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Steps for localization of a lesion in the spinal cord. (6)
- 1- gait and posture
- 2- postural reactions
- 3- pelvic limb tone and reflexes
- 4- thoracic limb tone and reflexes
- 5- cutaneous trunci reflex
- 6- spinal palpation
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Conscious proprioceptive deficits in both pelvic limbs; the lesion is _________.
caudal to T2
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When ataxia is present, crossing is a sign of ___________.
proprioceptive deficit
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What spinal cord segment is this?
cervical
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What spinal cord segment is this?
Thoracic; lateral grey column is unique to TL region
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What spinal cord segment is this?
Lumbar
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What spinal cord segment is this?
Sacral; cauda equina
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Proprioceptive ataxia is a sign of damage to the ____________.
spinocerebellar tract
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Describe the sequence of appearance of signs in compressive spinal cord lesions. (4)
proprioceptive ataxia with mild paresis--> ataxia with severe paresis--> paralysis and urinary incontinence--> loss of nociception
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Conscious proprioception is a ________ pathway than the nociception pathway, which is __(3)__; therefore,...
simpler; complex, highly resistant, and multi-synaptic; to damage the nociception system requires a severe spinal cord injury.
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Define a LMN.
originates in the cervical or lumbar intumescence in the spinal cord and innervates muscles in the limbs; consider a peripheral n.
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Define an UMN.
Start in the brain and stay within the spinal cord
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Pool of neurons in the brain that go down in the spinal cord to influence the LMNs.
UMNs
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What are the functions of UMNs? (5)
initiate voluntary movements, postural adjustment, maintenance of muscle tone, stimulate flexor mm., inhibit extensor mm.
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Clinical signs of lesions affecting UMNs. (3)
paresis/paralysis, normal to increased muscle tone and reflexes, mild muscular atrophy
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Describe the pathway of a LMN, along which any lesions will cause LMN dysfunction signs.
motor neuron in ventral grey column of spinal cord--> nerve root--> spinal nerve--> peripheral n.--> target muscle
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What are the functions of LMNs? (3)
Final common pathway, manifest motor activity that is voluntary and reflexes
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Clinical signs of LMN dysfunction.
paresis/paralysis, decreased to absent muscle tone and reflexes, severe muscular atrophy
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With a combined UMN and LMN injury, the ______ signs will always prevail b/c it is the ___________.
LMN; final common pathway
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Describe signs associated with lesions in each region of the spinal cord.
- C1-C5- TL UMN, PL UMN
- C6-T2- TL LMN, PL UMN
- T3-L3- PL UMN
- L4-S3- PL LMN
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The dog can't move any of it's limbs; where is the lesion possibly located? How can you differentiate it?
lesion is either C1-C5 or C6-T2; C1-C5 UMN signs in both PL and TL; C6-T2 LMN TL and UMN PL
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Under what circumstances will you see LMN signs?
only if the lesion is in the C6-T2 or L4-S3 regions, where the brachial plexus and lumbosacral plexus come from, respectively
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Spinal cord lesions in motor tracts are always __________.
ipsilateral
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Ataxia, tetraparesis, reflexes normal to increased in all limbs; where is the lesion?
C1-C5
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Ataxia, tetraparesis/plegia, decreased/absent reflexes in thoracic limbs, normal to increased reflexes in pelvic limbs; where is the lesion?
C6-T2
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Ataxia, paraparesis/plegia, normal to increased reflexes in the pelvic limb; where is the lesion?
T3-L3
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Mild ataxia, paraparesis/plegia, decreased to absent reflexes in the pelvic limbs; where is the lesion?
L4-S3
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C6-C8 is an important subdivision that is associated with ___________; what signs would be associated with this disorder? (5)
Wobbler's Syndrome; pelvic limb ataxia, spastic thoracic limb gait, increased extensor tone in TL, normal or decreased flexor tone in TL, normal to increased tone in PL
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In the thoracic limb, everything is a balance between flexion, the _________ nerve in the __________ portion of the brachial plexus, and extension, the __________ nerve in the ___________ portion of the brachial plexus.
musculocutaneous; cranial; radial; caudal
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In what vertebral bodies are the L4-S3 spinal cord segments housed?
L4 and L5 vertebral bodies
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In what vertebral bodies are S1-S3 spinal cord segments housed?
all in the L5 vertebral body (caudal to this point, cauda equina)
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What causes the Schiff-Sherrington Syndrome posture?
severe lesion in the TL (T2-L5) region
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What is the Schiff-Sherrington Syndrome posture?
ONLY WHEN THE DOG IS IN LATERAL RECUMBANCY, increased extensor tone in the TLs (UMN signs); in sternal recumbency, TLs are normal
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With Schiff-Sherrington, there is damage to the ___________.
propriospinal tract
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To further localize a T3-L3 lesion, what two tests do you use?
cutaneous trunci reflex and or spinal palpation
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Crossed externsor reflex/ninja kick indicates...
UMN lesion and chronicity.
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Describe what signs you would see in each if these situations, assuming the red dots are lesions.
- 1- LMN TL, UMN PL
- 2- UMN all 4 limbs; find second lesion by spinal palpation and cutaneous trunci reflex
- 3- LMN TL, UMN PL; find second lesion by spinal palpation and cutaneous trunci reflex
- 4- LMN PL
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What is the most common presentation, and where is this lesion?
UMN signs in the PL; T3-L3 myelopathy
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What causes LMN signs in the PLs and the TLs?
lesion is outside the spinal cord- neuropathic, junctional, myopathic, botulism
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Diseases that cause LMN signs in all four limbs do NOT cause ____________.
proprioceptive ataxia
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With brain lesions, what are the 3 possible lesion locations?
brainstem, cerebellum, thalamocortex (forebrain)
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The brainstem contains the ___________, a common site of lesions.
vestibular system
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What signs are associated with brainstem lesions? (2)
CN deficits and altered mentation
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What are the components of the brainstem?
reticular formation (ARAS), CN III-XII, sensory (ascending) and motor (descending UMN) pathways
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Mentation is controlled by the ___________.
Ascending reticular activating system (reticular formation)
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Lesions in the sensory (ascending) and motor (descending UMN) pathways in the brainstem cause __(2)__.
tetraparesis and ataxia
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The ascending reticular activating system maintains a state of ____________; clinical signs of lesions affecting this system include... (3)
wakefulness; somnolence, stupor, coma
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Head tilt indicates a dysfunction in __________, which is a lesion in the __________.
vestibular function; rostral medulla (CN VIII)
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What CN(s) are in the mesencephalon?
CN III and IV
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What CN(s) are within the pons?
CN V (motor, sensory)
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What CN(s) are within the rostral medulla?
CN V (sensory), VI, VII, VIII
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What CN(s) are within the caudal medulla?
CN IX-XII
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What are clinical signs of lesions within the mesencephalon? (3)
strabismus, ocular paralysis, mydriasis
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What are clinical signs of lesions in the pons? (1)
atrophy of masticatory muscles
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What are clinical signs of lesions in the rostral medulla? (3)
head tilt, facial paralysis, absence of palpebral reflex
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What are clinical signs of lesions in the caudal medulla? (4)
dysphonia, dysphagia, sterterous breathing, tongue paralysis
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The more _________ the brainstem lesion in sensory and motor pathways, the less severe the gait abnormalities.
rostral
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Lesions in the thalamocortex cause __________ deficits.
contralateral
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What is the function of the vestibular system?
balance and position of eyes, neck, trunk, and limbs
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What are the 4 vestibular nuclei in the rostral medulla connected to?
- cerebellum- projections flocculonoduar lobe
- reticular formation
- medial longitudinal fasciculus
- vestibulospinal tracts
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Clinical signs of vestibular disease. (5)
head tilt, +/- vestibular ataxia, +/- strabismus/nystagmus, somnolence (central lesion), proprioceptive deficits (central lesion)
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What part of the vestibular system is associated with motion sickness?
reticular formation
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What part of the vestibular system connects C VIII to CNs II, IV, and VI?
medial longitudinal fasciulus
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How can you differentiate a central and peripheral vestibular lesion?
central has proprioceptive deficits and somnolence (not peripheral)
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Describe nystagmus associated with peripheral vestibular lesions.
horizontal that goes opposite the head tilt ("running away from the lesion")
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Clinical signs associated with cerebellar disease. (8)
head/body tremors (intentional tremors), ataxia, wide-based stance, truncal sway, dysmetria, hypermetria, ipsilateral absence of menace response, +/- vestibular signs if flocculonodular lobe is involved
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With cerebellar disease, there is a(n) ___________ absence of ___________.
ipsilateral; menace response
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What clinical signs should NOT be present if it solely cerebellar disease (no involvement of any other structures)? (2)
no proprioceptive deficits, no weakness (strength preserved)
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Clinical signs of thalamocortex/forebrain disease. (8)
abnormal behavior, circling, compulsiveness, seizures, central blindness, [contralat. deficits] menace, postural reactions, nasal sensation
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With thalamocortical disease, there are __________ deficits in... (3)
contralateral; menace response, postural reactions, and nasal sensation.
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What specific tests can you use to assess thalamocortical function? (4)
mental status, menace response, nasal sensation, proprioception/hopping
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