Histological characteristics of intra-temporal facial nerve paralysis in temporal bone malignancies

Objective: To describe the histopathologic findings and clinical presentation of intra-temporal facial nerve invasion in primary and metastatic malignancies of the human temporal bone (TB). Materials and Methods: Retrospective analysis of all medical records of patients diagnosed with peripheral facial nerve palsy (PFnP) of a malignant origin was performed. Temporal bones underwent standard processing for histologic examination. Hematoxylin and eosin (H&E)–stained slides were examined by light microscopy. The histologic findings were compared to premortem clinical data. Results: Eighteen TBs were identified in 16 patients. The male to female ratio was 9:7. The median (range) age of death was 56.5 years (27 months to 75 years). The median time interval from facial nerve injury to death was 5.5 months. There were 11 carcinomas and seven sarcomas identified. Primary TB malignancies were identified in seven TBs (39%), and the rest (11 TBs, 61%) were of metastatic origin. Complete facial nerve paralysis (House-Brackmann [HB] grade VI), was the most common clinical presentation affecting nine patients (10 TBs, 56%). Neural involvement was multifocal in nature (16 of 18 TBs, 89%). The most commonly involved cranial nerve (CN) VII segment was the meatal segment (13 TBs, 72%), followed by the labyrinthine, tympanic, and vertical segments (nine, eight, and six TBs, respectively). Conclusion: PFnP can be the result of local, regional, or distant malignancy, and is associated with poor survival. The facial nerve can serve as a route of tumor progression intracranially. Whereas every segment of CNV II can be violated by tumors, not all PFnP are related to direct tumor invasion. Level of Evidence: 4. Laryngoscope, 130:E358–E367, 2020.