unreported data on in vivo UBO microstructure in NF1.

Methods

3-Tesla dMRI data were acquired on 17 NF1 patients, covering 30 white matter UBOs. Diffusion tensor, kurtosis and neurite orientation and dispersion density imaging parameters were calculated within UBO sites and in contralateral normal appearing white matter (cNAWM). Analysis of MET2 parameters was performed on 24 UBO–cNAWM pairs.

Results

No significant alterations in the myelin water fraction and intra- and extracellular (IE) water fraction were found. Mean T2 time of IE water was significantly higher in UBOs. UBOs furthermore showed increased axial, radial and mean diffusivity, and decreased fractional anisotropy, mean kurtosis and neurite density index compared to cNAWM. Neurite orientation dispersion and isotropic fluid fraction were unaltered.

Conclusion

Our results suggest that demyelination and axonal degeneration are unlikely to be present in UBOs, which appear to be mainly caused by a shift towards a higher T2-value of the intra- and extracellular water pool. This may arise from altered microstructural compartmentalization, and an increase in ‘extracellular-like’, intracellular water, possibly due to intramyelinic edema. These findings confirm the added value of combining dMRI and MET2 to characterize the microstructural basis of T2 hyperintensities in vivo.

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We examine MRI white matter T2-weighted hyperintense lesions, “UBOs” in NF1.

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Myelin water and intra- and extracellular water fractions are unchanged in UBOs.

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Diffusivity is higher, while mean kurtosis and neurite density are lower in UBOs.

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The combined measures suggest that UBOs may arise from intramyelinic edema.

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Combining diffusion MRI and multi-exponential T2 relaxation has added value.

Concomitant meningioma and glioma within the same optic nerve in neurofibromatosis type 1

A patient with neurofibromatosis type 1 and the rare finding of concomitant meningioma and optic pathway glioma within the same optic nerve is presented. A 4-year-old boy was admitted to our hospital with right-sided proptosis. He also had numerous café-au-lait macules and axillary freckling on physical exam. According to National Institutes of Health (NIH) criteria, he met the diagnostic criteria for neurofibromatosis type 1. On magnetic resonance imaging (MRI), a mass originating from the right optic nerve sheath with normal appearance of the optic nerve was observed, which was consistent with optic nerve sheath meningioma. Another mass lesion was observed in the prechiasmatic region of the same optic nerve, which was consistent with optic nerve glioma. Two different types of optic pathway tumors in the same optic nerve is an extraordinary case. It is important to recognize imaging findings of these tumors and make correct diagnosis.

Globus pallidus high-signal lesions: A predominant MRI finding in children with neurofibromatosis type 1

Introduction:

Lesions of the brain, recognized as unidentified bright objects (UBOs), are commonly observed as areas of increased T2-weighted signal intensity on magnetic resonance imaging (MRI) in children with neurofibromatosis type 1 (NF1). Identification of these lesions is not currently encompassed in the National Institute of Health (NIH) diagnostic criteria for NF1.

Objective:

We aimed to determine the prevalence of UBOs in children with NF1 and identify areas of the brain that are commonly affected by these lesions, allowing us to evaluate whether UBOs should be included in the diagnostic criteria for the diagnosis of NF1.

Materials and Methods:

We reviewed the cranial MRI scans of 22 children who had been diagnosed with sporadic or familial NF1 in accordance with the criteria established by NIH. UBOs were present in 81% of the children with NF1.

Results:

These lesions have a predilection for specific areas of the brain, including the globus pallidus (72%), cerebellum (66%), brainstem (27%) and cerebral hemispheres (16%). The prevalence of UBOs identified varied significantly with age and sex; they were infrequent in children less than 4 years of age but were common in those aged between 4 and 12 years of age. UBOs were more commonly seen in males (66.6%) compared with females (33.3%). Repeat MRI scan on a subset of these patients with UBOs did not show any significant changes despite a worsening in clinical symptoms.

Conclusion and Discussion:

We have shown that UBOs are a common finding in children with NF1, and are most prevalent between the ages of 4 and 12 years. Many sites of the brain are affected by these lesions, most notably the globus pallidus and the cerebellum. Further research must be conducted to elucidate the significance of UBOs in patients with NF1 and whether these lesions have any utility in the clinical detection of NF1.

Clinical sensitivity and specificity of multiple T2-hyperintensities on brain magnetic resonance imaging in diagnosis of neurofibromatosis type 1 in children: diagnostic accuracy study

Aim

To determine the prevalence, number, and location of multiple (≥2) T2-hyperintensities on brain magnetic resonance imaging (MRI) in children with neurofibromatosis type 1 (NF1) and their correlation with age, and to establish their sensitivity, specificity, and accuracy for the diagnosis of NF1 in children, especially in the early age (2-7 years).

Methods

We performed a cross-sectional study of 162 patients with NF1 from Croatian Neurofibromatosis Association Database and 163 control children between the ages of 2 and 18 years who underwent brain MRI between 1989 and 2009.

Results

Multiple T2-hyperintensities were present in 74% of NF1 patients and 1.8% of controls. They were mainly located in the basal ganglia, brainstem, and cerebellum and were significantly decreased in prevalence and number in the older age. T2-hyperintensities had excellent diagnostic accuracy with the area under the receiver operating characteristic (ROC) curve of 0.849 and 95% confidence interval (CI) of 0.805-0.886. The diagnostic sensitivity, specificity, and accuracy rate of T2-hyperintensities for NF1 were highest in the youngest age (2-7 years): 81% (95% CI 71%-89.1%), 99% (95% CI 92.3%-100%), and 85.8 (95% CI 83.3-93.8), respectively.

Conclusion

This study strongly suggests the inclusion of T2-hyperintensities on brain MRI on the list of diagnostic criteria for NF1, especially in children of early age, when the clinical penetration of the NF1 gene has not yet been completely finished.

Intracranial and extracranial fusiform aneurysms in a patient with neurofibromatosis type 1: a case report

Neurofibromatosis type 1 (NF-1) has a variety of localized or systemic manifestations. Among them, Cerebrovascular dysplasia can be very rare finding of neurofibromatosis which can be very rarely seen. Here we report a case of 17-year-old boy representing bilateral giant fusiform aneurysms of extracranial internal carotid arteries and intracranial aneurysms of left middle cerebral artery. He showed no related symptoms at all, but screening for vascular lesions and close monitoring is warranted in NF-1 patients considering that it can be symptomatic unexpectedly.

Differential diagnosis for bilateral abnormalities of the basal ganglia and thalamus

The basal ganglia and thalamus are paired deep gray matter structures that may be involved by a wide variety of disease entities. The basal ganglia are highly metabolically active and are symmetrically affected in toxic poisoning, metabolic abnormalities, and neurodegeneration with brain iron accumulation. Both the basal ganglia and thalamus may be affected by other systemic or metabolic disease, degenerative disease, and vascular conditions. Focal flavivirus infections, toxoplasmosis, and primary central nervous system lymphoma may also involve both deep gray matter structures. The thalamus is more typically affected alone by focal conditions than by systemic disease. Radiologists may detect bilateral abnormalities of the basal ganglia and thalamus in different acute and chronic clinical situations, and although magnetic resonance (MR) imaging is the modality of choice for evaluation, the correct diagnosis can be made only by taking all relevant clinical and laboratory information into account. The neuroimaging diagnosis is influenced not only by detection of specific MR imaging features such as restricted diffusion and the presence of hemorrhage, but also by detection of abnormalities involving other parts of the brain, especially the cerebral cortex, brainstem, and white matter. Judicious use of confirmatory neuroimaging investigations, especially diffusion-weighted imaging, MR angiography, MR venography, and MR spectroscopy during the same examination, may help improve characterization of these abnormalities and help narrow the differential diagnosis.

Gastrointestinal and retroperitoneal manifestations of type 1 neurofibromatosis

BACKGROUND

Type 1 neurofibromatosis (NF1) is a genetic disease characterized by neoplastic and not neoplastic disorders, involving tissues of neuroectodermal or mesenchymal origin. The mainly involved districts are skin, central nervous system, and eye, and there is a wide range of severity of clinical presentations.

DATA SOURCES

Abdominal manifestations of NF1 comprehend five categories of tumors: neurogenic with neurofibromas, malignant peripheral nerve sheath tumors and ganglioneuromas, neuroendocrine with pheochromocytomas and carcinoids, non-neurogenic gastrointestinal stromal tumors, i.e., GISTs, and embryonal tumors and miscellaneous.

CONCLUSIONS

Early diagnosis of these abdominal manifestations is very important given the risk of malignancy, organic complications such as in the case of pheochromocytomas or hemorrhagic-obstructive complications such as in the case of the tumors of the gastrointestinal tract (GISTs and neurofibromas). The importance of an annual clinical evaluation on the part of a multidisciplinary pool of clinicians in highly specialized centers allows early detection of complications and of neoplastic transformation.

Imaging of acoustic neuromas. 1992

Diagnosis of acoustic neuromas has been simplified considerably by computed tomography (CT) and magnetic resonance imaging (MRI). Either enhanced method will visualize almost every acoustic neuroma. MRI is more sensitive inside the internal auditory canal. Currently, a gadolinium-enhanced MRI scan is considered an accurate indicator of whether or not an individual has an acoustic neuroma, although there have been false-positive enhanced MRI scans recently reported.

BRAINSTEM LESIONS IN NEUROFIBROMATOSIS TYPE 1

OBJECTIVE

The presence of multiple, nonenhancing areas of hyperintensity without mass effect are well recognized on magnetic resonance imaging scans in children with neurofibromatosis type 1 (NF1). Focal regions of brainstem enlargement with or without contrast enhancement are considerably less frequent; the neuroimaging characteristics and natural history of these lesions in patients with NF1 are poorly understood. The objective of this study was to define the clinical and radiographic course of brainstem lesions in children with NF1.

METHODS

We retrospectively reviewed the neuroimaging studies of all patients with NF1 between 2000 and 2006 to determine the prevalence of brainstem lesions. Clinical features, previous treatments, and neuroimaging studies of the brainstem lesions were evaluated.

RESULTS

A total of 125 patients underwent neuroimaging studies; of these, 23 patients (18.4%) showed evidence of brainstem mass lesions and had follow-up magnetic resonance imaging scans available for review. Eight patients in this cohort received additional treatment with surgery, radiation, or chemotherapy. Of these, two patients underwent surgery for lesions distant from the brainstem, and six patients underwent treatment that included the brainstem and were thought to potentially affect the natural history or progression of the brainstem abnormality. With a median follow-up period of 67 months for untreated patients (17 out of 23) and 102 months for patients who received therapy (six out of 23), only one previously untreated patient experienced radiographic and clinical progression. All patients but one remain alive.

CONCLUSION

We conclude that brainstem lesions in NF1 are prevalent and behave in a biologically indolent nature; most do not require therapeutic intervention.

Guidelines for the diagnosis and management of individuals with neurofibromatosis 1

Neurofibromatosis 1 (NF1) is a common neurocutaneous condition with an autosomal dominant pattern of inheritance. The complications are diverse and disease expression varies, even within families. Progress in molecular biology and neuroimaging and the development of mouse models have helped to elucidate the aetiology of NF1 and its clinical manifestations. Furthermore, these advances have raised the prospect of therapeutic intervention for this complex and distressing disease. Members of the United Kingdom Neurofibromatosis Association Clinical Advisory Board collaborated to produce a consensus statement on the current guidelines for diagnosis and management of NF1. The proposals are based on published clinical studies and on the pooled knowledge of experts in neurofibromatosis with experience of providing multidisciplinary clinical and molecular services for NF1 patients. The consensus statement discusses the diagnostic criteria, major differential diagnoses, clinical manifestations and the present strategies for monitoring and management of NF1 complications.

Associations of osseous abnormalities in Neurofibromatosis 1

The characteristic sites of Neurofibromatosis 1-associated osseous manifestations are the long bones (usually the tibia and fibula), vertebrae and sphenoid wing. Although these focal bony lesions may cause profound clinical consequences, a minority of people with NF1 are affected. However, most people with NF1 are shorter than expected for their age, gender and family. The pathogenesis of NF1 focal osteopathy and its relationship, if any, to short stature are unknown. We examined associations between the occurrence of various osseous lesions in 3377 NF1 probands from the Children's Tumor Foundation NF International Database. Using logistic regression analysis among 260 NF1 probands who had undergone radiological examination of both the spine and skull, we found associations between the occurrence of sphenoid wing and long bone osteopathy (conditional odds ratio [OR] = 6.1; 95% confidence interval [CI] = 1.7-22.3; P = 0.006) and between sphenoid wing and vertebral osteopathy (OR = 16.9; 95% CI = 5.3-53.3; P < 0.001) after adjusting for age and gender. Similar findings were observed from all 3377 NF1 probands using a multivariate probit regression model. In a separate analysis, we found lower age- and gender-standardized height in patients who had characteristic vertebral or sphenoid wing lesions than in people who did not (P < 0.05). We found no relationship between height and tibial osteopathy. We conclude that some people with NF1 are more likely to develop osseous manifestations than others and speculate that there may be a common pathogenetic mechanism responsible for the development of osseous abnormalities and that of the vertebrae and long bones.

Is osseous dysplasia a primary feature of neurofibromatosis 1 (NF1)?

Characteristic skeletal lesions are a cardinal feature of the autosomal dominant condition, neurofibromatosis 1 (NF1). The most frequently involved skeletal sites are the sphenoid wing, vertebrae, and tibia. Osseous lesions may range in severity in NF1 but are often progressive. They may lead to serious clinical consequences and be resistant to treatment. The skeletal lesions of NF1 are usually considered to be 'dysplasias', i.e. primary defects of bone, although there is no direct evidence supporting this interpretation. Moreover, it is difficult to understand why a generalized dysplasia of bone would produce focal lesions that show such a striking predisposition to only a few bones. We review the clinical and pathological features of NF1 skeletal lesions and propose that they result from an abnormal response of NF1 halpoinsufficient bone to abnormal mechanical forces rather than from a primary osseous dysplasia.

Neuroimaging findings in neurofibromatosis type 1 and 2

Neuroimaging, particularly MR imaging, plays an important role in the diagnosis and management of the patient with neurofibromatosis type 1 and 2. These phakomatoses are complex disorders affecting multiple cell types and multiple systems of the body with a wide range of expression. This article summarizes the neuroradiologic central nervous system findings in these neurocutaneous disorders.

Structural anomalies revealed by neuroimaging studies in the brains of patients with neurofibromatosis type 1 and large deletions

PURPOSE

The basis for cognitive problems in patients with neurofibromatosis type 1 (NF1) is unknown. A subset of NF1 patients with deletion of the entire NF1 gene has severe learning problems or mental retardation. We have reviewed neuroimaging studies (CT and MRI) in five such patients to determine whether structural anomalies in the brain are present and might explain the impaired cognitive function.

METHODS

Five patients with NF1 and deletion of the entire gene were identified by FISH studies. A retrospective review was conducted of CT and MRI images, as well as of data from developmental assessments.

RESULTS

All five patients had severe developmental impairment. None had been exposed to chemotherapy or radiation therapy. All had multiple regions of bright T2 signal intensity. Structural anomalies were seen in three of the five patients and included callosal dysgenesis in one, septum cavum vergae and pellucidum in two, mega cisterna magna in one, and Chiari I malformation with severe hydrocephalus in one patient.

CONCLUSION

Individuals with NF1 and large gene deletions have an increased frequency of structural anomalies of the brain not usually seen in NF1 patients. This suggests that the mental retardation in these individuals is due, at least in part, to abnormal brain development rather than a defect in brain function due to haplosufficiency of the NF1 gene product.

Seizures in neurofibromatosis 1

Neurofibromatosis 1 is a common, genetically transmitted neurodevelopmental disorder with a high potential to cause subcortical focal brain lesions. Although seizures occasionally complicate neurofibromatosis 1, they have not been characterized adequately in the disease. Other phacomatoses with attendant subcortical focal brain lesions have been associated with an evolution from generalized to focal-onset epilepsy. This evolution may be related to the cortical dysplasias that also appear in such disorders. Cortical dysplasias, although occasionally found in neurofibromatosis 1 epileptic patients, are not as frequent as in other phacomatoses. The authors retrospectively screened 499 neurofibromatosis 1 patients for the prevalence and etiology of seizures, their response to therapy, and the evolution of seizure type over time. The prevalence of epileptic seizures (4.2%) was about twice the prevalence in the general population. There were no significant cortical dysplasias identified radiographically nor was there a relationship among the presence of subcortical focal brain lesions and seizure type, response to treatment, or evolution of epilepsy in the neurofibromatosis 1 population. The authors' data do not suggest an ontogeny of epilepsy in neurofibromatosis 1 that is different from the general epileptic population.

Bony orbital morphology in neurofibromatosis type 1 (NF1)

We retrospectively compared patients with NF1 with and without optic pathway gliomas (OPG) to determine the incidence and range of orbital developmental abnormalities and compared the incidence of OPG in African-Americans and whites. From cranial MR scans, we manually measured 14 orbital dimensions, compared them to published standards of Waitzman et al, calculated orbital volumes, and determined the presence or absence of volumetric symmetry (delta v) (delta v < or = 3 cm3 was considered to be symmetrical). We compared the results of orbital configurational assessment between patients with (group I) and those without OPG (group II). The study population comprised 58 patients, 24 boys, 18 African-American, and one Hispanic. Median age at imaging was 7 years (range 0.5-25.5 years). Fifty-eight percent had conformational abnormalities, 16 of whom had more than one abnormality (28%), the most frequent being increased intertemporal distance (n=10), increased lateral orbital distance (n=8), increased medial wall length (n=6), and decreased medial wall length (n=6). The increased intertemporal and lateral orbital distances may contribute to the appearance of hypertelorism. Only two patients had sphenoid wing hypoplasia. We found a high incidence of orbital dimensional abnormalities in the total population but more often saw multiple abnormalities in patients with OPG. However, no pattern of configurational abnormality emerged. OPG is less frequent in African-Americans. Orbital volumetric disparity seems to be independent of the presence of OPG.

Symptomatic hamartoma of the spinal cord associated with neurofibromatosis type 1. Case report

The authors present a case in which a symptomatic hamartoma was found in the spinal cord of a patient with neurofibromatosis type 1 (NF-1). This 52-year-old woman presented with painful urinary incontinence. Magnetic resonance (MR) imaging revealed an intramedullary lesion within the lower thoracic spinal cord and conus medullaris, which was surgically removed. Pathological investigation showed a hamartomatous lesion consisting of glial cells, ganglion cells, abundant disoriented axons, and thin-walled vessels. This case provides a pathological correlate to the hamartomatous lesions demonstrated on MR imaging in patients with NF-1 and illustrates that these benign lesions may become symptomatic and require neurosurgical intervention.

The neurosurgical aspects of neurofibromatosis 2: diagnosis and management

NF-2 is an extremely rare form of neurofibromatosis (NF) characterized by central system (CNS) neural crest-derived tumors and frequently cafe au lait spots (CLS). The purpose of this study was to report the clinical and imaging findings of seven patients with this disorder and to stress that value of surgical treatment in its management. Seven patients between 8 and 32 years of age who had NF-2 were included in the study. Clinical charts, surgical and pathological findings, and imaging studies were reviewed retrospectively. Patients were followed up for to 142 months. Clinical evaluation and neuroimaging studies detected the clinical criteria of NF-2 in all patients. Two deaths occurred after surgical intervention in our series. None of the patients suffered from recurrent tumor following surgery. Our results show that NF-2 is an uncommon entity which has a good prognosis after surgical intervention, in spite of the presence of multiple cranial and/or spinal lesions.

Familial colloid cyst of the third ventricle: case report and review of associated conditions

The cases of a father and his son who were diagnosed with pathologically confirmed colloid cysts of the third ventricle are presented. The familial occurrence of this tumor is rare and suggests that genetic factors may play a role in its formation. Consistent with the concept that the cyst originates as a developmental abnormality, it is associated with a variety of congenital defects. The conditions that are associated with these tumors are discussed.

Absence of the greater sphenoid wing in neurofibromatosis type I: congenital or acquired: case report

unilateral absence of the greater wing of the sphenoid bone is a distinctive but uncommon manifestation of Type I neurofibromatosis, which has until now been regarded as a developmental anomaly of mesodermal origin. A computed tomographic scan was obtained in a 4-week-old infant with an abnormal left eye. The scan demonstrated an intact ipsilateral sphenoid bone, except for minor expansion of the medial end of the left superior orbital fissure. Another computed tomographic scan was obtained 6 years later, when the child had café-au-lait patches, axillary freckling, Lisch nodules, and left phthisis bulbi. This later scan showed typical sphenoid dysplasia. Much of the greater wing was absent, and the anterior temporal pole was displaced anteriorly. In this article, we discuss the implications of this case in terms of the cause of this condition and the diagnosis of Type I neurofibromatosis.

Cerebral glucose metabolism in neurofibromatosis type 1 assessed with [18F]-2-fluoro-2-deoxy-D-glucose and PET

Cerebral PET with [18F]-2-fluoro-2-deoxy-D-glucose has been performed in four patients with neurofibromatosis type 1 (NF1) to assess the relation between cerebral metabolic activity, MRI, and the presence of neurological symptoms, including seizures, as well as mental and language retardation. Widespread hypometabolism occurred in three of the patients. The lesions on MRI, which were localised in the subcortical white matter and grey structures, had normal rates of glucose metabolism. This finding suggests that the abnormalities seen on MRI are not due to defective blood supply, localised oedema, or grey matter heterotopic foci as previously hypothesised. The presence of the hypometabolic areas seems to be inconsistently related to the occurrence of seizures and is not proportional to the degree of mental impairment. This study provides evidence of a widespread cerebral hypometabolism that is not related to the presence of MRI abnormalities; conversely normal metabolism was present in the areas with an abnormal MRI signal.

Radiological investigation of neurofibromatosis type 2

The radiological findings in six patients fulfilling the criteria of neurofibromatosis type 2 (NF2) were reviewed. Subtle cutaneous lesions were found in three. All patients had bilateral acoustic schwannomas; two had small acoustic tumours and normal hearing. In these patients the presenting symptoms were caused by multiple intracranial meningiomas and spinal neurofibromas, respectively, whereas the remaining four patients presented with hearing loss. Two patients had other cranial nerve tumours. Three patients had rapidly growing multiple intracranial meningiomas; two had multiple spinal neurofibromas and one a spinal meningioma. NF2 is a rare disease with few cutaneous but frequent, typical radiological findings in the central nervous system. The presenting symptom is most commonly hearing loss due to acoustic schwannomas, although symptoms emanating from other intracranial or tumours are not uncommon. The discovery of multiple meningiomas or multiple spinal neurofibromas without cutaneous lesions should initiate a search for acoustic schwannomas even when the patient has normal hearing.

Central nervous system imaging in reevaluation of patients with neurofibromatosis type 1

We report the results of the reevaluation of 24 patients with neurofibromatosis type 1 (NF1) using central nervous system (CNS) imaging techniques. The first examination by computed tomography (CT) or magnetic resonance imaging (MRI) indicated the presence of optic glioma in three cases, "unidentified bright objects" (UBOs) in six, and a suspected right frontal tumor in one. In two patients optic glioma and UBOs were both present and in one of them a bulbar tumor was also suspected. Later imaging examinations revealed the appearance of optic glioma in three more cases and UBOs in nine. In two of these patients both optic glioma and UBOs were present. This study indicates that the likelihood of detecting imaging abnormalities in patients with NF1 increases when systematic follow-up is performed. Optic gliomas are characteristic of pediatric patients; they rarely give rise to clinical manifestations (1/6 cases) and in general progress very slowly. For these reasons, therapeutic strategy must be carefully considered and individually decided. UBOs are very frequent findings in pediatric patients with NF 1 and therefore they must be considered diagnostically relevant. They are not related to clinical manifestations and spontaneous regression has been observed. The nature of these imaging abnormalities is still unknown, but because they do not behave like tumors, useless and dangerous therapeutic procedures should not be employed.

MRI in neurofibromatosis 1. The nature and evolution of increased intensity T2 weighted lesions and their relationship to intellectual impairment

Thirty eight patients with neurofibromatosis 1 (NF1) had neurological examinations, intellectual assessments and MRI scans. Increased intensity lesions on T2 weighted images were found in 13 patients. These abnormalities were more common in patients aged under 18 years. The lesions occurred predominantly in the basal ganglia, brainstem and cerebellum, and were multiple in 11 patients. They did not produce symptoms or neurological deficit in any patient and did not enhance with gadolinium-meglumine-triamine-pentaacetic acid contrast medium (Gd-DTPA). In 2 patients, however, the abnormalities exerted mass effect distorting the brain and in 3 patients they occurred in conjunction with known gliomas. The lesions remained unchanged over a three year follow up period. The nature of the lesions is uncertain but the fact that they may produce mass effect and occur in association with gliomas suggests that they have malignant potential. There was no correlation between the presence of these abnormalities and intellectual impairment.

The association of Chiari type I malformation and neurofibromatosis type 1

The association of neurofibromatosis type 1 (NF1) with Chiari malformations of the cerebellum and brain stem has been reported on only two previous occasions. The pathogenesis of both conditions has remained unclear, although the Chiari type I malformation is most likely due to hypoplasia of the posterior fossa with subsequent extension of the cerebellum through the foramen magnum. NF1 is also associated with a variety of cerebral dysplasias. We present a patient with both of these dysplastic lesions whose Chiari malformation was asymptomatic.

CT detection of basal ganglion lesions in neurofibromatosis type 1: correlation with MRI

Prospective study of CT and MRI in 41 consecutive children with suspected type 1 neurofibromatosis revealed basal ganglion lesions on T2-weighted spin echo images in 22 cases (54%) and on CT in only 7 of those (32%). T2-weighted spin-echo MRI also revealed multiple signal changes in the supra- and infratentorial white matter and brain stem that went completely unnoticed on CT.

Imaging considerations of central nervous system manifestations in pediatric patients with neurofibromatosis type 1

CT and MRI were used in a prospective study of the central nervous system (CNS) manifestations in 41 consecutive children with neurofibromatosis type 1 (NF-1). Gadolinium-DTPA was used in 15 patients. MRI was more effective than CT in delimiting the extension of the optic pathway glioma and in evaluating associated cerebral malformations. MRI visualized lesions generally undetected by CT, in the form of iso- or hyperintense foci with respect to the cerebral cortex in T2-weighted sequences. Well-delimited lesions of high signal intensity were observed in the globus pallidus (22 cases), the internal capsule (6 cases), corpus callosum (2 cases), anterior commissure (1 case) and semioval center (2 cases). Poorly defined hyper- or isointense areas were also observed affecting the cerebellar white matter (21 cases) and brain stem (17 cases). None of these lesions showed Gadolinium-DTPA enhancement, and were of no clinical significance. MRI has displaced CT in the initial diagnosis of patients with NF-1. Periodic annual MRI controls are only justified in patients with MRI changes to evaluate the progression or stabilization of the lesions.

Definitive radiation therapy in the management of symptomatic patients with optic glioma. Survival and long-term effects

We reviewed 24 children who had symptomatic gliomas that involved the optic chiasm and were treated with definitive radiation therapy from 1971 to 1986. In eight patients (33%), histologic confirmation of low-grade astrocytoma was obtained. Patients had radiation therapy only if there was evidence of visual deterioration or other clinical or radiographic evidence of disease progression. Radiation doses ranged from 4500 to 5660 cGy (median, 5400 cGy) with up to a 17-year follow-up period (median, 6 years). The 6-year actuarial freedom from disease progression and overall 6-year survival are 88% and 100%, respectively. Visual improvement or stabilization was seen in 21 (91%) patients after radiation. A high incidence of endocrine abnormalities is reported, with 15 of the 18 patients evaluated after treatment showing growth hormone deficiency. We conclude that definitive radiation therapy is associated with tumor control in most of the patients with progressive optic chiasm gliomas. However, neuropsychiatric and endocrine abnormalities are significant problems that need additional evaluation in these children.