The clinical/demographic backgrounds of patients with sudden sensorineural hearing loss (SSNHL) vary from healthy young people to elderly people with multiple pre-existing diseases. Herein, we report the case of a 65-year-old male lung adenocarcinoma patient with brain metastasis who presented with SSNHL in the left ear. As expected from the pre-existing disease, brain MRI suggested metastatic disease in the left internal auditory canal including the cochlear nerve fibers, as the cause of the SSNHL. With steroid administration, the pure tone audiometry thresholds on the left side improved within one week, even though the speech discrimination score of the left ear was low. After two months, further improvement of the pure tone audiometry thresholds in the left ear was observed, but the hearing level at high frequencies in the right ear was notably worse as compared with that at the patient’s first visit.
SSNHL carrying a poor prognosis has occasionally been reported to be caused by metastasis in the internal auditory canal in patients with any adenocarcinoma. Interestingly, the hearing thresholds in our SSNHL patient improved markedly with steroid administration, which is rather rare, even though his speech discrimination score was low. The differences in the onset times and severity of sensorineural hearing loss between the left and right ears could possibly be explained by differences in the time of onset and size of the metastatic tumors in the auditory pathway between the two sides, although we could not find any evidence of metastatic disease in the right internal auditory canal in this patient, even on follow-up MRI.
In conclusion, we encountered a case of metastatic lung adenocarcinoma who presented with bilateral SSNHL. MRI was useful for the diagnosis of SSNHL caused by metastasis in the internal auditory canal from the lung adenocarcinoma. The cause of SSNHL is often difficult to determine, but the patient’s background is sometimes helpful for a definitive diagnosis of the cause of SSNHL.
