Tractography Guided and Verified Interstitial Laser Hemispherotomy – Outcome in 10 cases

Introduction: Functional open and endoscopic hemispherectomy is an effective treatment of hemispheric epilepsy but carries significant morbidity including malabsorptive hydrocephalus and additional neurologic deficits. As the objective of the surgery is disconnection and not volume removal a logical extension is to use tractography to guide the disconnection individually in each patient , instead of anatomically, verify the degree of disconnection with tractoraphy and also reduce the invasiveness to a minimum. Both can be achieved by using an interstitial laser approach with integration of the tractography into the surgery and the real time monitoring of ablation.

Methods: In 10 children with refractory epilepsy due to perinatal stroke or Sturge-Weber Syndrome we used deterministic DTI-imaging employing a 3T-Phillips Ingenia scanner to guide the laser implantation and plan the disconnection using a volumetric modeling of seed tracts. 5-6 laser fibers were implanted to achieve a complete disconnection and a 980nm laser with a maximum energy of 15 Watts (Visualase, Medtronic) was used as well as continuous phase-shift temperature monitoring during the ablation.

Results: Median follow-up was 1.8+ 0.6 years and median inpatient stay was 2.1+0.5 days.
2 small asymptomatic hemorrhages were seen postoperatively and no patient developed hydrocephalus. The Sturge-Weber patient had a temporary worsening of a pre-existent hemiparesis which resolved completely. Seizure outcome at last follow-up was Engel I in 9 patients and Engel class III in one patient who later underwent open hemispherectomy. Postop tractography showed a 90+8.9% disconnection of the hemisphere congruent with the calculated damage map from the laser ablation.

Conclusion : Tractography guided Interstitial laser hemispherectomy is a highly effective alternative to open or endoscopic hemispherectomy with a significantly lower morbidity and shorter hospital stay indicating also superior cost-effectiveness.