Suppression of unformed visual hallucinations in homonymous hemianopia from occipital stroke using TMS.

Visual hallucinations represent the dissociation between visual perception and sensory input. We present the case of a 31-year old patient who perceived continuous unformed hallucinations in the hemianopic field immediately following right occipital cortex stroke, which have remained unchanged over 2 years. We performed 1 Hz repetitive transcranial magnetic stimulation (TMS) to the lesioned area for 30 minutes per day over 5 days in an attempt to suppress the perpetual hallucinations. fMRI was performed prior to and after TMS treatment to assess plasticity changes. Pre-TMS, the patient showed greater immediate activation at the boundary of the lesion compared to healthy controls; in the cuneus, lingual gyrus and surrounding areas. The associated "hyperactivity" corresponded to a reported perceptual increase in visual hallucinations. In addition, the patient displayed greater right frontal lobe activity compared to controls prior to TMS, indicative of a greater level of distress (Bartolic et al., 1999). During daily TMS sessions, the perception of hallucinations was greatly reduced. Post-TMS fMRI showed suppression of activity in the previously associated regions of "hyperactivity" to a level similar to that of controls. This is consistent with our previous work showing a decrease in occipital activation with TMS results in a decrease of frontal activity, thereby indicating connections between ventral regions and the frontal lobe (Rafique et al., 2014). Notably, the patient displayed greater activity post-TMS in the inferotemporal and parietal lobes when viewing images of objects and scenes respectively, demonstrating a redistribution of activity most likely regarding object and attention processing. This case provides evidence of an infarct resulting in excitatory discharges at the border of the lesioned area, which stimulate neighbouring areas, and thus results in abnormal visual perception. We causally demonstrate that repetitive TMS provides a valuable method of modulating hallucinations from occipital injury or infarct. Meeting abstract presented at VSS 2015.