Abstracts

Rationale: Frontal lobe (FL) seizures may be associated with a variety of characteristic features including early clonic activity, asymmetric tonic posturing, and hypermotor activity. While certain signs are often noted with FL onset seizures, an increasing number of reports have described the potential for an extrafrontal epileptogenic zone (EZ) for even the most typical FL semiology. Studies have applied statistical methods to compare semiology in frontal and extrafrontal lobe onset seizures. Such comparative data is important, in part, because it provides statistical validation of the localizing value of a particular sign. Positive predictive values (PPV) have been described as useful in the analysis of seizure semiology. PPV provide a quantitative estimate of the proportion of patients with a given semiology who will be correctly localized. The purpose of this study was to: 1) systematically review the literature in order to provide a comprehensive list of semiology that is statistically associated with a FL EZ, and 2) to summarize predictive values for signs associated with FL seizures.Methods: A systematic literature review was conducted using PubMed in order to indentify studies which met the inclusion criteria: 1) studies must describe a statistically significant localizing sign or signs for seizures determined to have frontal lobe EZ, and 2) analyses must compare semiology of patients with frontal EZ to patients with extrafrontal EZ. An exhaustive search of titles and abstracts was undertaken to identify relevant articles. Full-text articles of potentially relevant studies were then reviewed to determine eligibility.Results: Our search strategy yielded 3,752 abstracts; 19 articles met inclusion criteria. Thirty-nine signs have been identified as statistically associated with FL EZ. Four of 19 studies (21%) required that the localization of FL EZ be identified by seizure freedom after surgery ( gold standard method). The remaining studies identified the EZ by other methods such as MRI or EEG localization. The mean number of FL patients in the studies was 28.6 (range 8-84). PPV could be calculated for 26/39 (67%) of the statistically validated signs. The signs that had multiple analyses that supported a statistical association with FL EZ included: tonic activity (PPV range 70.7-100%), head turning early in seizure (PPV 81.3%), clonic activity (PPV range 84-100%), and hypermotor seizure (PPV 53.9-100%). See table for list of signs with PPV available.Conclusions: Our systematic review describes 39 statistically validated signs associated with FL EZ. FL semiology can have a PPV of > 80%. Most of the included studies did not localize the EZ using the gold standard (seizure freedom after surgery). Our review provides clinicians a relatively comprehensive listing of localizing signs and PPV of statistically validated semiology associated with FL EZ. This information may be useful in the presurgical evaluation.