5.2\ Brain Tumor Surgery

and Treatment Accessories

5.2.1\ Stereotactic Biopsy

5.2.1.1\ Discussion

Stereotactic biopsy is an image-guided procedure that is commonly performed to obtain tissue samples of intracranial lesions. Hemorrhage is one of the most common findings after stereotactic brain biopsy, occurring in up to 9% of cases. Hemorrhage along the biopsy trajectory has a characteristic linear configuration. Small amounts of blood products along the path of the biopsy that may only be discernible on T2* GRE or SWI sequences are usually of no clinical concern and resolve spontaneously. Rather, such findings serve to delineate the path of the biopsy needle and can help account for new neurological deficits­

(Fig. 5.7). In addition, the blood products left along the biopsy path that are apparent on MRI can also serve as a useful indicator of whether the lesion was appropriately sampled. Nevertheless, some operators prefer to insert a metal marker in the biopsy cavity as a reliable indicator that is visible on imaging (Fig. 5.8). Although off-target biopsy can yield tumor cells if the lesion is an infiltrative tumor, the grade may be underestimated. Ideally, biopsy of the enhancing portion of the tumor with the highest cerebral blood volume (CBV) on perfusion-weighted MRI should be performed. Another uncommon, but notable complication of stereotactic biopsy is tumor seeding (Fig. 5.9). Otherwise, a mild degree of enhancement in the brain parenchyma along the biopsy path is often encountered on early postoperative imaging as an incidental finding that typically resolves within a couple of months (Fig. 5.10).

Fig. 5.10  Expected biopsy path enhancement. Initial coronal post-contrast T1-weighted MRI (a) obtained soon after left transfrontal biopsy shows enhancement along the path of the biopsy needle (arrow). Follow-up coronal

post-contrast T1-weighted MRI (b) obtained 3 months later shows that the enhancement has resolved, leaving behind a small area of low signal due to encephalomalacia (arrow)