Hypertrophic Pachymeningitis of the Internal Auditory Canal: A Rare Case of Unilateral Sudden Sensorineural Hearing Loss

Objectives: To describe and increase awareness of a rare cause of unilateral sudden sensorineural hearing loss. Methods: Case report and literature review. Results: We present a 66-year-old female who suffered left-sided sudden sensorineural hearing loss and dizziness. Diagnostic magnetic resonance imaging (MRI) did not reveal masses or lesions along the eighth cranial nerve or in the inner ear. Upon eventual referral to neurotology clinic, hypertrophic pachymeningitis of her left internal auditory canal and adjacent middle and posterior fossa dura were identified. The ensuing laboratory workup for autoimmune and infectious etiology revealed mild elevation of ACE 93 (9-67) but otherwise normal results. Conclusions: Idiopathic hypertrophic pachymeningitis is a diagnosis of exclusion. Neoplastic, infectious, and autoimmune causes must be ruled out. The prevailing treatment for this condition is high-dose corticosteroids. This entity should be considered when evaluating MRI scans obtained in the setting of sudden sensorineural hearing loss.