[Unilateral auditory hallucinations due to left temporal lobe ischemia: a case report]

Unilateral auditory hallucinations are a rare lateralization phenomenon experienced in one ear or from one direction. We recently encountered a 63-year-old right-handed man who developed transient unilateral auditory hallucinations associated with pure word deafness. The patient had a past history of myocardial infarction, lung cancer and aortic aneurysm, but no previous psychiatric or convulsive disorders. About six months before admission, he developed right hemiparesis and motor aphasia caused by a hemorrhagic left parietal infarct. These symptoms gradually improved over three weeks. Two days before admission, he suddenly lost the ability to understand spoken words. He concurrently experienced auditory hallucinations arising from the right anterior direction. On admission, he was very embarrassed to simple verbal commands. He was unable to comprehend spoken words and repeat speech, although he could fairly follow written commands. Confrontation naming, reading aloud, comprehension, spontaneous writing remained relatively unaffected, although he occasionally made paraphasic errors. He could distinguish environmental sounds such as a telephone ringing or running water. After gradual improvement of his auditory incomprehension, he began to describe auditory hallucinations of verbal, musical and elementary types. He was fully aware of the hallucinatory nature of his experience, and took some notes. Two days before admission, from the right anterior side of his head he heard a familiar radio announcer reporting news about the earthquake in Osaka Prefecture and the recommended places of refuge. After similar experiences over several days, he repetitively heard a familiar Japanese traditional song from the right side, which was followed by elementary auditory hallucinations such as a car engine and a siren. These symptoms spontaneously disappeared after nine days. Besides his auditory hallucinations, visual hallucinations and illusional emotion were temporarily present. The Wechsler adult intelligence scale revealed a verbal IQ of 91 and a performance IQ of 100. Pure tone audiometry revealed bilateral, mild peripheral sensorineural hearing loss. Brainstem auditory evoked potentials were unrevealing. The EEG showed slow activities in the left temporoparietal region. Magnetic resonance imaging of the brain failed to reveal any relevant abnormalities except for an old hemorrhagic parietal infarct. The SPECT with Tc99m-HMPAO, however, showed reduced blood flow in the left temporal lobe including the first temporal convolution as well as in the left parietal lobe. Based on the SPECT findings, unilateral auditory hallucinations in our patient are considered to have resulted from the left temporal lobe ischemia. Our case indicates that unilateral auditory hallucinations may have a clinicoanatomical correlation with contralateral temporal lobe lesions.