Dear Editor: Disorders of perceptions can be seen in schizophrenia, mania, delirium, metabolic and endocrinal disorders, epilepsy, brain tumors and drug intoxication, or by direct effects of some drugs (for example, hallucinogens). They can also be seen in the electrical stimulus of structures such as the amygdale and temporal cortex and in other pathologies of the brain (1). Perceptual disorders can also be observed, except for brain pathology or psychopathology. In these cases, it is largely suggested that the reason for perceptual disorders is sensory deprivation. Even though the mechanism is not well known, it is believed to be similar to phantom extremity phenomenon (2).
In the literature, there are articles about visual hallucinations observed in patients having visual defects without suffering from any psychiatric disorder (2-6). This was first claimed by Charles Bonnet, a Swiss scientist. Bonnet's grandfather experienced live visual hallucinations at age 89 years, 11 years after having cataract surgery (3). Interestingly, Bonnet himself suffered from visual defects and afterward had similar symptoms. Morisier first named this Charles Bonnet Syndrome (CBS) in 1938 (4). Once the syndrome was named, many similar cases were reported, and diagnostic criteria were developed for CBS (5,6). In this article, we report on the case of a patient with auditory hallucinations in the left ear only. The patient has suffered from hearing loss in the left ear for 5 years, but has not used a hearing and for the last 2 years.
A woman, aged 63 years, complained that she was hearing voices for the past 1 ½ to 2 years and that the voices had increased in the last month, especially at night. At first, she was afraid of the voices and thought she was mad; then she realized they were not real. She had hearing loss in her left ear following a car accident 5 years ago, and it was recommended that she use a hearing aid. Since the aid disturbed her ear, she used it irregularly for 3 years and not at all thereafter. Five to 6 months later, she started to hear voices. Everything was normal in the patient's psychiatric examination except for auditory hallucinations and anxious mood. There was no substance use or psychiatric illness in her history. Complete blood count, biochemical tests, thyroid function test, EEG, cranial computed tomography scan, and neurological examinations of the patient were normal. Her score on the Mini-Mental State Exam was 27. The Minnesota Multiphasic Personality Inventory and Beier Sentence Completion tests were evaluated as normal. Treatment was started with olanzapine 10 mg daily and diazepam 10 mg daily. Later, diazepam was stopped and continued by olanzapine 5 mg daily only. On the tenth day of treatment, the auditory hallucinations disappeared. The patient was observed for 10 months at regular intervals; she took olanzapine 5 mg daily and used a hearing aid for 7 months. During this time, no psychopathology had been detected.
How could sensory deprivation cause disorders of perception? Even though the mechanism is not well known, it is believed to work similarly to phantom extremity phenomenon. In phantom extremity phenomenon, the sensory deprivation could be due to amputation of a body part, damage of the sensory nerve, brachial plexus, or blockage of the spinal cord by anesthetic agent (2). In this case report, the sensory deprivation now caused by damage to the auditory ways after an accident. In both cases, the stimuli going to the cortex were blocked. However, how the perceptual disorders occur is still not known. Perhaps the hallucinations are due to receptor hypersensitivity. …