NCMP-10. Unilateral sudden sensorineural hearing loss with vertigo as an initial presenting symptom of leptomeningeal metastases

BACKGROUND Leptomeningeal metastases (LM) involve diffuse or multifocal infiltration of the central nervous system. While the third, fifth, and seventh cranial nerves are most commonly affected, isolated eighth nerve involvement is rare and typically bilateral. CASE: A healthy 43-year-old woman presented to a local otolaryngology clinic with sudden-onset left-sided hearing impairment and vertigo for several days. Pure-tone audiometry documented profound sensorineural hearing loss (SNHL) across all frequencies, and vestibular function tests were consistent with acute peripheral vestibulopathy on the left. Initial non-contrast brain MRI were interpreted as non-specific. Empirical intravenous corticosteroids and intratympanic steroid injections were administered. However, she was referred to our hospital two months later due to persistent hearing loss and newly developed left-sided facial numbness and truncal imbalance. Retrospective review of the initial T2-weighted imaging revealed a hypointense lesion involving the left internal auditory canal. Follow-up gadolinium-enhanced brain MRI demonstrated irregular enhancement lesions involving the fourth ventricle, bilateral internal auditory canals, and the left trigeminal nerve. Cerebrospinal fluid cytology confirmed malignant cells consistent with metastatic adenocarcinoma. She was finally diagnosed with metastatic carcinoma of unknown primary site despite comprehensive diagnostic workup. DISCUSSION Sudden SNHL (with vertigo) can result from a variety of causes, including infectious, autoimmune, and microvascular etiologies. Otherwise, it may rarely be caused by a cerebrovascular accident due to occlusion of the anterior inferior cerebellar artery. Additionally, approximately 3% of cases are attributed to neoplasms such as vestibular schwannoma, meningioma, or acoustic neuroma. A literature review indicated that LM-related SNHL commonly occurs bilaterally in patients with known primary malignancies, particularly lung or breast cancer, and in association with involvement of other cranial nerves. This case highlights that LM, although rare, can present as unilateral sudden SNHL with vertigo, even in the absence of underlying malignancy. Meticulous initial evaluation and close neurologic monitoring are warranted.