Category:Cranial Nerve Examination - Horse

• The cranial nerves are numbered 1-12 from the most rostral to the most caudal.
• A systematic examination of the cranial nerves can aid accurate identification of the site of a lesion.

Cranial Nerve I

• Cranial nerve I is the olfactory nerve.
  • Abnormalities are rarely detected in this nerve.

Neurological Eye Examination - Horse

Face Sensation

Vestibular System Examination

Pharyngeal and Laryngeal Function

• The pharynx and larynx are innervated by:
  • CN IX - the glossopharyngeal nerve
  • CN X - the vagus nerve
  • CN XI - the accessory nerve
• Pharyngeal and laryngeal function is best studied by:
  1. Observing the horse eat and swallow
  2. Endoscopy

Laryngeal Dysfunction

• Left recurrent laryngeal hemiplegia is the most common dysfunction in horses.
  • The left recurrent laryngeal nerve is a branch of the vagus nerve.
  • Horses are known as "roarers".

Pharyngeal Dysfunction

• Pharyngeal paralysis in horses is commonly associated with peripheral disease.
  • Especially guttural pouch disease.
    • Endoscopy of the guttural pouches should be therefore be performed in horses that are dysphagic.

Tongue Movement

• The hypoglossal nerve, CN XII provides motor innervation to the tongue.
• Normally, a horse resists the tongue being retracted from the mouth.
  • The horse will quickly return the tongue after it is pulled out to the side.
• Horses with hypoglossal weakness appear differently.
  • The tongue may protrude from the mouth.
  • Chronic unilateral hypoglossal lesions may result in unilateral tongue atrophy.
  • Bilateral hypoglossal lesions may result in difficulty prehending food.
• Horses with cerebral dysfunction may have signs corresponding to tongue weakness.
  • However, tongue atrophy is not present in these animals.