GENERAL RULES OF WORK ON BRAIN TISSUE
The methods used for performing punctures, incisions, haemostasis, excisions and all other standard neurosurgical techniques differ from those in general surgery. Despite the extensive use of microsurgical technique over the past three decades, some manipulations are still performed macroscopically.
Once the dura is opened, the flaps produced are turned over the edges of the cranial defect. They are covered with wet cottonoids together with all other exposed tissues. The cortical surface should be protected from drying by irrigation with saline and cottonoids. The saline solution used to irrigate the brain should be at body temperature, i.e. about 38 degrees C to prevent neuronal injury. It also has a haemostatic effect upon minor bleeding. Before use, the saline must be checked by the surgeon on his glove (a useful custom to prevent thermal brain injury), independently of the thermometer in the scrub nurse's pot.
Brain tissue and the lateral ventricles can be punctured through the exposed cortical sur-face. This puncture is performed with special cannulas having blunt tips and side openings after coagulating the preselected point of penetration. Precision of these techniques has increased significantly with the introduction of the intraoperative ultrasonic B-scan, localising beforehand the location of the lesion or the ventricle.
Incisions of the cortex are usually made on the most convex part of a gyrus, avoiding major blood vessels. The pia-arachnoid is coagulated and cut at the place where the incision is intended. Then the surgeon penetrates to the depth of the tissue by transsecting the white matter with fine tip forceps, microdissectors and a fine suction tube. The border of the incision is protected with wet cottonoids.
Haemostasis during the incision and penetration into the brain tissue is achieved through bipolar coagulation, with small pieces of oxidised cellulose or, if the bleeding is from bigger vessels, by clipping.
Irrigation with saline while the brain is being resected is also useful. The liquid serves to clean the operative field and, when the site where the bleeding is occurring is filled, the source of bleeding in the resected area can be established by observing the thin spurt that is clearly visible in the transparent liquid. The usually available warm saline also has some haemostatic action as it evokes vascular spasm and thereby facilitates blood coagulation.
If the ventricular system should be penetrated, the opening is closed with small wet cottonoids to prevent blood or tissue debris from entering the ventricular system.