Auditory neuropathy as the first sign of leptomeningeal metastasis

Introduction: Auditory neuropathy is a hearing disorder characterized by impaired temporal coding of acoustic signals in the auditory nerve fibers, resulting in abnormal auditory perceptions relying on temporal cues. We describe the case of a woman with a history of cancer who developed auditory neuropathy as the first manifestation of leptomeningeal metastasis. Case summary: A woman in her sixties complained of severe difficulties in understanding speech despite preserved sensitivity to sounds, which had begun two months before audiological assessment. Her past medical history was remarkable for an occult cancer, possibly breast cancer, diagnosed seven years earlier. Pure-tone audiometry showed mild bilateral sensorineural hearing loss associated with markedly reduced speech intelligibility. Otoacoustic emissions were normal, indicating preserved outer hair cell function, whereas auditory brainstem responses (ABRs) were absent despite preserved hearing thresholds. Contrast-enhanced brain magnetic resonance imaging (MRI) only demonstrated bilateral enhancement of the eighth cranial nerve. However, a brain MRI performed one month later revealed diffuse leptomeningeal enhancement, while cerebrospinal fluid (CSF) cytology was positive for atypical malignant cells, both findings consistent with leptomeningeal metastasis. Discussion: This case illustrates that the onset of auditory neuropathy in a patient with a clinical history of cancer may represent an early clinical sign of leptomeningeal metastasis, highlighting the importance of prompt neuroimaging and CSF analysis.