Familial neurilemmomatosis: report of a case

Historical Development of Diagnostic Criteria for NF2-related Schwannomatosis

NF2-related schwannomatosis (NF2; previously termed neurofibromatosis type 2) is a tumor-prone disorder characterized by development of multiple schwannomas and meningiomas. The diagnostic criteria of NF2 have been regularly revised. Clinical criteria for NF2 were first formulated at the National Institutes of Health Consensus Conference in 1987 and revised in 1990. Revised criteria were also proposed by the Manchester group in 1992 and by the National Neurofibromatosis Foundation (NNFF) in 1997. The 2011 Baser criteria improved the sensitivity of diagnostic criteria, particularly for patients without bilateral vestibular schwannomas. Revisions to the Manchester criteria were published in 2019, with replacement of "glioma" by "ependymoma," removal of "neurofibroma," addition of an age limit of 70 years for development of vestibular schwannomas, and introduction of molecular criteria, which led to the most widely used criteria. In 2022, the criteria were reviewed and updated by the international committee of NF experts. In addition to changes in diagnostic criteria, the committee recommended the use of "schwannomatosis" as an umbrella term for conditions that predispose to schwannomas. Each type of schwannomatosis was classified by the gene containing the disease-causing pathogenic variant. Molecular data from NF2 patients led to further clarification of the diagnostic criteria for NF2 mosaic phenotypes. Given all these changes, the diagnostic criteria of NF2 may be confusing. Herein, to help healthcare professionals who diagnose NF2 conditions in the clinical setting, we review the historical development of diagnostic criteria.

ERN GENTURIS clinical practice guidelines for the diagnosis, treatment, management and surveillance of people with schwannomatosis

A Guideline Group (GG) was convened from multiple specialties and patients to develop the first comprehensive schwannomatosis guideline. The GG undertook thorough literature review and wrote recommendations for treatment and surveillance. A modified Delphi process was used to gain approval for recommendations which were further altered for maximal consensus. Schwannomatosis is a tumour predisposition syndrome leading to development of multiple benign nerve-sheath non-intra-cutaneous schwannomas that infrequently affect the vestibulocochlear nerves. Two definitive genes (SMARCB1/LZTR1) have been identified on chromosome 22q centromeric to NF2 that cause schwannoma development by a 3-event, 4-hit mechanism leading to complete inactivation of each gene plus NF2. These genes together account for 70-85% of familial schwannomatosis and 30-40% of isolated cases in which there is considerable overlap with mosaic NF2. Craniospinal MRI is generally recommended from symptomatic diagnosis or from age 12-14 if molecularly confirmed in asymptomatic individuals whose relative has schwannomas. Whole-body MRI may also be deployed and can alternate with craniospinal MRI. Ultrasound scans are useful in limbs where typical pain is not associated with palpable lumps. Malignant-Peripheral-Nerve-Sheath-Tumour-MPNST should be suspected in anyone with rapidly growing tumours and/or functional loss especially with SMARCB1-related schwannomatosis. Pain (often intractable to medication) is the most frequent symptom. Surgical removal, the most effective treatment, must be balanced against potential loss of function of adjacent nerves. Assessment of patients' psychosocial needs should be assessed annually as well as review of pain/pain medication. Genetic diagnosis and counselling should be guided ideally by both blood and tumour molecular testing.

Diagnosis and management of pediatric cervical vagal schwannoma

Schwannomas arising from the vagus nerve are extremely rare in children, with only 15 cases reported in the world literature. We describe a pediatric case of cervical vagal nerve schwannoma successfully treated with cranial nerve-sparing surgery. Our patient presented extensive mass in the right side of the neck with ipsilateral Horner's syndrome. Her first sign, anisocoria, was diagnosed at the age of 1.5 y, making her the youngest vagal schwannoma case ever reported. Using an ultrasonic surgical aspirator and nerve monitoring, a multidisciplinary team successfully removed the mass with no recurrence after 2 years of follow-up.

Peripheral tumors of the intercostal nerves

Fewer than 10% of primary neural tumors of the chest originate peripherally from intercostal nerves; most neural tumors of the chest arise in the mediastinum. Most patients with primary tumors of the intercostal nerve are asymptomatic. We report a case of neurilemmoma arising from an intercostal nerve in a woman seen for severe pain in the chest wall. Resecting the tumor relieved the pain. Recent medical literature describing peripheral tumors of thoracic nerves is reviewed.

Neurilemmomatosis, NF2, and juvenile xanthogranuloma

The gene locus for neurilemmomatosis has been reported to lie within the neurofibromatosis type 2 gene region, suggesting that these 2 diseases may be identical. We describe an adolescent girl with multiple neurilemmomas and juvenile xanthogranulomas, who was found to have bilateral acoustic neuromas and multiple central nervous tissue tumors as seen in patients with a diagnosis of neurofibromatosis type 2. This case and recent genetic studies suggest that neurilemmomatosis and neurofibromatosis type 2 are the same disease.

Multiple schwannomas, multiple nevi, and multiple vaginal leiomyomas: a new dominant syndrome

We report on a family of seven affected with a new syndrome of multiple deep schwannomas, multiple nevi (both intradermal and compound types), and multiple leiomyomas of the vagina. Inheritance is dominant, whether autosomal or X-linked cannot be determined at this time. The nevi, which are congenital, appear to be a marker for the syndrome. Both the schwannomas and leiomyomas do not manifest until adulthood.

Phenotypic diversity of neurofibromatosis 2: association with plexiform schwannoma

AIMS

Plexiform schwannoma (PS) is a rare variant of benign schwannoma characterized by a multinodular and plexiform growth pattern. In contrast to plexiform neurofibroma. PS is not associated with neurofibromatosis 1 (NF-1; von Recklinghausen's disease) and has no propensity for malignant transformation. The purpose of this study was to clarify the relationship between PS and the entities of neurofibromatosis 2 (NF-2; bilateral acoustic neurofibromatosis) and schwannomatosis.

METHODS AND RESULTS

Six cases of PS associated with NF-2 or meningioma were retrospectively studied clinicopathologically and immunohistochemically. Four cases of PS were found among the patients with NF-2, and all of these had multiple PSs; three cases also had multiple schwannomas of the spinal nerve roots and two of these had meningioma. Two other patients had meningioma, but not NF-2. Four patients were male and two were female. The ages ranged from 18 to 52 years (mean 29.6 years). Histologically, PS showed the histological features that have been previously described, i.e. schwannoma composed of a predominant Antoni A-type component with a plexiform growth pattern. Immunohistochemically, the tumour cells were positive for S100 protein. Each nodule was surrounded by perineural cells which were positive for epithelial membrane antigen.

CONCLUSIONS

It is important to recognize that PS could be associated with NF-2 or meningioma. The combination of PS and meningioma may be a 'formes frustes' of NF-2, and is clinically overlapped with schwannomatosis.

Vagus nerve imaging with ultrasound: anatomic and in vivo validation

To provide the anatomic basis and demonstrate the reproducibility of ultrasound studies for the identification of the vagus nerve within its course in the carotid sheath in the neck, cadaveric and in vivo imaging studies were conducted. On transverse B-mode images of the neck, there is a centrally hypoechoic and peripherally hyperechoic structure between the common carotid artery and the jugular vein inside the carotid sheath. This structure was also identified in a fresh, nonpreserved cadaver and was marked with a hypodermic needle by means of a transdermal approach. Neck dissection was performed leaving the carotid sheath intact. B-mode imaging yielded detailed anatomic information about the structures in the carotid sheath. Further dissection showed the vagus nerve as the target of the needle. One hundred consecutive transverse carotid scans were reviewed, and the characteristic echo patterns of the vagus nerve were identified in 97 instances. A distinct and reproducible, round, hypoechoic structure was defined adjacent to the common carotid artery and jugular vein as the vagus nerve. On the basis of this study, a new, noninvasive, and highly reproducible method to locate the vagus nerve in the carotid sheath is introduced. This may lead to further clinical application such as presurgical localization or ultrasound-guided needle studies. Stimulation of the vagus nerve has been proposed for seizure therapy. The diagnosis of vagus nerve tumors may be improved.

Cutaneous plexiform schwannoma associated with neurofibromatosis type 2

BACKGROUND

Plexiform schwannoma (PS) is a rare benign tumor of the nerve sheath that can be located either in the deep soft tissues or in the dermis or subcutis. The tumor predominantly affects young adults and occurs most commonly as a slowly growing asymptomatic solitary nodule in the head and neck region, trunk, and upper extremities.

METHODS

A cutaneous PS located in the preauricular region of a 19-year-old white female is reported. The patient exhibited six "café-au-lait" spots in the trunk and the extremities. Magnetic resonance imaging examination showed bilateral tumors in both acoustic nerves (considered schwannomas) and also masses in the right major sphenoidal wing, falx, and T2-T3 level of rachis and a solid and cystic tumor in the low medulla oblongata. Tumors of the preauricular region, medulla oblongata, spinal cord at level T2-T3, and major sphenoidal wing area were surgically removed. The tumors were studied by immunohistochemistry and diagnosed as PS, pilocytic astrocytoma, and meningiomas, respectively.

RESULTS

Seventy-eight cases of PS have been reported in the literature: 8 (10.2%) have been associated with clinical schwannomatosis, 6 (7.7%) with multiple cutaneous schwannomas syndrome, and only 3 (3.8%) with neurofibromatosis type 1 (NF-1).

CONCLUSIONS

In this report, to the authors' knowledge, for the first time PS is described associated with neurofibromatosis type 2. The tumor does not appear to have significant association with NF-1. Plexiform schwannoma should be recognized because it may be misdiagnosed as plexiform neurofibroma or other plexiform malignant tumors. Differentiation from plexiform neurofibroma is important, because the latter is virtually pathognomonic of neurofibromatosis type 1 and has a propensity for malignant transformation.