EEG and clinical changes in patients with chronic seizures associated with slowly growing brain tumors.

The goal of this study was to define the electroencephalographic (EEG) and clinical features in 25 patients with chronic seizures (szs) associated with slowly growing (three to 36 years) brain tumors (BTs). A matched control group was also studied. When all EEGs were considered together without regard to their changes, no significant differences were found between the two groups, especially with respect to the high incidence (60%) of EEG abnormalities both ipsilateral and contralateral to the tumor. Exact localization of the BT by EEG (within one electrode) was found in 88% of patients. When changes in time were considered, the BT group more often showed increasing slow waves, increasing sharp-wave discharges, depression of normal rhythms, a change in type of sz, increase in frequency of szs, and a change in neurological signs and symptoms, especially motor. For single, double, or triple criteria, a change in clinical signs was the most discriminative, with a deteriorating EEG as the next best indication of a tumor. Patients with the latter signs should then be selected for a computed tomographic or magnetic resonance imaging scan, even if the scan was normal initially, rather than following the expensive policy that all patients at all ages with chronic szs should undergo these later tests.