Letters to the Editor
Mirtazapine for Charles Bonnet Syndrome
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.
Case Report
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 atrophic 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-HT3 receptor antagonists (8) and have been shown to treat CBS. Mirtazapine is a presynaptic alpha 2 antagonist that acts by increasing noradrenergic and serotonergic neurotransmission (8). The enhancement of serotonergic neurotransmission is specifically mediated via 5-HT1 receptors, as mirtazapine is a postsynaptic serotonergic 5-HT2 and 5-HT3 antagonist. Second, mirtazapine has very weak muscarinic anticholinergic and antihistaminic properties and is routinely used by geriatric psychiatrists to treat elderly patients. Third, atypical antipsychotics are associated with several risks, including adverse metabolic effects. Although this patient was receiving dialysis, he was not taking erythropeoitin, which can itself cause visual hallucinations (10).
We believe that, because of its unique pharmacologic properties, mirtazapine is a safe, effective, and well-tolerated treatment option for CBS. Last, reassurance and physician awareness are also vital to successful management of this condition.
References
1. Manford M, Andermann F. Complex visual hallucinations. Clinical and neurobiological insights. Brain 1998;121:1819–40.
2. Saiz Gonzales D, Diaz Marsa M. The Charles Bonnet syndrome: a case report and a brief review. Actas Esp Psiquiatr 2003;31(1):48–52.
3. Maeda K, Shirayama Y, Nukina S, Yoshioka S, Kawahara R. Charles Bonnet syndrome with visual hallucinations of childhood experience: successful treatment of 1 patient with risperidone. J Clin Psychiatry 2003;64:1131–2.
4. Bathia MS, Khastgir U, Malik SC. Charles Bonnet syndrome. Br J Psychiatry 1992;161:409–10.
5. Batra A, Bartels M, Wormstall H. Therapeutic options in Charles Bonnet syndrome. Acta Psychiatr Scand 1997;96:129–33.
6. Hori H, Terao T, Shiraishi Y, Nakamura J. Treatment of Charles Bonnet syndrome with valproate. Int Clin Psychopharmacol 2000;15:117–9.
7. Ranen NG, Pasternak RE, Rovner BW. Cisapride in the treatment of visual hallucinations caused by vision loss: the Charles Bonnet syndrome. Am J Geriatr Psychiatry 1999;7:264–6.
8. Zoldan J, Friedberg G, Livneh M, Melamed E. Psychosis in advanced Parkinsons’ disease: treatment with ondansetron, a 5HT3 receptor antagonist. Neurology 1995;45:1305–8.
9. Folstein MF, Folstein SE, McHugh PR. Mini-Mental State: a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975;12:189–98.
10. Fawcett J, Barkin RL. Review of the results from clinical studies on the efficacy, safety and tolerability of mirtazapine for the treatment of patients with major depression. J Affect Disord 1998;51:267–85.
11. Steinberg H, Saravay SM, Wadhwa N, Pollack S, Maesaka J. Erythropoietin and visual hallucinations in patients on dialysis. Psychosomatics 1996;37:556–63.
Zakaria Siddiqui, MD
Sriram Ramaswmay, MD
Frederick Petty, MD
Omaha, Nebraska
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