Leptomeningeal carcinomatosis is often associated with acoustic nerve and facial nerve involvement, similar to the case in acoustic nerve tumors, hence, distinction between the two is often difficult. We report a patient of leptomeningeal carcinomatosis who was initially treated as a case of acoustic nerve tumor (AT), but was diagnosed after several months during follow-up as a case of leptomeningeal carcinomatosis. An 82-year old man with bone metastases from lung cancer visited us with the complaint of difficulty in hearing on the left side. Soon thereafter, he developed difficulty in moving the left side of the face. Based on the findings of MRI, we assumed the diagnosis of AT and began to treat the patient with steroids. However, the symptoms began to get worse and started to spread to the opposite side. A cerebrospinal fluid examination revealed the presence of atypical cells. Based on this finding, we diagnosed the patient as having leptomeningeal carcinomatosis.
