Walsh & Hoyt: Seizures

About one third of adults who experience new onset of seizures harbor an intracranial tumor. Thus, when seizures develop in a previously healthy person, particularly when that person is over 20 years of age, an intracranial tumor must be assumed to be present until evidence to the contrary is obtained. Focal seizures or focal seizures with secondary generalization are particularly ominous. Generalized seizures in which there is a focal neurologic deficit postictally (Todds paralysis) are also of concern for an underlying structural lesion. Although there are common focal seizure patterns that suggest a lesion in a particular intracranial location, a precise correlation between seizure pattern and intracranial location does not always exist. Nevertheless, when a seizure is associated with forced turning of the head and eyes (versive movement), the seizure focus is almost always in the hemisphere contralateral to the direction of head and eye movement. Seizures are more common with tumors that are supratentorial and involve the cortex, especially astrocytomas and oligodendrogliomas. In one study of patients with gliomas, seizures occurred in 59% of frontal tumors, 42% of parietal tumors, 35% of temporal tumors, and 33% of occipital tumors. Others have noted the especially high frequency of seizures in patients with tumors in the limbic regions, particularly the temporal lobe. Seizures may be the presenting sign of brain tumor in up to 50% of patients. Gilles et al. reported seizures in 14% of 3,291 children with central nervous system (CNS) tumors, but the incidence increased with patient age, supratentorial location, and isocortex involvement.