Small Animal Neuroradiology: The Spine Lecture 2 – Degenerative Diseases, Diseases causing...

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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

VCA 341 – The Spine

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Spondylosis Deformans

VCA 341 – The Spine 3Matthews

Courtesy Dr. L. Pack

Intervertebral Disc Disease

Anatomy

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Thrall Veterinary Diagnostic Radiology 5th Ed

Protrusion Herniation Extrusion

http://www.backandneckpain.ca/understanding-your-spine/499-2/

Chondroid degeneration Chondrodystrophic breeds Dehydration and mineralization of the nucleus Hansen Type I lesions

• 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

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Fibroid degeneration Non-chondrodystrophic breeds Fibrous metaplasia of the nucleus Hansen Type II lesions

• 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

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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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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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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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Narrow IVD space Narrow IV foramen Narrow articular facet joint

TUSCVM

Mineralized material in plane of vertebral canal over IVD space

TUSCVM

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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Need loss of visibility of the contrast column to say lesion is compressive

Atlantoaxial Instability

Space between the dorsal arch of C1 and the spinous process of C2

Dens (odontoid process)

Wings of C1 (atlas)

TUSCVM

Ligaments of the A-A joint Dorsal atlanto axial ligament Alar ligaments (2) Apical ligament Transverse ligament

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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Agenesis of the dens

Normal

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Fracture of dens

TUSCVM

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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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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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

• 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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Articular facet degenerative joint disease

TUSCVM

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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

Courtesy L. Pack

Example of Dynamic lesion

Example of Dynamic and Static Lesion

Flexed view – compression of spinal cord with tipping of vertebral body and mineralized material

Traction view – the spinal cord remains compressed

TUSCVM

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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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

• Higher incidence seen in animals with a transitional vertebra

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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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Spondylosis

Articular facet osteoarthrosis

TUSCVM

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Sclerosis and irregularity of

endplates

Wedged IVD space

TUSCVM

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

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Vertebral endplate fracture with subluxation of endplate and widening of the articular facet joint. Note the vertebral canal malalignment

Vertebral Injury

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Vertebral canal malalignment due to subluxation of vertebral bodies

TUSCVM

Vertebral Injury

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Compression fracture

TUSCVM

Vertebral Injury

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Complete luxation

TUSCVM

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• Similarly, resolution of radiographic changes lags behind

clinical improvement

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Discospondylitis

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Collapsed IVD spaceEndplate lysis with adjacent sclerosis

Irregularity of endplatesSpondylosis

Discospondylitis

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Discospondylitis with vertebral subluxation

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

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Migrating grass awn – causing fuzzy, periosteal reaction

Spondylitis

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Vertebral physitis – reaction adjacent to endplate

Endplate spared PhysitisTUSCVM

Neoplasia

Benign tumors Relatively rare Osteoma Chondroma Multiple cartilaginous extostoses - MCE

(osteochondromatosis)

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Cross, J. & Tromblee, T. What is your diagnosis? J Am Vet Med Assoc (2007).

Neoplasia

Malignant tumors Primary bone tumors

• Osteosarcoma, Chondrosarcoma, Fibrosarcoma Multiple myeloma…

Metastatic neoplasia Axial skeleton (ribs, vertebra) most common site of

metastasis• Carcinomas (prostatic, bladder, mammary, perianal)

• Primary bone tumors

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Neoplasia

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Osteosarcoma – primarily osteoproductive lesion

TUSCVM

Neoplasia

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Multiple myeloma – “punched out” lesion through axial skeleton

TUSCVM

Neoplasia

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Histiocytic sarcoma – osteolytic lesion

TUSCVM

Neoplasia

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Metastatic prostatic carcinoma TUSCVM

The End

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Small Animal Neuroradiology: The Spine Lecture 2 – Degenerative Diseases, Diseases causing...

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