6.4 Stereotactic Neurosurgery
This computer-assisted image-guided technique is mainly used to take biopsies of deep-located brain tumors. Some neurosurgeons use stereotactic techniques also for brain tumor removal.
An external device, i.e. stereotactic frame, is applied to the skull. Then, the anatomical data collected by CT Scanning, while the patient has the frame on, are processed and a target is chosen using the three spatial coordinates: x, y, and z.
Stereotactic neurosurgery is mostly used for functional neurosurgery: Parkinson's disease, other movement disorders and so on.

Biopsia stereotassica
Fig.6.8: Left, MRI of a diffuse deep right temporal lesion (glioma) not suitable for open neurosurgery. Right, imaging of the stereotactic biopsy procedure, supported by the neuronavigator and by the CT Scan-calculated coordinates.
6.5 Radiosurgery
The same principle is applied in radiosurgery. The target is centered with stereotactic techniques and radiation is then given in a single dose with either Linear Accelerator, Co60 or Cyber-Knife (working without a frame). Radiosurgery should be reserved for deep-seated small metastases, small angiomas, small remnants of meningioma, small acoustic neurinomas. The limits of radiosurgery lie in the volume of the target, which must not exceed 4-5 cc3. Radiosurgery is an ultra-specialist technique, generally used by dedicated neurosurgeons and/or radiotherapists. Radionecrosis and possible radiation-induced second tumor are the most severe side effects

Fig.6.9: Radionecrosis after radiosurgery for kidney cancer brain metastases, as seen in different MRI scans. The red arrow shows the necrotic part of the brain, the yellow the surrounding brain edema.
6.6 Endoscopy
The endoscope is a device with a light source coupled with a camera. It permits intra-operative 360-degree observation of the operating field. Some neurosurgical procedures may be performed with dedicated endoscopes. Obstructive hydrocephalus may be treated by perforating the floor of the 3rd ventricle to the basal cisterns and thus avoiding the application of permanent artificial systems: 3rd ventricle-cisternostomy. With the endoscope, it is also possible to remove colloid cysts from the 3rd ventricle and to perform biopsies of intraventricular brain tumors.

Fig.6.10: 3rd ventricle colloid cyst (top) that has been removed endoscopically; on the right, intra-operative view. On the bottom, MRI images taken after 3 years.

Fig.6.11: Top left, the blue arrow points to a large intraventricular brain tumor at axial MRI. Right, endoscopic view of the tumor. Bottom left, the tumor after biopsy. Bottom right, a communication is created between the ventricles to allow the CSF to flow. This is done with a laser.

Fig.6.12: On the left, direct transnasal approach to a pituitary adenoma; the instrument enters through the nostril and reaches the anterior wall of the sella turcica (yellow arrow). On the right, endoscopic appearance of the pituitary adenoma (blue arrow) as seen with the angled endoscope, very useful to explore the hidden parts of the cavity.

Fig.6.13: Same case as in Fig. 6.7: the endoscopic view is matched with the data from the neuronavigator.
6.7 Laser
In neurosurgery, the laser permits cutting, coagulation and, at times, vaporization of some parts of brain tumors. The laser is a "knife" and not a magical instrument. There are several kinds of lasers that can be used also through the operating microscope.
It must be kept in mind that the surgical laser is a non-invasive instrument, which is applied directly on the skin and then does the miracle.
6.8 Ultrasonic Aspirator
This is a daily instrument in use for brain tumor neurosurgery, maybe the most important one introduced in the last 20 years. It permits to demolish the pathological tissue and aspirate it without traction on the surrounding tissues or vessels. It is mandatory in neurosurgery either for brain tumors or for spinal cord tumors.
aspetto RMN di un ependimoma intramidollareaspetto RMN di un ependimoma intramidollare
Fig.6.14: Above left, MRI of a cervical intramedullary ependymoma (red arrows). Above right, the swollen cervical cord under the operating microscope. Bottom left, the tumor is being removed with the ultrasonic aspirator (yellow arrow); right, the spinal cord after radical removal of the tumor.