Stereotactic laser ablation for completion corpus callosotomy

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Completion corpus callosotomy can offer further remission from disabling seizures when a prior partial corpus callosotomy has failed and residual callosal tissue is identified on imaging. Traditional microsurgical approaches to section residual fibers carry risks associated with multiple craniotomies and the proximity to the medially oriented motor cortices. Laser interstitial thermal therapy (LITT) represents a minimally invasive approach for the ablation of residual fibers following a prior partial corpus callosotomy. Here, the authors report clinical outcomes of 6 patients undergoing LITT for completion corpus callosotomy and characterize the radiological effects of ablation.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>A retrospective clinical review was performed on a series of 6 patients who underwent LITT completion corpus callosotomy for medically intractable epilepsy at Stanford University Medical Center and Lucile Packard Children’s Hospital at Stanford between January 2015 and January 2018. Detailed structural and diffusion-weighted MR images were obtained prior to and at multiple time points after LITT. In 4 patients who underwent diffusion tensor imaging (DTI), streamline tractography was used to reconstruct and evaluate tract projections crossing the anterior (genu and rostrum) and posterior (splenium) parts of the corpus callosum. Multiple diffusion parameters were evaluated at baseline and at each follow-up.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>Three pediatric (age 8–18 years) and 3 adult patients (age 30–40 years) who underwent completion corpus callosotomy by LITT were identified. Mean length of follow-up postoperatively was 21.2 (range 12–34) months. Two patients had residual splenium, rostrum, and genu of the corpus callosum, while 4 patients had residual splenium only. Postoperative complications included asymptomatic extension of ablation into the left thalamus and transient disconnection syndrome. Ablation of the targeted area was confirmed on immediate postoperative diffusion-weighted MRI in all patients. Engel class I–II outcomes were achieved in 3 adult patients, whereas all 3 pediatric patients had Engel class III–IV outcomes. Tractography in 2 adult and 2 pediatric patients revealed time-dependent reduction of fractional anisotropy after LITT.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>LITT is a safe, minimally invasive approach for completion corpus callosotomy. Engel outcomes for completion corpus callosotomy by LITT were similar to reported outcomes of open completion callosotomy, with seizure reduction primarily observed in adult patients. Serial DTI can be used to assess the presence of tract projections over time but does not classify treatment responders or nonresponders.</jats:p></jats:sec>

Emerging indications for stereotactic laser interstitial thermal therapy in pediatric neurosurgery

“…Fractional anisotropy (FA) can be used as a measure to quantify the anisotropic diffusion in white matter fiber tracts, reflecting the directionality and structural organization of white matter and may be used in planning or post-ablation evaluation of LITT callosotomy. This study showed that in four of the patients that had pre and postoperative FA data, including two pediatric patients, FA in the corpus callosum decreased after surgery, suggesting that the LITT procedure was effective at disrupting the organization and structure of the callosal fiber tracts [55]. Similar to other emerging indications for LITT, further work is necessary to characterize the long-term outcomes of LITT callosotomy.…”

“…LITT callosotomy can be complete, anterior two-thirds only, or complete callosotomy using additional laser trajectories (Figure 2). In a previous study investigating the effectiveness of LITT in completion callosotomy, two adult patients saw zero recurrence of targeted atonic seizures, while the remaining four (including two pediatric) saw substantial reduction in the frequency of their targeted atonic or generalized tonic clonic seizures [55]. Fractional anisotropy (FA) can be used as a measure to quantify the anisotropic diffusion in white matter fiber tracts, reflecting the directionality and structural organization of white matter and may be used in planning or post-ablation evaluation of LITT callosotomy.…”

Expanding the Treatment Landscape for Lennox-Gastaut Syndrome: Current and Future Strategies

“…Corpus callosotomy is performed either as an anterior two-thirds disconnection of corpus callosum or as a complete disconnection [158], generally performed either through an open approach via a standard craniotomy with the aid of an operating microscope, or alternatively via a mini-craniotomy with endoscope assistance, with the latter having the benefit of a smaller incision, minimised brain retraction, and lower postoperative pain [158]. More recently, a minimally invasive method-magnetic resonance imaging (MRI)-guided stereotactic laser interstitial thermal therapy (LITT)-has shown promising results in case reports [159][160][161][162][163][164][165][166][167]. In the largest study to date, investigating MRI-guided stereotactic laser anterior corpus callosotomy (SLACC) in 10 patients with LGS (median age 33 years, range 11-52 years), eight (80%) patients had > 80% reduction in drop attacks, of whom five (50%) became free of drop attacks, and six (60%) achieved > 80% seizure reduction, with two (20%) becoming seizure free [167].…”

Stereotactic laser anterior corpus callosotomy for Lennox‐Gastaut syndrome

“…Engel class I-II outcomes were achieved in all three adult patients, whereas all three pediatric patients had Engel III-IV outcomes. 21 Roland et al reported 11 pediatric callosotomy procedures performed with LITT, including five SLACC procedures primarily using a crossing-cannula technique. They found complete or near-complete freedom from targeted seizures in one of five patients, significant target seizure reduction in two, and minimal benefit in two.…”

“…A study of completion corpus callosotomy via LITT actually found fewer tract projections >1 month after surgery compared to postoperative day 1 in two patients; another patient had a splenial residual seen on delayed DTI, after DTI on postoperative day 1 failed to identify any crossing projections. 21 Finally, although DTI processing parameters were standardized, DTI acquisition parameters varied between patients and could have affected assessment of disconnection. Delayed follow-up DTI with uniform acquisition parameters could test the average 62% estimated disconnection reported in this study.…”