Method 2: Transverse craniotomy
When using the transverse craniotomy technique in cattle, it is advisable to leave the head attached and immobilise for sawing by tensioning nose grips to a vehicle or other solid object. Alternatively, flex the neck and tie the nose grips to the hock. In small ruminants, removing the head is recommended.
Step 1
Stabilise the head for sawing by placing it on a non-slip surface or mat. The head does not need to be skinned, but a knife cut through the skin at the intended line of sawing is recommended.
Step 2
Begin sawing vertically in a line one centimetre rostral to external ear canal and extend the cut through the bone until the cranium hinges apart. Remove the head at the atlanto-occipital joint if still attached.
Step 3
Begin with the rostral half of the skull. Using curved scissors, cut the ventral nerve roots and the olfactory bulbs. Remove the rostral brain.
Step 4
Shell out the occipital lobes in the caudal half of the skull to expose the opaque tentorium cerebelli.
Step 6
Using scissors, cut the cranial nerves on the ventral and lateral surfaces inside the cranium and then around the cut spinal cord at the foramen magnum. Using a finger or plunger from a syringe, gently push the hindbrain and cerebellum rostrally out of the cranium.
Step 7
Fix the three brain segments whole in 10% buffered formalin.
Note: For TSE exclusion testing, remove the dorsal cerebellum (sheep only) and 2-3cm spinal cord and submit these sections fresh. Fix remainder of brain in 10% buffered formalin.