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To the Editor: Charles Bonnet syndrome refers to formal, complex, persistent, stereotypical visual hallucinations that are not accompanied by any other psychotic symptoms in cognitively unimpaired individuals (1). Although multiple sclerosis can produce diverse neuropsychiatric manifestations, we know of no reports of Charles Bonnet syndrome in patients with this illness.
Ms. A, a 56-year-old woman with no cognitive impairment, claimed to see vivid and complicated images after losing her vision for 4 months as a result of optic neuritis. These images changed in shape, color, and size and included Chinese and English characters, vegetables, and small animals that could penetrate into her abdomen. She recognized them as unreal, but they existed at all times, whether she had her eyes open or closed.
She had suffered from multiple sclerosis for about 20 years and had no comorbid psychiatric disorders. Besides her temporary loss of vision, she experienced effects on her cervical and thoracic spinal cord. She became bedridden and completely dependent on the care of others. In an assessment of cognitive functioning, she scored 25 out of 30 points on the Mini-Mental State Examination, excluding the items that require vision (5 points). Magnetic resonance imaging of her brain revealed high signal intensity in both periventricular and white matter regions of the parietal lobes. Carbamazepine treatment, 200 mg t.i.d., was initiated, and Ms. A’s visual hallucinations were significantly reduced. However, after she stopped taking carbamazepine, the visual hallucinations returned, but they disappeared after she resumed taking carbamazepine.
A literature search revealed that a greater risk of Charles Bonnet syndrome has been found with advanced age, cerebral impairment, and ocular pathology (2). It is therefore not unusual that Charles Bonnet syndrome has been found in younger people with certain diseases involving the eyes and brain. Therapy targeting the underlying ocular or cerebral diseases might alleviate the hallucinations. In addition, anticonvulsants such as carbamazepine and valproate are effective for treatment because their antiseizure properties can reduce "irritable cortex," a condition that has been hypothesized to cause a "phantom visual phenomenon" (3). Despite prevalent ocular and cerebral involvement in multiple sclerosis, to our knowledge, there have been no reports of hallucinations that are consistent with the Charles Bonnet syndrome. Plausible explanations are 1) that visual hallucinations seldom occur without cognitive impairment and other psychotic symptoms in multiple sclerosis, 2) that there are few voluntary expressions of visual hallucinations, and 3) that physicians are unfamiliar with this syndrome. The last two explanations might account for an underestimation of Charles Bonnet syndrome in multiple sclerosis. It is suggested that psychiatrists, neurologists, and ophthalmologists pay more attention to the nature of hallucinations in order to diagnose Charles Bonnet syndrome, which can be treated effectively with anticonvulsants.
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