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Stereotactic-EEG-guided radiofrequency multiple hippocampal transection (SEEG-guided-RF-MHT) for the treatment of mesial temporal lobe epilepsy: a minimally invasive method for diagnosis and treatment Volume 23, numéro 5, October 2021

TEST YOURSELF

(1) What patients would be appropriate candidates for SEEG-guided-RF-MHT?

 

(2) What would be the disposition of the electrodes in mesial temporal structures in patients for whom SEEG guided-RF-MHT would be considered as a treatment option?

 

(3) What radiofrequency settings are required in order to produce effective coagulative lesions that would disconnect the longitudinal fibers at the amygdalo-hippocampal complex at 2-3 points?

 

 

 

 

 

 

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Answers

(1) This technique can be considered in patients with suspected mesial temporal lobe epilepsy in the language-dominant lobe and preserved verbal memory. These patients are at high risk of memory decline using other techniques which involve resection or ablation of the lateral temporal stem and/or the amygdala hippocampal complex.

 

(2) Three orthogonal electrodes are implanted through the lateral temporal cortex targeting the amygdala (electrode AM), head and body of the hippocampus (electrodes HH and HB). Two additional electrodes are implanted from posterior to anterior, along the longitudinal axis of the hippocampal/entorhinal complex; one superior (electrode ES) at the level of the orthogonal electrodes, and one lateral and inferior (electrode EI) targeted to an area between the subiculum, entorhinal area, and inferior longitudinal fasciculus. The ES and EI electrodes are separated by 8-10 mm.

 

(3) The RF power was progressively increased over 5-10 seconds to achieve a power of 3 W and then maintained for 180 seconds or until the current flow spontaneously collapsed. A lesion was considered complete when an abrupt rise in impedance and fall in current was observed, indicating that coagulation necrosis was complete. This protocol was adopted based on the in vitro and in vivo observations of Staudt and Miller in which the largest confluent lesions between adjacent electrodes were created using a power of 3 W at all inter-electrode distances up to 12 mm, compared to higher power settings. Staudt and Miller also observed that using higher RF power (as used by prior authors utilizing radiofrequency current) actually produced smaller lesions, thus power was maintained below 3 W for all lesions produced in this study.

 

 

 

 

 

 

 

 

 

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