Thermal injury to corticospinal tracts and postoperative motor deficits after laser interstitial thermal therapy

Abstract

<jats:sec> <jats:title>OBJECTIVE</jats:title> <jats:p>Laser interstitial thermal therapy (LITT) has been increasingly used to treat deep-seated tumors. Despite its being minimally invasive, there is a risk of LITT damaging adjacent critical structures, including corticospinal tracts (CSTs). In this study, the authors investigated the predictive value of overlap between the hyperthermic field and CSTs in determining postoperative motor deficit (PMDs).</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>More than 140 patients underwent an LITT procedure in our institution between April 2011 and June 2015. Because of the tumor's proximity to critical structures, 80 of them underwent preoperative diffusion tensor imaging and were included in this study. Extent of the hyperthermic field was delineated by the software as thermal-damage-threshold (TDT) lines (yellow [43°C for 2 minutes], blue [43°C for 10 minutes], and white [43°C for 60 minutes]). The maximum volume and the surface area of overlaps between motor fibers and the TDT lines were calculated and compared with the PMDs.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>High-grade glioma (n = 46) was the most common indication for LITT. Postoperative motor deficits (partial or complete) were seen in 14 patients (11 with permanent and 3 with temporary PMDs). The median overlap volumes between CSTs with yellow, blue, and white TDT lines in patients with any PMD (temporary or permanent) were 1.15, 0.68, and 0.41 cm<jats:sup>3</jats:sup>, respectively. The overlap volumes and surface areas revealed significant differences in those with PMDs and those with no deficits (p = 0.0019 and 0.003, 0.012 and 0.0012, and 0.001 and 0.005 for the yellow, blue, and white TDT lines, respectively). The receiver operating characteristic was used to select the optimal cutoff point of the overlapped volumes and areas. Cutoff points for overlap volumes and areas based on optimal sensitivity (92%–100%) and specificity (80%–90%) were 0.103, 0.068, and 0.046 cm<jats:sup>3</jats:sup> and 0.15, 0.07, and 0.11 mm<jats:sup>2</jats:sup> for the yellow, blue, and white TDT lines, respectively.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>Even a minimal overlap between the TDT lines and CSTs can cause a PMD after LITT. Precise planning and avoidance of critical structures and important white matter fibers should be considered when treating deep-seated tumors.</jats:p></jats:sec>

Ablation dynamics during laser interstitial thermal therapy for mesiotemporal epilepsy

“…To compare TDE maps with postoperative ablation zone boundaries, the 2D TDE maps were rigidly deformed to the intraoperative MRIs and visualized together with slices of the manually-traced ablation volumes through the same imaging plane as the TDE maps. Pixel overlap between two regions (A and B) aligned in the same imaging cut was calculated using the dice similarity coefficient (DSC): which ranges from 0 to 1, where 0 indicates no overlap and 1 indicates complete overlap [ 12 , 22 , 27 ].…”

“…However, the accuracy of TDE maps at predicting LITT ablation zone boundaries is not clear. Although recent reports on the topic do suggest these estimates generally are accurate, variability has been observed [ 9 , 20 – 22 ]. Limitations of these prior studies is their focus on brain tumors, where ablation targets vary tremendously in size, shape, and location, and lack of proper image normalization tools.…”

Laser thermal therapy in the management of high-grade gliomas

“…Tractography has been used with LITT in order to avoid the damage of the white matter pathways around the tumor. Sharma et al study the extent of involvement of the corticospinal tract by the threshold lines defined in the NeuroBlate System [63]. They showed that even minimal involvement of the CST by the ablation area can cause motor deficit after ablation.…”

The use of laser interstitial thermal therapy in the treatment of brain metastases: a literature review

“…Tumor location plays a major role in neurological outcomes for patients treated with LITT [35]. Thermal damage to eloquent white matter tracts is the major cause of neurological deficits [45]. For lesions with large volume and important mass effect pre-operatively, it is important to be aware of potential symptomatic cerebral edema [46].…”