EEG CORRELATIONS OF GRAY AND WHITE MATTER DISEASES IN DIFFUSE ENCEPHALOPATHIES

Objectives: To determine electroencephalographic correlates of gray and white matter lesions. Methods: Retrospective chart review of patients with diseases affecting cortical gray matter, cortical (CGM) and/or subcortical gray matter (CSGM), cortical and subcortical gray and white matter (CGWM), and white matter only (WM) (Brain 1968; 91:779–802), all with radiological and electroencephalographic (EEG) evidence for the diagnosis of diffuse encephalopathy, at the Hospital for Sick Children, Toronto, Canada between 1997 and 2003.

Results: We found 47 patients that were categorized into the following groups: CGM (n=13, 28%), CSGM (n=8, 17%), CGWM (n=13, 28%), WM (n=13, 28%). The EEG background activity is abnormal in all groups. Epileptiform discharges were highly predictable in cortical gray matter abnormalities more than subcortical gray matter and rarely in gray/white matter or white matter involvement alone. Polymorphic delta activity was associated with both gray/white and white matter diseases, in more than 50% of cases. The similarities with Gloor's study were: background activity was abnormal in all groups. The polymorphic delta activity was found in both WM and CGWM diseases. And the paroxysmal bilaterally synchronous epileptiform activity in WM group, was seen in one case only. The bilateral paroxysmal synchronous discharges were not a prominent feature in our CGWM gray and white matter disease group.

Conclusion: EEG is a useful tool in the differential diagnosis of diffuse encephalopathies, although it does not point to one specific diagnosis, it directs the search towards a particular group of diseases.