The role of intraoperative MRI in resective epilepsy surgery for peri-eloquent cortex cortical dysplasias and heterotopias in pediatric patients

Abstract

<jats:sec> <jats:title>OBJECTIVE</jats:title> <jats:p>Previous studies have demonstrated that an important factor in seizure freedom following surgery for lesional epilepsy in the peri-eloquent cortex is completeness of resection. However, aggressive resection of epileptic tissue localized to this region must be balanced with the competing objective of retaining postoperative neurological functioning. The objective of this study was to investigate the role of intraoperative MRI (iMRI) as a complement to existing epilepsy protocol techniques and to compare rates of seizure freedom and neurological deficit in pediatric patients undergoing resection of perieloquent lesions.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>The authors retrospectively reviewed the medical records of pediatric patients who underwent resection of focal cortical dysplasia (FCD) or heterotopia localized to eloquent cortex regions at the Children's National Health System between March 2005 and August 2015. Patients were grouped into two categories depending on whether they underwent conventional resection (n = 18) or iMRI-assisted resection (n = 11). Patient records were reviewed for factors including demographics, length of hospitalization, postoperative seizure freedom, postoperative neurological deficit, and need for reoperation. Postsurgical seizure outcome was assessed at the last postoperative follow-up evaluation using the Engel Epilepsy Surgery Outcome Scale.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>At the time of the last postoperative follow-up examination, 9 (82%) of the 11 patients in the iMRI resection group were seizure free (Engel Class I), compared with 7 (39%) of the 18 patients in the control resection group (p = 0.05). Ten (91%) of the 11 patients in the iMRI cohort achieved gross-total resection (GTR), compared with 8 (44%) of 18 patients in the conventional resection cohort (p = 0.02). One patient in the iMRI-assisted resection group underwent successful reoperation at a later date for residual dysplasia, compared with 7 patients in the conventional resection cohort (with 2/7 achieving complete resection). Four (36%) of the patients in the iMRI cohort developed postoperative neurological deficits, compared with 15 patients (83%) in the conventional resection cohort (p = 0.02).</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>These results suggest that in comparison with a conventional surgical protocol and technique for resection of epileptic lesions in peri-eloquent cortex, the incorporation of iMRI led to elevated rates of GTR and postoperative seizure freedom. Furthermore, this study suggests that iMRI-assisted surgeries are associated with a reduction in neurological deficits due to intraoperative damage of eloquent cortex.</jats:p></jats:sec>

<p>Histological type of focal cortical dysplasia is associated with the risk of postsurgical seizure in children and adolescents</p>

“…Recently, intraoperative MRI has been reported to be helpful in improving postoperative seizure freedom and reducing neurological deficits due to surgical damage 22. Intracranial electrode implantation was another significant predictive variable of unfavorable outcomes in our series.…”

Epilepsy surgery near or in eloquent cortex in children—Practice patterns and recommendations for minimizing and reporting deficits

“…Unfortunately, however, our ability to accurately predict seizure‐free outcomes is limited as there remains substantial ambiguity as to how EZ is defined. Within the context of discrete MRI lesions, a lesionectomy generally achieves seizure freedom in the majority of patients; the use of neuronavigation or intraoperative MRI helps to identify residual lesions that can be resected . Extending the resection to include EC revealing functional abnormality, that is, a “complete” resection, purportedly increases the rates of seizure freedom, but a substantial proportion of patients continue to have seizures .…”

“…With regard to language cortex, although most respondents accept age of 5 years as the upper limit beyond which plasticity starts to decline, a minority believed that full plasticity extended to the end of the first decade; a presumption that prompts resection strategies carrying risk of incurring long‐term deficits. Irrespective of one's biases toward the handling of EC, wider usage of protective strategies such as awake surgery when feasible, tractography and intraoperative navigation tools, and intraoperative functional mapping is justified and strongly recommended . There is also increasing emphasis on ensuring the integrity of white matter tracts via subcortical mapping to maximize preservation of eloquent function and deployment of minimally invasive surgical strategies …”

“…Within the context of discrete MRI lesions, a lesionectomy generally achieves seizure freedom in the majority of patients 19 ; the use of neuronavigation or intraoperative MRI helps to identify residual lesions that can be resected. 20 Extending the resection to include EC revealing functional abnormality, that is, a "complete" resection, purportedly increases the rates of seizure freedom, [21][22][23][24][25][26] but a substantial proportion of patients continue to have seizures. 27 Thus, one could argue against resecting EC uninvolved in a discrete anatomic lesion on the basis of functional abnormalities alone and in favor of adopting a staged strategy with an initial conservative EC-sparing resection in MRI lesional cases,…”

“…Irrespective of one's biases toward the handling of EC, wider usage of protective strategies such as awake surgery when feasible, tractography and intraoperative navigation tools, and intraoperative functional mapping is justified and strongly recommended. 3,20,32,33,34,35 There is also increasing emphasis on ensuring the integrity of white matter tracts via subcortical mapping to maximize preservation of eloquent function 36 and deployment of minimally invasive surgical strategies. 37 The respondents varied considerably in their expectation of the chances of seizure freedom that were considered acceptable thresholds to "justify" a new deficit ranging from 50% to exceeding 90%.…”