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.
Tan CSH, Sabel BA. Charles Bonnet Syndrome After Occipital Cortical Resection for Cortical Dysplasia May Be Related to Denervation Supersensitivity. Arch Neurol. 2005;62(9):1479. doi:10.1001/archneur.62.9.1479-a