Abstract
OBJECTIVE: Recent studies in patients with drug-resistant epilepsy (DRE) have shown that including areas of ictal spread in resections may result in better postoperative seizure control. However, it remains unclear whether the extent or speed of ictal spread affects neuropsychological test (NP) performance. In the present study, we assessed the relationship between the speed of initial ictal spread and preoperative measures of language and memory, as well as postoperative seizure outcomes in patients with refractory focal epilepsy. METHODS: A retrospective chart review and analysis of patients with DRE who underwent intracranial EEG (iEEG) monitoring and surgical resections from 2008 to 2016 was conducted at the level 4 epilepsy center at the University of Nebraska Medical Center. The scores reflecting immediate and delayed verbal and visual memory functions were extracted from the preoperative Logical Memory I, II, and Visual Reproduction I, II tests of the Wechsler Memory Scale III or IV, respectively. The scores defining the language function were extracted from the preoperative Boston Naming or Neuropsychology Assessment Battery Naming test. The relevant demographic and clinical data were also collected. Raw tracings of the ictal iEEG recordings were reviewed independently by two epileptologists, and the speed of ictal spread was labeled as early or late based on the 10-second cutoff. The postoperative seizure outcomes were assessed using the Engel score. The patient's performance on the preoperative NP tests and their postoperative seizure status were compared between the early and late ictal spread groups. RESULTS: Of 111 patients who underwent iEEG during the target period, 68 met the inclusion criteria. Based on the iEEG recordings and other studies, temporal epilepsy was diagnosed in 64.7% of patients, while temporal plus epilepsy and extratemporal epilepsy were found in 25% and 10.3% of patients, respectively. Early ictal spread was identified in 38 (55.9%) patients, while late onset was found in 30 (44.1%) patients. Immediate verbal memory scores (median and interquartile range) in early and late ictal spread groups were 37.0 (5.0; 63.0) and 26.5 (5.0; 56.5), respectively, while immediate visual memory scores in the same groups were 25.0 (3.5; 50.0) and 37.0 (16.0; 63.0), respectively. The naming scores were 18.0 (7.0; 46.0) and 8.0 (1.0; 21.0) in the early and late ictal spread groups. There were no differences in the performance on the verbal and visual memory or language tests in patients with early and late ictal spreads. Further, there were no differences in postoperative seizure outcomes in these two groups. SIGNIFICANCE: We found that the speed of ictal spread assessed with iEEG does not influence performance on the standard preoperative tests of memory and language or postoperative seizure outcomes in patients with DRE. To detect such differences, a more refined approach targeting the selected subtests of the language and memory functions during presurgical evaluation may be required.