Introduction: Laser ablation is becoming a key component of the neurosurgeon’s arsenal, with clear applications in the treatment of tumors and epilepsy. While structures with regular shapes can be readily targeted with a laser, complex structures are a challenge. Directional lasers represent a solution to this problem. Here we report the first application of a directional laser for volumetric ablation of the hippocampus and amygdala. We also discuss an alternative strategy for lesioning irregularly contoured structures.
Methods: A 24 year old man with intractable complex partial epilepsy, found to have a right mesial temporal seizure focus, was deemed a candidate for laser ablation therapy of the amygdala and hippocampus. This was done successfully using the directional NeuroBlate™ (Monteris Inc, Minneapolis) laser probe. Figure 1a shows a coronal post-ablation MRI – the ablation zone is directed relative to the probe’s position. Figure 1b shows a previous case where a diffuse tip laser was used.
Separately, Vanderbilt Engineering and Neurosurgery have prototyped a robot that steers a needle through foramen ovale and takes non-linear path to a target using MRI guidance (Figure 2). Named MERLIN (MRI-Enabled Robotic non-Linear Incision-less Neurosurgery), it may help redefine the treatment of tumors, epilepsy, and low-flow vascular lesions.
Results: The directional laser achieved a radial ablation distance of 1.2cm (half this distance in the opposite direction). This allowed contouring of the target in regions that would otherwise be difficult to lesion. The ablation has, to date, achieved the goal of seizure freedom.
Conclusions: We present the first successful ablation of the hippocampus/amygdala using a directional laser. MERLIN represents an alternative strategy for ablating irregular contours. Its use of anatomical foramina and curved trajectories to reach targets without violating eloquent brain may be a foundation for minimally-invasive MRI-guided ablation techniques for the treatment of complex lesions.
Patient Care: It will help lay the foundation for maximally-precise, minimally-invasive lesioning of targets in the brain such as tumors, seizure foci, and low-flow vascular lesions.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the advantages of directional laser ablation, and 2) Describe the strategy behind the MERLIN robot, and 3) List various types of lesions that can be treated with laser/thermal ablation.