Low grade gliomas: comparison of intraoperative ultrasound characteristics with preoperative imaging studies

Abstract

Thirty-three patients with low grade gliomas were evaluated with preoperative computed tomography (CT), magnetic resonance (MR) and intraoperative ultrasound (IOUS). Six patients had undergone previous surgical exploration. Tumor borders were marked with cortical letters and corresponding depths calculated. Resection of tumor corresponded to these ultrasound dimensions. The histology of biopsy specimens from tumor and ultrasound determined margins was studied on formalin fixed permanent sections using hematoxylin and eosin (H&E) and immunocytochemistry (GFAP). Tumors were all seen on preoperative MR studies and most commonly showed a decreased T1 and increased T2 signal. Seven tumors showed variable enhancement with gadolinium. On CT two tumors were not seen, twenty-three tumors were hypodense and eight hyperdense. Three tumors showed variable CT contrast enhancement. All tumors were hyperechoic on ultrasound. Twenty-five (75%) tumors were well defined with distinct margins compared to adjacent brain. Eight tumors had poorly defined borders on ultrasound; five (62%) of these lesions had previously undergone surgery. Eight tumors invaded functional brain identified by stimulation mapping techniques (e.g., speech cortex), thus limiting the resection. Five resections were limited because of involvement of important anatomical structures (e.g., corpus callosum). Of the remaining 20 tumors, seventeen (85%) had ultrasound defined margins that were histologically free of solid tumor (normal brain or sparse atypical cells only). Low grade gliomas are readily identified and their margins well defined by intraoperative ultrasound regardless of preoperative imaging patterns. The results suggest that IOUS may enhance intraoperative delineation and extent of resection for low grade gliomas.

Correlation of intra-operative ultrasound with histopathologic findings after tumour resection in supratentorial gliomas

“…[51] had shown for low-grade gliomas, correlating the sonographic with histopathological findings, that IOUS may influence gross total tumour resection. According to their findings the preoperative sonographically determined tumour-borders reliably reflect tumour extension.…”

The value of intraoperative sonography in low grade glioma surgery

“…On the other hand the hyperechoic rim around the resection cavity is a non-specific finding [13]. Even edema could be distinguished from solid tumor and improve tumor extension as shown in a study by LeRoux [9,10]. In our experience however, intra-operative ultrasound was very useful in identifying the tumor and delineating its margins before starting tumor removal.…”

“…Apart from this, intraoperative MRI is expensive and not available in every neurosurgical center whereas ultrasonography is associated with lower costs. Intraoperative ultrasound identifies low grade gliomas as hyperechoic and homogenous tumors and helps to localize subcortical lesions under a normal appearing brain surface [8][9][10]. At the beginning of the use of ultrasound by Reid in 1978 [11] the image quality was low therefore the method was not used by neurosurgeons routinely.…”

Fusion imaging for intra-operative ultrasound-based navigation in neurosurgery

“…In our opinion, the main application of this technique is surely for intra-parenchymal tumors removal, because iUS can be of help in identifying the lesion and residual mass with great sensitivity [21,22], but we should not underestimate its use in skull base tumors, abscesses, cysts, hematomas or aneurysms.…”