York University research has shown that the use of long-term, repetitive transcranial magnetic stimulation (TMS) has potential as a therapeutic tool in treating certain visual disorders.
Researchers in Professor Jennifer Steeves’ lab (Faculty of Health) studied a patient who was experiencing persistent and disruptive “phosphenes” – or bright flashes of light – in one area of her visual field after suffering a stroke. The stroke left a lesion in the occipital cortex, which is the visual part of the brain.
The study, titled “rTMS Reduces Cortical Imbalance associated with Visual Hallucinations after Occipital Stroke,” is published in the journal Neurology and shows that repetitive TMS to the occipital cortex greatly reduced the presence of phosphenes in the patient.
“We applied long-term, non-invasive brain stimulation with repetitive transcranial magnetic stimulation (TMS) to this region of the brain and were able to significantly reduce the experience of the bright lights,” said Steeves, who notes the study’s lead author is Sara A. Rafique, who conducted the research as part of her doctoral studies at York.
The patient had 30 minutes of TMS applied at a low frequency for five days, and a functional magnetic resonance imaging (fMRI) was performed before and after TMS treatment.
The fMRI comparisons showed that following the long-term TMS, an imbalance of activity across the two hemispheres was restored to be more similar to that of healthy controls, with normalized activity around lesions and associated regions of the brain.
The patient also reported a daily gradual reduction in phosphene presence during the treatment.
“This research is the first known study to perform long-term repetitive TMS to visual parts of the brain and shows that TMS can potentially be used as a therapeutic tool for treatment of such visual disorders,” said Steeves.
TMS is currently used as a therapeutic treatment in Canada for conditions such as depression and schizophrenia, however, treatment in those cases is performed over several months.
Steeves further noted that this particular study quantifies the effects of TMS quite well through the ability to measure the presence or absence of visual phosphenes.
“We were hoping to see these results,” said Steeves, “but it was a lot more dramatic than what we expected.”
Rafique will continue to research the effects of TMS therapy during the remaining studies of her PhD dissertation, this time with a focus on patients with Charles Bonnet Syndrome, where individuals experience disruptive visual hallucinations subsequent to early visual system degeneration.
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