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Heart rate variability remains reduced and sympathetic tone elevated after temporal lobe epilepsy surgeryPURPOSE: There is evidence of autonomic dysregulation in temporal lobe epilepsy. The structures removed during temporal lobectomy are important centers of central cardiovascular control; therefore surgery may conceivably alter the cardiovascular autonomic function. The effects of temporal lobectomy on autonomic cardiac control are controversial. We investigated the effects of temporal lobectomy on heart rate variability (HRV) in the early and late postoperative periods. METHODS: We used 1-h ECG recordings to assess heart rate variability by spectral analysis in 24 consecutive patients who underwent temporal lobectomy due to intractable temporal lobe epilepsy. ECG recordings were performed before and twice (early and late) after surgery. The results were compared with age and sex matched controls. RESULTS: When compared with controls, all the time and frequency domain indices (SDRR, RMSSD, TP, LF and HF) were significantly lower in the patient group before surgery. Findings were similar in the early and late post-operative periods except that the LF/HF ratio increased in the patient group after the late post-operative period. Within the patient group, compared to pre-operative results, normalized HF was increased in the early post-operative period; however in the late post-operative period, LF/HF ratio was increased. CONCLUSIONS: These findings show that in patients with intractable temporal lobe epilepsy, HRV is decreased globally in both sympathetic and parasympathetic domains. While the total HRV remains reduced throughout the postoperative periods, the LF/HF ratio, i.e., sympathovagal balance is altered, in favor of parasympathetic side early after surgery, but towards the sympathetic side after the first postoperative month. rights reserved.
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Reduction in apathy following epilepsy surgeryIntroduction: Surgical treatment for patients with epilepsy who do not respond to antiepileptic medication can lead to changes in behavior, including new onset of neuropsychiatric symptoms such as depression and anxiety. In other cases, neuropsychiatric symptoms present before surgery may be alleviated. Because application of diagnostic criteria for primary psychiatric disorders may not be valid in assessing behavior in epilepsy populations, we sought to determine the feasibility of measuring behaviors associated with frontal-subcortical dysfunction using the Frontal Systems Behavior Scale (FrSBe) in patients who had received surgical intervention for medically refractory epilepsy. Materials and Methods: Twenty-three patients who had previously undergone epilepsy surgery and their family member informants completed the FrSBe. The FrSBe includes separate forms for patients and informants to rate symptoms associated with three frontal lobe syndromes - executive dysfunction, disinhibition, and apathy - prior to and following a neurological condition. Patients and informants were asked to rate frontal lobe behaviors before and after epilepsy surgery using the FrSBe. Results: Informants rated patients as showing a significantly greater reduction in apathy on the FrSBe compared to either disinhibition or executive dysfunction subscales. A trend in reduction of apathy following right hemisphere resection was found. Conclusions: Patients who have undergone epilepsy surgery show a reduction in apathy but it is unclear whether this behavioral change is directly related to the surgical intervention. We suggest that these preliminary findings support the utility of implementing dimensional scales such as the FrSBe to study behavioral changes following epilepsy surgery.
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Functional MRI of Rat and Monkey Models of Absence Epilepsy: A DissertationA seizure is defined as an abnormal electrical discharge from the brain that results in the affected area losing its normal function and reacting uncontrollably. A particular subset of seizures, known as absence seizures, are characterized by brief, paroxysmal losses of consciousness that are associated with bilaterally synchronous 3 Hz spike and wave discharges (SWDs) on electroencephalography (EEG). The optimal way to understand any disease state is to study it within the human. Unfortunately, well controlled experiments in humans are difficult due to small patient populations, treatment medications which alter the seizure, and the ethical problems associated with invasive experimental procedures. Animal models of absence seizures provide a means of avoiding the above difficulties but the model should mimic, as closely as possible, the human condition. The goal of this thesis was to develop an animal model of absence epilepsy that could be used to explore, non-invasively, the underlying mechanisms of absence seizures. Functional magnetic resonance imaging (fMRI) was used to non-invasively monitor brain activity during absence seizures in various animal models. In this dissertation I report the development of a pharmacological rat model of absence seizures for use in fMRI investigations. Imaging was performed after absence seizure induction using γ-butyrolactone (GBL) and it was found that the cortico-thalamic circuitry, critical for the formation of SWDs, showed robust signal changes consistent with electroencephalographic recordings in the same animals. Since a major disadvantage of the GBL rat model is that it produces acute, drug-induced seizures, a genetic rat model with spontaneous absence seizures was subsequently developed for fMRI. EEG-triggered fMRI was used to identify areas of brain activation during spontaneous SWDs in the epileptic WAG/Rij rat strain under awake conditions. Significant signal changes were apparent in several areas of the cortex and several important nuclei of the thalamus. These results draw an anatomical correlation between areas in which there is increased fMRI signal and those where SWDs have been previously recorded using electrophysiologic techniques. One way in which absences differ between humans and both of these rat models is that the SWD frequency in humans is classically 3 Hz while in rats it varies from 7 to 11 Hz. Marmoset monkeys were found to model the human absence seizure condition better than other animals because GBL administration in these non-human primates results in the formation of 3 Hz SWDs. This monkey model was developed for awake functional imaging and changes in signal intensity in the thalamus and sensorimotor cortex correlated with the onset of 3 Hz SWDs. The change in BOLD signal intensity was bilateral but heterogeneous, affecting some brain areas more than others.
