Small Animal Neuroradiology: The Spine

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Small Animal Neuroradiology: The Spine
Lecture 2 –Degenerative Diseases, Diseases causing Instability, Vertebral
Injury, Infection and Neoplasia
VCA 341 Fall 2011
Andrea Matthews, DVM, Dip ACVR
Assistant Professor of Radiology
Spondylosis Deformans
Bone on ventral aspect of the vertebral bodies
arising from the endplates
Sometimes bridges the entire intervertebral disc
space
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Spondylosis Deformans
Courtesy Dr. L. Pack
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Intervertebral Disc Disease
Anatomy
Thrall Veterinary Diagnostic Radiology 5th Ed
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Intervertebral Disc Disease
Protrusion
Herniation
Extrusion
http://www.backandneckpain.ca/understanding-your-spine/499-2/
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Intervertebral Disc Disease
Chondroid degeneration
 Chondrodystrophic breeds
 Dehydration and mineralization of the nucleus
 Hansen Type I lesions
•
•
•
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Extrusion of disc material into vertebral canal
Acute – neurologic signs due to spinal cord
compression
Most commonly between T12-L2 and C2-3 in
cervical region
Matthews
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Intervertebral Disc Disease
Fibroid degeneration
 Non-chondrodystrophic breeds
 Fibrous metaplasia of the nucleus
 Hansen Type II lesions
•
•
•
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Stretching, partial rupture or hypertrophy of annulus
with bulging into vertebral canal
Chronic progressive course
Can cause neurologic signs, typically chronic and
progressive in nature and milder than the acute
extrusion
Matthews
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Intervertebral Disc Disease
High velocity, low volume disc extrusion
 Young to middle aged dogs
 No degeneration of nucleus
•
•
Gelatinous nucleus extrudes into vertebral canal
Usually secondary to trauma
 Causes concussive spinal cord injury
 Sometimes referred to as Type III disc extrusion
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Intervertebral Disc Disease
Clinical features
 Dachshunds are over-represented
 Less common in cats
 Neurologic signs are related to the site of
extrusion
•
•
UMN versus LMN
C1-5, C6-T2, T3-L3, L4-S3
 Intercapital ligaments from T2-T10 joining rib
heads usually prevent extrusion in thoracic spine
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Intervertebral Disc Disease
Survey radiographs
 Mineralized material in plane of intervertebral disc
space
•
Indicative of degeneration, not necessarily extrusion
 May see mineralized material in plane of vertebral
canal in case of disc extrusion
•
Important to use 2 views
 Narrowing of intervertebral disc space
•
May be wedged in appearance
 Narrowing of the articular facet joint space
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Intervertebral Disc Disease
Narrow IVD space
Narrow IV foramen
Narrow articular facet joint
TUSCVM
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Intervertebral Disc Disease
Mineralized material in plane of vertebral canal over IVD space
TUSCVM
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Intervertebral Disc Disease
Myelography
 97% accurate in identifying site and lateralizing
disc hernia
CT
 Good for mineralized disc material; need
myleogram if disc material not mineralized
MRI
 Good for all types of spinal cord compression
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Intervertebral Disc Disease
Need loss of visibility of the contrast column to say lesion is compressive
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Intervertebral Disc Disease
CT
MRI
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Atlantoaxial Instability
Space between the
dorsal arch of C1 and
the spinous process of
C2
C1
C2
Dens (odontoid
process)
Wings of C1 (atlas)
TUSCVM
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Atlantoaxial Instability
Ligaments of the A-A joint
 Dorsal atlanto axial ligament
 Alar ligaments (2)
 Apical ligament
 Transverse ligament
C2
C1
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Atlantoaxial Instability
Radiographic findings
 Increased distance between dorsal spinous process
of C2 and dorsal arch of C1
 Dorsal deviation of C2 causing step in vertebral canal
 Absent or small odontoid process
 Fractured odontoid process
Views
 Lateral, ventrodorsal, lateral oblique
 Flexed lateral must be performed after survey
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Atlantoaxial Instability
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Atlantoaxial Instability
Normal
Agenesis of the dens
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Atlantoaxial Instability
Fracture of dens
TUSCVM
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Cervical Vertebral Instability
Large breed dogs
 Young Great Danes (<1year)
 Older Dobermans (3-9 years)
 St. Bernards, Mastiffs, Basset Hounds…
Males affected more commonly than females
Caudal cervical spine most common (C5-7)
 Also C2-4 but less frequently
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Cervical Vertebral Instability
Abnormalities
 Congenital malformation and malarticulation of
vertebral bodies, articular facets, vertebral arches and
pedicles
•
•
Dorsal vertebral tipping and subluxation
Degenerative joint disease of articular facets
 Ligamentum flavum hypertrophy
 Hypertrophy of the dorsal annulus fibrosus and
stretching/hypertrophy of the dorsal longitudinal
ligament
 Intervertebral disc disease (Hansen type II)
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Cervical Vertebral Instability
Static lesion
 Does not change with different positions of the neck
(neutral, flexion, extension or traction)
•
Usually due to IVD herniation or bony abnormalities
(malformation, facets proliferation)
Dynamic lesion
 Changes according to the position of the neck
•
•
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Due to ligamentous hypertrophy
Traction or flexion of the neck will the severity of the
lesion; Extension will exacerbate the lesion
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Cervical Vertebral Instability
Articular facet
degenerative joint
disease
TUSCVM
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Cervical Vertebral Instability
Example of Dynamic lesion
Funnel shaped
appearance of cranial
aspect of vertebral body
with dorsal tipping of
cranial aspect of vertebral
body
Narrowing of vertebral canal with
spinal cord compression
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Matthews
Courtesy L. Pack
Cervical Vertebral Instability
Example of Dynamic and Static Lesion
Flexed view – compression of
spinal cord with tipping of
vertebral body and
mineralized material
TUSCVM
Traction view – the spinal cord
remains compressed
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Lumbosacral Instability
Also known as…
 Cauda equina syndrome
 Lumbosacral stenosis…
Congenital or acquired abnormalities
causing biomechanical changes
 Cause compression of nerve roots
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Lumbosacral Instability
Cauda equina
 Nerves exiting the terminal spinal cord
•
Spinal cord termination- L4 in large breeds and
cranial aspect ofL6 in small breeds
Clinical features
 Seen in cats and dogs
 German shepherds are predisposed
•
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Higher incidence seen in animals with a transitional
vertebra
Matthews
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Lumbosacral Instability
Etiologies
 Disc herniation at L6-7 or L7- S1
 Spondylosis deformans and facet osteoarthrosis (DJD)
 Congenital lumbosacral canal stenosis
Radiographic findings
 Static or dynamic condition
 Narrow and wedged intervertebral disc space
 Narrow vertebral canal
 Ventral and lateral spondylosis deformans
 Articular facet osteoarthrosis
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Lumbosacral Instability
Articular facet
osteoarthrosis
Spondylosis
TUSCVM
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Lumbosacral Instability
Wedged IVD
space
Sclerosis and
irregularity of
endplates
TUSCVM
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Lumbosacral Instability
Contrast techniques
 Myelography
 Epidurography
 Discography
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Vertebral Injury
Fractures
 Important points
• Care in handling the patient
• Perform lateral view firs to rule out major fractures
before proceeding
 Fracture of vertebra
• Body, lamina, pedicles
• Transverse or spinous processes
• Endplates (young animals)
 Compression fracture
 Subluxation/ luxation
 Pathologic fracture
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Vertebral Injury
Vertebral endplate fracture with subluxation of endplate and widening
of the articular facet joint. Note the vertebral canal malalignment
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Vertebral Injury
Vertebral canal malalignment due to subluxation of vertebral bodies
TUSCVM
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Vertebral Injury
Compression fracture
TUSCVM
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Vertebral Injury
Complete luxation
TUSCVM
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Discospondylitis
Infection involving the intervertebral disc and adjacent
endplates
 Mostly through hematogenous route
•
Sources – bladder, heart, teeth and skin
 Staphylococcus spp, Escherichia coli, Brucella canis most
common
 Also Streptococcus spp., Pasteurella multocida, yeast-like
organisms, etc
 Fungal organisms also reported
Seen in young adult, male, large breed dogs
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Discospondylitis
Radiographic findings
 Can affect any disc space
•
L7-S1, caudal cervical and mid-thoracic spine most
common
 Radiograph entire spine if find one lesion as there can
be multiple
 Can take 3-4 weeks after onset of clinical signs for
radiographic changes to become visible
•
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Similarly, resolution of radiographic changes lags behind
clinical improvement
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Discospondylitis
Collapsed IVD space
Endplate lysis with adjacent sclerosis
Irregularity of endplates
Spondylosis
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Discospondylitis
Discospondylitis with vertebral subluxation
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Discospondylitis
Alternative imaging
 Myelography
 CT
 MRI
 Nuclear scintigraphy
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Spondylitis
Infection of a vertebral body = osteomyelitis of spine
 Hematogenous spread of infection from elsewhere
 Extension from infection of surrounding soft tissues
•
Migrating grass awn
 Iatrogenic
•
Post spinal surgery
Vertebral physitis
 In younger animals, adjacent to the endplate
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Spondylitis
Radiographic findings
 Poorly marginated osteolysis
 Ill-defined periosteal reaction on ventral vertebral
body
•
•
Sometimes extends to lateral aspect of vertebra
Extends to mid vertebral body, unlike spondylosis
deformans
 Variable sclerosis of vertebral bodies
 Often multiple vertebral bodies affected
DDX – metastatic carcinoma
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Spondylitis
Migrating grass awn – causing fuzzy, periosteal reaction
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Spondylitis
Vertebral physitis – reaction adjacent
to endplate
Endplate spared
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Physitis
TUSCVM
47
Neoplasia
Benign tumors
 Relatively rare
 Osteoma
 Chondroma
 Multiple cartilaginous extostoses - MCE
(osteochondromatosis)
MCE
Cross, J. & Tromblee, T. What is
your diagnosis? J Am Vet
Med Assoc (2007).
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Neoplasia
Malignant tumors
 Primary bone tumors
•
Osteosarcoma, Chondrosarcoma, Fibrosarcoma
 Multiple myeloma…
Metastatic neoplasia
 Axial skeleton (ribs, vertebra) most common site of
metastasis
•
•
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Carcinomas (prostatic, bladder, mammary, perianal)
Primary bone tumors
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Neoplasia
Osteosarcoma – primarily osteoproductive lesion
TUSCVM
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Neoplasia
Multiple myeloma – “punched out”
lesion through axial skeleton
TUSCVM
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Neoplasia
Histiocytic sarcoma – osteolytic lesion
TUSCVM
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Neoplasia
Metastatic prostatic carcinoma
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TUSCVM
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The End
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