This now-validated tool showed an ability to accurately identify focal seizure-onset zone, which may help epilepsy centers when faced with the challenge of whether a patient should undergo implantation.
The 5-point 5-SENSE score, a developed tool to predict focality of the seizure-onset zone in patients with drug-resistant epilepsy, demonstrated a high specificity in a multicenter validation analysis, and thus may be used to predict patients in whom steroelectroencephalography (SEEG) is unlikely to identify a focal seizure-onset zone.
Senior author Brigit Frauscher, MD, PhD, associate professor of neurology, McGill University, and colleagues concluded that once the focal seizure-onset zone is located, "patients with small likelihood to benefit from this invasive and resource-intensive investigation can be identified earlier avoiding unnecessary procedure-related burden on patients and overutilization of health care resources."
A total of 128 patients (median age, 31 [range, 13-58] years) with drug-resistant epilepsy underwent SEEG and were grouped as focal and non-focal seizure-onset zone after analysis. Patients were included in the study if they had 2 or more seizures in EEG and had available neuropsychological and neuroimaging datasets. After factoring demographic, clinical, EEG, neuroimaging, and neuropsychology data, investigators created a multiple logistic regression model for developing the 5-SENSE score tool, which is comprised of 5 predictive variables (FIGURE).
All patients were followed up for a minimum of 1 year. At the conclusion of the analysis, the 5-SENSE score demonstrated a high discrimination based on the area under the curve of 0.83 (95% CI% 0.757-0.906), with a sensitivity of 83.3% (95% CI, 72.3-94.1%) and a specificity of 76.3% (95% CI, 66.7-85.8%). The final score, calculated by applying the standard logistic regression model formula, showed an optimal mean cutoff value of 37.6 (standard deviation [SD], 3.5), meaning that values above 37.6 pointed to focality, whereas values below that mark were in favor of finding no focal seizure-onset zone on SEEG.
Following the monocentric cohort study for score development, 207 patients (median age, 32 [range, 16-70]) were analyzed for validation. A total of 11 patients (54%) had a focal and 96 (46%) had a nonfocal seizure-onset zone. Surgery was performed following SEEG exploration in 164 of 207 (80%) patients with a curative intent, in 80 of the 111 patients (72%) in the focal and in 34 of 96 patients (35%) in the nonfocal group (95% CI, 2.5-8.9; P <.001).
Investigators thus calculated the sensitivity and specificity of the tool in the in the validation cohort, using the cutoff of 37.6 from the exploratory model building steps. Using those values, results showed a sensitivity of 54% (95% CI, 44.8-63.3) and specificity of 69% (95% CI, 59.5-78%). After applying the 3.5 SD, which raised the cutoff to 41.1, specificity increased to 76% (95% CI, 67.5-84.6%), with minor decrease of sensitivity to 52% (95% CI, 43-61.5).
Factors such as no observed lesion (OR, 0.1 [95% CI, 0.03-0.33]; P <.001; model coefficient = –2.26) or a nonfocal lesion on MRI (OR, 0.12 [95% CI, 0.03-0.37]; P <.001; model coefficient –2.15) strongly pointed to a nonfocal seizure-onset zone on SEEG, whereas a focal lesion on MRI was strongly associated with a focal seizure-onset zone. Furthermore, a focal or lobar ictal scalp EEG onset was associated with focality (OR, 2.33 [95% CI, 0.61-9.54]; P = .22; model coefficient = 0.844) compared with a bilateral synchronous ictal EEG onset, no ictal EEG changes, and a multilobar or diffuse ictal EEG onset (OR, 0.44 [95% CI, 0.12-1.7]; P = .23; model coefficient = –0.81).
Frauscher et al also found that bilateral independent interictal EEG changes increase the probability of a nonfocal seizure-onset zone compared with no IEDs (OR, 6.08 [95% CI, 0.88-58.97]; P = .08; model coefficient = 1.806) or all others (OR, 3.26 [95% CI, 0.7-23.26]; P = .16; model coefficient = 1.18). Additionally, a nonlocalizing neuropsychological deficit was associated with a nonfocal seizure onset zone (OR, 0.77 [95% CI, 0.26-2.05]; P = .60; model coefficient = –0.26) compared with a localizing neuropsychological deficit, whereas patients with no deficit pointed to focality (OR, 3.17 [95% CI, 0.54-19.56]; P = .20; model coefficient = 1.15).