(0912) Cochlear Schwann Cell and Microglia Distribution in Human Temporal Bones With Neurofibromatosis Type 2

Introduction: Sensorineural hearing loss can be associated with loss of auditory neurons. In Neurofibromatosis Type 2 (NF2) with bilateral vestibular schwannomas, neural loss has often been attributed to local pro-inflammatory tumor microenvironment or direct tumor compression. However, there is indication that aberrant Schwann cell function and activation of local microglia may contribute to sensorineural hearing loss. Here, we aim to identify and characterize Schwann cells and microglia within the cochlea of human temporal bones with NF2 compared to age matched normal controls.

Methods: This was a histopathological analysis of human temporal bone sections. Immunohistochemical analysis was performed in celloidin embedded archival temporal bone samples of NF2 patients with vestibular schwannomas along with normal age-matched controls using antibodies for SOX10, IBA1, and neuronal markers. Fluorescent quantification of Schwann cells and microglia was compared to traditional hematoxylin and eosin (H&E) stainings in the National Temporal Bone Database (NIDCD).

Results: Fluorescent immunohistochemistry allowed for quantification and characterization of both cell types in control and NF2 positive cochleas. Preliminary results suggested a predominant SOX10 positive Schwann cell population within NF2 cochleas, in addition to a smaller subset of IBA1 positive microglial cells. Microglial cell numbers did not change significantly between controls and NF2 patients, but we observed an activated microglial phenotype with ameboid morpholology in NF2 cochleas.

Conclusions: Immunohistochemical analysis of nonneural cells within the cochlea for the first time allowed characterization of Sox10 positive Schwann cells and activated microglia in human temporal bones with NF2.