Abstracts

Rationale: Rapid bilateral eye blinking (RBEB) is commonly seen during generalized absence seizures, and is the defining character of seizures in the Jeavons syndrome. Complex partial seizures (CPSs) in focal epilepsy are usually associated with the opposite semiology - fixed staring - though we have also observed RBEB in CPSs. In this pilot study we surveyed the electroclinical associations of RBEB in a cohort of focal epilepsy patients with CPSs. Methods: We retrospectively reviewed scalp video-EEG monitoring seizure data on all patients with proven partial epilepsy and CPSs encountered over a 12-month period (year 2009). Seizures with RBEB were identified by obvious excessive eyeblink artifact on the EEG that lasted ≥ 10 seconds at any time during the seizure. The total number of eye blinks for the duration of the seizure, as well as the 10-second epoch with the highest number of eye blinks (peak blink rate) was noted.The ictal EEG of each seizure (whether with RBEB or not) was classified as having a lateralized or nonlateralized onset pattern. Results: 156 partial seizures (n=156) were recorded in 41 patients (N=41) that fit the above criteria. Ninety-one seizures (n1=91) had clearly lateralized ictal EEG onsets; the remainder (n2 = 65) had nonlateralized onsets. Four patients had 8 seizures (m=8) that showed RBEB; in each such seizure, RBEB was confirmed by peak eye blink rates during the seizure significantly higher than at baseline (p < 0.001). Assuming N and n as population figures, the probabilities of a random seizure having lateralized versus nonlateralized onset were n1/N ≈ 0.58 versus n2/N ≈ 0.42. Thus, the probability of m seizures with RBEB all having nonlateralized onset was p = (0.42)8 < 0.001 Conclusions: (i) RBEB, a semiological feature often seen in seizures arising in generalized epilepsy syndromes, may occur rarely in seizures in focal epilepsy (4/41 ≈ 10% of patients and 8/156 ≈ 5% of seizures, in this series). (ii) There is a statistically significant association between seizures with RBEB and a diffuse (nonlateralized) ictal EEG pattern at onset. This observation argues for direct bihemispheric propagation of seizures with RBEB, or alternatively, preferential spread of such seizures to regions (e.g. the orbital and medial frontal cortices) that secondarily project to widespread brain areas. Functional imaging studies demonstrate medial and orbital frontal activation with spontaneous eye blinking (Tsubota et al, Exp Eye Res 69(1):1-7, 1999; Yoon et al, Neurosc Lett 381(1-2):26-30, 2005). These brain areas are also among those that display an early increase in the BOLD signal during generalized spike-wave paroxysms in simultaneous EEG-fMRI studies (Benuzzi et al, Epilepsia 53(4):622-30, 2012). (iii) It is therefore plausible that in CPSs with RBEB, seizure spread occurs early to ‘eye-blink eloquent' brain areas that results in both rapid eye blinking as well as a diffuse ictal EEG. The further associations of RBEB with epilepsy syndrome and treatment responsiveness will be investigated in a larger study that confirms these preliminary findings.