Abstracts

Rationale: Autonomic symptoms commonly occur during epileptic seizures. In particular, heart rate (HR) often fluctuates during any type of seizure. Tachycardia is the most common pattern of ictal HR changes. However, right hemispheric seizures are associated with tachycardia more frequently than left; whereas left hemispheric seizures are occasionally but more often associated with bradycardia than right; but right and left seizures show no clear differences. This study investigated the relationship between seizure lateralization and patterns of ictal HR changes in patients with temporal lobe epilepsy. Methods: A total of 25 patients with unilateral temporal lobe epilepsy (9 men, aged 13-44 years) were recruited from the database of Tohoku University Hospital Epilepsy Monitoring Unit, Sendai, Japan, who underwent long-term video EEG monitoring for 4 or 5 days in 2012. Thirty-three right temporal lobe seizures (TLSs) were identified from 10 patients and 51 left TLSs from 15 patients. Onset time of EEG seizure was defined as zero, and time series of HR from -100 s to +300 s were extracted for analysis. Onset time of tachycardia was identified as described by van Elmpt et al. (Seizure, 2006). Medians (M₁(t) and M₂(t)) of HR were compared at two intervals ([t - 20 s, t] and [t, t + 10 s]), and the onset time (t₀) of tachycardia identified if M₂(t₀) - M₁(t₀) was larger than a threshold value d (= 5 or 20). The larger d value reduced detectability of HR increase. Some small or slow increases of HR with large threshold values were omitted. Patterns of ictal HR changes were classified into the following 3 groups: Group A (detectable with d = 20), Group B (detectable with d = 5, but undetectable with d = 20), and Group C (undetectable with d = 5). Results: Twenty-seven right (82%) and 27 left (53%) TLSs were classified into Group A (precipitous increase), 6 right (18%) and 20 left (39%) TLSs into Group B (gradual increase), and 0 right (0%) and 4 left (8%) TLSs into Group C (no obvious increase). Contingency table analysis revealed significant correlations between seizure lateralization and patterns of HR increase (Fisher's exact test, bilateral p = 0.016). Conclusions: Right TLSs were correlated with precipitous HR increase more frequently than left. Right TLSs may induce direct HR increase, whereas left TLSs may provoke indirect HR increase or decrease.