Frameless stereotactic brain biopsy: Techniques and limitations

The gold standard for brain biopsy target localization is frame-based stereotaxy. Recently, frameless stereotactic brain biopsy has become accepted as a surgical method that is interchangeable with frame-based biopsy; however, this method has some limitations relative to frame-based biopsy. Here, we describe the limitations of frameless stereotactic brain biopsy and recommend techniques to overcome these limitations. A structural limitation of frameless biopsy is that the tilt angle of the catheter from the entry point to the target is narrow. Accordingly, it is necessary to plan a suitable entry point using preoperative MR images or three-dimensional images reconstructed with a neuronavigation system. Additionally, incorrect directionality or size adjustment of the hole at the entry point can make impossible to access the target. In cases of posterior fossa lesions, the attachment of a screw marker to the occipital bone over the lesion can improve the accuracy of the biopsy.