Abstract
ObjectiveGiant insular tumors are commonly not amenable to complete resection and are associated with a high postoperative morbidity rate. Transcortical approach and brain mapping techniques allow to identify peri-insular functional networks and, with neurophysiological monitoring, to reduce vascular-associated insults. Cognitive functions to be mapped are still under debate, and the analysis of the functional risk of surgery is currently limited to neurological examination. This work aimed to investigate the neurosurgical outcome (extent of resection, EOR) and functional impact of giant insular gliomas resection, focusing on neuropsychological and Quality of Life (QoL) outcomes.MethodsIn our retrospective analysis, we included all patients admitted in a five-year period with a radiological diagnosis of giant insular glioma. A transcortical approach was adopted in all cases. Resections were pursued up to functional boundaries defined intraoperatively by brain mapping techniques. We examined clinical, radiological, and intra-operative factors possibly affecting EOR and postoperative neurological, neuropsychological, and Quality of Life (QoL) outcomes.ResultsWe finally enrolled 95 patients in the analysis. Mean EOR was 92.3%. A Gross Total Resection (GTR) was obtained in 70 cases (73.7%). Five patients reported permanent morbidity (aphasia in 3, 3.2%, and superior quadrantanopia in 2, 2.1%). Suboptimal EOR associated with poor seizures control postoperatively. Extensive intraoperative mapping (inclusive of cognitive, visual, and haptic functions) decreased long-term neurological, neuropsychological, and QoL morbidity and increased EOR. Tumor infiltration of deep perforators (vessels arising either medial to lenticulostriate arteries through the anterior perforated substance or from the anterior choroidal artery) associated with a higher chance of postoperative ischemia in consonant areas, with the persistence of new-onset motor deficits 1-month post-op, and with minor EOR. Ischemic insults in eloquent sites represented the leading factor for long-term neurological and neuropsychological morbidity.ConclusionIn giant insular gliomas, the use of a transcortical approach with extensive brain mapping under awake anesthesia ensures broad insular exposure and extension of the surgical resection preserving patients’ functional integrity. The relation between tumor mass and deep perforators predicts perioperative ischemic insults, the most relevant risk factor for long-term and permanent postoperative morbidity.
Highlights
Resection of insular gliomas always represented a challenge for neurosurgeons because of the complex functional involvement of the insular lobe and opercula and the intricate vascularization of the area
Each insular zone presents a different degree of surgical accessibility and functional and vascular involvement; generally, tumors belonging to zones I and IV are those with the higher chance of complete resection, while tumors localized in zones II and III present major surgical difficulties, a minor extent of resection, and a higher rate of permanent morbidity
The transopercular corridor to get to the insula is delimited, in the frontal lobe, by the superior longitudinal fascicle III (SLF III) and the arcuate fascicle (AF) long segment superiorly, the AF posterior segment postero-superiorly; in the temporal lobe, by the AF terminations in the posterior portion of the superior temporal gyrus, the inferior frontooccipital fasciculus (IFOF) and optic radiations superiorly and posteriorly, and the inferior longitudinal fascicle (ILF) inferiorly and posteriorly
Summary
Resection of insular gliomas always represented a challenge for neurosurgeons because of the complex functional involvement of the insular lobe and opercula and the intricate vascularization of the area. Each insular zone presents a different degree of surgical accessibility and functional and vascular involvement; generally, tumors belonging to zones I and IV (anterosuperior and anteroinferior quadrants, respectively) are those with the higher chance of complete resection, while tumors localized in zones II and III (posterosuperior and posteroinferior quadrants, respectively) present major surgical difficulties, a minor extent of resection, and a higher rate of permanent morbidity. Insular gliomas occupying all four zones are termed “giant” and are the most demanding: they are less amenable of complete resection and, in the most extensive series, associated with the highest rate of neurological morbidity due to delicate surgical access to this area, frequent larger tumor volume at diagnosis, and involvement of many surrounding functional networks and vascular structures [3,4,5,6]. Main vascular structures to deal with the insular lobe include: the middle cerebral artery (MCA) and its opercular branches anteriorly and laterally; the lenticulostriate arteries (LSA complex); and other deep perforators arising from the anterior choroidal artery (AChA)
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