MEG Frequency Analysis Depicts the Impaired Neurophysiological Condition of Ischemic Brain

MEG revealed statistically significant laterality in affected MCA regions, including 4–8 Hz waves in MCAa, and 0.3–4 Hz and 4–8 Hz waves in MCAp (95% confidence interval: 0.020–0.190, 0.030–0.2 07, and 0.034–0.213), respectively. Results stated that 0.3–4 Hz waves in MCAp were highly correlated with CBF in MCAa and MCAp (r = 0.74, r = 0.68, respectively), whereas 4–8 Hz waves were moderately correlated with CBF in both the MCAa and MCAp (r = 0.60, r = 0.63, respectively). Also that at 4–8 Hz waves in MCAp were statistically significant for misery perfusion identified on 15O-PET (p<0.05).

Quantitatively imaged spontaneous neuromagnetic fields using the automated ROI setting enabled clear depiction of cerebral ischemic areas. Frequency analysis may reveal unique neural activity that is distributed in the impaired vascular metabolic territory, in which the cerebral infarction is in process.

MRI lesion distribution of 37 patients using SPM.

This image shows the lesion distribution on MRI of the 37 patients. The numbers of patients with ischemic lesions are shown by color-coding. Lesions that were hypointense on T1WI are colored blue to green, whereas lesions that were hyperintense on DWI are colored red to yellow. The lesions are seen predominantly in the affected hemisphere, and the distributions show the watershed type of infarction. The images were anatomically standardized by SPM. AH: affected hemisphere, nAH: non-affected hemisphere.

The absolute values from 15O-PET and MEG images of the 37 patients using SPM

These images show the absolute value from 15O-PET and MEG images of 37 patients, showing CBF (a), OEF (b), 0.3- to 4-Hz waves (c), and 4- to 8-Hz waves (d). The averages of the absolute values are encoded with color (values are shown in the color bars). The images were anatomically standardized by SPM. CBF values are decreased and OEF values are increased predominantly in the affected hemisphere. Both 0.3- to 4-Hz and 4- to 8-Hz waves of MEG are distributed predominantly in the affected hemisphere, from the posterior temporal to parietal regions. The absolute value from MEG images also suggested that the 4- to 8-Hz waves were distributed in the parietal area contralateral to cerebral hemisphere affected by the occlusive ICA lesion (Fig 4d, yellow arrows). AH: affected hemisphere, nAH: non-affected hemisphere.