Neurological Examination Flashcards
Describe what you should assess on the static portion of the equine neurologic exam
-mentation, stance, cutaneous reflexes, tail tone, muscle symmetry
-palpation, range of motion (neck and hips)
-cranial nerves
What cranial nerves are assessed with the menace response? Dazzle? PLR?
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)
What are the muscles of mastication in the horse?
Masseter muscles, temporalis muscles, pterygoid muscle, digastricus
- atrophy with damage to cranial nerve 5
What is the thoracolaryngeal adductor response?
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
What are some things that should be included in a dynamic neurologic examination?
-straight line walk and trot
-serpentine
-circles
-head elevated walking
-hill and curb
-tail pull
-blindfold
What does each grade of the modified Mayhew grading scale indicate?
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
What signs localize a lesion to the brain?
Changes in mentation, head pressing, circling, central blindness (normal PLR, absent menace), seizures
What signs localize a lesion to the brainstem?
Somnolence, multiple CN deficits
What signs localize a lesion to the cerebellum?
Hypermetria, intention tremors, paradoxic vestibular signs
With a cranial nerve exam, how can you differentiate central vs peripheral disease?
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)
Compare and contrast peripheral, central and paradoxical vestibular disease
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
What is temporohyoid osteoarthropathy?
Proliferation of bone at articulation of stylohyoid to base of skull
-causes cranial nerve 7 and 8 deficits
What signs are seen with a C1-C2 lesion?
All 4 limbs are affected, and the pelvic limbs are typically worse than the thoracic limbs
What signs are seen with a C6-T2 lesion?
All 4 limbs are affected- decreased CP, ataxia and paresis
-thoracic limbs experience weakness (toe dragging)
What signs are seen with a T3-L2 lesion?
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
What is a sidewinder lesion?
A thoracic vertebrae lesion that results in a horses hind end tracking on very different course than front limbs
What signs are seen with a L3-S3 lesion?
-normal thoracic limbs
-pelvic limbs weak or toe dragging
-fecal/urinary incontinence with an easily expressed bladder, poor tail tone
What signs are seen with a S3-caudal lesion?
-no ataxia
-fecal/urinary incontinence
-sabulous cystitis (accumulation of debris at bottom of bladder-hard to reverse)
What are some ancillary tests that can be conducted for equine neurologic disease?
-diagnostic imaging
-radiographs
-CT
-cerebrospinal fluid evaluation
What are the main areas that should be assessed when evaluating radiographs of the equine spinal canal?
-intervertebral foramen, intervertebral disc space, transverse processes, articular facets, alignment
How can you determine if the spinal canal is wide enough to ensure there is not compression of the spinal cord on a radiograph?
Ratio of spinal canal at narrowest and vertebral body at widest
- should be >50%
-sensitivity and specificity of 89%
Describe the myelogram for identifying spinal cord compression
-injection of iodinated contrast into the subarachnoid space to evaluate for cervical stenotic myelopathy
-best to perform with a CT
What should normal CSF look like?
-clear and colorless
-TNCC <6/ul (majority mononuclear cells)
-protein <100 mg/dL
-RBC 0-1/uL
If CSF is yellow, what may this indicate?
-xanthochromia
-indicates trauma or vasculitis in the CNS (metabolized RBCs)
