BALTIMORE – according to an analysis presented at the annual meeting of the American Epilepsy Society. Long-term seizure outcomes, however, are similar between resected and nonresected patients. In addition, sparing a normal-appearing hippocampus is correlated with a lower risk of verbal deficits, but long-term outcomes are unclear.
Neurologists have not arrived at a consensus about the best surgical management of patients with temporal lobe epilepsy and a hippocampus that appears normal on MRI. Few studies have examined seizure and neuropsychologic outcomes in this population, and this scarcity of data makes counseling patients difficult.
A review of data for surgical patients
To investigate this question, Marcia E. Morita-Sherman, MD, from the Cleveland Clinic, and colleagues retrospectively reviewed data for 152 patients who underwent surgery for temporal lobe epilepsy at the Cleveland Clinic during 2010-2018. Eligible participants were older than 16 years, and the researchers excluded patients with MRI or pathologic signs of hippocampal sclerosis and those with prior surgeries from the analysis.
To examine neuropsychological outcomes, Dr. Morita-Sherman and colleagues compared measures of verbal memory, visual memory, and confrontation naming that had been obtained before surgery and at 6 months after surgery. They measured hippocampal volume using Neuroquant. They categorized resections as dominant or nondominant according to patients’ handedness or language lateralization. The investigators classified 74 patients as having a spared hippocampus and 78 patients as having a resected hippocampus. They classified neuropsychological outcomes as showing decline or no decline using epilepsy-specific reliable change indexes.
Type of surgery affected memory and naming
Approximately 40% of patients had seizure recurrence within 1 year after surgery, and 63% had seizure recurrence within 6 years after surgery. The rate of invasive EEG was similar between patients with a spared hippocampus (50%) and those with a resected hippocampus (47%). In a univariate analysis, male sex, longer epilepsy duration, normal MRI, history of invasive evaluation, and acute postoperative seizures were associated with a higher risk of seizure recurrence. Patients with a spared hippocampus had a higher risk of early seizure recurrence, compared with patients with a resected hippocampus, but the difference was not statistically significant. Long-term seizure outcomes were similar between the two groups.
Neuropsychological outcomes were available for 86 patients. Among 56 patients who underwent surgery on the dominant side, those with spared-hippocampal surgery, compared with those with resected-hippocampal surgery, had lower rates of clinically meaningful declines in verbal memory (39.7% vs. 70.4%) and naming (40.7% vs. 79.2%). The investigators found no significant difference in the 30 patients with nondominant surgeries.
“Sparing the hippocampus in a tailored temporal lobe resection doesn’t necessarily prevent any memory decline. Close to 40% of our patients where the hippocampus was spared had a clinically significant memory loss,” said, an epileptologist at the Cleveland Clinic and one of the investigators. “Including the hippocampus in the resection seems to correlate with better odds of seizure freedom, at least in the short term. We need more research to study the long-term memory and naming implications of hippocampal sparing versus resection.”
The study was funded by a grant from the National Institutes of Health. The investigators reported no conflicts of interest. email@example.com
SOURCE: Morita-Sherman ME et al. AES 2019, Abstract 1.336.