Authors :
Peter Warnke, MD – The University of Chicago
Douglas Nordli, MD – The University of Chicago
David Satzer, MD – University of Chicago
Daniel Biro, MD, PhD – University of Chicago
Presenting Author: Yasmine Alkhalid, MD – The University of Chicago
Rationale:
Functional hemispherectomy is a highly effective treatment for medically refractory hemispheric epilepsy but carries significant morbidity. Furthermore as the objective is disconnection of the diseased hemisphere a more refined approach targeting fiber connections should be possible with the available functional imaging and stereotactic referencing avoiding maximally invasive and highly mechanical procedures. Given that the majority of patients are suffering from perinatal strokes with a distorted anatomy an image guided procedure based on fiber tracking seems ideal striving for higher efficacy, a more individualized approach and reduced morbidity.
Methods:
In patients undergoing an Interstitial laser hemispherectomy employing 3T MRI 32 direction DTI imaging pre- and post ablation tract-based spatial statistics (TBSS) was used to quantify voxel -level degrees of disconnection. In addition fractional anisotropy (FA) maps were created pre-and post ablation for interhemispheric and individual tracts namely the corpus callosum, cortico-spinal tract, uncinate fasciculus and arcuate fiber bundle. Presurgical tracts were used as controls in individual patients as normalized atlas maps were not applicable in these patients with distorted anatomy.
Results:
12 patients underwent an interstital laser hemispherectomy with a median follow-up of 2.0+0.8 years. Pathologies include perinatal and early childhood strokes as well as Sturge-Weber. 10 out of 12 patients had an Engel class I outcome with a median disconnection of 90+8.9% of all string-containing voxels in interhemispheric tracts. Only two asymptomatic hemorrhages were observed and median hospital stay was 2.1 days. TBSS showed that both patients who were not seizure-free had a remaining cluster in the splenium and the uncinate of 8.3 and 9.7% respectively compared to the rest with remaining clusters of 2.1+0.7% (p< 0.0001) and correspondingly FA maps showed a significantly higher delta value in the seizure-free group (p< 0.00001) . Measuring the distance between perceived anatomic tracts based on MR morphology and actual tracts identified by DTI showed up to 1.5 cm differences in the anterior-posterior axis and up to 1.8 cm in the medial-lateral axis.