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Magnetoencephalography (MEG) for post-stroke cognition

Sein Cho




As part of our research, we are interested in higher level cognitive processes such as attention and multi-tasking. Even after small strokes, these activities can become impaired. This results in the inability for previously high-functioning individuals (school teachers, musicians, CEOs) to re-integrate into their prior home and workplace environments. It results in divorce, loss of jobs, and poor quality of life. The cognitive difficulties seem to occur regardless of the location of the stroke, and the underlying cause is poorly understood. It may be because the brain functions as a network (in other words, you require all of your brain to be functioning normally to be at your best). In order to determine if this is the case and how connections change after stroke, we are partnering with the University of Maryland to determine what is happening in the brain to impair cognition. Eligible patients with small strokes and difficulty with cognition on testing in our clinic travel to our partnering institute where they undergo magnetoencephalography (MEG). Similar to an MRI, the MEG records which areas of the brain are active during various activities. Testing is performed about 1 month after stroke and repeated at 6, 12, and 24 months. Our preliminary data are exciting! A 42-year-old executive presented to clinic with a small stroke, slow processing speed, and poor executive functioning that prohibited him from returning to work and leading meetings. The stroke itself did not explain his symptoms, but MEG showed diffuse abnormal activation within the frontal lobes, an important area for higher level processing (see left figure). These findings indicate that our hypotheses may be correct, but larger studies are needed. If we can determine the brain changes responsible for post-stroke cognitive impairment, we will be able to predict who is most likely to recover, devise better treatment strategies, and promote faster and fuller recovery after stroke. 




Our pilot MEG study is complete! We compared cerebral activation patterns for stroke patients during a word-picture matching task one month post-stroke compared to a group of age-matched controls and found decreased amplitude and temporal dispersion in the areas of the brain that are responsible for visual word processing. These results demonstrate that disruption of network dynamics may be responsible for difficulty with attention and concentration after stroke. These differences persisted 6 months after infarct, though clinical exams continued to improve, and we are currently bringing participants back to explore chronic changes, greater than 12 months post-stroke.



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