Summary:An interesting case is reported of an 11-year-old girl who experienced a sudden, profound right-sided hearing loss at the age of 5 years after hearing a “pop” and the sound of rushing water in her right ear. At that time the patient was thought to have Mondini's deformity, and a perilymphatic fistula of the oval window in the right ear. Six years later she was diagnosed with a juvenile pilocytic astrocytoma of the pons with an exophytic component extending into the cerebellopontine angle. Of particular interest in this case is the presence of evoked otoacoustic emissions in the right ear with a profound neural hearing loss. The presence of transient evoked and distortion product otoacoustic emissions confirmed normal sensory outer hair cell function and an intact peripheral auditory system in a clinically deaf ear, thus indicating hearing loss due to a neural component instead of a sensory component, which was previously assumed.