Surgery in NF2-Schwannomatosis.

Schwannomatosis (SWN) is a distinct cancer predisposition syndrome caused by germline pathogenic variants in the genes NF2, SMARCB1, or LZTR1. There is a significant clinical overlap between these syndromes with the hallmark of increased risk for cranial, spinal, and peripheral schwannomas. Neurofibromatosis type 2 was recently renamed as NF2-related SWN and is the most common SWN syndrome, with increased risk for bilateral vestibular schwannomas, intradermal schwannomas, meningiomas, and less commonly, ependymoma. SMARCB1-related SWN is a familial SWN syndrome associated with peripheral and spinal schwannomas and an increased risk for meningiomas and malignant peripheral nerve sheath tumors, even in the absence of radiation. These individuals do not develop bilateral vestibular schwannomas. Finally, patients with LZTR1-related SWN typically present with peripheral schwannomas, and unilateral vestibular schwannomas have been reported. The following perspective is intended to highlight the clinical presentation and international tumor surveillance recommendations across these SWN syndromes.

Vestibular schwannomas (VS) are common benign tumors of the vestibular nerve and spinal schwannomas (SS) arise form nerves within the spinal canal. SS are the most common intradural extramedullary spinal tumors, representing 30% of such lesions and both VS and SS both cause significant morbidity. The current treatment strategies for VS and SS include surgery or radiation with each treatment option having associated complications and side effects. The transcriptional landscape of schwannoma remains largely unknown. We first performed gene expression profiling of 49 VS schwannomas and seven normal control vestibular nerves to identify tumor-specific gene expression patterns. We identified over 2000 differentially expressed genes between control and schwannoma with network analysis uncovering proliferation and anti-apoptotic pathways previously not implicated in VS. Furthermore, using several distinct clustering technologies, we could not reproducibly identify distinct VS subtypes or significant differences between sporadic and germline NF2 associated schwannomas suggesting that VS comprises of a highly similar entity. We next performed a transcript analysis comparing VS to SS. Surprisingly; we identified few differential transcripts demonstrating that schwannoma in general is a homogenous entity. Current studies are focused on copy number, DNA methylation profiling and genome wide sequencing analysis. Preliminary data suggests that NF2 is the major driver of schwannoma as previously implicated. Interestingly, we identified several novel and recurrent point mutations of NF2 in exon 1 of both VS and SS, which may lead to loss of function. Our most recurrent activated pathway in schwannoma was overexpression of PI3K/AKT/mTOR signaling pathway, which is directly druggable and evaluated this pathway for therapeutic targeting. Testing compounds BEZ235 and PKI-587, both novel dual inhibitors of PI3K and mTOR, attenuated tumor growth in a pre-clinical cell line model of schwannoma (HEI-293). Our In vitro findings demonstrated that pharmacological inhibition of the PI3K/AKT/mTOR pathway with next generation compounds lead to decreased cell viability, and increased cell death in VS, SS but not normal schwann cells. Future work is testing these compounds in vivo using relevant cell lines and primary cultures of VS/SS. Our findings implicate aberrant activation of the PI3K/AKT/mTOR pathway as a molecular mechanism of pathogenesis in VS and suggest inhibition of this pathway as a potential treatment strategy.

Neurofibromatosis type 2 (NF2; MIM # 101000) is an autosomal dominant disorder characterized by the occurrence of vestibular schwannomas (VSs), schwannomas of other cranial, spinal, and cutaneous nerves, cranial and spinal meningiomas, and/or other central nervous system (CNS) tumors (e.g., ependymomas, astrocytomas). Additional features include early-onset cataracts, optic nerve sheath meningiomas and retinal hamartomas, dermal schwannomas (i.e., NF2-plaques), and few cafe au lait spots. Clinically, NF2 children fall into two main groups: (1) congenital NF2 , with bilateral VSs detected as early as the first days to months of life, which can be stable/asymptomatic for one to two decades and suddenly progress; and (2) severe prepubertal ( Wishart type ) NF2 , with multiple (and rapidly progressive) CNS tumors other than VS, which usually present first, years before VSs (vs. the classic adult [ Gardner type ] NF2 , with bilateral VSs presenting in young adulthood, sometimes as the only disease feature). Some individuals can develop unilateral VS associated with ipsilateral meningiomas or multiple schwannomas localized to one part of the peripheral nervous system (i.e., mosaic/segmental NF2 ) or multiple non-VS, non-intradermal cranial, spinal, and peripheral schwannomas (histologically proven) ( schwannomatosis ). NF2 is caused by mutations in the NF2 gene at chromosome 22q12.1, which encodes for a protein called merlin or schwannomin , most similar to the ezrin-radixin-moesin (ERM) proteins; mosaic NF2 is due to mosaic phenomena for the NF2 gene, whereas schwannomatosis is caused by coupled germ-line and mosaic mutations either in the SMARCB1 gene (SWNTS1; MIM # 162091) or the LZTR1 gene (SWNTS2; MIM # 615670), both falling within the 22q region and the NF2 gene. Data driven from in vitro and animal studies on the merlin pathway allowed biologically targeted treatment strategies (e.g., lapatinib, erlotinib, bevacizumab) aimed to multiple tumor shrinkage and/or regression and tumor arrest of progression with functional improvement. In the present review we focus on the pathophysiology of merlin structure and function and on its posttranslational and upstream/downstream regulation in the different forms of NF2 in the pediatric age.

Neurofibromatosis type 2 (NF2), also known as NF2‐related schwannomatosis (SWN), is a rare dominantly inherited genetic disorder mainly characterized by the presence of vestibular schwannomas (VSs) in addition to a range of other tumors that affect both the central and peripheral nervous systems. These tumors include cranial, spinal, peripheral nerve, and intradermal schwannomas, cranial and spinal meningiomas, and intrinsic central nervous system (CNS) tumors, usually spinal ependymomas. Juvenile cataracts are also common in patients with NF2, with most symptoms at presentation being hearing loss and visual disturbances. We present the case of a previously healthy 12‐year‐old girl who presented with postprandial right upper quadrant pain and was found to have a large hydrops of the gallbladder on ultrasound scan of the abdomen. Pathology of the gallbladder post laparoscopic cholecystectomy showed diffuse involvement of the gallbladder by a benign nerve sheath tumor that was suggestive of schwannoma. Further testing confirmed the diagnosis of NF2. This case helps shed light on unusual NF2 symptoms and underscores the importance of recognizing atypical presentations for timely intervention and management. It also adds value to a multidisciplinary approach in diagnosing and managing NF2.

SUMMARYNeurofibromatosis type 2 [NF2; MIM # 101000] is an autosomal dominant disorder characterised by the occurrence of vestibular schwannomas (VSs), schwannomas of other cranial, spinal and cutaneous nerves, cranial and spinal meningiomas and/or other central nervous system (CNS) tumours (e.g., ependymomas, astrocytomas). Additional features include early onset cataracts, optic nerve sheath meningiomas, retinal hamartomas, dermal schwannomas (i.e., NF2-plaques), and (few) café-au-lait spots. Clinically, NF2 children fall into two main groups: (1) congenital NF2 - with bilateral VSs detected as early as the first days to months of life, which can be stable/asymptomatic for one-two decades and suddenly progress; and (2) severe pre-pubertal (Wishart type) NF2- with multiple (and rapidly progressive) CNS tumours other-than-VS, which usually present first, years before VSs [vs. the classical adult (Gardner type) NF2, with bilateral VSs presenting in young adulthood, sometimes as the only disease feature]. Some individuals can develop unilateral VS associated with ipsilateral meningiomas or multiple schwannomas localised to one part of the peripheral nervous system [i.e., mosaic NF2] or multiple non-VS, non-intradermal cranial, spinal and peripheral schwannomas (histologically proven) [schwannomatosis]. NF2 is caused by mutations in the NF2 gene at chromosome 22q12.1, which encodes for a protein called merlin or schwannomin, most similar to the exrin-readixin-moesin (ERM) proteins; mosaicNF2 is due to mosaic phenomena for the NF2 gene, whilst schwannomatosis is caused by coupled germ-line and mosaic mutations either in the SMARCB1 gene [SWNTS1; MIM # 162091] or the LZTR1 gene [SWNTS2; MIM # 615670] both falling within the 22q region and the NF2 gene. Data driven from in vitro and animal studies on the merlin pathway [e.g., post-translational and upstream/downstream regulation] allowed biologically targeted treatment strategies [e.g., Lapatinib, Erlotinib, Bevacizumab] aimed to multiple tumour shrinkage and/or regression and tumour arrest of progression with functional improvement.

Schwannomatosis is a recently recognized form of neurofibromatosis characterized by multiple noncutaneous schwannomas, a histologically benign nerve sheath tumor. As more cases are identified, the reported phenotype continues to expand and evolve. We describe the spectrum of clinical findings in a cohort of patients meeting established criteria for schwannomatosis. We retrospectively reviewed the clinical records of patients seen at our institution from 1995-2011 who fulfilled either research or clinical criteria for schwannomatosis. Clinical, radiographic, and pathologic data were extracted with attention to age at onset, location of tumors, ophthalmologic evaluation, family history, and other stigmata of neurofibromatosis 1 (NF1) or NF2. Eighty-seven patients met the criteria for the study. The most common presentation was pain unassociated with a mass (46%). Seventy-seven of 87 (89%) patients had peripheral schwannomas, 49 of 66 (74%) had spinal schwannomas, seven of 77 (9%) had nonvestibular intracranial schwannomas, and four of 77 (5%) had intracranial meningiomas. Three patients were initially diagnosed with a malignant peripheral nerve sheath tumor; however, following pathologic review, the diagnoses were revised in all three cases. Chronic pain was the most common symptom (68%) and usually persisted despite aggressive surgical and medical management. Other common diagnoses included headaches, depression, and anxiety. Peripheral and spinal schwannomas are common in schwannomatosis patients. Severe pain is difficult to treat in these patients and often associated with anxiety and depression. These findings support a proactive surveillance plan to identify tumors by magnetic resonance imaging scan in order to optimize surgical treatment and to treat associated pain, anxiety, and depression.

Diagnosis, Management, and New Therapeutic Options in Childhood Neurofibromatosis Type 2 and Related Forms

Clinical features of multiple spinal schwannomas without vestibular schwannomas

Neurofibromatosis 2 (NF2) is an autosomal-dominant genetic disorder characterized by bilateral vestibular schwannomas (VS), meningiomas, ependymomas, spinal and peripheral schwannomas, optic gliomas, and juvenile cataracts. Ongoing studies provide new insight into the role of the NF2 gene and merlin in VS tumorigenesis. As NF2 tumor biology becomes increasingly understood, therapeutics targeting specific molecular pathways have been developed and evaluated in preclinical and clinical studies. NF2-associated VS are a source of significant morbidity with current treatments including surgery, radiation, and observation. Currently, there are no FDA-approved medical therapies for VS, and the development of selective therapeutics is a high priority. This manuscript reviews NF2 tumor biology and current therapeutics undergoing investigation for treatment of patients with VS.

Water is the single most abundant substance in cells and organisms and is an important molecule involved in several biochemical processes present in living cells. In humans 60-70% of body weight is water which equilibrates across the lipid bilayer in cell membranes. Forty years ago, a small number of scientists argued that specialized water-selective pores are necessary to explain the high water permeability of red blood cells and renal tubules. Therefore, the molecular identification of a 28 kDa integral membrane protein in these cells has characterized a new stream of research. Aquaporins (AQPs) are membrane proteins that transport water and, in some cases, also small solutes such as glycerol and urea. Each subtype has its own cellular distribution and distinct regulatory mechanisms of their expression. Their classical role in facilitating trans-epithelial fluid transport is well understood, as in the urinary concentrating mechanism and gland fluid secretion, while the molecular mechanisms to regulate water permeability in the nervous system are still unclear. Maintenance of the ionic and osmotic composition and volume of interstitial, glial and neuronal compartments within the nervous system is essential for normal function. Small changes in intracellular or extracellular ion or solute composition can dramatically modify bi-directional water pathway between the brain and blood vessels and alter cerebrospinal fluid formation, neural signal transduction and information processing. To date, only some AQP isoforms (AQP1, 3, 4, 5, 8, 9) have been reported in the central nervous system being identified in choroidal cells (AQP1), astrocytes (AQP1, 3, 4, 5, 8, 9), oligodendrocytes (AQP8), neurons (AQP1, 5, 8), tanycytes (AQP9) and ependymal cells (AQP1, 4, 9). In contrast to numerous studies of AQP localization and function in the central nervous system, little information is available on the expression and function of AQPs in peripheral nervous system. This issue includes six review articles in which the authors report and explore the recent findings about the involvement of AQPs both in peripheral and central nervous system. The paper by B. Buffoli summarizes the data about the structure, regulation and function of AQPs, giving more importance to their involvement in the nervous system and underlying the development of new methods for diagnosis and therapy diseases. The review of R. Albertini and R. Bianchi is focused on the different isoforms of AQP protein that have been identified in glial cells in central and peripheral nervous system and in reactive microglial. The chapter supports the idea that AQPs are involved in water homeostasis during different glial cell functions, such as differentiation, metabolism and excitability of neurons. F. Bonomini and R. Rezzani emphasize the role of some AQPs present in glial cells in the maintenance or/and in the regulatory mechanisms of blood brain barrier. On the basis of the role of AQPs in brain edema, a personal account of the role of AQPs is then presented by C. Loreto and E. Reggio, who summarized the implication of different isoforms of these proteins in relation with vascular diseases and nervous system. In the literature, there is a lot of evidence that indicates a correlation between the expression of AQPs and the development of neurodegenerative diseases in which preservation of brain homeostasis is at risk. The review of E. Foglio and L.F. Rodella was to consider this topic concentrating on some neurodegenerative diseases, such as Neuromyielitis Optica, Alzheimer’s Diseases, Parkinson’s Diseases, Amyotrophic lateral sclerosis, Transmissible Spongiform Encephalopathies. Recent evidence suggests a novel role of AQPs in pain transmission both in the central and peripheral nervous system. In this issue, E. Borsani reports the modulation of AQPs both in inflammatory and neuropathic pain considering different animal models and knock-out animals. In the future, the numerous ongoing studies will certainly reveal other multifunctional roles of these proteins in humans. These roles might be exploited clinically by the development of drugs to alter AQP expression or function that could serve in the treatment of different diseases associated to peripheral and central nervous system.

Chemoprevention for neurofibromatosis 2: just over the horizon?

Limited data exist on the disease course of neurofibromatosis type 2 (NF2) to guide clinical trial design. A prospective database of patients meeting NF2 diagnostic criteria, reviewed between 1990 and 2020, was evaluated. Follow-up to first vestibular schwannoma (VS) intervention and death was assessed by univariate analysis and stratified by age at onset, era referred, and inheritance type. Interventions for NF2-related tumors were assessed. Cox regression was performed to determine the relationship between individual factors from time of diagnosis to NF2-related death. Three hundred and fifty-three patients were evaluated. During 4643.1 follow-up years from diagnosis to censoring, 60 patients (17.0%) died. The annual mean number of patients undergoing VS surgery or radiotherapy declined, from 4.66 and 1.65, respectively, per 100 NF2 patients in 1990-1999 to 2.11 and 1.01 in 2010-2020, as the number receiving bevacizumab increased (2.51 per 100 NF2 patients in 2010-2020). Five patients stopped bevacizumab to remove growing meningioma or spinal schwannoma. 153/353 (43.3%) had at least one neurosurgical intervention/radiation treatment within 5 years of diagnosis. Patients asymptomatic at diagnosis had longer time to intervention and better survival compared to those presenting with symptoms. Those symptomatically presenting <16 and >40 years had poorer overall survival than those presenting at 26-39 years (P = .03 and P = .02, respectively) but those presenting between 16 and 39 had shorter time to VS intervention. Individuals with de novo constitutional variants had worse survival than those with de novo mosaic or inherited disease (P = .004). Understanding disease course improves prognostication, allowing for better-informed decisions about care.

To describe the whole-body magnetic resonance (WB-MRI) features of peripheral schwannomas in patients with NF2-related schwannomatosis (SWN) treated with bevacizumab for target progressive/symptomatic vestibular schwannomas (VSs). In this multi-institution, open-label phase II clinical trial, WB-MRI at 3.0T was performed at baseline, 25-weeks, and 49-weeks after treatment with bevacizumab using STIR, DWI/ADC mapping, pre- and post-contrast T1-weighted imaging. Two readers recorded size and signal characteristics of non-target peripheral lesions (maximum 5 lesions per patient (each from a different body region)). 2D-area (product of two perpendicular measurements), inter-reader reliability and percent change (baseline-49 weeks) was calculated. Radiological response was defined as complete response (CR, disappearance), partial response (PR, > 20% decrease), progressive disease (PD, > 20% increase), and stable disease (SD). Baseline WB-MRI detected 119 non-target peripheral schwannomas (median:8; range:0-37). Thirty-three peripheral schwannomas in 11 patients (median age (years): 30(range:14-79)) were characterized. Median size(mm) at baseline, 25-weeks, and 49-weeks was 26 (range: 10-88), 26 (range: 10-86), and 25 (range: 9-86), respectively. Lesions were measured with high inter-reader reliability (ICC range 0.990-0.997). Based on largest lesion diameter, all non-target lesions were stable at 49-weeks. Based on 2D-area, the majority of the lesions were SD (31/33 (94%) followed by PR (1/33;3%) and PD (1/33; 3%). There was no change in ADC values or other signal characteristics at 49-weeks. In NF2-related SWN, WB-MRI enables detection and characterization of peripheral non-target schwannomas as small as 10mm with high-inter reader reliability. Despite histological similarities to central VSs (targeted for progression), non-target peripheral schwannomas predominantly remained stable on bevacizumab.

Clinical experience suggests that the majority of schwannomas arise within sensory ganglia, suggesting that intraganglionic glial cells represent a potential cell of origin for schwannomas. To support this clinical impression, we reviewed magnetic resonance imaging (MRI) studies performed over a 5-year period at our institution to determine the relationship of cranial and spinal nerve schwannomas with the ganglia of the associated nerves. Retrospective cohort study. Tertiary referral center. Patients undergoing imaging study at our institution over a 5-year period. Radiographic images at our institution were reviewed as well as published studies to determine the anatomic location of schwannomas. Anatomic location of schwannomas. A total of 372 patients were found over the 5-year study period, 31 of those were diagnosed with neurofibromatosis Type 2 (NF2). Vestibular schwannomas comprised the greatest number of schwannomas, followed by spinal schwannomas. In NF2 patients, spinal schwannomas were the most common tumor, followed by vestibular schwannomas. In NF2 patients and those with sporadic schwannomas, the overwhelming majority of tumors arose in nerves with a sensory component and were associated with the sensory ganglia of the nerves (562/607, 92.6%). Very few tumors arose from pure motor nerves. This is supported by review of published articles on anatomic location of schwannomas. Schwannomas are strongly associated anatomically with the ganglia of sensory nerves. These findings raise the possibility that intraganglionic glial cells give rise to the majority of schwannomas.

Schwannomas are common benign tumors of the vestibular nerve, or arise from nerves within the spinal canal. Although benign, both Spinal schwannoma (SS) and vestibular schwannoma (VS) cause significant morbidities. The current treatment strategies for VS and SS include surgery or radiation with each treatment option having associated complications and side effects. The transcriptional landscape of schwannoma remains largely unknown. We interrogated the transcriptome by gene-expression array analysis of 49 schwannomas and seven normal control vestibular nerves to identify tumor-specific gene expression patterns. We identified over 4000 differentially expressed genes between control and schwannoma with network analysis uncovering proliferation and anti-apoptotic pathways previously not implicated in VS. Using several distinct clustering technologies, we could not reproducibly identify VS subtypes or significant differences between sporadic and germline NF2 associated schwannomas suggesting that VS comprises of a highly similar entity. We next performed a transcript analysis comparing VS to SS. Surprisingly; we identified few differential transcripts demonstrating that schwannoma maybe a homogenous entity. Current studies are focused on DNA methylation profiling and genome wide sequencing analysis. To date our group and others have identified that inactivating mutations in NF2 is the most recurrent aberration in schwannoma. The most recurrent activated pathway in schwannoma was over-expression of PI3K/AKT/mTOR signaling pathway, which is directly druggable and we evaluated this pathway for therapeutic targeting. Testing compounds BEZ235 and PKI-587, both novel dual inhibitors of PI3K and mTOR, attenuated tumor growth in a cell line model of schwannoma. Our In vitro findings demonstrated that pharmacological inhibition of the PI3K/AKT/mTOR pathway with next generation compounds lead to decreased cell viability, and increased cell death. Future work is testing these compounds in vivo using relevant cell lines and primary cultures of schwannoma. Our findings implicate that targeting the PI3K/AKT/mTOR pathway may serve as a potential treatment strategy.