Solitary Lung Metastasis of the Internal Auditory Canal: A Case Report

Background: Metastases of the internal auditory canal (IAC) are rare, but their occurrence dramatically affects the patient's prognosis. We report a case of an isolated non-small cell lung carcinoma (NSCLC) metastasis to the internal auditory canal (IAC), aiming to improve diagnosis and management of these cases. Case presentation: A 58-year-old man who had received concomitant chemoradiotherapy and immunotherapy for NSCLC (T4N1M0) diagnosed in 2021, developed sudden left hypoacusis, left facial palsy, and loss of balance. Magnetic resonance imaging (MRI) showed contrast enhancement in the VII and VIII nerves extending from the cerebellopontine angle (CPA) to the left IAC. A provisional diagnosis of an isolated IAC metastasis was made. An endoscopic retro-sigmoidal biopsy of the lesion confirmed this diagnosis.

Conclusion: Metastasis to the IAC is rare, but its diagnosis should be evoked in patients with rapidly evolving acoustic- facial bundle symptoms and oncological history.