Go Inokuchi, Daisuke Yamashita, Hirokazu Komatsu, Takeshi Fujita, Shingo Hasegawa and Ken-ichi Nibu
Unilateral idiopathic sudden sensorineural hearing loss is often encountered, but bilateral progressive hearing
loss is rare. Here we present a case of a 46-year-old man who was diagnosed as the leptomeningeal carcinomatosis
(LC) from lung adenocarcinoma. An enhanced magnetic resonance imaging (MRI) showed a strong enhancement
effect of bilateral vestibulocochlear nerves. High-resolution T2-weighted imaging additionally revealed the
accompanying metastasis in bilateral internal auditory canals (IACs). Hearing loss due to LC started from in higher
frequencies and rapidly progressed from unilateral to bilateral. Otoacoustic emission showed the positive response
inconsistent with the poor hearing results in pure tone audiometry, but this response disappeared soon with the
rapid deterioration of hearing. IAC metastasis with LC caused an irreversible cochlear damage and the hearing of
this patient could not recover even after the IAC mass disappeared on MRI. Audiometric evaluation, including PTA
and OAE, would provide diagnostic clues and we should proceed with the investigation of brain MRI and CSF
cytology urgently to reach the earlier diagnosis of LC.