title: Electroencephalographic coherence analysis in multiple sclerosis: correlation with clinical, neuropsychological, and MRI findings.
abstract: OBJECTIVE
  To explore functional corticocortical connections in multiple sclerosis by means of coherence of the EEG, and to evaluate their correlations with the degree of cognitive impairment and with brain lesion load assessed by MRI.
  
  
  METHODS
  EEG coherence was studied from 28 patients with clinically definite multiple sclerosis. Ten minutes of resting EEG were recorded with 20 scalp electrodes, with binaural reference. FFT power and coherence were calculated in artifact free epochs of 1 second and compared with values from 22 control subjects of comparable age and sex distribution. Patients also underwent MRI (n=27) and neuropsychological examination (n=21).
  
  
  RESULTS
  Compared with controls, patients with multiple sclerosis showed increased theta power in the frontotemporal-central regions (p<0.005). theta Band coherence was decreased between homologous areas (p<0.02). alpha Band coherence was decreased both in the local and long distance connections (p<0.0005). These findings were most striking both in patients with high MRI subcortical lesion load and in patients with cognitive involvement. A significant correlation was found between interhemispheric theta (p=0.02) and alpha (p=0. 017) and anteroposterior alpha (p=0.013) coherence and subcortical MRI lesion load, but not with exclusively periventricular lesion load.
  
  
  CONCLUSIONS
  These findings support the hypothesis that cognitive impairment in multiple sclerosis is mostly dependent on involvement of corticocortical connections related to demyelination and/or axonal loss within the white matter immediately underlying the cortex.
authors.affiliation: Department of Clinical Neurophysiology, Scientific Institute H San Raffaele, Via Olgettina 60, 20132 Milan, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Leocani
authors.forename: T
authors.initials: T
authors.lastname: Locatelli
authors.forename: V
authors.initials: V
authors.lastname: Martinelli
authors.forename: M
authors.initials: M
authors.lastname: Rovaris
authors.forename: M
authors.initials: M
authors.lastname: Falautano
authors.forename: M
authors.initials: M
authors.lastname: Filippi
authors.forename: G
authors.initials: G
authors.lastname: Magnani
authors.forename: G
authors.initials: G
authors.lastname: Comi
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology / Q000503:physiopathology*; D001931:Brain Mapping; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D009483:Neuropsychological Tests; D012720:Severity of Illness Index