EDUCATION CORNER

Minimally Invasive Options in Neurosurgery: MRI-guided Laser Ablation Therapy

George Koutsouras, DO; Zulma Tovar-Spinoza, MD
Department of Neurosurgery, SUNY Upstate Medical University,
Syracuse New York

Zulma Tovar-Spinoza, MD
Zulma Tovar-Spinoza, MD
MRI-guided laser interstitial thermal therapy (MRIgLITT) is a burgeoning field in neurosurgery used to treat various intracranial pathologies, including neoplastic lesions, epileptic foci and radiation-induced necrosis. Initially, most commonly treated by MRIgLITT were high grade gliomas and metastatic intracranial tumors.1

MRIgLITT uses thermal thin-laser delivered energy to destroy tissue by generating heat through the absorption of light. The energy generated aims to disrupt intracellular DNA, creating breaks in DNA and initiating apoptotic processes. This minimally invasive intervention is an option for refractory epilepsy cases and deep tumors or lesions where extensive surgical resections may be difficult. Additionally, patients may be unable to sustain tumor or epileptogenic foci resection due to their health condition, low functional status, and inability to tolerate general anesthesia.1,2 Therefore, alternative therapies, such as MRIgLITT and other minimally invasive treatments may be indicated.

Procedure
The procedure is typically conducted with a stereotactic frame that is placed on the patient’s head or through navigation guided technology. The surgery can be performed under local anesthesia, moderate sedation or general anesthesia. A drill hole through the skull is first made, and a bone anchor is inserted into the hole. A MRI-compatible laser applicator is inserted into the lesion and the ablation is performed under MRI guidance. The laser uses a cooling system to diminish the heat from the probe tissue interface, minimizes vaporization, creates greater tissue treat volumes and allows for less probe failure by decreasing adherence of the laser probe to tissue.3 Real time magnetic resonance thermography allows thermal mapping, providing precision of the treated area. The laser can be repositioned by the surgeon to increase the area of ablation until completing the presurgical planned target.3

Postoperative Edema
Mild post ablation edema is the major concern following ablation. As an expected complication of the ablation, this edema may be prophylactically treated with intraoperative steroids and with a course of steroids postoperatively. Patients are admitted to the intensive care unit or step-down post operatively for at least a day. Due to the decreased incision size, patients typically have a short hospital course postoperatively.4 In the case of refractory edema, alternative agents such as VEGF inhibitors, bevacizumab may be used.5 Case discussions recommend the number of laser insertion sites to three at most to limit the extent of edema.

LITT Indications 
Neoplastic lesions:
The literature on the utility of MRIgLITT is growing with expanding usage in various benign and malignant neoplastic processes in both adults and children. In malignant gliomas and metastatic tumors, MRIgLITT therapy can be provided to a patient as first or second line therapy. However, the literature is not entirely clear as to the benefit of MRIgLITT in first line therapy, as surgical resection may be standard of care in resectable tumors. In a meta-analysis, studying malignant gliomas where cytoreduction is the standard of care, MRIgLITT provides comparable survival outcomes to cytoreductive surgery in high grade gliomas, as well as up to five months of progression free survival in recurrent high grade gliomas.6

Nevertheless, case reports have aimed to expand the role of MRIgLITT in cases that are deep in eloquent areas, such as in the corpus callosum tumors7 and large >10cm3 that may be in the thalamus or insula.8 In pediatric brain tumors, MRIgLITT may be an effective first or second line treatment as studies demonstrate tumor size decreases in short term follow ups (<6 months).9

Radiation necrosis:
LITT for radiation necrosis is also novel in its utility. A study conducted in Henry Ford Hospital demonstrated a decrease in radiation necrosis volume six months after follow-up ablation; however, no comparison group was studied. Occurring in up to 5-10% of patients following radiosurgery or radiotherapy, radiation necrosis can cause neurological deficits secondary to the lesion itself as well as surrounding edema. Literature details the usefulness of MRIgLITT in decreasing the lesion, the surrounding edema and resulting mass effect.10,11,12

Epilepsy:
The application of MRIgLITT for medically refractory epilepsy for lesionectomy or disconnection of epileptogenic foci is an active field.3 MRIgLITT has been used in cortical dysplasias, tumors (i.e hypothalamic hamartomas), cavernomas, corpus callosotomy and tuberous sclerosis.13 Long-term follow-up precludes the full investment of MRIgLITT in these cases; however short-term follow-up and case studies demonstrate epilepsy activity decrease post ablation.14,15

Conclusion
The promising nature of MRIgLITT therapy as an alternative form of treatment in intracranial pathologies continues to be a source of investigation. Utilizing 3-D printing reconstructions2 allows easier to decrease operative time and decreased need for stereotactic frame, and even robotic assisted devices for trajectory planning4 are under careful study. Evidence outlining the long-term results of MRIgLITT therapy in the treatments of malignant gliomas, brain tumors and metastasis, epilepsy and radiation necrosis continues to be encouraged.

References

  1. Missios S, Bekelis K, Barnett GH: Renaissance of laser interstitial thermal ablation. Neurosurg Focus 38:E13, 2015.
  2. Tovar-Spinoza Z, Choi H: Magnetic resonance-guided laser interstitial thermal therapy: report of a series of pediatric brain tumors. J Neurosurg Pediatr 17:723-733, 2016.
  3. Tovar-Spinoza Z, Carter D, Ferrone D, Eksioglu Y, Huckins S: The use of MRI-guided laser-induced thermal ablation for epilepsy. Childs Nerv Syst 29:2089-2094, 2013.
  4. Carpentier A, McNichols RJ, Stafford RJ, Guichard JP, Reizine D, Delaloge S, et al: Laser thermal therapy: real-time MRI-guided and computer-controlled procedures for metastatic brain tumors. Lasers Surg Med 43:943-950, 2011.
  5. Maraka S, Asmaro K, Walbert T, Lee I: Cerebral edema induced by laser interstitial thermal therapy and radiotherapy in close succession in patients with brain tumor. Lasers Surg Med, 2018.
  6. Ivan ME, Mohammadi AM, De Deugd N, Reyes J, Rodriguez G, Shah A, et al: Laser Ablation of Newly Diagnosed Malignant Gliomas: a Meta-Analysis. Neurosurgery 79 Suppl 1:S17-S23, 2016.
  7. Beaumont TL, Mohammadi AM, Kim AH, Barnett GH, Leuthardt EC: Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy for Glioblastoma of the Corpus Callosum. Neurosurgery, 2018.
  8. Wright J, Chugh J, Wright CH, Alonso F, Hdeib A, Gittleman H, et al: Laser interstitial thermal therapy followed by minimal-access transsulcal resection for the treat
  9. Tovar-Spinoza Z, Choi H: Magnetic resonance-guided laser interstitial thermal therapy: report of a series of pediatric brain tumors. J Neurosurg Pediatr 17:723-733, 2016.
  10. Rammo R, Asmaro K, Schultz L, Scarpace L, Siddiqui S, Walbert T, et al: The safety of magnetic resonance imaging-guided laser interstitial thermal therapy for cerebral radiation necrosis. J Neurooncol 138:609-617, 2018.
  11. Chan AY, Tran DK, Gill AS, Hsu FP, Vadera S: Stereotactic robot-assisted MRI-guided laser thermal ablation of radiation necrosis in the posterior cranial fossa: technical note. Neurosurg Focus 41:E5, 2016.
  12. Rahmathulla G, Recinos PF, Valerio JE, Chao S, Barnett GH: Laser interstitial thermal therapy for focal cerebral radiation necrosis: a case report and literature review. Stereotact Funct Neurosurg 90:192-200, 2012.
  13. Tovar-Spinoza Z, Ziechmann R, Zyck S: Single and staged laser interstitial thermal therapy ablation for cortical tubers causing refractory epilepsy in pediatric patients. Neurosurg Focus 45 (3): E9, 2018.
  14. Curry DJ, Gowda A, McNichols RJ, Wilfong AA: MR-guided stereotactic laser ablation of epileptogenic foci in children. Epilepsy Behav 24:408-414, 2012
  15. Waseem H, Vivas AC, Vale FL: MRI-guided laser interstitial thermal therapy for treatment of medically refractory non-lesional mesial temporal lobe epilepsy: Outcomes, complications, and current limitations: A review. J Clin Neurosci 38:1-7, 2017.

Back to top