Introduction: MRI Guided Laser interstitial thermal therapy (LITT) has emerged as a promising treatment for mesial temporal lobe epilepsy. Surgeons must understand the relevant anatomy that is traversed by the catheter, and potentially affected by ablation.
Methods: Three human cadaveric heads were implanted with laser catheters using a frameless stereotactic technique. MRI confirmed the satisfactory location of the catheter. The Visualase system (Medtronic,Inc) was utilized to ablate along the trajectory. Coronal and oblique axial slices were created. Fiber tract dissections were performed in a lateral-medial and inferior-superior scheme. Magnetic resonance tractography was acquired to illustrate the tracts dissected in relation to the catheter.
Results: Entry points occurred within 4 cm of the transverse and sagittal sinus, inferior to the lambdoid suture. The cortex of the inferior occipital gyrus was crossed in the region of the transverse occipital sulcus. The vertical occipital fasciculus was crossed en route to passing through the optic radiations. Much of the trajectory passed superior to the inferior longitudinal fasciculus. The catheter crossed through or inferior to the optic radiations before piercing the parahippocampal gyrus at about 4cm from the skull. The catheter entered the hippocampus as it pierced the superior margin of the parahippocampus at 6cm. The catheter pierced the head of the hippocampus to lie inferolateral to the amygdala in the last centimeter of the trajectory. Lateral deviation at the head may affect Meyer’s loops during ablation.
Conclusions: A strong understanding of the anatomic principles of laser trajectories will improve the ability to perform this procedure. This is the first study to examine the anatomy of the laser trajectory, and will hopefully create a foundation for future studies. This is one of the final projects conducted in the late Dr. Albert Rhoton’s lab, and it was his vision to see this project in its completion.
Patient Care: A strong understanding of the anatomic principles of laser trajectories will improve the ability to perform stereotactic laser amygdalohippocampotomy for our patients more safely.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the tracts related to amygdalohippocampotomy, 2) Describe the structures targeted in stereotactic amygdalohippocampotomy, 3) Identify the anatomy of an effective option to treat to epilepsy.