Detection of Neural Activity for Cerebrovascular Disease using MRI and EEG

Abstract

(CVD) such as stroke is the leading cause of long-term disability and third most common reason of death in the world. Due to the neuronal deficiency occurred by impaired blood flow to the brain, half of the stroke patients survive a severe cognitive impairment such as impaired speech, numbness in limbs, immobilization of limbs, visual impairment and many other observable symptoms. In the recent days, due to the gradual increase of hypertensive and diabetic patient, the risk of developing stroke is growing tremendously. The evaluation of actual neuronal status in stroke patient is thus very important to determine the indication of neurosurgical treatment. To diagnosis the type, source and location of stroke in the brain, generally, cerebral blood flow (CBF) test, neuroimaging, and electrical activity test are being used. Among all of these tests, electroencephalogram (EEG) is a useful tool for acute stroke detection and monitoring affected tissue owing to its relatively cheap and completely hazardless for quantitative and statistical analysis. Although a large number of studies have been performed on the ischemic stroke using EEG, no investigation has been carried out on the interplay between the infarcted cerebral hemisphere with other healthy part. Moreover, earlier studies are also limited only age-related changes in EEG activity or memory performance compared younger people between the ages of about 20 to 30 years with older participants between the ages of about 60 to 80 years. There is also no study at all for the child below the age of 20 years to show the change and compare the neuronal deterioration of the infarcted part of brain. This work focused on the correlation between the extent of infarction and the clinical effect to monitor the degree of hypo-activity of the affected part through the EEG analysis. An indication for the assessment of neuronal activity and the degree of severity of stroke patient has been proposed. A parallel study has also been carried out on healthy volunteers of under fifteen years to find the comparison of neural activity between different age group. From the analysis it is found that delta activities of EEG are highly unique of brain pathophysiology, and preservation of alpha and beta frequencies following stroke is evidently indicative of neuronal survival and a good prognosis. In order to assess brain vi pathophysiology in supratentorial brain lesion patients the delta/alpha ratio (DAR) and deltaplus- theta to alpha-plus-beta ratio (DTABR) have also been used. It is observed that the DAR and DTABR values of the left cerebral hemisphere of the patient are much higher than the right cerebral hemisphere. It is also higher in both cerebral hemispheres than the control. A threshold value of ~3.7 for DAR and ͂ 3.5 for DTABR has been obtained. It is observed that DAR and DTABR of left hemisphere of patient are greater than 3.7and 3.5 respectively for all the measurements indicating severe ischemic stroke in the fronto-temporal region of left hemisphere. The findings have been further confirmed by a neuroimaging technique such as magnetic resonance imaging (MRI).This study also show that DAR and DTABR of the healthier child is~1.It is also found that delta and DAR indices of the old age are two times more than the child indicating the diminishing of neuronal activity of old age is half of the child. These results could be important for stroke diagnosis, prognosis, re-habitation strategies, and proper neurosurgical treatment.