Within the highly ascertained North-West England population, schwannomatosis has less than half the birth incidence and prevalence of NF2.

Vestibular schwannomas (VS) account for approximately 85% of tumors in the cerebello-pontine angle, with a lifetime incidence of approximately 1 in 1000. Most are sporadic, with approximately 5% related to the tumor predisposition syndrome Neurofibromatosis Type 2 (NF2). The mainstays of management strategies are: observation, surgery, radiosurgery/radiotherapy and, for patients with NF2 and rapidly growing tumors or deteriorating neurologic function the targeted therapy bevacizumab. While morbidity and mortality rates related to treatment of VS have improved dramatically over the last decades, there are still significant improvements that could be made, in particular with regards to long-term facial nerve and hearing outcomes. Areas covered: The epidemiology and diagnosis of VS are discussed, followed by the different management strategies and outcomes of those for both sporadic and NF2 related tumors. An extensive literature review has been performed to inform this review article using PubMed and Google Scholar. Expert commentary: The future direction of VS management lies in obtaining longer-term follow-up data for patients with treated VS, and in improved understanding of cellular pathways and targeted therapies.

BackgroundInflammation is hypothesized to be a key event in the growth of sporadic vestibular schwannoma (VS). In this study we sought to investigate the relationship between inflammation and tumor growth in vivo using the PET tracer 11C-(R)-PK11195 and dynamic contrast enhanced (DCE) MRI derived vascular biomarkers.MethodsNineteen patients with sporadic VS (8 static, 7 growing, and 4 shrinking tumors) underwent prospective imaging with dynamic 11C-(R)-PK11195 PET and a comprehensive MR protocol, including high temporal resolution DCE-MRI in 15 patients. An intertumor comparison of 11C-(R)-PK11195 binding potential (BPND) and DCE-MRI derived vascular biomarkers (Ktrans, vp, ve) across the 3 different tumor growth cohorts was undertaken. Tissue of 8 tumors was examined with immunohistochemistry markers for inflammation (Iba1), neoplastic cells (S-100 protein), vessels (CD31), the PK11195 target translocator protein (TSPO), fibrinogen for vascular permeability, and proliferation (Ki-67). Results were correlated with PET and DCE-MRI data.ResultsCompared with static tumors, growing VS displayed significantly higher mean 11C-(R)-PK11195 BPND (−0.07 vs 0.47, P = 0.020), and higher mean tumor Ktrans (0.06 vs 0.14, P = 0.004). Immunohistochemistry confirmed the imaging findings and demonstrated that TSPO is predominantly expressed in macrophages. Within growing VS, macrophages rather than tumor cells accounted for the majority of proliferating cells.ConclusionWe present the first in vivo imaging evidence of increased inflammation within growing sporadic VS. Our results demonstrate that 11C-(R)-PK11195 specific binding and DCE-MRI derived parameters can be used as imaging biomarkers of inflammation and vascular permeability in this tumor group.