Discussion
Neurogenous tumors are rare amongst children, comprising only 2% of benign non-lymphadenomatous lesions.4 Pediatric cervical vagal schwannomas are especially rare. The median age of diagnosis is 44 years in vagal schwannoma patients undergoing surgery.2 The median maximum diameter of these tumors is 5 centimeters.2 Cervical schwannomas grow at a rate of 3 millimeters per year, and usually only become symptomatic once large enough to cause compressive symptoms.1 Our patient’s young age of 11 years old, in tandem with the large size of the lesion, makes her presentation extraordinarily uncommon.
Schwannomas arise from a single nerve fascicle and may cause cranial nerve dysfunction by exerting pressure on other fibers of the affected or local cranial nerves. Reported series to date differ widely on the prevalence of cranial nerve deficits at presentation. Interestingly, our patient did not exhibit signs of vagus nerve dysfunction, despite the nerve being involved intraoperatively, while she did have a long-standing hypoglossal nerve palsy, seemingly due to extrinsic compression from the vagal schwannoma. Although schwannomas do not typically present with cranial nerve palsies, when they do, dysfunction is usually of the index cranial nerve. Cranial nerve palsy may be suggestive of compression in a confined space or malignant schwannoma. Our patient’s presentation with a hypoglossal nerve palsy with intact vagal nerve function in the context of a benign vagal schwannoma is, therefore, unusual.
Surgical resection is the preferred treatment modality for vagal schwannoma, either with gross total resection or intracapsular enucleation. Gross total resection may be superior to enucleation with respect to cure, but often results in loss of ipsilateral vagal function distal to the lesion. Enucleation may have superior outcomes vis-à-vis preservation of vagal nerve function, but is generally reserved only for small schwannomas and is thought to be associated with higher rates of recurrence.
The transcervical approach is the most commonly employed technique to access vagal schwannomas.2 Our combined transcervical-mandibulotomy approach was necessitated by an inability to safely gain access to the superior aspect of the tumor due to close adherence to the jugular foramen/skull base and adjacent, displaced critical vascular structures. Mandibulotomy allowed for improved access, safe mobilization of the tumor, and dissection of vessels at the level of the skull base.
Vagal schwannoma can arise in the context of genetic syndromes, including Neurofibromatosis Type 2, Carney’s Complex, and schwannomatosis, with mutations in NF2 , SMARCB1 ,LZTR1 , PRKAR1a previously described. Genomic changes in these genes all lead to downstream alterations in the production or function of the protein merlin, which plays a role in a range of growth factor pathways.1 Our patient demonstrated no germline mutation or syndrome. Memorial Sloan Kettering Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) identified an isolated TET1 deletion of exons 1 and 2. TET1 plays a role in epigenetic tumorigenesis and may be implicated in schwannomatosis.5 The clinicopathologic significance of the alteration in the setting of pediatric vagal schwannoma is unclear.