About one third of patients with epilepsy have seizures refractory to the medical treatment. Electrical stimulation mapping is the gold standard for the identification of “eloquent” areas prior to resection of epileptogenic tissue. However, it is time-consuming and may cause undesired side effects. Broadband gamma activity recorded with extraoperative electrocorticography during cognitive tasks may be an alternative to ESM but until now has not proven of definitive clinical value. Considering their role in cognition, the alpha and beta bands could further (...) improve the identification of eloquent cortex. We compared gamma, alpha and beta activity, and their combinations for the identification of eloquent cortical areas defined by ESM. Ten patients with intractable focal epilepsy participated in a delayed-match-to-sample task, where syllable sounds were compared to visually presented letters. We used a generalized linear model approach to find the optimal weighting of each band for predicting ESM-defined categories and estimated the diagnostic ability by calculating the area under the receiver operating characteristic curve. Gamma activity increased more in eloquent than in non-eloquent areas, whereas alpha and beta power decreased more in eloquent areas. Diagnostic ability of each band was close to 0.7 for all bands but depended on multiple factors including the time period of the cognitive task, the location of the electrodes and the patient’s degree of attention to the stimulus. We show that diagnostic ability can be increased by 3–5% by combining gamma and alpha and by 7.5–11% when gamma and beta were combined. We then show how ECoG power modulation from cognitive testing can be used to map the probability of eloquence in individual patients and how this probability map can be used in clinical settings to optimize ESM planning. We conclude that the combination of gamma and beta power modulation during cognitive testing can contribute to the identification of eloquent areas prior to ESM in patients with refractory focal epilepsy. (shrink)

OBJECTIVES: Cognitive and sensory difficulties frequently jeopardize informed consent of frail elderly patients This study is the first to test whether preliminary research experience could enhance geriatric patients' capacity to consent. DESIGN/SETTING: A step-wise consent procedure was introduced in a study on fluid balance in geriatric patients. Eligible patients providing verbal consent participated in a try-out of a week, during which bioelectrical impedance and weight measurements were performed daily. Afterwards, written informed consent was requested. Comprehension, risk and inconvenience scores (ranges: (...) 0-10) were obtained before and after the try-out by asking ten questions about the study's essentials and by asking for a risk and inconvenience assessment on a ten-points rating scale. SUBJECTS AND RESULTS: Seventy of the 78 eligible subjects started the try-out and 53 (68%) provided written consent. The comprehension score increased from 5.0 (+/- 2.3) to 7.0 (+/- 1.9) following the try-out (P < 0.001). The number of subjects capable of weighing risks and inconveniences increased from 32 to 48 (P < 0.001). CONCLUSIONS: Research experience improved the capacity to consent, still enabling an acceptable participation rate. Therefore, experienced consent seems a promising tool to optimize informed consent in frail elderly subjects. (shrink)