The sole goal of stereotactic biopsy of brain lesions is to obtain a diagnosis. Owing to HGG histological heterogeneity, undergrading of the tumor occurs at a rate of approximately 10%. Overall risks from biopsy include anesthesia, bleeding, infection, and obtaining non-diagnostic tissue. The reported complication rates vary from 1% to 5%, while mortality rates are reported as 0-3% . Frameless sterotactic techniques provide the advantage of avoiding the discomfort of frame placement, but the disadvantage of some loss of accuracy. Typically, frame-based techniques offer accuracy within 5 mm.
When using general anesthesia, it is important to simulate the conditions at the time of the scan to maintain accuracy. Therefore, mannitol, hyperventilation and other methods for lowering ICP should not be used (unless they were also used during the time of scan acquisition). Following standard prepping and draping, a small incision is made. The entry site is chosen to provide the shortest, yet safest, course from the cortical surface to the lesion. Obvious regions to avoid include major blood vessels, the Sylvian fissure, and sulci. If the ventricle is entered, it is important not to remove CSF, as this may permit displacement of the target. A target site is chosen that will provide the most accurate diagnosis. Areas of enhancement and necrosis are more likely to yield the diagnosis of
HGG. Following tissue acquisition, frozen-section pathology helps to ensure that tumor tissue has been obtained. If this is not the case, a second target site should be sampled. If bleeding occurs with the biopsy, instillation of 0.1-0.3 cm3 of thrombin solution through the biopsy instrument may be helpful. However, significant hemorrhages may require open intervention. A post-operative CT scan is routinely obtained to verify the target site sampled and confirm that there has been no significant bleeding. It has been our practice to retain biopsy patients in the hospital overnight. Because the wound is small, radiotherapy may commence as soon as a final diagnosis has been provided by the pathologists.
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