Neurological Exam Large Animals Flashcards
What is the aim of the neurological exam?
Determine presence or absence of neurological disease (vs. musculoskeletal issue)
What are the 2 approaches to the neurological examination?
What is the most suitable approach for neurological assessment of the horse?
Systematic (modality) approach
Anatomic approach - head to tail
Combination of systematic and anatomic approaches is most suitable for the neurological assessment of horses
Where is white matter vs. grey matter in the brain vs. the spinal cord?
White matter - inside brain, outside spinal cord
Grey matter - outside brain, inside spinal cord
Label this photo of the spinal cord
What does the white matter consist of?
Myelinated nerve axons (traveling from cell bodies)
What does the grey matter consist of?
Neuron cell bodies
Supportive cells (astrocytes, glial cells, etc.)
Afferent is the _______ pathway while Efferent is the _______ pathway
(motor/sensory)
Afferent = sensory
Efferent = motor
What part of a neuro exam is ESSENTIAL?
Accurate history
What is the typical mentation of a horse with a forebrain problem? What kind of behavior do they have?
Mentation - Bright or depressed
Abnormal behavior - Circling, Hyperasthesia, Head turn, Odd postures, yawning
What is the function of the cerebellum?
Control center for ascending proprioceptive pathways and descending motor pathways (fine tunes control signals from higher centers)
How common is cerebellar disease in the horse?
Very rare
What are the signs of cerebellar disease in the horse?
Spastic or exaggerated movements
Absence or diminished menace response
Intention tremor
Ataxia with weakness
Which horse breed is predisposed to cerebellar disease and why?
Arabian Foals/Arabian Crosses
Autosomal recessive inherited genetic neurological condition which causes progressive death of neurons in the cerebellum
What structures does the brainstem include?
Pons and Medulla
Reticular formation
Cranial nerve nuclei
What does the reticular formation control? What common substance works here?
Controls level of consciousness (site of action of caffeine)
What are the ascending and descending pathways in the brainstem?
What does this mean about the symptoms associated with brainstem dysfunction?
Ascending proprioceptive pathways
Descending motor neuron pathways
Weakness and ataxia
Which cranial nerves originate in the brainstem?
How do we evaluate the cranial nerve nuclei?
Cranial nerves testing
What is afferent and efferent limb of the pupillary light reflex?
Afferent - optic nerve CN II
Efferent - oculomotor nerve CN III (parasympathetic fibers)
Does the animal need to be conscious for pupillary light reflex to occur?
No - reflexes are involuntary
What is important to remember about consensual pupillary response in pupillary light reflex testing?
Can be difficult to evaluate in horses/farm animals
Does the animal need to be conscious for menace response to occur?
Yes - responses require perception of stimulus at level of forebrain
What are the steps/structures involved in the menace response?
Perception of stimulus → optic nerve CN II → Optic chiasm → Thalamus → Opposite occipital cortex → facial nerve CN VII and nucleus → Cerebellum
What is the optic chiasm?
Part of the brain where the optic nerves cross
How is vision best assessed in a horse?
Best assessed by walking horse around and between obstacles
Perform fundic exam
How is the position of the eye controlled by the cranial nerves?
Oculomotor nerve CN III - controls all but 2 muscles of the eye
Trochlear nerve CN IV - controls diagonal movement of the eye (inward and downward)
Abducens nerve CN VI - controls lateral movement of the eye
What is the retractor oculi reflex and how is it tested?
Press on cornea through eyelid
Feel for reflex retraction of the globe (retractor bulbi)
What are the afferent and efferent pathways for the retractor oculi reflex?
Afferent - Trigeminal nerve CN V
Efferent - Abducens nerve CN VI
What is the trigeminal nerve responsible for?
V1 (ophthalmic) - sensory to the eye, scalp, nose, forehead
V2 (maxillary) - sensory to the face below orbits and above mouth
V3 (mandibular) - motor to all muscles of mastication
What nerve is affected if a horse has a left sided ear tilt and muzzle pulled to right side?
Which direction is the muzzle being pulled and why?
Which side is the drooping ear on?
Facial Nerve CN VII
Muzzle being pulled to normal side, because these muscles are still properly innervated (no counterbalance from left)
Drooping ear on left = abnormal innervation
What does the drooping ear in Facial nerve CN VII dysfunction tell you about the lesion?
Tells you the lesion is close to the base of the skull
If only muzzle is pulled to side, while the ear is normal, this tells you the lesion is more peripheral
What type of disease does nystagmus indicate?
Vestibular disease
Vertical nystagmus indicates a _________ problem while horizontal nystagmus indicates a _________ problem.
(central/peripheral)
Vertical = central
Horizontal = peripheral
Fast phase of nystagmus is always _________ from the side of the lesion.
AWAY
What are signs of pharyngeal and laryngeal dysfunction?
Which cranial nerves are affected?
Repeated swallowing, Vocalization, Endoscopy
Glossopharyngeal nerve CN IX
Vagus Nerve CN X
What causes Horner syndrome?
Interruption of sympathetic nerve pathway between hypothalamus and eye
What are the 6 symptoms of Horner Syndrome
Ptosis
Miosis
Enophthalmus
Prominent 3rd eyelid
Conjunctival and nasal hyperemia
Sweating
Why is sweating a symptom of Horner syndrome? How does this occur?
Sweat glands are controlled by the amount of blood supplied to them. If there is an interruption to the sympathetic supply, this increases parasympathetic stimulation → vasodilation → increased sweating
Where will a horse with Horner syndrome be sweating in relation to the location of a lesion?
Sweating at level of the lesion
Ataxia is a functional deficit associated with defective ___________.
Proprioception
What is the difference between hypermetria, hypometria and dysmetria?
What part of the brain would be damaged?
Hypermetria - overreaching during voluntary movement
Hypometria - underreaching
Dysmetria - inability to control the distance, speed, and range of motion necessary to perform smoothly coordinated movements
Cerebellum
What is truncal sway?
Front and back end not communicating, moving separately
What do UMN control? What do LMN control?
How do you differentiate pelvic limb lameness from ataxia?
Ataxia is generally associated with irregular irregularities of gait (always changing)
Lameness associated with consistent irregularities
What types of spinal cord lesions can produce signs similar to certain lamenesses?
Asymmetric spinal cord lesions
What are the 3 clues which can point toward ataxia?
Pacing - worse when head lifted
Circumduction - tight circles
Hypermetria - overreaching
What causes muscle weakness in horses with equine motor disease?
Loss of motor innervation to muscles → muscle atrophy → weakness
What are the symptoms of upper vs. lower motor neuron weakness?
What is exertional rhabdomyolysis? What are the clinical signs and when are they first observed? What is the common name for rhabdo?
Type of exertional myopathy associated with muscle fatigue, pain, or cramping associated with exercise, producing necrosis of striated skeletal muscle.
Clinical signs usually are observed shortly after onset of exercise.
Excessive sweating, tachypnea, tachycardia, muscle fasciculations, reluctance or refusal to move, and firm, painful lumbar and gluteal musculature
Also known as azoturia, “tying up” or “cording up”
What is the treatment and prognosis for exertional rhabdomyolysis?
Treatment - stop exercise immediately when signs are noticed, moved to well bedded stall with fresh water. Main goals of treatment0 relieve pain/anxiety with NSAIDs/opioids and correct acid/base imbalances. Only administer NSAIDs to well-hydrated horse.
Prognosis - Good. Most horses pain free within 24-48 hours and recovered within days to weeks.
How should you monitor the progress of a horse with a severe case exertional rhabdomyolysis?
Regular serum creatinine and BUN levels to assess extent of renal damage.
What is the proper protocol for return to exercise for horse recovering from exertional rhabdomyolysis?
Slow, gradual return to exercise with access to paddock with adequate water and bedding.
Endurance horses should be encouraged to drink electrolyte solution to supplement training.
What is polysaccharide storage myopathy?
Chronic form of rhabdomyolysis aka. exertional myopathy.
Type 1 - Dominantly inherited mutation in the glycogen synthase 1 (GYS1) gene which causes rhabdomyolysis with little exercise at a young age.
Type 2 - Issues with glycogen storage without GYS1 gene mutation.
What is ischemic myopathy? What is another name for this condition?
Formation of blood clots that block the iliac artery results in extensive damage and death of muscle tissue of the hindlimb due to a lack of blood supply.
Aka - aorto-iliac thrombosis
Which levels should you measure to diagnose lameness caused by muscle disease?
Measure CK and AST (will be elevated in presence of disease)
What kind of condition is closely related to aorto-iliac thrombus in the horse?
Usually related to movement of large strongyle parasites, which set up thrombus at level of iliac, leading to ischemia of pelvic limbs
Limb weakness can indicate damage where in the nervous system?
Spinal cord
If a horse is standing, what can you assume (neuro exam related)?
Spinal reflexes are intact
Which reflexes are the most useful in an adult horse?
Withdrawal reflexes are useful
Reflex arcs (patellar reflex, etc.) - not useful
What are the signs associated with damageto the sacral/perineal (lumbar) spinal segments?
Reduced perineal reflex, reduced sensation, tail flaccidity, rectal exam (flaccidity), urinary incontinence
