Resection of insular gliomas: the importance of lenticulostriate artery position

Clinical article

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Object

The object of this study was to identify characteristic preoperative angiographic and MR imaging features of safely resectable insular gliomas and describe the surgical techniques and postoperative clinical outcomes.

Methods

Thirty-eight patients with insular gliomas underwent transsylvian resection between 1995 and 2007. Patient demographics, presenting symptoms, pathological findings, and neurological outcomes were retrospectively reviewed. Preoperative MR imaging–defined tumor volumes were superimposed onto the preoperative stereotactic cerebral angiograms to determine whether the insular tumor was confined lateral to (Group I) or extended medially around (Group II) the lenticulostriate arteries (LSAs).

Results

Twenty-five patients (66%) had tumors situated lateral to the LSAs and 13 (34%) had tumors encasing the LSAs. Insular gliomas situated lateral to the LSAs led to significant medial displacement of these vessels (161 ± 39%). In 20 (80%) of these 25 cases the boundaries between tumor and brain parenchyma were well demarcated on preoperative T2-weighted MR images. In contrast, there was less displacement of the LSAs (130 ± 14%) in patients with insular gliomas extending around the LSAs on angiography. In 11 (85%) of these 13 cases, the tumor boundaries were diffuse on T2-weighted MR images. Postoperative hemiparesis or worsening of a preexisting hemiparesis, secondary to LSA compromise, occurred in 5 patients, all of whom had tumor volumes that extended medial to the LSAs. Gross-total or near-total resection was achieved more frequently in cases in which the insular glioma remained lateral to the LSAs (84 vs 54%).

Conclusions

Insular gliomas with an MR imaging–defined tumor volume located lateral to the LSAs on stereotactic angiography displace the LSAs medially by expanding the insula, have well-demarcated tumor boundaries on MR images, and can be completely resected with minimal neurological morbidity. In contrast, insular tumors that appear to surround the LSAs do not displace these vessels medially, are poorly demarcated from normal brain parenchyma on MR images, and are associated with higher rates of neurological morbidity if aggressive resection is pursued. Preoperative identification of these anatomical growth patterns can be of value in planning resection.

Abbreviations used in this paper: ICA = internal carotid artery; LSA = lenticulostriate artery; MCA = middle cerebral artery; MEP = motor evoked potential; SSEP = somatosensory evoked potential.

Article Information

Address correspondence to: Patrick J. Kelly, M.D., Department of Neurosurgery, New York University Medical Center, 530 First Avenue, Suite 8R, New York, New York 10016. email: patrick.kelly@med.nyu.edu.

© AANS, except where prohibited by US copyright law.

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Figures

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    Cerebral angiogram and MR image obtained in a patient with a large left-sided insular glioma that extended into the basal frontal and temporal lobes. The LSAs are seen to arise (B) from the M1 segment of the MCA and are massively displaced medially (C) supplying the basal ganglia and internal capsule. Numerous small insular arteries (D) that arise from the M2 division of the MCA (A) on the surface of the insula are also seen. The insular arteries (D) that normally supply the insular cortex, claustrum and extreme capsule are enlarged and supply most of the large tumor mass.

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    Artist's illustration depicting the 2 types of insular gliomas that were differentiated by superimposing the MR imaging–defined tumor volume onto the stereotactic cerebral angiogram. In one tumor type (left), the LSAs were medially displaced by an insular mass that remained confined lateral to these vessels (Group I). These tumors often had sharp boundaries on T2-weighted MR images. This tumor type confers the most favorable anatomical arrangement for resection without neurological morbidity. In the other tumor type (right), the LSAs were coursing through the tumor volume as the tumor expanded brain parenchyma both medial and lateral to these vessels (Group II). These tumors often had diffuse appearing boundaries from surrounding brain tissue on T2-weighted MR images. This tumor type provides an unfavorable condition for aggressive resection.

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    Representative stereotactic cerebral angiograms demonstrating the LSAs in 2 patients with intrinsic insular gliomas. Outlines of the T2-weighted MR imaging–defined tumor volume reconstructed in an anterior–posterior plane are displayed overlying the ICA cerebral angiogram. The relationship of the medial tumor boundary to the LSAs can be visualized. Tumors were classified as either confined to the insula and lateral to the LSAs (Group I, left) or involving the basal ganglia and encasing the LSAs (Group II, right).

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    Preoperative cerebral angiogram and pre- and postoperative contrast-enhanced T1- and T2-weighted MR images obtained in 4 representative patients with intrinsic insular gliomas. A: Images obtained in a 36-year-old man who had a generalized tonic-clonic seizure and was found to have a well-circumscribed right-sided insular glioma extending into the temporal root. Stereotactic imaging demonstrated that the lesion was confined lateral to the LSAs, which were medially displaced (Group I). During surgery the tumor was noted to be rubbery, and a surgical plane was easily developed. Postoperatively, the patient remained neurologically intact, and pathological examination revealed a low-grade mixed glioma. B: Images obtained in a 35-year-old woman who had a complex partial seizure and was found to have a well-circumscribed right-sided insular glioma extending into the anterior temporal lobe. The LSAs were medially displaced and the tumor was located completely lateral to these vessels when evaluated with stereotactic imaging (Group I). A surgical plane was easily developed during surgery. Postoperatively the patient remained neurologically intact and pathological examination revealed a ganglioglioneurocytoma. C: Images obtained in a 33-year-old man who presented with generalized tonic-clonic seizures and was found to have a right-sided poorly circumscribed insular glioma extending into the lateral putamen and the anterior temporal lobe. The LSAs appeared to go through the center of the tumor, which extended medially into the basal ganglia on stereotactic imaging (Group II). The patient underwent a grosstotal resection of both insular and anterior temporal components with no intraoperative diminution of SSEP and MEP recordings. Postoperatively he had a left-sided hemiparesis, and small infarcts within the posterior limb of the internal capsule were observed on postoperative MR images, probably secondary to lenticulostriate compromise. Pathological examination revealed an oligodendroglioma. D: Images obtained in a 38-year-old man who presented with a generalized seizure and was found to have a poorly circumscribed insular glioma extending into the putamen and the internal capsule. The LSAs were noted to course through the lesion, which extended into the basal ganglia (Group II). The patient underwent a transsylvian resection that was stopped once the LSAs were encountered in the medial aspect of the tumor. Tumor extending medial to these vessels was not pursued aggressively. Postoperatively the patient remained neurologically intact and pathological examination revealed an oligodendroglioma.

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