Distribution and immunoreactivity of cerebral micro-hamartomas in bilateral acoustic neurofibromatosis (neurofibromatosis 2)

Miniature Palpebral Plexiform Neurofibroma in Neurofibromatosis Type 2

A 27-year-old woman with well-documented neurofibromatosis 2 developed a soft, painless, nodular lesion on the skin surface of the left upper eyelid over 2 years. Following excision, histopathology revealed a plexiform neurofibroma with intradermal nodules comprised of benign round and spindle cells that reacted diffusely with immunohistochemical stains SOX-10 and S100. A subset showed focal reactivity for neurofilament and CD34. A perineurium surrounded each nodule with cells staining positively for markers EMA (epithelial membrane antigen) and GLUT1 (glucose transporter 1). Plexiform neurofibromas are rare tumors that occur in 5%-15% of patients with neurofibromatosis 1. Cutaneous abnormalities in neurofibromatosis 2 have not been widely studied although reports have described schwannomas, plexiform schwannomas, and occasional neurofibromas. Plexiform neurofibromas in neurofibromatosis 2 have rarely been illustrated and the current case represents a unique bona fide eyelid example to date.

Variations and natural history of primary intraparenchymal lesions associated with neurofibromatosis type 2

The study aimed to investigate the clinical implications and natural history of primary intraparenchymal lesions in patients with neurofibromatosis type 2. Radiological findings of 15 neurofibromatosis type 2 cases were retrospectively collected. Twenty-seven primary intraparenchymal lesions were observed in 7 out of 15 patients (47%). Cortical/subcortical T2 hyperintense lesions and enlarged Virchow-Robin spaces were the most common findings in five and four patients, respectively. During the follow-up period (median 84 months), one new primary intraparenchymal lesion was identified and increased lesions were observed in two cases on contrast-enhanced MRI. Surgical resection was performed in one case pathologically diagnosed with atypical meningioma. Twenty-five other lesions without contrast enhancement presented no apparent growth during follow-up. Although most primary intraparenchymal lesions are benign, a subset of cases would present newly developed or increased lesions on contrast-enhanced MRI. Careful monitoring is necessary for such cases, and pathological confirmation should be considered.

Developmental malformations in Huntington disease: neuropathologic evidence of focal neuronal migration defects in a subset of adult brains

Neuropathologic hallmarks of Huntington Disease (HD) include the progressive neurodegeneration of the striatum and the presence of Huntingtin (HTT) aggregates that result from abnormal polyQ expansion of the HTT gene. Whether the pathogenic trinucleotide repeat expansion of the HTT gene causes neurodevelopmental abnormalities has garnered attention in both murine and human studies; however, documentation of discrete malformations in autopsy brains of HD individuals has yet to be described. We retrospectively searched the New York Brain Bank (discovery cohort) and an independent cohort (validation cohort) to determine whether developmental malformations are more frequently detected in HD versus non-HD brains and to document their neuropathologic features. One-hundred and thirty HD and 1600 non-HD whole brains were included in the discovery cohort and 720 HD and 1989 non-HD half brains were assessed in the validation cohort. Cases with developmental malformations were found at 6.4–8.2 times greater frequency in HD than in non-HD brains (discovery cohort: OR 8.68, 95% CI 3.48–21.63, P=4.8 × 10^-5; validation cohort: OR 6.50, 95% CI 1.83–23.17, P=0.0050). Periventricular nodular heterotopias (PNH) were the most frequent malformations and contained HTT and p62 aggregates analogous to the cortex, whereas cortical malformations with immature neuronal populations did not harbor such inclusions. HD individuals with malformations had heterozygous HTT CAG expansions between 40 and 52 repeats, were more frequently women, and all were asymmetric and focal, aside from one midline hypothalamic hamartoma. Using two independent brain bank cohorts, this large neuropathologic series demonstrates an increased occurrence of developmental malformations in HD brains. Since pathogenic HTT gene expansion is associated with genomic instability, one possible explanation is that neuronal precursors are more susceptible to somatic mutation of genes involved in cortical migration. Our findings further support emerging evidence that pathogenic trinucleotide repeat expansions of the HTT gene may impact neurodevelopment.

An update on the CNS manifestations of neurofibromatosis type 2

Neurofibromatosis type II (NF2) is a tumor predisposition syndrome characterized by the development of distinctive nervous system lesions. NF2 results from loss-of-function alterations in the NF2 gene on chromosome 22, with resultant dysfunction of its protein product merlin. NF2 is most commonly associated with the development of bilateral vestibular schwannomas; however, patients also have a predisposition to development of other tumors including meningiomas, ependymomas, and peripheral, spinal, and cranial nerve schwannomas. Patients may also develop other characteristic manifestations such as ocular lesions, neuropathies, meningioangiomatosis, and glial hamartia. NF2 has a highly variable clinical course, with some patients exhibiting a severe phenotype and development of multiple tumors at an early age, while others may be nearly asymptomatic throughout their lifetime. Despite the high morbidity associated with NF2 in severe cases, management of NF2-associated lesions primarily consists of surgical resection and treatment of symptoms, and there are currently no FDA-approved systemic therapies that address the underlying biology of the syndrome. Refinements to the diagnostic criteria of NF2 have been proposed over time due to increasing understanding of clinical and molecular data. Large-population studies have demonstrated that some features such as the development of gliomas and neurofibromas, currently included as diagnostic criteria, may require further clarification and modification. Meanwhile, burgeoning insights into the molecular biology of NF2 have shed light on the etiology and highly variable severity of the disease and suggested numerous putative molecular targets for therapeutic intervention. Here, we review the clinicopathologic features of NF2, current understanding of the molecular biology of NF2, particularly with regard to central nervous system lesions, ongoing therapeutic studies, and avenues for further research.

Schwannosis in Three Foals and a Calf

Proliferation of ectopic Schwann cells within the central nervous system (CNS) parenchyma (schwannosis) in early life is most commonly associated with human neurofibromatosis type-2 and has been unrecognized in domestic animals. Three foals and a calf, 5 to 11 weeks old, with progressive neurological signs from birth were studied. Histologically, at multiple levels of the spinal cord, all animals had bilateral plaques of proliferative spindle cells, predominantly affecting the white matter adjacent to dorsal and ventral nerve roots and variably extending into the gray matter. Proliferating cells had strong intracytoplasmic immunoreactivity for the Schwann cell markers myelin protein zero and periaxin, highlighting the formation of peripheral nervous system (PNS) myelin within the spinal cord. In all cases, foci of disorganized neural tissue (glioneuronal hamartomas) were present, which in 2 cases formed a mass effect that resulted in syringohydromyelia. Neonatal presentation suggests a congenital maldevelopment of the nervous system, with spontaneous invasion of PNS-derived Schwann cells into the CNS.

Incidental parenchymal magnetic resonance imaging findings in the brains of patients with neurofibromatosis type 2

PURPOSE

Whereas T2 hyperintensities known as NF-associated bright spots are well described in patients with neurofibromatosis type I (NF-1), there is a paucity of data on incidental findings in patients with neurofibromatosis type II (NF-2). We aim to characterize unexplained imaging findings in the brains of patients with NF-2.

MATERIALS AND METHODS

This study is retrospective, HIPAA-compliant and approved by the institutional review board. 34 patients with NF-2 underwent brain magnetic resonance imaging (MRI) between January 2000 and December 2012. T2 and T1-weighted imaging characteristics, diffusion weighted imaging (DWI) characteristics, and enhancement patterns were analyzed by visual inspection. Clinical information at time of imaging was available for all patients. Neuropathologic data was available for one patient.

RESULTS

We found unexplained T2 hyperintensities present on initial imaging in 23/34 patients (67%). Of the 23 patients with unexplained MRI findings, 15 (65%) had wedge-shaped T2 hyperintensities in the subcortical white matter extending to the cortex suggestive of a cortical dysplasia. 3 additional cases (17%) had a lesion within the cerebellum suggestive of a neuronal migration anomaly. In one patient where the MRI was suggestive of focal cortical dysplasia, histopathologic analysis revealed dysplastic glial foci without other alterations of cortical architecture or other cytologic abnormalities.

CONCLUSION

Unexplained T2 hyperintensities occur frequently in patients with NF-2. While they may not be the NF-2 equivalent of NF-associated bright spots seen in NF-1, some of these T2 hyperintensities in patients with NF-2 may represent underlying disorders of neuronal migration. Further studies are needed to validate our findings.

An uncommon case of neurofibromatosis type 2: a tribute to the intracranial calcifications

Neurofibromatosis Type 2 (NF2) is a genetic disorder associated with schwannomas, meningiomas, and ependymomas. Intracranial calcifications, either tumoral or non-tumoral, are relatively lesser known features of NF2. Here, we present a case of NF2, in which the diagnosis was suspected due to the presence of choroid plexus and subependymal calcifications, although no obvious schwannoma or meningioma was detected initially on standard computed tomography or magnetic resonance imaging. This case highlights the importance of further evaluation with appropriate imaging techniques.

Tumors of central and peripheral nervous system associated with inherited genetic syndromes

There are several genetic syndromes that predispose to the development of tumors of the nervous system. In the present study, we provide a review of the tumors that are associated with neurofibromatosis type 1, neurofibromatosis type 2, tuberous sclerosis complex, von Hippel-Lindau disease, Li-Fraumeni syndrome, Cowden disease, Turcot syndrome, nevoid basal cell carcinoma syndrome (Gorlin syndrome) and rhabdoid predisposition syndrome, which are the most common.

Astrocytic hamartoma of the optic disc and multiple café-au-lait macules in a child with neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is a heritable syndrome characterized by multifocal proliferation of neural crest-derived cells. The characteristic and diagnostic finding of NF2 is bilateral vestibular nerve schwannomas (acoustic neuromas). In addition to other tumors involving the central and peripheral nervous systems, ophthalmic manifestations, including posterior subcapsular and peripheral cortical cataracts, optic nerve meningiomas, epiretinal membrane, and combined pigment epithelial and retinal hamartomas, are common to NF2. Herein we present an 8-year-old girl with NF2 and astrocytic hamartoma of the optic disc. This patient had been previously diagnosed with NF1 on the basis of multiple CAL macules and suspected subcutaneous neurofibromas. However, neuroimaging revealed bilateral acoustic neuromas, leading to a clinical diagnosis of NF2. Subsequent molecular genetic analysis confirmed the NF2 diagnosis. Multiple CAL macules and astrocytic hamartomas, while associated with NF1, are rarely associated with NF2. Specifically, we are not aware of any reported cases of optic disc astrocytic hamartoma in the setting of NF2.

Hereditary genodermatoses with cancer predisposition

In this article hereditary genodermatoses with cancer predisposition are reviewed, including nevoid basal cell carcinoma syndrome, neurofibromatosis types 1 and 2, tuberous sclerosis complex, xeroderma pigmentosum, and dyskeratosis congenita. Hereditary melanoma is also included, though it differs from the others in several respects. The underlying genetic aberrations causing these syndromes are largely known, allowing novel treatments to be developed for some of these disorders. Early recognition and diagnosis allows for close follow-up and surveillance for associated malignancies.

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.

Ophthalmologic findings and long-term course in patients with neurofibromatosis type 2

PURPOSE

To evaluate ophthalmologic findings and long-term course in patients with neurofibromatosis type 2 (NF2).

DESIGN

Retrospective observational case series.

METHODS

SETTING

Single-center institutional practice.

STUDY POPULATION

Thirty referred patients with NF2 were enrolled from 1991 to 2003 and underwent at least one thorough neuroophthalmologic examination. Follow-up of 23 patients ranged from 4.3 to 12.5 years.

MAIN OUTCOME MEASURES

Visual function, structural ocular abnormalities, onset and type of presenting NF2-related symptoms, and number of central nervous system tumors.

RESULTS

Initial symptoms for patients with early-onset NF2 mostly comprised ophthalmologic symptoms (n = 7) and lower motor neuron extremity weakness (n = 6), as opposed to eighth nerve impairment (n = 11) in late disease onset. NF2-specific ocular findings were noted in 83% of all patients (94% childhood onset; 67% adult onset): 67% had cataracts, 40% epiretinal membranes, 3% hamartoma, 13% disk gliomas, and 27% optic nerve sheath meningiomas. Only 14% in the childhood-onset group-as opposed to 78% in the adult-onset group-sustained visual acuity of 1.0 in both eyes at final examination. Significantly more patients with early onset of symptoms developed multiple central nervous system tumors (P = .004) and showed a higher amount of NF2-specific findings (P = .015).

CONCLUSIONS

Initial manifestations of NF2 differ between children and adults. NF2-specific ophthalmologic findings can help establish the diagnosis. Symptom onset at a young age is clearly a risk factor for marked disease progression. These patients should be carefully followed because survival rates have increased, and vision becomes increasingly important as the disease progresses.

Insights into meningioangiomatosis with and without meningioma: a clinicopathologic and genetic series of 24 cases with review of the literature

Meningioangiomatosis (MA) is a rare seizure-associated lesion of presumed hamartomatous or developmental origin. It is occasionally combined with a neoplasm, most commonly meningioma (MA-M). In the current study, we examined 24 cases (14 pure MA, 10 MA-M) using immunohistochemistry for merlin, protein 4.1 B, progesterone receptor (PR), and MIB-1, as well as FISH for NF2 and 4.1B gene dosages. Nine cases of MA-M (90%) had gene deletions (NF2/4.7B), protein losses (merlin/protein 4.1B), and/or PR positivity, with a similar or identical phenotype in both components. No PR positivity or gene deletions were seen in pure MAs, though merlin and/or protein 4.1B were immunonegative in six cases. Our data suggest that in most MA-Ms, the MA component is neoplastic, likely representing an exuberant perivascular pattern of spread from the meningioma, rather than an underlying hamartoma. This pattern of spread may be facilitated by meningiomas that are predominantly leptomeningeal or intracerebral in origin. It remains important to distinguish this pattern from true brain invasion, given the more ominous prognostic significance of the latter. In contrast, most perivascular spindled cells of pure MA are genetically and immunohistochemically similar to non-neoplastic meningothelial cells, consistent with current histogenetic theories.

Unique intracerebral tumor with divergent differentiation in a patient presenting as NF2: report of a case with features of astrocytoma, ependymoma, and PNET

Patients with neurofibromatosis 2 (NF2) are predisposed to a variety of neoplastic and dysplastic lesions, including schwannomas, neurofibromas, meningiomas, astrocytomas, and ependymomas, as well as entities such as meningioangiomatosis, schwannosis, and hamartomas. This study reports a unique intracerebral frontotemporal tumor in a 6-year-old boy with presumed NF2, on the basis of bilateral cerebellopontine tumors consistent with acoustic neuromas. The intracerebral tumor revealed a variety of histological patterns, including foci of primitive neuroectodermal tumor (PNET), low-grade astrocytoma and ependymoma, as well as neuroepithelial rests with immature ganglion cells and hamartomatous areas. The MIB-1 labeling index ranged from 63% in the foci of PNET to 4-7% in other foci. The PNET component revealed immunopositivity for synaptophysin and neurofilament and showed cells with delicate intercellular junctions, profiles of rough endoplasmic reticulum, mitochondria, and dense core granules, and cell processes with microtubules and neurofilaments. The glial and ependymal components showed bundles of glial filaments and prominent cell junctions, cilia, and microvilli. The hamartomatous component also included aggregates of cells with hyaline eosinophilic cytoplasm. By EM these cells contained abundant amorphous flocculent material. This constellation of pathologic findings, especially the finding of PNET, is unique and not previously reported in the setting of NF2.

The neuroimaging and clinical spectrum of neurofibromatosis 2

Neurofibromatosis 2 (NF2) is an autosomal dominant disease predisposing to multiple tumors of the central and peripheral nervous system. Bilateral vestibular schwannomas are the hallmark of the disease. To define the clinical spectrum of the disease, we performed gadolinium-enhanced magnetic resonance imaging of the brain and spine as well as neurological, dermatological, and ocular examinations in 48 patients with NF2 diagnosed with the National Institutes of Health diagnostic criteria. Patients were ascertained from patient workshops and publications and from referral as a result of vestibular schwannoma surgery. Vestibular schwannomas were found in 46 patients (96%, 43 bilateral and 3 unilateral), spinal tumors were found in 43 (90%), posterior subcapsular cataracts were found in 30 (63%), meningiomas were found in 28 (58%), and trigeminal schwannomas were found in 14 (29%). The presenting symptoms included hearing loss or tinnitus in 15 patients (31%), multiple or nonspecific symptoms in 15 (31%), skin tumors in 12 (25%), and ocular symptoms in 6 (13%). When the complete spine was imaged, spinal tumors were more common in patients with NF2 than has previously been reported. This is a noteworthy finding, because spinal tumors are a major cause of NF2 morbidity and mortality.

Neuropathology and molecular genetics of neurofibromatosis 2 and related tumors

Neurofibromatosis 2 (NF2) is an uncommon, autosomal dominant disorder in which patients are predisposed to neoplastic and dysplastic lesions of Schwann cells (schwannomas and schwannosis), meningeal cells (meningiomas and meningioangiomatosis) and glial cells (gliomas and glial hamartomas). Clinical and genetic criteria that distinguish NF2 from neurofibromatosis 1 have allowed more accurate assignment of specific pathological features to NF2. The NF2 tumor suppressor gene on chromosome 22q12 encodes a widely expressed protein, named merlin, which may link the cytoskeleton and cell membrane. Germline NF2 mutations in NF2 patients and somatic NF2 mutations in sporadic schwannomas and meningiomas have different mutational spectra, but most NF2 alterations result in a truncated, inactivated merlin protein. In NF2 patients, specific mutations do not necessarily correlate with phenotypic severity, although grossly truncating alterations may result in a more severe phenotype. In schwannomas, NF2 mutations are common and may be necessary for tumorigenesis. In meningiomas, NF2 mutations occur more commonly in fibroblastic than meningothelial subtypes, and may cluster in the first half of the gene. In addition, in meningiomas, a second, non-NF2 meningioma locus is probably also involved. Future efforts in NF2 research will be directed toward elucidating the role of merlin in the normal cell and the sequelae of its inactivation in human tumors.

Early childhood diagnosis of acoustic neuromas in presymptomatic individuals at risk for neurofibromatosis 2

We report on a family in which individuals at risk for NF 2 were investigated with the use of gadolinium-enhanced MRI. This technique has allowed the diagnosis of small (less than 8 mm) acoustic neuromas in two asymptomatic children (age 7 and 11), one of whom had normal audiometric and brainstem-evoked response testing. To our knowledge these are the youngest asymptomatic patients in whom the diagnosis of NF 2 has been demonstrated. It is possible that acoustic neuromas develop at an early age more commonly than recognized previously. The early diagnosis of acoustic neuromas with the use of gadolinium-enhanced MRI may lead to better outcome following surgery. This technique will provide the opportunity to better determine the natural course of this disease.