Abstracts

Rationale: Traditional open anterior temporal lobectomy and selective amygdalohippocampectomy (AH) are effective for treating mesial temporal lobe epilepsy (MTLE), but can be associated with cognitive deficits from collateral temporal lobe injury due to the surgical approach. We describe a novel minimally invasive stereotactic technique for producing an AH ablation in patients with medically intractable MTLE utilizing computer-controlled laser induced interstitial thermal therapy with real-time magnetic resonance thermal image guidance, and we report initial outcomes. Methods: 8 consecutive patients (ages 18-64 y) with medically intractable MTLE were offered standard AH or SLTAH and selected the latter. 2 patients were operated prior to initiation of a prospective clinical protocol, resulting in parahippocampal without hippocampal ablation. 7 patients (6 de novo; 1 with previous parahippocampal ablation) enrolled in the prospective clinical trial and were examined prospectively. A saline-cooled fiber optic laser applicator targeting anterior hippocampus and terminating in the amygdala was inserted from an occipital trajectory utilizing a stereotactic frame under general anesthesia. Laser energy was delivered during continuous MR imaging (Figure 1). Temperature-sensitive phase images and estimates of thermal damage during heating were superimposed on anatomical images in real-time. Prospective baseline and post-operative seizure diaries, quality of life measures, and neuropsychometric testing are being performed. Results: In the first 2 patients, both without mesial temporal sclerosis (MTS), ablations limited to the parahippocampal gyrus did not yield seizure-freedom. All subsequent procedures, with patients followed prospectively, produced technically successful anterior AH ablations. Of these, four patients with MTS were Engel class I at 3-6 months. Of 3 patients without MTS, 2 were Engel class II at 3-6 months (Figure2), and the third was Engel class IV (additional EEG monitoring revealed bilateral seizure onsets and non-epileptic seizures). One of original 2 patients underwent a repeat laser procedure resulting in successful amygdalohippocampotomy but also a homonymous hemianopsia possibly resulting from deflection of the introducing cannula superiorly through the thalamus . Conclusions: SLTAH is technically feasible with ablations consistently conforming to the mesial temporal structures without involving the thalamus or midbrain. Preliminary results indicate that seizure outcomes with SLTAH might differ in patients with and without MTS. The safety and efficacy of SLTAH, an appealing minimally-invasive approach, needs to be carefully evaluated with larger cohorts over periods of at least one year.