Cardiovascular autonomic functions in well-controlled and intractable partial epilepsies
Mukherjee S, Tripathi M, Chandra PS, Yadav R, Choudhary N, Sagar R, Bhore R, Pandey RM, and Deepak KK (2009) Cardiovascular autonomic functions in well-controlled and intractable partial epilepsies. Epilepsy Res 85:2-3 261–9.
Abstract: BACKGROUND: Epilepsy is associated with imbalance of sympathetic and parasympathetic activity which may lead to sudden unexplained death in epilepsy (SUDEP). Well-controlled (WcE) and intractable epilepsy (IE) subjects may present different autonomic profiles, which can be helpful in explaining the predisposition of the latter to SUDEP. PURPOSE: To compare inter-ictal cardiovascular autonomic function in subjects with partial WcE and IE. METHODS: Thirty WcE and 31 IE subjects underwent a battery of autonomic function tests: deep breathing, Valsalva maneuver, isometric exercise, cold pressor and tilt-table. Autonomic tone was assessed by heart rate variability (HRV). Their autonomic severity score and anxiety status was also assessed. RESULTS: IE subjects had elevated low frequency component (52.0 vs. 37.6, p=0.047) and decremented high frequency component (114 vs. 397, p=0.013) of HRV and higher diastolic BP (75.62+/-9.77 vs. 68.64+/-0.43, p=0.036). In deep breathing test, they had lesser HR changes (20+/-10.18 vs. 29.68+/-11.23, p=0.007) and lower E:I (1.29+/-0.16 vs. 1.43+/-0.21, p=0.008). IE subjects had higher dysautonomia (chi square 165.0, p<0.0001). CONCLUSIONS: We observed a higher vasomotor tone, higher sympathetic tone, lower parasympathetic tone, lower parasympathetic reactivity and more severe dysautonomia in the IE subjects. Refractoriness may lead to an alteration in cardiovascular autonomic regulation, which might be a predisposing factor for SUDEP.
Keywords: SUDEP, well-controlled epilepsy; Intractable; Autonomic tone; Inter-ictal; Dysautonomia
Context
- Prospective study of the effect of intractable epilepsy on autonomic function. The study is strengthened by the large size of groups, approximately 30 patients in each. The patients with intractable disease showed less variation of the high-frequency component of heart rate. Their lower drop in heart rate with deep breathing suggested reduced parasympathetic tone. (An even stronger argument might be made by additional consideration of a ‘dose-response’ relationship between seizure severity and autonomic dysfunction in the refractory group.) The findings suggest that ongoing seizure activity worsens the overall picture of autonomic control, but it is also possible that genetic abnormalities in ion channels, for example, that make the epilepsy more resistant to treatment also lead to worsened autonomic function. Longitudinal evaluation of the patient cohort might provide this information – do patients whose epilepsy remains refractory worsen in autonomic function over time in proportion to their seizure frequency?