How Do Doctors Visualize a TIA?
Approximately 200,000 to 500,000 transient ischemic attacks (TIA) or mini strokes occur annually in the United States. Symptoms are not specific and continue be challenging for physicians to diagnose, as a result the estimated group affected varies broadly. The imaging technique of choice for physicians making a diagnosis is magnetic resonance imaging (MRI) and when this is not available, they use computed tomography (CT) scan. Unfortunately, neither scanning machine is guaranteed to detect evidence of a block in the blood flow within the brain. TIA carries a high short-term risk of stroke and 15% of TIA victims experience a stroke within the preceding 3 months.This presents a unique opportunity to prevent a future stroke which causes damage to brain tissue and permanent disability in 2/3 of those affected.
The recently FDA-approved transcranial magnetic stimulation is a non-invasive technology that generates targeted magnetic fields. It works by sending a pulse of electric current into a specific region of the brain. Scientist and clinicians can measure the amount of
current required to activate that region of the brain. It has been used most commonly to treat pain and mood disorders. In the quest to improved the diagnosis of transient ischemic attacks (TIA), it occurred to one neuroscientist that transcranial magnetic stimulation just might be a valuable diagnostic tool.
Dr. Lara Boyd of the Brain Research Center at Vancouver Costal Health Research Institute and the University of British Columbia used this technique in a group of patients who had suffered a TIA within the previous month and compared the results to those in age-matched healthy volunteers. This group of patients sought treatment for clinical signs that rapidly resolved. Two weeks after the TIA, patients were of the belief they suffered no permanent damage.
“[W]e wondered if we could maybe detect something with neurophysiology, with electro-physiology, that has previously gone unnoticed,” Lara Boyd.
Her research was the first to demonstrate suppression of electrical activity in the hemisphere of the brain affected by a TIA. This was in the absence of clinical signs or focal lesions (indicating lack of blood flow) picked up by an MRI. These changes were also associated with ABCD2 scores, the clinical scoring system designed to assess the risk of stroke within 2 day of a TIA. Boyd currently oversees a longitudinal study of 60 case. She hopes in transcranial magnetic imaging “[proves] a useful tool in predicting who’s at most risk for going on and having a full-blown stroke?”
It remain imperative that those suffering a TIA seek medical attention as quickly as possible as it can be the warning of a future stroke.
Johnston SC, Fayad PB, Gorelick PB, Hanley DF, Shwayder P, van Husen D, et al. Prevalence and knowledge of transient ischemic attack among US adults. Neurology. May 13 2003;60(9):1429-34
Kleindorfer D, Panagos P, Pancioli A, et al. Incidence and short-term prognosis of transient ischemic attack in a population-based study. Stroke. Apr 2005;36(4):720-3.