Can semiology differentiate between bilateral tonic-clonic seizures of focal-onset and generalized-onset? A systematic review

Objective: Bilateral tonic-clonic seizures are encountered in both focal and generalized epilepsies. We reviewed the literature regarding the presence of focal signs in generalized-onset tonic-clonic seizures (GOTCS) and the utility of semiology in differentiating those from focal to bilateral tonic-clonic seizures (FBTCS). Methods: We conducted a comprehensive literature search using four electronic databases (Medline, Embase, Web of Science, and Psychinfo) and constructed a systematic review in keeping with the Preferred Items for Systematic Reviews and Meta-analyses guidelines. Results: We included 13 studies on focal semiological features of GOTCS. These studies included a total of 952 participants. The key focal signs described in GOTCS included: early head version, figure of four sign, asymmetric seizure termination, and a multitude of auras as well as automatisms. Additionally, we reviewed five studies that investigated the use of semiology to differentiate GOTCS from FBTCS; these studies had a total of 289 participants. Asymmetry in clonic phase, side-to-side axial movements, asymmetrical seizure termination, figure of four sign, index finger pointing, and fanning posture of the hand were found to be significantly more frequent in FBTCS compared with GOTCS. Furthermore, combinations of focal semiological features occurring in a single seizure were found to be suggestive of FBTCS rather than GOTCS. Conclusion: Focal signs are often evident in GOTCS. Though the observation of multiple focal signs within a given seizure may be in favor of an FBTCS, our findings caution against differentiating between the two seizure types based on semiology alone due to considerable overlap in focal features. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

This review examined the presence of focal signs in generalized-onset tonic-clonic seizures (GOTCS) and the utility of semiology in differentiating those from focal to bilateral tonic-clonic seizures (FBTCS). Focal signs are often evident in GOTCS, but the observation of multiple focal signs within a given seizure may be more indicative of FBTCS. However, caution is advised against differentiating between the two seizure types based solely on semiology due to significant overlap in focal features.