Decrease of sympathetic cardiovascular modulation after temporal lobe epilepsy surgery
Hilz MJ, Devinsky O, Doyle W, Mauerer A, and Dütsch M (2002) Decrease of sympathetic cardiovascular modulation after temporal lobe epilepsy surgery. Brain 125:Pt 5 985–95.
Abstract: In temporal lobe epilepsy (TLE), there is evidence of ictal and interictal autonomic dysregulation, predominantly with sympathetic overactivity. The effects of TLE surgery on autonomic cardiovascular control and on baroreflex sensitivity (BRS) have not been studied. To evaluate such effects, we monitored heart rate (HR), systolic blood pressure (BP(sys)) and respiration in 18 TLE patients 3-4 months before and after TLE surgery. We used Blackman-Tukey spectral analysis to assess sympathetic and parasympathetic modulation as powers of HR and BP(sys) oscillations in the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.5 Hz) bands. BRS was determined as the LF transfer function gain between BP and HR. After surgery, HR, BP(sys), respiration and HF powers remained unchanged, while LF powers of HR (1.57 +/- 1.54 bpm(2)) and BP(sys) (2.19 +/- 1.34 mmHg(2)) and BRS (0.68 +/- 0.31 bpm/mmHg) were smaller than pre-surgical LF powers of HR (3.87 +/- 3.26 bpm(2)) and BP(sys) (4.80 +/- 3.84 mmHg(2)) and BRS (1.12 +/- 0.39 bpm/mmHg; P < 0.05). After TLE surgery, there is a reduction of sympathetic cardiovascular modulation and BRS that might result from decreased influences of interictal epileptogenic discharges on brain areas involved in cardiovascular autonomic control. TLE surgery seems to stabilize the cardiovascular control in epilepsy patients by reducing the risk of sympathetically mediated tachyarrhythmias and excessive bradycardiac counter-regulation, both of which might be relevant for the pathophysiology of sudden unexpected death in epilepsy patients (SUDEP). Thus, TLE surgery might contribute to reducing the risk of SUDEP.
Keywords: autonomic nervous system, baroreflex sensitivity, central autonomic network, epilepsy surgery, interictal sympathetic tone
- Study of autonomic function in 18 patients before and after epilepsy. HR and BP are essentially unchanged after temporal lobectomy (complete or partial), but LF variation increases in power after the procedure. The authors take this as an indication that the temporal lobe provides high sympathetic tone, decreasing HRV. In contrast to other studies from the same group, there does not seem to be a lateralizing effect. The authors also discuss the possibvility that seizure itself, rather than the temporal lobe, contributes to the apparent high basal sympathetic tone.