Dear Editor: Charles Bonnet syndrome (CBS) is characterized by complex visual hallucinations in psychologically normal people; it is usually seen in elderly people in the context of ocular pathology causing visual deterioration (1). The main hypothesis is that these hallucinations represent release phenomena attributable to deafferentation of the visual association areas of the cerebral cortex that leads to a form of phantom vision. Most intriguingly, unlike visual hallucinations associated with psychiatric disorders, patients with CBS have insight and report the hallucinations as nonthreatening. Several modalities have been tried to treat this condition, including valpromide (2), reperidone (3), carbamazepine (4), melperone (5), valproate (6), cisapride (7), and ondansetron (8).
We report a case of CBS successfully treated with mirtazapine.
An African-American man, aged 59 years, was admitted to a tertiary care community hospital for pneumonia. The patient had a history of type 2 diabetes, chronic renal failure requiring dialysis, and bilateral macular degeneration. His visual acuity was almost "hand motion." On the fifth day of his hospitalization, psychiatry was consulted because he was experiencing visual hallucinations. The patient had no psychiatric history and had never taken any psychotropics. To everyone's astonishment, he had been visually hallucinating for at least 3 years and had never mentioned this to any one except his family members. His hallucinations consisted of seeing groups of people and farm animals, more frequently in the evening. They usually occurred during periods of wakefulness and with his eyes open. He reported them as nonthreatening and felt comfortable seeing very vivid pictures. He acknowledged some sleep problems and inconsistent appetite but gave no evidence of having depressive disorder or any other psychiatric condition. His cognition was intact, as he scored 27/30 on the Mini-Mental State Examination (3), only losing points on the visual items. A complete blood count and complete metabolic profile revealed results consistent with chronic renal failure. A magnetic resonance imaging study showed age-related atrophie changes. He was given the diagnosis of CBS, and we started him on mirtazapine 7.5 mg at bedtime. Supportive therapy and therapy to increase insight into his condition were also considered. His antibiotics were gradually weaned as his pneumonia slowly resolved. The patient's sleep pattern improved, and his visual hallucinations remitted within the next 3 days. He had no recurrence of visual hallucinations after a month of follow-up with his primary care physician.
We chose mirtazapine for several reasons. First, cisapride and ondansetron are also 5-HT^sub 3^ receptor antagonists (8) and have been shown to treat CBS. Mirtazapine is a presynaptic alpha 2 antagonist that acts by increasing noradrencrgic and serotonergic neurotransmission (8). …