Nervi craniales
Horses, like other mammals, have 12 pairs of cranial nerves (CN I–XII) that emerge from the brain and brainstem. They provide sensory, motor, and parasympathetic innervation to the head and certain viscera. In the horse several have heightened clinical importance: - CN VII (facial) is vulnerable to trauma as it crosses the face. - CN X (vagus) gives rise to the recurrent laryngeal nerves; the left is particularly long and prone to neuropathy (“roaring”). - CN IX, X, XI, and XII, together with the internal carotid artery, travel in or near the wall of the guttural pouches, unique equine structures, so guttural-pouch disease can be life-threatening. A systematic cranial-nerve examination is a core part of every neurologic work-up.
Facial-nerve paralysis, recurrent laryngeal neuropathy, guttural-pouch mycosis (with possible cranial-nerve and arterial involvement), and vestibular disease (CN VIII) are common clinical entities. Endoscopy, radiographs, and advanced imaging are used as indicated. The guttural pouches must always be considered when multiple caudal cranial nerves are affected.
## Overview Facial nerve (cranial nerve VII) paralysis results in ipsilateral facial muscle weakness. Classic signs are lip and ear droop, muzzle deviation to the opposite side, feed packing in the c
## Overview Guttural pouch mycosis is a fungal infection (usually Aspergillus) of the guttural pouch. Fungal plaques commonly form over major arteries. Erosion of the vessel wall causes potentially f
Dysfunction of the vestibulocochlear nerve causing balance disturbances. Peripheral (inner ear, nerve) causes include THO, otitis media/interna, and guttural pouch disease. Central causes include EPM
## Overview Trigeminal neuritis is inflammation of the trigeminal nerve (cranial nerve V), which supplies the muscles of mastication. It may occur with polyneuritis equi or idiopathically. Bilateral
Progressive proliferative osteoarthropathy of the temporohyoid joint that may cause fusion of the joint and fracture of the petrous temporal bone, damaging CN VII and CN VIII as they traverse the bone
Drooping lip or ear, difficulty swallowing, roaring noise during exercise, head tilt, or nasal discharge with neurologic signs all warrant prompt veterinary examination. Do not delay if a horse shows sudden difficulty swallowing or nosebleeds; guttural-pouch disease can be an emergency.
## Overview Facial nerve (cranial nerve VII) paralysis results in ipsilateral facial muscle weakness. Classic signs are lip and ear droop, muzzle deviation to the opposite side, feed packing in the cheek, and inability to close the eyelid. Corneal exposure is the most immediate threat to vision. ## Causes Peripheral trauma, compression, or central neurologic disease. ## Diagnosis Neurologic examination. Additional testing if brainstem disease is suspected. ## Treatment Supportive care focused on corneal protection, anti-inflammatories, and time. Treat any underlying cause. ## Recovery and Prognosis Guarded to fair. Peripheral lesions have a better chance of improvement than central ones. ## Prevention Minimize facial trauma and pressure. Signs include: lip droop; ear droop; inability to close eyelid; feed accumulation in cheek; muzzle deviation to unaffected side
## Overview Guttural pouch mycosis is a fungal infection (usually Aspergillus) of the guttural pouch. Fungal plaques commonly form over major arteries. Erosion of the vessel wall causes potentially fatal nosebleeds. Dysphagia and cranial-nerve deficits also occur. ## Causes Aspergillus infection. Predisposing factors are unclear. ## Diagnosis Endoscopy showing fungal plaques, often over the internal carotid or other arteries. History of epistaxis is highly suggestive. ## Treatment Occlusion of the affected artery (coil or balloon embolization) to prevent fatal hemorrhage, plus topical antifungal medication. Medical treatment alone is slow and less reliable for preventing bleeds. ## Recovery and Prognosis Guarded. Successful arterial occlusion prevents fatal hemorrhage in many cases. Neurologic deficits may persist. ## Prevention None specific. Signs include: epistaxis (can be fatal); nasal discharge; difficulty swallowing; cranial nerve deficits
Dysfunction of the vestibulocochlear nerve causing balance disturbances. Peripheral (inner ear, nerve) causes include THO, otitis media/interna, and guttural pouch disease. Central causes include EPM and EHV-1. Signs include: Head tilt toward affected side; horizontal or rotary nystagmus; circling; ataxia with falling/leaning to affected side; strabismus (ventral deviation of ipsilateral eye)
## Overview Trigeminal neuritis is inflammation of the trigeminal nerve (cranial nerve V), which supplies the muscles of mastication. It may occur with polyneuritis equi or idiopathically. Bilateral atrophy of the masseter and temporalis muscles produces a sunken face, and the horse may be unable to close the mouth (dropped jaw), leading to difficulty eating and weight loss. ## Causes Nerve inflammation, idiopathic or associated with polyneuritis equi. ## Diagnosis Clinical signs of bilateral masticatory muscle atrophy and dropped jaw. Further testing for polyneuritis equi if indicated. ## Treatment Supportive care, including assisted feeding. Corticosteroids are sometimes used. Recovery is variable. ## Recovery and Prognosis Guarded. Some horses improve. Others have permanent deficits. ## Prevention None. Signs include: bilateral masseter and temporalis atrophy (sunken face); inability to close the mouth (dropped jaw); difficulty eating; weight loss
Progressive proliferative osteoarthropathy of the temporohyoid joint that may cause fusion of the joint and fracture of the petrous temporal bone, damaging CN VII and CN VIII as they traverse the bone. Signs include: Consult veterinarian for specific symptoms.; Head shaking; difficulty eating; ear rubbing; acute onset vestibular signs (head tilt, nystagmus, circling); facial nerve paralysis; keratitis (corneal ulceration from inability to blink)
Facial-nerve paralysis, recurrent laryngeal neuropathy, guttural-pouch mycosis (with possible cranial-nerve and arterial involvement), and vestibular disease (CN VIII) are common clinical entities. Endoscopy, radiographs, and advanced imaging are used as indicated. The guttural pouches must always be considered when multiple caudal cranial nerves are affected.
Drooping lip or ear, difficulty swallowing, roaring noise during exercise, head tilt, or nasal discharge with neurologic signs all warrant prompt veterinary examination. Do not delay if a horse shows sudden difficulty swallowing or nosebleeds; guttural-pouch disease can be an emergency.
See the Cranial Nerves on our interactive 3D horse model. Open 3D Model