Upgraded implantation method hones epileptogenic zone targeting

By Peter Sergo, medwireNews Reporter

Stereoelectroencephalography (SEEG) methodology is accurate for identification of brain regions that are susceptible to seizures and serves as a reliable presurgical evaluation of patients with drug-resistant epilepsy.

Researchers succeeded in 6496 SEEG intracerebral electrode implantations in 500 consecutive patients, allowing for a more precise localization of their epileptogenic zone (EZ). All the procedures were carried out at one center between 1996 and 2011 with the initial 419 procedures applying the traditional Talairach method of two surgical steps - stereotactic angiography and electrode implantation.

After fall of 2009, the workflow updated the rest of 81 procedures to a one-step surgical technique that acquired computerized, 3-dimensional brain angiography (3-D DSA) and magnetic resonance imaging in frameless and markerless conditions, advanced multimodal planning, and robot-assisted implantations.

With the use of 3-D DSA in the new workflow, brain angiographies were obtained outside of the operating room without the requirement of anesthesia - with the exception of pediatric patients.

The traditional workflow resulted in a median entry point localization error (EPLE) of 1.43 mm, which was significantly larger than the 0.78 mm of the upgraded technique. The same trend was seen in the median target point localization errors (TPLE) with 2.69 mm and 1.77 mm, respectively.

Commenting on the new workflow, Francesco Cardinale (Claudio Munari Center for Epilepsy and Parkinson Surgery, Milan, Italy) and colleagues write in Neurosurgery that "[a]ccurate preimplantation and postimplantation 3-D imaging…made it easier to understand the electrode position. This tool led to a computer-aided representation of the brain anatomy and individualized electrode placement for each patient…[which] facilitated the definition of the EZ…and the planning of respective surgery."

The study counted 12 major and 12 minor cases of complications; a 79.1% majority of them pertaining to traditional workflow patients, including four cases of major hemorrhage that were due to the cortical entry location of the electrode. "No major bleeding was observed with the new workflow, probably owing to the lower EPLE," the authors conclude.

Of note was a 3-year-old traditional workflow patient who died 2 days after implantation from severe hyponatremia and massive edema, which the authors attributed to severe hydroelectrolytic imbalance unrelated to the actual surgical procedure.

While noting the importance of Cardinale at al's study in an accompanying commentary, Jorge Gonzales-Martinez (Cleveland Clinic, Ohio) observed the need to compare long-term outcome results between SEEG and subdural methods to better refine indication criteria.

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