Large Animal Neurology

Question 1

In the horse, what muscle contracts the neck muscle (like cutaneous trunci) and what nerve innervates this muscle?

Answer 1

Cutaneous colli muscle innervated by the facial nerve

(DeLahunta)

Question 2

Cause for focal loss of cutaneous nociception in the sacrocaudal region of the horse? cattle?

Answer 2

Focal loss of cutaneous sensation in the sacrocaudal region of the horse = polyneuritis equi

cattle = sacrocaudal fracture

(DeLahunta)

Question 3

What innervates cutaneous sensation to the coronary band or bulb of the thoracic limb in the horse?

Answer 3

Median and ulnar nerves in the horse

Radial nerve (and others) in the lg animal….

(DeLahunta)

Question 4

In horses, dysfunction of __________ results in ipsilateral whole-body sweating

Dysfunction of ______________ results in focal sweating

Answer 4

Dysfunction of UMN sympathetic spinal cord segments (lateral funiculus) results in ipsilateral whole-body sweating

Dysfunction of intermediate gray horn anywhere from L1-4 results in focal sweating (where the skin is deprived of sympathetic innervation)

* the only difference between UMN vs. LMN lesion of this system is the extent of clinical signs (whole body vs. focal)

(DeLahunta)

Question 5

How is the laryngeal adduction test performed, what is the pathway?

Answer 5

Stand beside the neck of the horse, one hand grasp the larynx, other hand slap the area of the thorax - elicits a brief closure of the glottis via adduction of the vocal folds which can be felt

Stimulation of cutaneous branches of the thoracic spinal nerves –> dorsal horn –> synapse on long interneurons in the ipsilateral dorsal gray horn

Interneurons cross to the contralateral fasiculus proprius to the medulla –> synapse on GSE LMN of the nucleus ambiguus (contralateral to side slapped) –> vagus nerve –> thorax –> recurrent laryngeal nerve –> larynx –> close glottis

Allows one to test the CONTRALATERAL cervical spinal cord function (slap right side, tests function of left ascending spinal cord tracts)

(DeLahunta)

Question 6

Recurrent laryngeal neuropathy causing laryngeal paralysis is more common on the right or left side?

Answer 6

Left (slap test will be absent when slapping the RIGHT side in these horses)

(DeLahunta)

Question 7

What are grades 0-5 for para/tetraparesis in horses?

Answer 7

Grade 0: Normal strength and coordination

Grade 1: Normal gait when walking straight. Slight deficit on walking in tight circles or walking with the neck/head extended or when pulled by the tail (sway)

Grade 2: Mild spastic tetraparesis and ataxia at all times and espeically during the manipulations described for grade 1

Grade 3: marked spastic tetraparesis and ataxia with a tendency to buckle and fall on vigorous circling, backing, or swaying

Grade 4: Spontaneous stumbling, tripping, falling

Grade 5: Recumbent, unable to stand

(DeLahunta)

Question 8

What is the vertebral formula for horses?

Answer 8

Cervical 7 (8 segments)

Thoracic 18

Lumbar 6 (some have 5)

Sacral 5

Caudal 15-21

(DeLahunta)

Question 9

An inherited malformation that involves the occipital and cranial cervical somites occurs in the ________ breed and is termed ____________

Answer 9

Arabian breed

Termed congenital occipitoatlantoaxial malformation

(de Lahunta)

Question 10

What are the 2 forms of equine cervical vertebral stenosis

Answer 10

Vertebral stenosis in the young horse

• Stenosis of 1+ vertebral foramina - failure of bone surrounding the vertebral foramen to resorb
• Most common in male thoroughbred
• Most commonly C3-6
• Can be prevented by restricting dietary calcium and energy content
• 2 categories: static vs. dynamic

Degenerative joint disease

• DJD of the synovial joints at the articular processes
• More common in older horses, caudal cervical region
• Osteochondrosis when young –> chronic malarticulation –> DJD
• May see compression on myelogram with neck extended

(de Lahunta)

Question 11

Where are the histopathologic lesions most prominent in horses with equine degenerative myeloencephaloapthy?

Answer 11

Primary lesions; axonopathy that predominates in the superficial tracts of the dorsolateral and ventral funiculi

• SPHEROIDS
• Medial cuneate and gracilic nuclei
• Nucleus thoracicus (nucleus of the dorsospinocerebellar tract)
• Dorsal funiculi relatively spared
• Also olivary nuclei, reticular formation, vestibular nuclei
• Accumulation of lipopigment in endothelial cells (and pigment epithelium of the retina)

(de Lahunta)

Question 12

What kind of patients get equine degenerative myeloencephalopathy vs. equine motor neuron disease?

Answer 12

Both related to decreased vitamin E

Young horses get EDM, older horses get equine motor neuron disease

(de Lahunta)