Abstracts

Rationale: Guidelines for optimum EEG recording and video telemetry are well established and most laboratories follow standardized protocols to ensure accurate data acquisition and clinical interpretation. On the other hand, the process of reviewing video-EEG monitoring (VEM) data varies from centre to centre. Many centers review the entire VEM dataset, while others implement a sampled approach, whereby a set amount of VEM data is reviewed per hour of recording (typically 5-10 min per hour), together with the data recorded in relation to events identified by button presses or by seizure or spike detection programs. This study was designed to compare continuous versus sampled reviewing of VEM data to validate whether the diagnostic yield would be different. Methods: VEM data acquired from 50 consecutive patients admitted to the seizure monitoring unit were reviewed by two independent electroencephalographers, one using the continuous review method, and the other sampling the first 5 minutes of each hour together with events identified by button presses and by automated seizure detection function. The patients were monitored for periods ranging between 3-21 days. The reviewers were asked to complete an identical data form summarizing the following information in three areas: i) demographic data, 2) interictal discharge location, frequency of occurrence, and 3) seizures or other clinical event types, quantity, location of onset, and certainty of classification (ordinal scale of 0-7; 0 = not certain, 7 = extremely certain). Descriptive statistics were obtained for the variables of interest. Overall agreement between reviewers was calculated using the Kappa statistic except when comparing the total number of clinical events between the two review methods in which case Pearson’s correlation coefficient was used. Results: Fifty patients were studied (31 females, 44 right handed) whose seizures began at the age of 19.1 +/- 12.83 years of age. There was poor agreement on the frequency of occurrence of interictal discharges (Κ = 0.44) with continuous review of VEM yielding a greater quantity of interictal discharges. Better agreement was seen for the side of the discharge (Κ = 0.87) but less for the specific lobe (K = 0.68). The total number of clinical events identified were similar between the two review methods (Pearson’s coefficient = 0.92). The electroclinical diagnoses were similar between the groups (K = 0.72) with better agreement for the side of onset (K = 0.80), and perfect agreement for those patients with focal onset seizures (K = 1.00). Conclusions: This study demonstrates that sampled review of VEM data can yield datasets that are similar to those produced by continuous review. However, there was poor agreement for the quantification of interictal discharges and seizures. Only a moderately good correlation was seen between electroclinical diagnoses. Thus, using this particular method of comparison in our clinical setting, continuous VEM more comprehensively captured the information of interest. Our findings require replication in different settings, including a larger patient population.