Dipole-tracing of abnormal slow brain potentials after cerebral stroke--EEG, PET, MRI correlations.

A patient with major neurological deficits 5 years after a left cerebral infarction underwent correlative EEG, MRI and PET studies of cerebral blood flow and oxygen metabolism. The EEG showed abnormal slow electroencephalographic activity in the frontopolar region. The intracranial location of the slow electrical activity was estimated, as an equivalent current dipole, by using a newly developed dipole tracing (DT) method. The DT analysis showed that the dipole equivalent of the slow wave is approximately located at the frontal part of the left cingulate gyrus, away from the margins of the infarction and enlarged left lateral ventricle demonstrated by MRI, and in a region with intact oxygen consumption rate. The genesis of the slow wave is discussed.