Incidence of tethered cord syndrome in neurofibromatosis types 1 and 2 pediatric patients: a population-level analysis

PURPOSE

Tethered spinal cord syndrome (TCS) is characterized by cutaneous attachments on the filum terminale that stretch the spinal cord, leading to musculoskeletal and urogenital sequelae. While the neurocutaneous associations with TCS remain undefined, a recent study reports a high incidence of TCS among a pediatric neurofibromatosis (NF) cohort. This present study utilizes a population-level database to estimate TCS incidence among pediatric patients with neurofibromatosis types 1 and 2 (NF1, NF2).

METHODS

The TriNetX Research Network was queried to identify patients diagnosed with NF and/or TCS before the age of 21. Symptomatic TCS requiring surgical intervention was identified using corresponding procedural codes within 12 months following TCS diagnosis. Odds ratios (OR) were calculated to measure the associations of NF1/NF2 with TCS.

RESULTS

19,426 pediatric NF patients were evaluated (NF1: 18,383, NF2: 1042). The average ages of TCS diagnosis among NF1, NF2, and non-NF patients were 12, 16, and 9 years, respectively. The incidence of TCS was 1.2% in NF1 patients and 7.3% in NF2 patients, compared to 0.074% in the general population. The associations of NF incidence with TCS were significantly increased in both NF1 (OR 16.42; 14.38-18.76) and NF2 (OR 105.58; 83.56-133.40) patients compared to the general population. Symptomatic TCS requiring surgical intervention was not significantly associated with NF1/NF2 patients compared to the general TCS population.

CONCLUSION

This analysis demonstrates a high incidence of TCS but delayed intervention in pediatric NF patients. Considering TCS counseling, spinal MRI, and earlier intervention may be warranted for NF patients experiencing musculoskeletal symptomatology.

Sporadic and neurofibromatosis type 2-associated meningioma in children and adolescents

PURPOSE

Pediatric meningioma differs not only in its rare incidence from the adult meningioma, but also in its clinical characteristics. Many treatment approaches of pediatric meningioma are based on the study results of adult meningioma studies. The aim of this study was to explore the clinical and epidemiological characteristics of pediatric meningioma.

METHODS

Data on pediatric patients diagnosed between 1982 and 2021 with NF2-associated or sporadic meningioma and recruited in the trials/registries HIT-ENDO, KRANIOPHARYNGEOM 2000/2007 and KRANIOPHARYNGEOM Registry 2019 were retrospectively analyzed for clinical characteristics, etiology, histology, therapy, and outcome.

RESULTS

One hundred fifteen study participants were diagnosed with sporadic or NF2-associated meningioma at a median age of 10.6 years. There was a 1:1 sex ratio, with 14% of study participants suffering from NF2. 46% of the meningiomas were located hemispherically, 17% at the optic nerve/ intraorbital and 10% ventricularly. Multiple meningiomas were detected in 69% of NF2 patients and in 9% of sporadic meningiomas. 50% of the meningiomas were WHO grade I, 37% WHO grade II and 6% WHO grade III. Progressions or recurrences occurred after a median interval of 1.9 years. Eight patients (7%) died, 3 of them due to disease. The event-free survival was higher for WHO grade I than for WHO grade II meningioma patients (p = 0.008).

CONCLUSIONS

The major difference to the preceding literature could be found in the distribution of different WHO grades and their influence on event-free survival. Prospective studies are warranted to assess the impact of different therapeutic regimens.

CLINICAL TRIAL REGISTRATION NUMBERS

NCT00258453; NCT01272622; NCT04158284.

COVID-19 in people with neurofibromatosis 1, neurofibromatosis 2, or schwannomatosis

PURPOSE

People with pre-existing conditions may be more susceptible to severe COVID-19 when infected by SARS-CoV-2. The relative risk and severity of SARS-CoV-2 infection in people with rare diseases such as neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), or schwannomatosis (SWN) is unknown.

METHODS

We investigated the proportions of people with NF1, NF2, or SWN in the National COVID Cohort Collaborative (N3C) electronic health record data set who had a positive test result for SARS-CoV-2 or COVID-19.

RESULTS

The cohort sizes in N3C were 2501 (NF1), 665 (NF2), and 762 (SWN). We compared these with N3C cohorts of patients with other rare diseases (98-9844 individuals) and the general non-NF population of 5.6 million. The site- and age-adjusted proportion of people with NF1, NF2, or SWN who had a positive test result for SARS-CoV-2 or COVID-19 (collectively termed positive cases) was not significantly higher than in individuals without NF or other selected rare diseases. There were no severe outcomes reported in the NF2 or SWN cohorts. The proportion of patients experiencing severe outcomes was no greater for people with NF1 than in cohorts with other rare diseases or the general population.

CONCLUSION

Having NF1, NF2, or SWN does not appear to increase the risk of being SARS-CoV-2 positive or of being a patient with COVID-19 or of developing severe complications from SARS-CoV-2.

Prevalence and natural history of schwannomas in neurofibromatosis type 2 (NF2): the influence of pathogenic variants

This study explores the natural history of vestibular, trigeminal and lower cranial nerve schwannomas (VS, TS, LCNS) in patients with Neurofibromatosis type 2 (NF2), to understand how pathogenic variants (PVs) of the NF2 gene affect tumour burden and growth rate, via a retrospective analysis of a UK NF2 centre database and imaging. VS, TS and LCNS location and size were measured in accordance with a standardised protocol. PVs were categorised in accordance with the UK NF2 Genetic Severity Score (GSS). 153 patients (age 5-82) had 458 schwannomas, of which 362 were previously untreated comprising: 204 VS, 93 TS, and 65 LCNS (IX, X, XI). 322 schwannomas had sequential imaging allowing growth rate analysis with a mean follow-up of 45 months. VS were universally present, and bilateral in 146/153 cases. 65% of tumours grew >2 mm during the study period at mean rate 2.0 mm/year. Significant association was found between increasing GSS and growth rate. TS occurred in 66/153 patients (bilateral in 27/153); 31% of tumours showed growth (mean 1.8 mm/yr). Significant increase in tumour prevalence was noted with increasing GSS. LCNS were found in 47/153 patients (bilateral in 19/153); 27% of tumours showed growth (mean 1.9 mm/yr). The trend for increased prevalence with increasing GSS did not reach significance. VS growth rate was significantly influenced by GSS and they were much more likely to grow than TS and LCNS. TS prevalence also correlated with increasing GSS.

Neurofibromatosis type 2

Type 2 neurofibromatosis (NF2) is an autosomal dominant disorder caused by mutations in the NF2 tumor suppressor gene NF2 on chromosome 22. Around 1 in 33000 people are born with an NF2 mutation although more than one-third of the 60% of de novo cases are not conceived with the mutation but this develops later in embryogenesis (mosaics). NF2 has a substantial effect on life expectancy and individuals with a constitutional truncating mutation have the worst prognosis. The vast majority of people with NF2 will develop bilateral vestibular schwannomas with many developing schwannomas on other cranial, spinal and peripheral nerves. Cranial and spinal meningiomas and intraspinal low grade indolent ependymomas are the other major tumor features. Cutaneous features can be subtle with only 70% having evidence of intracutaneous plaque-like schwannomas or subcutaneous lesions on peripheral nerves. Café-au-lait patches are more frequent than in the general population but in only around 1% will meet NIH criteria for NF1.

Neurofibromatosis type 2

Neurofibromatosis type 2 is an autosomal-dominant multiple neoplasia syndrome that results from mutations in the NF2 tumour suppressor gene located on chromosome 22q. It has a frequency of one in 25,000 livebirths and nearly 100% penetrance by 60 years of age. Half of patients inherit a germline mutation from an affected parent and the remainder acquire a de novo mutation for neurofibromatosis type 2. Patients develop nervous system tumours (schwannomas, meningiomas, ependymomas, astrocytomas, and neurofibromas), peripheral neuropathy, ophthalmological lesions (cataracts, epiretinal membranes, and retinal hamartomas), and cutaneous lesions (skin tumours). Optimum treatment is multidisciplinary because of the complexities associated with management of the multiple, progressive, and protean lesions associated with the disorder. We review the molecular pathogenesis, genetics, clinical findings, and management strategies for neurofibromatosis type 2.

[Neurofibromatosis type 2]

INTRODUCTION

Neurofibromatosis 2 (NF2) is a rare autosomal dominant disease whose hallmark is the development of bilateral vestibular schwannomas.

STATE OF THE ART

Other features of NF2 include schwannomas, meningiomas, ependymomas, localized along the central nervous system, schwannomas of the peripheral nerves, cutaneous and ophthalmological manifestations. NF2 can be diagnosed in patients without bilateral vestibular schwannoma with sets of diagnostic criteria. Disease phenotype is variable among patients. Main negative prognostic factors are a young age at onset of symptoms and a high number of tumors at diagnosis. NF2 tumor suppressor gene encodes Merlin/Schwannomin, and is also involved in most sporadic schwannomas and meningiomas. Its functions remains largely unknown.

PERSPECTIVES AND CONCLUSIONS

Treatment and follow of NF2 patients up require oto-neurosurgical teams experienced in NF2. Yearly and life time surveillance is mandatory. A clinical screening protocol is suggested. Classically, only symptomatic lesions are to be treated. Some authors advocate an early proactive strategy against vestibular schwannoma in order to preserve hearing. When a treatment is advisable, surgery remains the treatment of choice for tumors. Auditory brainstem implant must be taken into account in hearing rehabilitation.

Stereotactic radiation techniques in the treatment of acoustic schwannomas

Medical decision-making is based on benefit-to-cost analysis. Optimally, treatment obtains a high degree of benefit while minimizing the physical, social, and financial costs. The goals of the treatment of acoustic schwannomas are prohibiting tumor growth and alleviation of symptoms caused by damage to local structures. These symptoms-tinnitus, ataxia, and hearing loss--secondary to eighth nerve dysfunction, as well as symptoms arising from damage to adjacent structures such as the facial nerve, trigeminal nerve, or pons, can be caused by tumor growth or treatment. Determination of optimal therapy must also take into account an understanding of the natural history of the disease, because acoustic schwannomas are slow-growing benign tumors that when left untreated, usually enlarge over time and cause problems.

Safety of radiosurgery applied to conditions with abnormal tumor suppressor genes

OBJECTIVE

To assess the risk of radiosurgery inducing malignancy in neurofibromatosis-2 (NF2) and von Hippel-Lindau disease.

METHODS

A retrospective cohort study of 118 NF2 and 19 von Hippel-Lindau disease patients, totalling 906 and 62 patient-years of follow-up data, respectively.

RESULTS

Two cases of intracranial malignancy were identified, both of which occurred in NF2 patients. One of these was thought to have arisen before the radiosurgery; the other was a glioblastoma diagnosed 3 years after radiosurgery.

CONCLUSION

Because gliomas may occur in as many as 4% of NF2 patients, this may not represent an increased risk. We continue to offer radiosurgery treatment to selected NF2 and von Hippel-Lindau disease patients and consider that the late risk of malignancy arising after irradiation must be put in the context of the condition being treated, the treatment options available to these individuals, and their life expectancy.

STEREOTACTIC RADIOSURGERY FOR VESTIBULAR SCHWANNOMAS IN PATIENTS WITH NEUROFIBROMATOSIS TYPE 2

OBJECTIVE

Vestibular schwannomas present significant management challenges in patients with neurofibromatosis Type 2 (NF2). We evaluated the results of gamma knife radiosurgery for the management of these tumors, focusing on tumor response, hearing preservation, and other factors affecting outcomes.

METHODS

Stereotactic radiosurgery was performed to manage 74 schwannomas in 62 patients. Ipsilateral serviceable hearing was present in 35% of tumors before the procedure. The mean tumor volume was 5.7 cm3. The mean margin and maximum dose used were 14 and 27.5 Gy, respectively. Cox regression analyses were performed to identify factors affecting outcomes.

RESULTS

The median follow-up period was 53 months, and two patients were lost to follow-up. Actuarial local control rates at were 85, 81, and 81% at 5, 10, and 15 years, respectively. Tumor volume was significant as a predictor of local control. Since 1992, using current radiosurgery techniques (magnetic resonance imaging scan targeting and reduced margin dose to 14 Gy or less), the actuarial serviceable hearing preservation rate is 73% at 1 year, 59% at 2 years, and 48% at 5 years after radiosurgery. Facial neuropathy occurred in 8% of tumors, trigeminal neuropathy occurred in 4%, and vestibular dysfunction occurred in 4%. Radiation dose and tumor volume were predictive of development of new deficits. No radiosurgery-associated secondary tumors or atypical or malignant changes were noted.

CONCLUSION

Stereotactic radiosurgery is a safe and effective management modality for neurofibromatosis Type 2 vestibular schwannomas. Although results do not seem to be as good as for patients with sporadic unilateral tumors, gamma knife radiosurgery results seem favorable and indicate that radiosurgery should be strongly considered for primary tumor management in selected patients.

Incidence of vestibular schwannoma and neurofibromatosis 2 in the North West of England over a 10-year period: higher incidence than previously thought

OBJECTIVE

To determine the incidence of vestibular schwannoma (VS) in sporadic, neurofibromatosis type 2 (NF2) germ-line and mosaic form in a 10-year period.

STUDY DESIGN

Review of all incident cases of VS presenting to the four main neurosurgical centers for a population of 4.1 million from 1990 to 1999 and cross-referencing with the regional cancer registry.

SETTING

Population based.

PATIENTS

All patients presenting with VS detected on magnetic resonance imaging scan.

RESULTS

A total of 419 sporadic and 64 NF2-related VS were identified over the study period. This represented an incidence of 10.4 per million per year for sporadic VS and 11.8 per million per year including NF2-related tumors. The incidence rose to 14 per million per year in the latter 5 years. The NF2 patient diagnoses represent an estimated birth incidence of 1 in 25,000, and 7% of the patients with VS had NF2, which is higher than previous estimates.

CONCLUSIONS

The incidence of VS is rising almost certainly due to increasing diagnosis in the magnetic resonance imaging era. At current rates, 1 per 1,000 individuals will be diagnosed with VS in their lifetime. More VS than previously thought are due to NF2, which may be because of recognition of mosaic forms of the disease.

Spinal tumors in neurofibromatosis type 2. Is emerging knowledge of genotype predictive of natural history?

OBJECT

The authors conducted a study to examine the incidence, classification, and progression of spinal tumors in patients with neurofibromatosis Type 2 (NF2) treated at a single center, and to examine relationships with the known mutational subtypes of NF2.

METHODS

They performed a retrospective review of clinical records, neuroimaging studies, and genetic data obtained in 61 patients with NF2. Forty-one (67%) of 61 patients harbored one or more spinal tumors. Thirty-four patients had undergone serial spinal magnetic resonance imaging during a mean follow-up period of 52 months (range 10-103 months; median 53 months). In 16 patients there were multiple extramedullary tumors smaller than 5 mm, which did not progress. Fourteen patients harbored at least one extramedullary tumor that was greater than 5 mm; of these, radiological progression was demonstrated or spinal tumor excision was performed during the follow-up period in eight cases (57%). Eleven patients harbored intramedullary cord tumors in addition to small and large extramedullary tumors, three (27%) of which exhibited radiological progression. In cases in which genotypes were known, protein-truncating mutations were significantly more likely to be associated with the presence of spinal tumors than in other types (p = 0.03, Fisher exact test). No associations between clinical behavior of spinal tumors and genotype, however, could be demonstrated.

CONCLUSIONS

Spinal tumors in cases involving NF2 are heterogeneous in type, distribution, and behavior but larger-size tumors are more likely to progress significantly. Intramedullary tumors usually accompany multiple extramedullary tumors. In the authors' experience subtyping of the NF2 mutation has not yet influenced management. Protein-truncating mutations are associated with an increased prevalence of spinal tumors.

Neurofibromatosis type 2-living with the complications: a case study

Neurofibromatosis is a disease caused by a chromosomal defect that can occur spontaneously or be inherited. The disease is grossly disfiguring and carries with it significant psychological sequelae. It is characterized by tumors on nerve sheaths that can arise anywhere in the body. The rate and frequency of occurrence is unpredictable. More than nine different types of neurofibromatosis have been identified, but other than types 1 and 2, they are quite rare. All types of neurofibromatosis persist for a lifetime, so nurses from different backgrounds may encounter such a patient for various reasons. Nursing care should focus not only on the medical issues the patient presents with, but also on the psychosocial needs that may arise.

Clinical characteristics of spinal nerve sheath tumors: analysis of 149 cases

OBJECTIVE

Spinal nerve sheath tumors arise from the spinal nerve root and grow along it. There are two sites at which the growth of a tumor is restricted: the dural aperture for the spinal nerve root and the intervertebral foramen. This article describes the growth pattern of a spinal nerve sheath tumor along the spinal nerve root at various spinal levels.

METHODS

We retrospectively reviewed the records for 149 patients with spinal nerve sheath tumors who were treated between 1980 and 2001. Of these, 176 resected tumors were classified into five groups according to the relationship to the dura mater and/or the intervertebral foramen.

RESULTS

Strictly intradural tumors compose 8% of nerve sheath tumors of the first two cervical nerve roots. The percentage of these tumors increased gradually from the high cervical region to the thoracolumbar region, where it was more than 80%. In contrast, the percentage of strictly extradural tumors gradually decreased from the rostral portion to the caudal portion. Similarly, a percentage of tumors extending outside the spinal canal decreased from the rostral portion to the caudal portion. These changes of the growth pattern may be explained by the anatomic features of the spinal nerve roots, which have a longer intradural component at the more caudal portion of the spinal axis.

CONCLUSION

The anatomic relationship of a nerve sheath tumor with the dura mater and the intervertebral foramen varies depending on the level of the tumor. This knowledge may help us to create a strategy for total resection of a nerve sheath tumor.

The phakomatoses

The "phakomatosis" concept was formulated early in the twentieth century by the ophthalmologist van der Hoeve. He included 3 disorders in the group-neurofibromatosis, tuberous sclerosis complex, and von Hippel-Lindau syndrome--on the basis of the occurrence of patchy ophthalmologic manifestations in each disorder. Since the name was coined, much has been learned about the pathogenesis of these 3 disorders. It is clear that 2 of them--neurofibromatosis and tuberous sclerosis--are collective terms for multiple disorders. Each of the conditions is caused by distinct genetic defects, with little commonality in terms of protein function. Yet, in some respects, the disorders share a pathogenetic mechanism, that of the tumor suppressor gene. This review will briefly describe these disorders in light of what has been learned about underlying molecular pathogenesis. In each case, genetic testing is beginning to be available; principles of the use of genetic tests will be described.

[Radiosurgery of vestibular schwannomas after microsurgery and combined radio-microsurgery]

Significant morbidity is expected after microsurgery for recurrent or growing residual vestibular schwannoma (VS). In order to avoid this procedure, radiosurgery appeared as an interesting alternative. The purpose of this study is to analyze the results of Gamma Knife radiosurgery in this indication. Between July 1992 and January 2002, 60 patients (including 12 NF2 patients) underwent radiosurgical treatment after one or more attempts of surgical resection (including 27 growing remnant VS and 19 recurrent VS) and could be followed with enough informations, out of 103 patients (10% of the VS population treated during the same period). Mean interval between surgical removal and radiosurgery was 71.5 Months (1.8-127.8 Months). Technical difficulties during the procedure were observed in the 12 cases, mainly due to problems in identifying the target. Median follow-up was 51.6 Months. Four out of 58 patients (7%, confidence interval: 1.9-16.7) were diagnosed as failure. Statistical study failed to find significant parameters influencing failure. Facial and trigeminal nerves were not impaired while one case of severe bulbopontine radio-induced injury leading to a lower cranial nerve deficit was observed. These results show that, in spite of additional difficulties to treat these patients with radiosurgery, this treatment is efficient with acceptable morbidity and can avoid another microsurgical procedure. The strategy of planned combined micro-and radiosurgical treatment of large VS deserves additional investigations to be validated.

[Surgical management of vestibular schwannomas secondary to type 2 neurofibromatosis]

To evaluate the results of Gamma Knife radiosurgery treating vestibular schwannomas (VS) secondary to type 2 neurofibromatosis (NF2) we reviewed our clinical experience. Among the VS that have been treated between July 1992 and January 2002, we could analyze retrospectively the data of 50 VS from 37 patients. Fourteen patients had the mild phenotype while 23 were affected by the severe form. Before radiosurgery, one or two microsurgery attempts had been undertaken in 16 VS. Tumor Volume ranged from 120 to 14405 mm3 (mean: 3468 mm3) at the time of treatment; 12 tumors were Koos stade 4. Median clinical and radiological follow-up was 62 Months and ranged from 27 to 123 Months. The 5-Year and 10-Year actuarial survival rates without failure justifying tumor removal were 90 and 85% respectively. The 5-Year actuarial survival rate without hearing decreasing was 36% when selecting the cases of useful hearing (Gardner I & II) at the time of treatment. Severe phenotype (p=0.05) and dose (>12 Gy) delivered at the tumor margin (p=0.032) were correlated to hearing deterioration at univariated analysis. Permanent facial neuropathy occurred in 2%. Even though the level of tumor control and hearing preservation is not the same as for sporadic VS, these results show that Gamma Knife radiosurgery is a valuable alternative treatment for VS in NF2 patients. Future orientation of early proactive radiosurgical treatment of intracanalicular VS will probably improve these results.

Age at symptom onset and long-term survival in patients with neurofibromatosis Type 2

OBJECT

Neurofibromatosis Type 2 (NF2) is an intractable disorder predisposing to multiple, recurrent tumors of the central nervous system (CNS). To clarify the survival rate and characteristics that predict poor survival, we retrospectively reviewed clinical data in cases of NF2.

METHODS

From among 283 patients with neurofibromatosis who had been registered in a nationwide study in Japan between 1986 and 1987, 74 patients with bilateral vestibular schwannomas were analyzed. The mean duration of follow up after diagnosis was 121 months (range 2-287 months). Results of a Kaplan-Meier product-limit analysis indicated that overall 5-, 10-, and 20-year patient survival rates following diagnosis of NF2 were 85, 67, and 38%, respectively. Early onset of the initial symptom significantly compromised survival; 5-, 10-, and 20-year survival rates in patients with symptom onset at an age younger than 25 years were 80, 60, and 28%, respectively, whereas in patients with symptom onset at an age of 25 years or older the rates were 100, 87, and 62%, respectively. Patients with small vestibular schwannomas at diagnosis (< 2 cm in diameter) had better rates of survival. Other variables such as sex, additional tumors in the CNS, or dermal abnormalities did not significantly affect survival.

CONCLUSIONS

This first report of long-term follow-up results concerning the survival of patients with NF2 indicates an adverse effect of early symptom onset.

Occurrence and characterization of peripheral nerve involvement in neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disorder characterized by the occurrence of bilateral vestibular schwannomas, various brain and spinal tumours as well as peripheral nerve tumours, cutaneous tumours and juvenile posterior lenticular opacity. NF2 is caused by mutations in both alleles of a tumour suppressor gene coding for a protein called schwannomin or merlin. It is suggested that the development of NF2 tumours is caused by complete inactivation of the merlin/schwannomin gene. Interestingly, in a NF2 mouse model, peripheral nerve pathology was more frequently described than schwannomas. However, review of the literature shows that patients suffering from NF2 seldom have unexplained clinical features of peripheral nerve lesion unrelated to tumour masses. Single case reports describe sural nerve biopsies, which histologically show onion-bulb-like formations, seemingly originating from Schwann cells. We have conducted a systematic investigation to determine the occurrence and aetiology of peripheral nerve involvement in NF2 patients. We investigated 15 patients with definite NF2 and in 10 of these found electrophysiological evidence of neuropathy. In this study we present the classification of neuropathy, correlation to clinical findings, and histological findings of a sural nerve biopsy. We conclude that peripheral neuropathy, mostly of axonal type, is a common clinical finding in NF2. We hypothesize that the aetiology of this frequent peripheral neuropathy syndrome in NF2 is caused by compression effects of multiple tumourlets, originating along the length of the peripheral nerves on adjacent nerve fibres, by local influences of the endoneurial pathological cells on adjacent nerve fibres and/or the inability of these cells to properly adhere to, or ensheath, the axon.

[Meningiomas: prognostic relevance of histopathologic and genetic markers]

The majority of meningiomas are histologically benign tumours. Location and invasion of tumour tissue in adjacent structures may hamper radical resections and give rise to recurrences. The rise in human life expectancy has prolonged the postoperative period and thus the risk of tumour recurrence has increased markedly. Infiltration in brain tissue and mitotic activity are important histologic features which negatively influence the disease-free duration of the postoperative period. Molecular studies of relevant genetic defects involved in meningioma are currently underway, but as yet these are of little clinical relevance.

Neurofibromatosis type 2

Neurofibromatosis type 2 is an often devastating autosomal dominant disorder which, until relatively recently, was confused with its more common namesake neurofibromatosis type 1. Subjects who inherit a mutated allele of the NF2 gene inevitably develop schwannomas, affecting particularly the superior vestibular branch of the 8th cranial nerve, usually bilaterally. Meningiomas and other benign central nervous system tumours such as ependymomas are other common features. Much of the morbidity from these tumours results from their treatment. It is now possible to identify the NF2 mutation in most families, although about 20% of apparently sporadic cases are actually mosaic for their mutation. As a classical tumour suppressor, inactivation of the NF2 gene product, merlin/schwannomin, leads to the development of both NF2 associated and sporadic tumours. Merlin/schwannomin associates with proteins at the cell cytoskeleton near the plasma membrane and it inhibits cell proliferation, adhesion, and migration.

Population-based analysis of sporadic and type 2 neurofibromatosis-associated meningiomas and schwannomas

OBJECTIVE

To estimate the incidence of meningiomatosis and schwannomatosis, and their familial occurrences and relation to type 2 neurofibromatosis (NF2) in a well-defined population.

METHODS

Patients with histologically verified intracranial, spinal, or peripheral schwannomas or meningiomas, who were residents of the Helsinki University Hospital catchment area (population, 1,713,000) from January 1, 1985, to December 31, 1995, were included in the study. The Population Register Center was used to identify relatives of all the patients, and their data were linked further to the Finnish Cancer Registry to find NF2-related tumors. Detailed pedigrees were constructed for the patients with NF2, schwannomatosis, meningiomatosis, patients with relatives with histologically verified schwannomas or meningiomas, and patients younger than 25 years of age at the time of diagnosis.

RESULTS

Approximately 3% (12 of 455) of the schwannoma patients had multiple schwannomas in association with NF2, and 2% (11 of 455) had schwannomatosis without NF2. Two of the patients with schwannomatosis (2 of 11) had familial schwannomatosis. Approximately 1% (7 of 823) of the patients with meningioma had multiple meningiomas in association with NF2, and 4% (29 of 823) had meningiomatosis without NF2. No families with meningiomatosis were found among the 823 patients with meningioma studied. The birth occurrence of NF2 was 1 in 87,410.

CONCLUSIONS

The current diagnostic criteria of type 2 neurofibromatosis (NF2) seem valid because NF2 patients were differentiated rather easily from patients with sporadic schwannomatosis and meningiomatosis. Familial meningiomatosis, if it truly exists, is very rare, and familial schwannomatosis is uncommon.

[Neurofibromatosis type 2 (NF2)--classical example of a rare familial cancer syndrome]

Type 2 neurofibromatosis (NF2) is a dominantly inherited disorder characterized by a predisposition to multiple tumours of the nervous system. The incidence in the Caucasian population is estimated between one in 35,000 and one in 40,000 of live births. The NF2 gene was isolated and shown to have mutations in NF2 patients. It is considered to belong to tumour suppressor gene family. Direct NF2 gene analysis enables verification of tentative clinical diagnosis and makes genetic counselling possible.

Management of vestibular schwannomas (acoustic neuromas): auditory and facial nerve function after resection of 120 vestibular schwannomas in patients with neurofibromatosis 2

OBJECTIVE

Vestibular schwannomas (VSs) affect young patients with Neurofibromatosis 2 (NF-2) and cause very serious problems for hearing, facial expression, and brain stem function. Our objective was to determine a therapy concept for the right timing and indication of neurosurgical therapy.

METHODS

In 1000 consecutive VS resections, 120 tumors in 82 patients with NF-2 were surgically treated by the same surgeon (MS) at the Department of Neurosurgery at Nordstadt Hospital from 1978 to 1993. The mean age of the patients was 27.5 years. Sixty tumors were surgically treated in 41 male patients, and 60 tumors were surgically treated in 41 female patients. Bilateral tumor resection was performed in 38 patients (76 operations, after previous partial surgery in 15 cases elsewhere), and unilateral operations were performed in 44 patients, 5 of whom had undergone ipsi- or contralateral surgery that was performed elsewhere. The operative and clinical findings are evaluated and compared with the data of patients without NF-2.

RESULTS

In 105 cases, complete tumor resections were achieved. In 15 cases, deliberate subtotal resections were performed. These were for brain stem decompression in 4 cases and for hearing preservation in the last hearing ear in 11 cases, with successful preservation in 8 of the 11. Pre- and postoperative hearing rates were higher in male than in female patients (70% in male versus 65% in female patients before surgery and 40.5 versus 31%, respectively, after surgery). Hearing was preserved in 29 of 81 ears (36%). The rate of preservation was 24% in cases of large tumors and 57% in cases of small tumors (<30 mm). Twenty-one of 82 patients (26%) were bilaterally deaf before surgery. Twenty-five patients had uni- or bilateral hearing after surgery (i.e., 41 % of those with preoperative hearing or 30.5% of the whole group). Anatomic facial nerve preservation was achieved in 85%. The facial nerve was reconstructed intracranially at the cerebellopontine angle by sural grafting in 17 cases and by hypoglossal-facial reanimation in 5. Two deaths occurred 1 and 3 months postsurgically as a result of malignant tumor growth with brain stem dysfunction and respiratory problems. In summary, for patients with NF-2, the presentation ages are lower, tumor progression is faster, the chances of anatomic and functional nerve preservation are lower, the chances of good outcomes are best when surgery is performed early and when there is good preoperative hearing function, and the danger of sudden hearing loss is higher. The chances and danger often differ from side to side among individual patients.

CONCLUSION

The indication and the timing of tumor resections are in some respects different from normal VS handling and are dependent on the tumor extension and related necessity of brain stem decompression and on the auditory function. As an optimal goal, completeness of resection with functional cochlear nerve preservation is formulated, and as an acceptable compromise, subtotal microsurgical resection with functional cochlear nerve preservation in the last hearing ear is suggested.

Comprehensive management of bilateral acoustic neuromas. Current perspectives

Bilateral acoustic neuromas are pathognomonic for neurofibromatosis 2. Patients with neurofibromatosis 2 present complex and challenging management problems, because growth or surgical removal of the acoustic neuroma may result in total hearing loss. Early diagnosis with gadolinium-enhanced magnetic resonance imaging and refinements in hearing preservation surgery have improved our ability to prevent total hearing loss. For patients with larger tumors or no useful hearing, the auditory brain-stem implant allows restoration of some auditory function when the tumor is removed. We describe our management strategy for patients with bilateral acoustic neuromas, and present case reports to show their diversity. We also discuss the newly identified neurofibromatosis 2 tumor suppressor gene.

Neurofibromatosis 2 (NF2): clinical characteristics of 63 affected individuals and clinical evidence for heterogeneity

To determine the spectrum of manifestations in neurofibromatosis 2 (NF2) and to assess possible heterogeneity, we evaluated 63 affected individuals from 32 families. Work-up included skin and neurologic examinations, audiometry, a complete ophthalmology examination with slit-lamp biomicroscopy of the lens and fundus, and gadolinium-enhanced MRI of the brain and, in some, of the spine. Mean age-at-onset in 58 individuals was 20.3 years; initial symptoms resulted from vestibular schwannomas (44.4%), other CNS tumors (22.2%), skin tumors (12.7%), and ocular manifestations including cataracts and retinal hamartomas (12.7%). Five asymptomatic individuals were diagnosed through screening. Vestibular schwannomas were documented in 62 individuals (98.4%); other findings included cataracts (81.0%), skin tumors (67.7%), spinal tumors (67.4%), and meningiomas (49.2%). Usually, clinical manifestations and course were similar within families but differed among families. To assess possible heterogeneity, we assigned affected individuals to three proposed subtypes (representing mild, intermediate, and severe NF2) based on age-at-onset, presence or absence of CNS tumors other than vestibular schwannomas, and presence or absence of retinal hamartomas. Comparisons among the three subtypes for many clinical parameters demonstrated that patients in the mild subtype differed from those in the other two subtypes for most parameters, but that none of the parameters distinguished patients in the intermediate subtype from those in the severe subtype. Thus, there are likely two rather than three subtypes of NF2. Classification of patients to subtype may aid in counseling about long-term prognosis and in formulating individualized guidelines for medical surveillance.

Germline mutations in the neurofibromatosis type 2 tumour suppressor gene

The recent identification of the NF2 tumour suppressor gene has enabled large scale screening for pathological mutations in the gene. We have sought germline mutations in the NF2 gene by SSCP and heteroduplex analysis of cDNA and genomic DNA samples followed by cloning and sequencing of mutant alleles. In the present report we describe 11 putative pathological mutations, including five nonsense mutations, three short insertions or deletions causing frameshifts and three missense mutations. Most stop mutations and frameshift mutations were found in individuals expressing a severe phenotype while one of the three missense mutations was associated with a mild phenotype. Four unrelated NF2 patients of the 93 tested were found to have identical nonsense mutations caused by a C to T transition (C169) in a CpG dinucleotide, which is a potential mutational hotspot in the NF2 tumour suppressor gene.

The neurofibromatosis type 2 gene is inactivated in schwannomas

Schwannomas are tumors arising from schwann cells surrounding peripheral nerves. Although most schwannomas are sporadic, they are seen in approximately 90% of individuals with neurofibromatosis type 2 (NF2), an autosomal dominantly inherited disease with an incidence of 1:40000 live births. The NF2 gene has recently been isolated on chromosome 22 and encodes a putative membrane organizing protein named schwannomin. It is believed to act as a tumor suppressor gene based on the high frequency of loss of heterozygosity (LOH) on this autosome in both sporadic and NF2 associated schwannomas and meningiomas and the identification of inactivating mutation in NF2 patients. In this study we examined 61 schwannomas including 48 sporadic schwannomas (46 of which are vestibular schwannomas) and 12 schwannomas obtained from NF2 patients, for mutations in 10 of the 16 coding exons of the NF2 gene. Twelve inactivating mutations were identified, 8 in sporadic tumours and 4 in tumors from people with NF2. These results support the hypothesis that loss of function of schwannomin is a frequent and fundamental event in the genesis of schwannomas.

Type 2 neurofibromatosis: the need for supraregional care?

The results of a U.K. study of 145 cases of type 2 neurofibromatosis has shown generally very poor operative results in terms of hearing and facial nerve preservation. Only 9 out of 118 vestibular schwannoma (acoustic neuroma) operations resulted in any clinically detectable hearing preservation and only 32 left the patient with good or normal (House grade I or II) ipsilateral facial nerve function. Although operation is still the definitive treatment of vestibular schwannoma (acoustic neuroma) and may be a lifesaving procedure, it appears that the evidence in favour of early operation is only valid when carried out in highly specialized centres. The special problems of NF2 cases who may go on to develop multiple spinal and cranial tumours making them wheelchair bound and blind as well as deaf warrants a careful experienced approach. Timing of operations may be critical for the enhancement of useful years of quality life. We therefore propose the setting up of a national NF2 register, with the management of cases at a few supraregional centres.

A genetic study of type 2 neurofibromatosis in the United Kingdom. I. Prevalence, mutation rate, fitness, and confirmation of maternal transmission effect on severity

A clinical and genetic study of type 2 neurofibromatosis (NF2) has been carried out in the United Kingdom. Virtually complete ascertainment of cases in the north-west of England was achieved and suggests a population incidence of 1 in 33,000 to 40,000. In the UK as a whole, 150 cases have been identified and been used to study the clinical and genetic features of NF2. The autosomal dominant inheritance of NF2 was confirmed, 49% of cases were assessed as representing new mutations, and the mutation rate was estimated to be 6.5 x 10(-6). Evidence to support a maternal gene effect was found in that age at onset was 18.17 years in 36 maternally inherited cases and 24.5 in 20 paternally inherited cases (p = 0.027). The preponderance of maternally inherited cases was also significant (p = 0.03). Data are presented which suggest that there are two types of NF2, one with later onset and bilateral vestibular schwannomas as the only usual feature, and the other with earlier onset and multiple other tumours. A considerable number of cases did not fall easily into one or other group and other factors such as maternal effect on severity and anticipation need to be considered.

Neurofibromatosis

The two types of neurofibromatosis are NF-1 and NF-2. Both cause abnormal cell growth in the central and peripheral nervous system. Each disease is inherited as an autosomal dominant trait, thus each child of an affected parent has a 50% chance of inheriting the disorder. Because there is no cure for either type of NF and treatment consists of amelioration of clinical symptoms, genetic counseling is the only preventive approach to this disease.

A clinical study of type 2 neurofibromatosis

The clinical features, age at onset of symptoms and survival of 150 patients with type 2 neurofibromatosis were studied. The mean age at onset was 21.57 years (n = 110) and no patients presented after 55 years of age. Patients presented with symptoms attributable to vestibular schwannomas (acoustic neuroma), cranial meningiomas and spinal tumours. In 100 patients studied personally by the authors 44 per cent presented with deafness and this was unilateral in the majority (35/44). Deafness was accompanied by tinnitus in a further 10 per cent and muscle weakness or wasting was the first symptom in 12 per cent. Less common presenting symptoms were seizures (8 per cent), vertigo (8 per cent) numbness and tingling (2 per cent) and blindness (1 per cent). Eleven patients were diagnosed asymptomatically through screening. Café au lait spots occurred in 43 per cent (n = 43) but only one case had six. Skin tumours were detected in 68 per cent (68/100) and 38 per cent (34/90) had an identifiable lens opacity or cataract. The mean age at death in 40 cases was 36.25 years and all but one death was a result of a complication of neurofibromatosis. There are marked inter-family differences in disease severity and tumour susceptibility.

Progress toward the isolation and characterization of the genes causing neurofibromatosis

Neurofibromatosis 1 and neurofibromatosis 2 are clinically distinct autosomal dominant disorders that affect an estimated 1.5 million individuals throughout the world. The genetic defect in each disorder has been mapped to different chromosomes, NF1 to chromosome 17 and NF2 to chromosome 22. Progress towards the cloning of the NF1 gene has proceeded rapidly. The NF1 locus was bracketed using genetic linkage analysis on NF1 affected pedigrees. Physical mapping methods were then used to precisely map the translocation breakpoints in each of two NF1 affected individuals who harbored constitutional chromosomal translocations in the putative NF1 region of chromosome 17. The region of DNA located between the two translocations has been cloned in cosmids and yeast artificial chromosomes and a number of RNA coding sequences have been identified. The identification of the NF1 gene will depend on finding mutations in the DNA of affected individuals. In the case of NF2, progress seems to have been less rapid, in part due to the lower availability of NF2 affected pedigrees. The genetic defect has been mapped to the long arm of chromosome 22 by studies of chromosomal loss in the tumours associated with this disease. Subsequent genetic mapping has confirmed this location. Flanking DNA markers for the NF2 locus have been identified. The region of DNA between these markers is in the order of 5-10 Mb. The identification of chromosomal aberrations in patients with NF2 that involve chromosome 22 will play an important role in the identification of the NF2 gene in much the same way as they have in NF1.