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We read with interest the article by Choi et al1 describing Charles Bonnet syndrome (CBS), which occurred after broad, right-sided occipital cortical resection for cortical dysplasia. These hallucinations were not associated with electrographic seizures.
Although CBS is more common with decreased visual acuity, it also occurs in patients with visual field defects and normal central acuity.2 - 3 Freiman et al3 described hallucinations occurring within visual field defects that developed after neurosurgery. Moreover, in a series of patients with cortical dysplasia, 3 (14%) of 22 patients developed visual field defects following surgical resection of abnormal brain tissue.4 Therefore, it would be interesting to know if the patient described by Choi et al experienced a decrease in visual acuity or developed a new (or enlargement of an existing) visual field defect following cortical resection. Either of these factors may possibly explain the development of CBS. The occurrence of hallucinations within the left visual field, which is represented in the right occipital cortex which was resected, further suggests that the hallucinations may be occurring within a visual field defect caused by resection of that area.
In visual pathway disorders, deafferentation leads to reorganization of the receptive field and increased sensitivity of the remaining functioning neurons to sensory input (denervation supersensitivity).5 We believe that stimulation of these regions of increased sensitivity by normal visual signals may result in visual hallucinations.6 This would explain why the intensity of the patient’s hallucinations increased when her eyes were open and varied with the blinking, brightness, and movement of the stimuli.1
We agree that CBS may be overlooked or underdiagnosed in patients who had cortical resection. This may be further compounded by the fact that in some patients, the visual hallucinations decrease in frequency or cease after some time, which may be the result of cortical neuroplasticity and reorganization.6 Thus, instead of recurrence of epileptic foci, the occurrence of visual hallucinations after neurosurgery may be indicative of attempts at visual recovery and may therefore be a good thing.
Correspondence: Dr Tan, The Eye Institute at Tan Tock Seng Hospital, National Healthcare Group, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore (colintan_eye@yahoo.com.sg).
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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