Overview
The bovine brain (encephalon) fills a relatively small cranial cavity, protected by the frontal bone and, in the adult, by the frontal sinus, which surrounds it dorsally and caudally. It continues into the spinal cord through the foramen magnum.
Parts
- Cerebrum (cerebrum): two hemispheres with gyri, separated by the longitudinal fissure. The cortex integrates vision, behaviour and voluntary movement.
- Cerebellum (cerebellum): caudal to the cerebrum, over the fourth ventricle; it coordinates movement and balance.
- Brainstem: midbrain, pons and medulla oblongata, from which most cranial nerves emerge.
- Blood supply: in the adult bovine, arterial blood reaches the brain mainly through the rostral epidural rete mirabile (rete mirabile epidurale rostrale) at the base of the skull.
Clinical relevance
- Polioencephalomalacia: necrosis of the cerebral cortex associated with thiamine deficiency or excess dietary sulphur. It causes cortical blindness, head pressing, opisthotonus and seizures; in the early stages it responds to thiamine.
- Listeriosis: Listeria monocytogenes, often from poorly fermented silage, forms microabscesses in the brainstem. It causes asymmetric cranial nerve deficits (facial paralysis, head tilt) and circling.
- Bovine spongiform encephalopathy: a prion disease spread by meat and bone meal; it causes vacuolation in the brainstem, and the obex is the reference sample for diagnosis. It is now rare thanks to the ban on feeding those meals to ruminants.
- Rabies: must be considered in any bovine with rapidly progressive neurological signs; necropsy and sample handling require precautions.
- Stunning and euthanasia: the captive bolt is aimed at the crossing of the lines running from the lateral canthus of each eye to the base of the opposite horn.