Magnetoencephalography assessment of evoked magnetic fields and cognitive function in subcortical ischemic vascular dementia patients.

OBJECTIVE: To investigate the relationship between cognitive impairment and somatosensory evoked magnetic field and auditory evoked magnetic field changes in elderly male patients with subcortical ischemic vascular dementia (SIVD). METHODS: Magnetoencephalography (MEG) was used to record evoked magnetic field changes from 4 SIVD patients (76-88 years), 3 patients with vascular cognitive impairment with no dementia (VCI-ND; 74-87 years), and 6 healthy volunteers (72-85 years). Latency peaks, equivalent current dipole (ECD) strength, and bilateral ECD position were recorded. The MEG data were superimposed on magnetic resonance imaging to produce magnetic source imaging. RESULTS: Compared to controls, SIVD patients showed increased M20 latency and ECD strength. There were no significant differences in M20 inter-hemispheric positions across diagnostic categories. At M100, SIVD patients showed delayed auditory evoked magnetic field latency compared to controls. However, ECD strength and 3-dimensional inter-hemispheric differences were similar across the groups at the M100 measurement. CONCLUSIONS: Changes in somatosensory and auditory evoked magnetic field changes correlated with cognitive impairment in SIVD patients. Magnetic field latency measures may provide an objective and sensitive index for early dementia detection and monitoring of cognitive function.