Myelopathies Flashcards
(34 cards)
grey matter is made of what? where in the CNS do we find it? what are the types of neurons?
neuronal cell bodies
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* Sensory neurons
> Dorsal root ganglion / dorsal horn
* Interneurons
* LMNs
> Ventral horn
> To muscles
Spinal cord: Anatomy
- at what vertebra does it terminate in large vs small dogs? cats?
◦ Large-breed dogs > L6 vertebra
◦ Small-breed dogs > L7 vertebra
◦ Cats > L7-S1vertebrae
- Spinal cord divided in segments:
(dog numbers) - how do spinal cord segments line up with vertebra
◦ 8 cervical
◦ 13 thoracic
◦ 7 lumbar
◦ 3 sacral
◦ ≥ 2 caudal
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note spinal segment numbers switch from exiting cranial to vertebral body to caudal at C8
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Segments NOT always lie in the same number vertebra
Most segments are cranial to vertebra Lesion localization: SEGMENTS
issues that affect gait (and posture)
- Ataxia
- Proprioceptive (spinal)
- Vestibular
- Cerebellar - Paresis (weakness)
- motor function - Lameness
Proprioceptive ataxia - what structures might we have issues with?
Sensory function:
1. Receptors (proprioceptors): Joints, tendons, muscles
2. Ascending proprioceptive tracts
3. To cerebral cortex (conscious perception)
Motor function
- what neurons are involved?
- deficits?
◦ Control activity muscles (brain to muscles)
◦ Required to move limbs (muscle contraction)
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Requires 2 neurons:
UMN
LMN
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◦ Deficit: PARESIS (weakness)
UMN and LMN - where are the cell bodies and axons? what do they do?
UMN
◦ Cell body: Brain
◦ Axons: descending WM
◦ “UMN tells LMNs what to do” (descending inhibition)
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LMN
◦ Cell body: ventral horn GM, brainstem nuclei
◦ Axon: PNS to muscle
◦ Responsible for the reflex motor activity (patellar reflex)
Paresis/paralysis - what is this? where might lesions be?
- Lost of voluntary motor function (weakness)
> Lesion affecting UMN or LMN - PARESIS: Partial loss
- PARALYSIS (-plegia): Complete absence
Monoparesis / Monoplegia
Paraparesis / Paraplegia > back limbs
Tetraparesis /Tetraplegia
Hemiparesis / Hemiplegia > both limbs on same side
UMN lesion clinical signs
Paresis (weakness)
Loss of descending inhibition
Spastic paresis / paralysis
Spinal reflexes: normal or increased
Increased muscle tone
Disuse muscle atrophy
Usually associated to proprioceptive ataxia
LMN lesion clinical signs
Paresis (weakness)
Flaccid paresis / paralysis
Spinal reflexes: decreased / absent
Decreased muscle tone
Neurogenic muscle atrophy
LMNs for limbs are in what regions
◦ Thoracic limbs: C6-T2 (cervical intumescence) ◦ Pelvic limbs: L4-S3 (lumbosacral intumescence)
Lesion localization: Spinal cord
Functional classification: (segments)
C1-C5
C6-T2
T3-L3
L4-S3
C1-C5 lesion signs
◦ Tetraparesis / tetraplegia
◦ Proprioceptive def 4 limbs
◦ UMN deficit for 4 limbs (spastic)
◦ Reflexes: normal/increased
C6-T2 lesion signs
◦ Tetraparesis / tetraplegia
◦ Proprioceptive def 4 limbs
◦ LMN deficit TLs (flaccid):
> Decreased/absent reflexes TLs
◦ UMN deficit PLs (spastic):
> Normal/increased reflexes PLs
T3-L3 lesion signs
◦ Paraparesis / paraplegia
◦ Normal TLs
◦ Proprioceptive def PLs
◦ UMN deficit PLs (spastic)
◦ Reflexes PLs: normal/increased
L4-S3 lesion signs
- Paraparesis / Paraplegia
- Normal TLs
- Proprioceptive def PLs
- LMN deficit PLs (flaccid)
- Reflexes PLs: decreased /absent
Classification or myelopathies
Lesion localization
Extradural
Intradural-extramedullary
Intramedullary
Clinical signs spinal cord compression
- order that signs appear?
- Back/neck pain
- Proprioceptive ataxia / deficits
- Paresis
- Paralysis, incontinence
- Loss of nociception
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improve in opposite direction
important rule out for neurodisease when we see weakness, pain
IMPORTANT! Rule out orthopedic disease
(bilateral cruciate rupture, long bone fractures, polyarthritis)
acute causes of myelopathies
- FCEM
- Spinal trauma
- Intervertebral disc herniation (IVDH): extrusion
intervertebral disc anatomy
a. Annulus fibrosus > outer layers
> type I collagen surrounding the nucleus pulposus in approximately 15-20 layer
b. Nucleus pulposus > inner, gelatinous material
Intervertebral disc herniation type
Extrusion - acute: nucleus pulosus breaks though annulus fibrosus, impinges on spinal cord
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Protrusion - chronic: annulus collagen over the years loses its consistency and the disc slowly loses its shape and impinges on the spinal cord
IVDH: extrusion
- pathogenesis
Chondroid degeneration nucleus pulposus
> (nucleus pulposus) becomes hard
HANSEN TYPE 1 DEGENERATION
Extrusion of mineralized nucleus pulposus into the vertebral canal
IVDH extrusion:
clinical signs
who gets this?
location?
Acute, progressive
Chondrodystrophic breeds (small breeds)
◦ Dachshund, Beagle, Cocker Spaniel, Shih tzu…
◦ But may occur in any breed!
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Age
◦ Peak 3-6 years-old (rare < 2y)
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Location:
◦ Caudal thoracic-lumbar: T11-L3 (T12-13,T13-L1)
◦ Cervical
◦ Very uncommon T1-T10 > Intercapital ligament stabilizes
