Neurological Examination

Question 1

Describe what you should assess on the static portion of the equine neurologic exam

Answer 1

-mentation, stance, cutaneous reflexes, tail tone, muscle symmetry
-palpation, range of motion (neck and hips)
-cranial nerves

Question 2

What cranial nerves are assessed with the menace response? Dazzle? PLR?

Answer 2

Menace: CN II, brain, CN VII (assess from all visual fields )
Dazzle reflex: CN II, brainstem
PLR: CN II, CN IIIVII (motor to muscles of facial expression), CN V (motor to muscles of mastication)
Facial sensation: CN V
Swallowing: Jaw tone, mastication (CN V), Tongue tone (CN XII), prehension (CN VII), protection of airway (CN IX, X, XI)

Question 3

What are the muscles of mastication in the horse?

Answer 3

Masseter muscles, temporalis muscles, pterygoid muscle, digastricus
- atrophy with damage to cranial nerve 5

Question 4

What is the thoracolaryngeal adductor response?

Answer 4

Also known as the slap test
- afferent is the cervical spinal cord and efferent is the vagus and recurrent laryngeal nerve (crosses over nucleus of vagus in the brain)
-slap the left withers- the right arytenoid should abduct
-best observed on thin horses
-assesses for laryngeal hemiplegia

Question 5

What are some things that should be included in a dynamic neurologic examination?

Answer 5

-straight line walk and trot
-serpentine
-circles
-head elevated walking
-hill and curb
-tail pull
-blindfold

Question 6

What does each grade of the modified Mayhew grading scale indicate?

Answer 6

Grade 0=normal
Grade 1=inconsistently abnormal under special circumstances
Grade 2= consistently abnormal under special circumstances
Grade 3= abnormal all the time
Grade 4=extremely ataxic, may fall
Grade 5= down, unable to rise

Question 7

What signs localize a lesion to the brain?

Answer 7

Changes in mentation, head pressing, circling, central blindness (normal PLR, absent menace), seizures

Question 8

What signs localize a lesion to the brainstem?

Answer 8

Somnolence, multiple CN deficits

Question 9

What signs localize a lesion to the cerebellum?

Answer 9

Hypermetria, intention tremors, paradoxic vestibular signs

Question 10

With a cranial nerve exam, how can you differentiate central vs peripheral disease?

Answer 10

Central: usually multiple CN affected, changes in mentation

Peripheral: normal mentation, usually only one nerve effected
-two nerves effected in the case of temporohyoid osteoarthropathy (THO) or otitis media/interna (7 and 8 both affected) or in the case of guttural pouch disease (9,10,11 can all be affected)

Question 11

Compare and contrast peripheral, central and paradoxical vestibular disease

Answer 11

Peripheral: head tilt toards lesion, leaning/circling towards lesion, horizontal nystagmus with rotary fast phase away from the lesion, base wide stance, staggering, normal mentation in most cases (only cranial nerve 7 affected)

Central (brain): same as peripheral, but variable nystagmus with position fast phase away from the lesion, CP deficits, and mentation is often altered (multiple CNs affected)

Paradoxical (cerebellum): head tilt away from the lesion, leading/circling away from the lesion, fast phase of nystagmus towards lesion, hypermetria, ipsilateral CP deficits, may or may not have mentation changes

Question 12

What is temporohyoid osteoarthropathy?

Answer 12

Proliferation of bone at articulation of stylohyoid to base of skull
-causes cranial nerve 7 and 8 deficits

Question 13

What signs are seen with a C1-C2 lesion?

Answer 13

All 4 limbs are affected, and the pelvic limbs are typically worse than the thoracic limbs

Question 14

What signs are seen with a C6-T2 lesion?

Answer 14

All 4 limbs are affected- decreased CP, ataxia and paresis
-thoracic limbs experience weakness (toe dragging)

Question 15

What signs are seen with a T3-L2 lesion?

Answer 15

Thoracic limbs are normal, pelvic limbs show signs of weakness, toe dragging or hypermetra
-urinary incontinence in severe cases- bladder distended and not easily expressed

Question 16

What is a sidewinder lesion?

Answer 16

A thoracic vertebrae lesion that results in a horses hind end tracking on very different course than front limbs

Question 17

What signs are seen with a L3-S3 lesion?

Answer 17

-normal thoracic limbs
-pelvic limbs weak or toe dragging
-fecal/urinary incontinence with an easily expressed bladder, poor tail tone

Question 18

What signs are seen with a S3-caudal lesion?

Answer 18

-no ataxia
-fecal/urinary incontinence
-sabulous cystitis (accumulation of debris at bottom of bladder-hard to reverse)

Question 19

What are some ancillary tests that can be conducted for equine neurologic disease?

Answer 19

-diagnostic imaging
-radiographs
-CT
-cerebrospinal fluid evaluation

Question 20

What are the main areas that should be assessed when evaluating radiographs of the equine spinal canal?

Answer 20

-intervertebral foramen, intervertebral disc space, transverse processes, articular facets, alignment

Question 21

How can you determine if the spinal canal is wide enough to ensure there is not compression of the spinal cord on a radiograph?

Answer 21

Ratio of spinal canal at narrowest and vertebral body at widest
- should be >50%
-sensitivity and specificity of 89%

Question 22

Describe the myelogram for identifying spinal cord compression

Answer 22

-injection of iodinated contrast into the subarachnoid space to evaluate for cervical stenotic myelopathy
-best to perform with a CT

Question 23

What should normal CSF look like?

Answer 23

-clear and colorless
-TNCC <6/ul (majority mononuclear cells)
-protein <100 mg/dL
-RBC 0-1/uL

Question 24

If CSF is yellow, what may this indicate?

Answer 24

-xanthochromia
-indicates trauma or vasculitis in the CNS (metabolized RBCs)

Question 25

What does increased neutrophils in CSF indicate? What about increased mononuclear cells?

Answer 25

Neutrophils: generally bacterial infection
Mononuclear cells- generally viral or neoplasia

Question 26

What may elevated protein indicate on CSF analysis?

Answer 26

Non-specific indicator of inflammation
-IgG index >0.27 indicates intrathecal production of IgG (particularly useful in EPM diagnosis)

Question 27

What are the landmarks for CSF tapping?

Answer 27

Lumbosacral space
- caudal aspect of tuber coxae between the sacral wings

C1-C2 CSF tap
- caudal to wing of C1
- 3 cm ventral to dorsal midline
- ultrasound guided
- always give banamine after and feed with the head elevated

Atlantooccipital space
- level of C1 at base of the ear
- perpendicular to the skin
- flexing the poll is very helpful