small animal neuroradiology: the spine lecture 1 – radiography and contrast techniques, anomalous...
TRANSCRIPT
Small Animal Neuroradiology: The Spine
Lecture 1 – Radiography and Contrast
Techniques, Anomalous Diseases
VCA 341 Fall 2011
Andrea Matthews, DVM, Dip ACVR Assistant Professor of Radiology
Normal Anatomy
Canine and feline vertebral formulas
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Cervical 7
Thoracic 13
Lumbar 7
Sacral 3 (fused)
Caudal Variable
Normal Anatomy – Cervical
C1 (or “atlas”) Central arch and two wide horizontal wings
perforated by transverse foramina
C2 (or “axis”) Long, thin spinous process which overlaps the
dorsal arch of C1 Odontoid process (dens)
C6 Expanded transverse process ventrally
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Normal Anatomy – Thoracic
Rib heads articulate with cranial aspect of corresponding vertebral bodies
Spinous processes change direction from caudal angulation to cranial angulation at the anticlinal vertebra (usually T11)
Accessory processes on last 4-5 thoracic vertebrae
T10-11 intervertebral disc space is normally narrow
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Thoracic Spine
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T10
T11
Anticlinal vertebra
Anticlinal disc space is narrow normally
Proximal ribs
TUSCVM
Normal Anatomy - Lumbar
Lumbar vertebral bodies are longer than thoracic vertebrae Especially in cats.
Transverse processes are angled cranially, laterally and somewhat ventrally
Accessory processes (present on the first four vertebrae) can be especially large in cats
“Fuzzy” ventral margin of L3 and L4 Due to attachment of the diaphragmatic crura
(especially in large dogs).
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}Do not mistake for mineralized intervertebraldisc material!
Sacral / Caudal Vertebra
Sacrum Lumbosacral angulation can vary significantly
between individuals• Changes with degree of flexion or extension
Caudal Vertebra Formerly known as coccygeal vertebrae Vary in number Hemal arches ventrally
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Ligamentous Structures
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Konig and Liebich, Veterinary Anatomy of Domestic Animals, 3rd Ed
Survey Radiography
Lateral and ventrodorsal views
Adequate relaxation is required for good positioning General anesthesia preferred
• Exception: Suspected fracture and/or luxation
• Can obtain lateral and horizontal beam
Collimation to improve quality
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Survey Radiography
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Lateral cervicalradiograph
Ventrodorsal cervicalradiograph
Survey Radiography
Beware of “pseudonarrowing” of disc spaces Artifactual narrowing due to divergence of x-rays
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Kishigami, Y.et al. Vet Radiol Ultrasound 41, 9–18 (2000).
Myelography
Introduction of contrast into subarachnoid space Water soluble, iodinated, non-ionic contrast media
Sites of injection Cisterna magna
• More likely to seizure• Difficult to get flow caudally in some cases
Lumbar (L5-6, L4-5)• Possible epidural leakage• More difficult technically• Fewer complications• Better flow of contrast typically
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Myelography
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Diaz, F. In Practice 27, 502-510 (2005).
Site for cervical injection
Site for lumbar injection
Myelography
Indications Neurologic signs with no
lesion on survey rads Multiple lesions seen on
survey rads Single lesion seen on
survey rads not consistent with clinical signs
Abnormality on survey rads which needs further characterization
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Contraindications
Inflammatory disease (meningitis)
Bleeding diatheses
Evidence of vertebral instability (could increase spinal cord damage)
Intramedullary Lesion
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Courtesy Dr. L. Pack
Widening of spinal cord due to spinal cord tumor (glioma)
Hemivertebra
Failure of vertebral body to develop fully Persistence of sagittal membrane (notochord)
Most commonly in thoracic spine May have focal kyphosis
Often incidental finding
Bulldogs, Boston terrier and pugs (“screw-tailed” breeds)
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Block Vertebra
Fusion of two or more adjacent vertebrae Involve bodies, laminae and pedicles or entire
vertebrae Incomplete development of intervertebral disc
Can occur at any location in spine
Incidental Differentiated from healing fractures, luxations,
discospondylitis
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Transitional Vertebra
Vertebra at the junction between two spinal regions that assumes the characteristics of both regions Thoracolumbar, lumbosacral and sacrocaudal
junctions
Usually incidental findings Important when identifying surgical site Make positioning of VD pelvis difficult Can be associated with lumbosacral instability
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Spina Bifida
Part of general defect called Spinal Dysraphism Failure of neural arch to close during
embryogenesis
Two types1. Spina bifida occulta
• No spinal cord or meningeal involvement
• No clinical signs typically
2. Spina bifida manifesta• Protrusion of the meninges (meningocele) or meninges
and spinal cord (meningomyelocele)
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Anomalous Diseases
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Common in screw-tailed breeds• Bulldogs, Boston Terriers, Pugs,
Manx cats
Failure of fusion of spinous processes
Other Anomalies
Scoliosis Lateral bowing as seen on a VD
or DV view
Lordosis Ventral bowing as seen on a
lateral view
Kyphosis Dorsal bowing as seen on a
lateral view
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Scoliosis (from Radiographic Interpretation for the Small Animal Clinician 2nd Ed)