Begin by optimally positioning the animal for the surgery after administering proper anesthesia. Place the animal in a prone position with the head raised and stabilized using sandbags such that the frontal bone is nearly horizontal. Identify the nuchal prominence and the caudal aspect of each superior orbital crest to define the expected sagittal midline.
Next, perform a midline incision using scalpel number 24 to cut through both the skin and the galea aponeurotica onto the periosteum of the frontal bone. Wipe away the blood with surgical swabs. Using a 12-millimeter flattened rongeur, gradually separate the galea aponeurotica from the underlying frontal bone around the incision.
Then use a surgical retractor to separate the galea aponeurotica and expose the underlying frontal bone. Identify the sagittal suture as a reference for the anatomical midline and the coronal suture. By manual palpation, identify the three bone structures forming a triangle, the nuchal prominence and the caudal aspect of both superior orbital crests.
Using a high-speed pneumatic drill with a rounded diamond-coated burr, define each corner of a rectangle within the borders of the previously defined triangle. Connect each corner with a four-millimeter rounded diamond burr to ensure the correct location of the opening. Gradually thin the frontal bone with the four-millimeter rounded diamond burr until the dura mater is exposed.
Use the first point of contact with the dura to visually assess the thickness of the remaining frontal bone. Then continue carefully thinning the frontal bone in the defined rectangle. Slide a three-millimeter dissector under the sufficiently thinned bone around the bone plate, and chip it off with gentle manual pressure to expand the opening to the dura mater.
Apply sterile saline with a syringe to clear the view. Insert the three-millimeter dissector under the bone plate and apply gradual downward pressure to its handle to break off the bone plate. Assess the integrity of the dura mater by visually inspecting for cerebrospinal fluid or CSF leakage.
Stop minor venous bleedings using saved bone dust or by carefully applying monopolar or bipolar coagulation with a cautery at low voltage. Finally, cover the exposed dura mater with a sterile surgical swab soaked in sterile saline to prevent the underlying tissue from drying out. After performing the craniectomy, the revealed underlying dura mater was found to be intact.
The opening in the frontal bone was centered, which was confirmed by the location of the dorsal sagittal sinus. These indicated the success of the procedure.
