Revisiting Intraoperative 2D USG with Saline-Air Mixture as Contrast for Resection of Eloquent Area Glioma in Resource-Deficient Countries.

 Advanced ultrasound, intraoperative magnetic resonance imaging (MRI), neuromonitoring, and aminolevulenic acid have improved the resection and safety of eloquent area gliomas. However, availability of these modern gadgets is a major concern in resource-deficient countries. A two-dimensional ultrasonography 2D USG is cheaper, provides real-time imaging, and is already established but underutilized instrument.  Here, we revisited the principles of 2D USG and used it for eloquent-area glioma surgery.  Fifty-eight patients with eloquent area gliomas were operated in last 2 years with the aid of 2D USG with 6-13 MHz curvilinear probe. Preoperative diagnosis was high-grade glioma in 38 and low-grade glioma (LGG) in 20 patients. Tumors were categorized as predominantly hyperechoic (27), uniformly hyperechoic (7), mixed echogenicity (21), and cystic (3).  Intraoperatively, 2D USG could define the tumor margins in 46 cases. Of these, USG suggested gross total excision in 38 patients and subtotal in 8 patients. The findings matched with follow-up MRI in 34 patients who showed hyperechogenicity (predominant/uniform). Injecting saline with air in to the resection cavity and insinuating through adjacent brain parenchyma helped in detecting residual lesion in three cystic gliomas and in two LGG where the tumor cavity collapsed.  2D USG is a helpful tool in eloquent area glioma surgery, especially in resource-limited countries. Visualization through adjacent parenchyma and injection of saline-air mixture in to the resection cavity helped in delineating residual lesion. Extent of resection is best monitored by 2D USG when tumor appeared hyperechoic (predominant/uniform).