UNAIR scientist studies brain symmetry as tool for stroke classification

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Illustration by Feri Fenoria

UNAIR NEWS – According to the World Health Organization (WHO), the definition of stroke is a collection of symptoms and clinical signs due to sudden disruption of local and global brain function, developing rapidly with symptoms that last for 24 hours or more that cause death, without other obvious cause than vascular.

According to Osmalina Nur Rahma, ST, M.Si., a lecturer from FST UNAIR, Stroke is one of the health problems that needs special attention. Impaired nerve function in stroke causes symptoms including; paralysis of the face or limbs, difficulty in speech, changing consciousness, impaired vision, and other symptoms.

“The prevalence of stroke in the group diagnosed by health workers and those who have a history of symptoms increases with age, the highest at age ≥75 years (43.1%) and (67.0 %),” she said.

According to Osmalina, EEG and Continuous EEG (CEEG) have been developed to detect acute cerebral ischemic during carotid artery surgery. Kenneth G. Jordan, Neurologist said that electroencephalography can help confirm or detect acute ischemic stroke as indicated by slowing of waves in the electroencephalogram (EEG) signal spectra, appearing delta signal activity and decreasing cerebral volume.

“EEG changes when there is a decrease in blood flow in the brain, such as a decrease or loss of fast beta and alpha frequencies, sometimes including spindle sleep and slowing waves (theta and delta). “Ischemia can be seen in the reversal phase of EEG even though anatomical imaging such as MRI remains normal,” hse explained.

When blood flow in the brain decreases, Osmalina said, frequency slowdown occurs in the part of the brain that experiences neuronal death (infarction). The ability of the EEG to detect ischemia at an early stage with a procedure carried out continuously is the basis for monitoring EEG in patients at high risk for ischemia.

Electroencephalographs performed continuously is the most sensitive neurodiagnostic tools for detecting acute cerebral ischemia, although it has not been able to replace the presence of Computed Tomography Scan (CT scan ) or Magnetic Resonance Imaging (MRI), but it has its advantages in terms of lower operational cost.

Brain Symmetry Index (BSI), according to Osmalina, is one of the parameters used in EEG analysis most often used and has been proven useful in assessing the degree of symmetricity of hemispheres. BSI can show a positive correlation between BSI and clinical assessment scores in acute ischemic stroke patients.

The National Institutes of Health Stroke Scale (NIHSS) and Xiyan Xin research, showed a positive correlation between BSI and clinical assessment scores in patients with acute hemorrhagic stroke, NIHSS, Glasgow Coma Scale (GCS) and Acute Physiology and Chronic Health Evaluation II (APACHE II) . Michael JAM van Putten and Tavy used the BSI method to monitor hemispheres in stroke patients using quantitative electroencephalograph and the results showed a correlation between BSI and NIHSS.

Based on the characteristics shown by ischemic stroke in EEG signals, it can cause slow waves and wave asymmetry in the hemisphere, this study used the value of Delta / Alpha Ratio (DAR), ( Delta + Theta ) / ( Alpha + Beta ) Ratio (DTABR) and Brain Symmetry Index (BSI) as an ELM input feature value obtained by Wavelet transformation (Daubechies 4) and Welch method to identify acute ischemic stroke.

Author: Fariz Ilham Rosyidi

Editor: Khefti Al Mawalia



Ji Ye ChanSastra K. WijayaPrawito, and Osmalina N. Rahma. 2019.ELM (extreme learning machine) method for detecting acute ischemic stroke using conventional and specific asymmetry BSI (brain symmetry index) features based on EEG signals, AIP Conference Proceedings 2092, 020023

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