Cranial nerve examination
Cranial nerve examination is an important, but often daunting, part of the neurological exam due to negative memories of neuroanatomy class. It’s fantastic if you know which cranial nerves are being tested for each test described below, as well as the origin and projection of each cranial nerve. Fortunately, the cranial nerves are conveniently numbered from rostral to caudal and, from a practical standpoint, you just need to remember the following to help you localize the lesion.
- Cranial nerves I and II are associated with the forebrain
- Cranial nerves III and IV originate in the rostral brainstem (midbrain)
- All other cranial nerves are in the caudal brainstem (pons, medulla oblongata)
- This is a learned response and NOT a reflex.
- Most dogs and cats have a positive menace response by 12 weeks of age.
- Some normal patients will not menace due to a stress response. Tap the head gently over the frontal sinus to get their attention.
- The contralateral forebrain must be functioning normally to interpret the “threatening” gesture.
- The ipsilateral cerebellum also plays a role in the menace response, but the exact pathway is uncertain.