Unit 3 - Neuro (CN, Reflexes, Diagnostics, Definitions) Flashcards
What are the four functionally different anatomic areas of the nervous system?
Cerebrum
Cerebellum
Brainstem and cranial nerves
Spinal cord and peripheral nerves
What are the three etiological categories of nervous illnesses?
Acquired biologic
Acquired nonbiologic
Congenital or hereditary
What should be observed on distant neurologic examination?
Mentation, posture, and gait
What spinal reflexes can be assessed in all ruminants?
Panniculus, withdrawal of forelimb/hind limb, patellar, and perineal reflex
What are the 6 broad types of abnormalities in mentation in ruminants?
- Excitement, mania, or hyperesthesia
- Seizures
- Depression
- Aimless circling, stupor, or coma
- Abnormal vocalization
- Blindness
T/F: Aimless circling and tight circles associated with vestibular lesions are caused by the same process.
False - aimless circling is due to serevral disease
What is gait?
The coordinated functioning of the cerebral cortex, extrapyramidal basal nuclei, and red nuclei which stimulates the flexor muscles and simultaneous inhibition of extensor muscles
What can cause gait abnormalities?
Cerebellar, brainstem, spinal cord, and peripheral nerve lesions
How do you assess conscious proprioception in ruminants?
During ambulation by placing obstacles in enclosures/alleyways
If an animal is halter broke, how do you assess conscious proprioception?
Walking in tight circles, walking across/up a curb, walking up and down a hill, and pulling the tail while walking strait
What neurologic signs can suggest the possible presence of proprioception deficits and exaggerated spinal reflexes?
Presence of ataxia, hypermetria, and truncal sway
What is posture maintained by?
The trunk muscles and extensor muscles of the proximal limbs
What facilitates posture?
The vestibulospinal and reticulospinal tracts from the medulla and pons
What are the three main aspects of posture?
Head, body, and limbs
What processes sensory input from pressure/stretch receptors in the limbs/body, vestibular system, and visual inputs?
The brainstem, cerebellum, and cerebrum
Abnormal head posture (continuous head tilt) indicates what?
Central or peripheral vestibular disease
What can cause abnormal trunk posture?
Congenital or acquired disorders such as scoliosis, lordosis, and kyphosis
What are some abnormal limb postures that can result from UMN or LMN disease?
Inappropriate positioning, weakness, knuckling, and a base-wide stance
What does the menace response evaluate?
The entire visual pathway, CN VII, and the cerebellum
What cranial nerves are involved in the menace response?
CN II and CN VII
T/F: The menace response is often absent in neonatal ruminants.
True
What cranial nerves do pupillary reflexes assess?
CN II and CN III
If the intraparenchymal visual pathways are affected (central or cortical blindness) what will the menace response be? The PLRs?
Menace - absent on the contralateral side of the lesion
PLR - intact
If the extraparenchymal visual pathways (peripheral blindness) are affected, what will the menace response be? PLRs?
Menace - blindness on the size of lesion; absent
PLRs - abnormal
What muscles does the CN III control?
Dorsal, ventral, and medial rectus muscles
Ventral oblique muscle
Levator palpebrae muscle
What do lesions of CN III result in?
Ipsilateral ventrolateral strabismus and mydriasis
What muscle does CN IV innervate?
Dorsal oblique muscle
What do lesions of CN IV result in?
dorsolateral strabismus
What does CN VI innervate?
The lateral rectus and retractor bulbi muscles
What do lesions of CN VI result in?
Medial strabismus with a more forward positioning of the globe
Failure to retract the globe during assessment of the palpebral (or corneal) reflex
T/F: The eyes of ruminants should try to maintain focus straight ahead, the result being that the eye moves slowly in the opposite direction of the head movement and then ‘jump’ quickly back towards the direction movement.
True
What are the three branches of the trigeminal nerve (CN V)?
Ophthalmic, maxillary, and mandibular
While all branches of CN V have sensory fibers, which branch has motor fibers as well?
Mandibular
Lesions to the mandibular branch of CN V result in what clinical signs?
Muscle asymmetry/loss, flaccid or lowered jaw, inability to close the jaw, inability/reduced mastication with dropping of feed and drooling, and protrusion of the tongue.
What do the corneal and palpebral reflexes test?
Sensory - CN V
Motor - CN VII
What branch of the trigeminal is assessed by touching the medial canthus? Lateral canthus?
Medial canthus - ophthalmic branch
Lateral canthus - maxillary branch
How is sensory function of the mandibular branch of CN V tested?
Touching/pinching the face, including the base of the ear
How is the consciously mediated, coordinated movement of the head away from noxious stimuli assessed?
Applying stimuli to the nasal septum
What CN tests test CN VII?
Menace response, palpebral reflex, corneal reflex
What does CN VII innervate?
Facial muscles of expression
Parasympathetic innervation to the lacrimal gland, and mandibular and submandibular salivary glands
Symmetry, posture, and movement of the eyelids, lips, and ears
What can lesions of CN VII cause?
Ear droop, lack of ear movement, eyelid droop (ptosis), and deviation of nasal philtrum
Lack if muzzle tone can result in protrusion of the tongue and driiping
Exposure keratitis
What is the vestibular portion of CN VIII responsible for?
maintaining head position and other structures relative to the pull of gravity
What is the cochlear division of CN VIII responsible for?
hearing
What are clinical signs associated with vestibular dysfunction?
Head tilt, nystagmus, ataxia, incoordination, positional strabismus, and head tilt towards the lesion (often will fall on the side of the lesion)
What do CN IX and CN X innervate?
Pharynx, larynx, and tongue
Striated muscles of the esophagus
CN X - abdominal viscera including the forestomach
How is the gag reflex performed?
Place a tongue depressor on the back of the tongue, which normally the animal should ‘throw’ back up
What does CN XII innervate?
Motor innervation of the tongue, controlling both protrusion and retraction
What signs are indicative of a CN XII lesion?
Difficult prehension and mastication feed
Unilateral damage results in a tongue to twist toward the affected side (if it is a facial nerve lesion the tongue will twist away from the lesion)
Evaluation of spinal reflexes is best achieved in what position?
Lateral recumbency
T/F: Spinal reflexes require conscious or voluntary input and test the integrity of LMN, but also provide information on UMN influence on LMN
False - they do NOT require conscious or voluntary input
Exaggerated (hyper-reflexive) reflexes are often observed with (LMN/UMN) lesions. A reduced/diminished or absent reflex indicates (LMN/UMN) lesions.
UMN
LMN
What does the extensor reflex test?
The radial nerve function of the forelimb
How do you perform the extensor reflex test?
Place the animal in lateral recumbency
Place a hand under the foot
With the limb positioned in extension and push it gently
What is the normal reflex for the extensor reflex?
For the animal to push back against your hand
What extensor reflex response is indicative of LMN disease? UMN disease?
LMN disease - decreased or absence of resistance
UMN disease - Increased tone of the triceps muscle
How is the panniculus reflex done?
Apply pressure on the cutaneous trunci starting caudally and move forward
The reflex arc for the panniculus reflex is the sensory fibers from each dermatome enters the spinal cord and then ascends to the ___ and ___ segments.
C8 and T1
How do you perform the withdrawal reflexes?
Apply adequate force and pinch the interdigital skin as well as the coronary band of each individual claw.
What do the withdrawal reflexes require to be intact for the front limbs?
C6-T2 and the axillary, median, and ulnar nerves
What do the withdrawal reflexes require to be intact for the back limbs?
L 5(6)- S1 and the sciatic nerve in the hind limb
T/F: A cross extensor reflex can be normal in neonates but in mature ruminants it can indicated interference with the normal UMN pathways.
True
What does the patellar reflex require to be intact?
L4, L5, and the femoral nerve
What is the normal response to the patellar reflex?
Obvious and repeatable extension of the stifle
What can cause an exaggerated patellar reflex response?
Both UMN damage and sciatic nerve damage
What causes decreased patellar reflex responses?
Lesions of L4, L5, the femoral nerve, and myonecrosis and white muscle disease
How is the perineal reflex done?
Pinching of the skin around the rectum
What is required for an intact perineal reflex?
Intact spinal cord segments S2-S4 and the pudendal and caudal rectal nerves
How is cerebrospinal fluid collected?
Palpate the hooks/wing of the ileum, and feel for depression slightly caudal to an imaginary line drawn in between the hooks. The spinal needle is placed in the lumbosacral space to the subarachnoid space
What is the rule of thumb for the amount of cerebrospinal fluid that can be collected?
Approximately 0.5 ml per 5 kg of body weight can safely be removed
What should normal cerebrospinal fluid look like?
Clear and colorless
What is cloudy or turbid cerebrospinal fluid indicative of?
Increased white cell concentration
What does a stable foam in cerebrospinal fluid indicate?
Icnreased protein concentration
What are normal WBC and protein levels in cerebrospinal fluid in cattle?
< 3 WBC/dL
< 30 mg/dl protein
What is the normal specific gravity of cerebrospinal fluid?
<1.010
Define depression.
Decreased responsiveness to stimuli
Define stupor.
Animal appears to be sleeping when undisturbed; mild stimuli will not induce arousal, but vigorous stimuli will induce arousal
Define coma.
An unconscious state in which spinal reflexes can be normal, but vigorous noxious stimuli does not induce arousal
Define seizure.
Involuntary episode of muscular activity that may be generalized or localized
If generalized - the animal becomes recumbent, has altered mentation, and has periodic episodes of muscular activity
Define opisthotonus.
Dorsiflexion of the head and neck
Define nystagmus.
Inappropriate and involuntary movements of the eyes; can be horizontal, vertical, rotary, or intermittent
Where does the fast component of nystagmus typically point? Slow?
Fast - away from the side of the lesion
Slow - towards the side of the lesion
Define intention tremor.
Inappropriate loss of fine motor control, particularly when the animal intends to eat or nurse
Define a tremor.
Small and rapid altering contractions of agonist and antagonist muscle groups that occur at rest or during movement
Define weakness.
Loss of muscle strength
Define paresis.
Partial loss of neural control of muscles
Define paralysis.
Complete loss of neural control of the muscles
Define proprioception.
Awareness of the location of the limb in space
Define circumduction.
Movement of a limb such that the distal portion describes a circle, with the proximal portion being fixed
Define ataxia.
Abnormal gait characterized by incoordination but without spasticity, weakness, or involuntary movements
What causes atexia?
Lesions in the proprioceptive pathways, vestibular system, or cerebellum
Define dysmetria.
Movements that are too short or too long
Define hypermetria.
The exaggerated movements of the limbs during locomotion; goose-stepping
If there is a lesion at C1-C5, what deficits will there be? Reflexes present?
UMN on all 4 limbs
Spastic paresis of both front and back limbs
Hyperactive to normal reflexes in all 4 limbs
If there is a lesion at C6-T2, what deficits will there be? Reflexes present?
UMN hindlimbs, LMN front limbs
Spastic paresis of back limbs
Flacid paresis of front limbs
Neurogenic muscular atrophy of front limbs only
Hyperactive to normal reflexes in rear limbs
Hypoactive reflexes in front limbs
If there is a lesion at T3-L3, what deficits will there be? Reflexes present?
UMN hindlimbs only Spastic paresis of back limbs Normal back limbs No neurogenic muscle atrophy Hyperactive to normal reflexes in hind limbs
If there is a lesion at L4-sacrum, what deficits will there be? Reflexes?
LMN hindlimbs only Flaccid paresis of hind limbs Normal thoracic limbs Neurogenic muscular atrophy in hindlimbs Hyporeflexive in hind limbs
What lesion would result in a flaccid bladder that is distended, abnormally large, and atonic urethral sphincter?
Sacral lesion S1 and S2
What lesion would result in a hypertonic bladder that has increased tone, high pressure, and a hypertonic urethral sphincter?
Lesion cranial to S1
