Hypermetabolism in the left thalamus and right inferior temporal area on positron emission tomography-statistical parametric mapping (PET-SPM) in a patient with Charles Bonnet syndrome resolving after treatment with valproic acid.

Charles Bonnet syndrome (CBS) is characterized by the occurrence of complex visual hallucinations in visually impaired patients who understand that what they see is unreal. The pathophysiologic mechanism of CBS is poorly understood. However, hypermetabolism of the thalamocortical pathway as a result of deafferentation was recently proposed as a possible mechanism. A 69-year-old patient with CBS presented with a 5-year history of visual hallucinations after bilateral visual impairment, which had progressed to troublesome images of many unreal people and animals. Positron emission tomography-statistical parametric mapping (PET-SPM) imaging studies initially revealed hypermetabolism in the right inferior temporal area and left thalamus, which disappeared after treatment with valproic acid. This case, using PET-SPM analysis, supports the thalamic hypermetabolism theory of CBS.