Although MRI examination is generally recommended
in patients with focal epilepsy, we
have encountered a population of individuals
with chronic epilepsy who have never undergone
a high-resolution imaging examination.
We sought to identify factors in the history
and prior evaluation that led to an incorrect
diagnosis of cryptogenic epilepsy with overlooked
lesions. We identified and retrospectively
reviewed 10 patients referred to a
tertiary-care hospital-based epilepsy clinic
from 1993–1999 with longstanding localization-
related epilepsy in whom initial brain
MRI, obtained years after seizure onset, demonstrated
focal lesions. Structural lesions
were identified on MRI in each case that were
concordant with the clinical, interictal, and
when available, ictal electrographic localization
of their seizure foci. Lesions included
gray matter heterotopia, low-grade glioma,
nonspecific gliosis, congenital encephalomalacia,
remote intraparenchymal hemorrhage,
cavernous malformation, and mesial temporal
sclerosis. Lesions identified in each case
were potentially amenable to surgical treatment.
In every case, the recognized lesion
was probably present decades before discovery.
The median duration of epilepsy prior to
MRI examination in this population was 26
years, indicating that the epilepsy diagnosis
was assigned before MRI became widely
available. We conclude that there is a population
of “MRI-naïve” epilepsy patients whose
diagnosis predates the widespread availability
of MRI and who harbor chronic lesions
that are causally related to their seizures and
are amenable to surgical resection. MRI may
be underutilized in patients with
longstanding epilepsy. Identification of unsuspected
lesions may decrease epileptic
morbidity and mortality.