PMC4268349_01
Preoperative MRI (top), PET (middle) and SPECT (bottom) demonstrating left insular encephalomalacia and associated hypometabolism.
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MRI performed with seizure protocol revealed a loss of architecture in the left hippocampal head and body as well as increased FLAIR signal throughout the left hippocampus. MRI also revealed a region of encephalomalacia with gliosis at the junction of the left frontal and temporal opercula within the frontal insular region suggesting a previous subclinical ischemic insult (Figure 1). PET scan demonstrated hypometabolism in the left insula (Figure 1).
Skull X-Rays showing invasive monitoring electrodes. Anterior-Posterior (left) and lateral (right) images show subdural electrocorticography strips placed through a single middle cranial fossa burr hole and a single multi-contact depth electrode placed with frameless stereotactic navigation through a frontal burr hole.
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F2
The depth electrode trajectory was from a frontal burr hole and multiple subdural electrodes were placed via a single middle-cranial fossa burr hole (Figure 2).
Targeting lesion for LITT. (A) AXiiiS mini-frame is mounted to the skull and (B) intraoperative navigation probe aligned through AXiiis mini-frame. (C) A burr hole is drilled for probe placement.
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The Monteris AXiiiS Stereotactic Mini-Frame was affixed to the skull (Figure 3A) and the Stealth Navigus probe (Medtronic Inc., Minneapolis MN, USA) was inserted into the AXiiiS mini-frame (Figure 3B). Both ablation trajectories were selected via the single access burr hole (Figure 3C).
Pre-ablation intraoperative MRI confirming laser probe location within the left insular target location on coronal (left) and sagittal (right) T1-weighted images.
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The probe was inserted via trajectories from the apex of the skull, and the ablation of the posterior portion of the defined seizure focus was delivered following confirmation of probe placement (Figure 4).
Intraoperative thermometry and thermal dosage lines (TDL) for ablation of epilepsy focus. (A) Intraoperative thermometry and TDL are shown for 45  C dose (left) and 52  C dose (right). Green area indicates thermometry monitoring zone and green line encompasses the target. Bold yellow line indicates 2nd trajectory 45  C TDL and light yellow line indicates 1st trajectory 45  C TDL. Bold blue line indicates 2nd trajectory 52  C TDL and light blue line indicates 1st trajectory 52  C TDL. Regions of color within the treatment zone represent thermometry recording illustrated within. Thermometry reference bar with  C is shown in center. (B) Cumulative TDLs are shown relative to target lesion (green) in axial, coronal and sagittal planes for 45  C TDL (yellow) and 52  C TDL (blue).
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Intraoperative thermal dosage lines and thermometry data confirmed successful laser ablation of the anterior portion of the insular encephalomalacia was completed (Figure 5).
Radiographic effects of laser interstitial thermal ablation of left insular epilepsy focus. Axial T1-weighted, fluid-attenuated inversion recovery (FLAIR) and T1-weighted with gadolinium MRI images are shown preoperatively (A), 1 day postoperatively (B) and 5-months post-operatively (C).
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This region corresponds to high intensity on T2-weighted MRI, surrounded by peri-lesional edema. T1-weighted images with gadolinium contrast show some new enhancement suggesting breakdown of blood brain barrier (Figure 6).