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What is Myelography?
Radiographic examination of:
spinal canal, spinal cord, and nerve roots
using contrast agent injected through a needle into space around spinal cord
Central nervous system
2 basic parts
Brain
Spinal Cord
Spinal Cord
• Continuous with medulla oblongata
• Extends from brain to approximately L2
• Connected to 31 pairs of spinal nerves
Meninges
Layered coverings of brain and spinal cord
- Protects them from rubbing against bone and skull
Pia mater- inner sheathHighly vascular
Arachnoid- central sheathSeparated from pia mater by
subarachnoid space
Dura mater- outer sheathOutermost, protective layer
Ventricles
• 4 cavities within brain
• Filled with cerebral spinal fluid (CSF)
• Communicate with each other through interventricular foramina)
Clear fluid produced in ventricular system
1. Protects brain from striking cranium when head jolted
2. Provides buoyancy -brain can float and be supported against gravity
3. Maintains chemical stability:
Excretes waste products to blood
Transports of hormones to other areas of brain
Cerebral Spinal Fluid
Hydrocephalus
“Water on the brain"
Abnormal accumulation of CSF in ventricles due to blockage of outflow from ventricles
May cause:
Increased intracranial pressure
Progressive enlargement of head of infants and children
Convulsions
Tunnel vision
Mental disability
Hydrocephalus
Enlarged Ventricles
Study of CT scans of ventricles in late 1970s found first "evidence" mental disorders may be biological in origin
Individuals with schizophrenia had (in terms of group averages)
enlarged ventricles compared to healthy subjects
Shunt to control flow of CSF
Valve controlled by magnet applied by Dr. to regulate flow of CSF
Tech takes x-ray to check if tiny radiopaque “clock face” of valve has actually been changed and to what degree
Myelography
Outpatient radiographic exam of spinal cord performed by radiologist
Detects abnormalities of spine, spinal cord, or surrounding structures
Contrast material injected into fluid-filled space around spinal cord
Fluoroscopy and overhead x-ray’s taken
CT and MRI have largely replaced exam (except for pacemakers or metallic spinal fusions)
Myelography Indications
Intraspinal abnormalities
Nerve root abnormalities
Disk prolapse (slipped disk)
Spondylosis- degenerative arthritis of spinal vertebra and related tissue
Spondylolisthesis
Spinal stenosis (spinal canal narrows and compresses spinal cord and nerves)
Tumors
Metastases
Preliminary Radiographs
AP
Lateral
Both anterior oblique views
Lateral L5-S1
Purpose of Preliminary Radiographs
To exclude pathologies that wouldn’t need myelography
Determine accurate bony anatomy
Distinguish congenital abnormalities
Compare later with myelogram, MRI and CT images
Early myelograms used airInjected via lumbar puncture
In 1922- iodized poppy seed oil(accidentally discovered - had no
apparent side effects)
Late 1970’s –nonionic, water-soluble compounds- demonstrated lower
neurotoxicity-(ability of drug or other agent to destroy or damage nervous tissue)
Contrast Agents
Injections Sites
Into subarachnoid space (space between arachnoid and
pia mater)
Cistern (below occipital bone -can be hazardous because the needle is inserted close to brain stem)
Cervical spine
Thoracic spine
Lumbar spine (most common)
Lumbar Myelogram
PA Lateral
Lumbar Myelogram
Lumbar puncture: needle inserted under
fluoroscopic guidance until fluid appears
(CSF may be taken for analysis)
Contrast material injected
Flow monitored fluoroscopically
Pt. tilted trendelenberg and reverse-trendelenberg:
to control flow of contrast during spot films & overheads
Radiographs taken during exam:
Generally: cross table lateral and PA
Why not routine views?
1. Pt has needle in spine
2. Don’t want to change contrast position by rotating pt
Myelography accuracy rate
Compared with surgical findings:
Myelography – 81%
CT – 57%
CT and Myelography together - 84%
MRI (alone) – 96%!
Cervical Myelogram
Cervical Myelography Radiographs
Overheads:
PAPA Oblique projectionsCross-table lateral films
(flexion and extension)
Maintain head in acute extension -avoid flow of contrast into brain!
Pneumoencephalography
MRI and CT make it obsolete
Introduced in 1919
Performed extensively throughout late 20th century
Small amount Cerebrospinal fluid drained from around brain
Then air, helium, or oxygen injected into lumbar subarachnoid space to provide contrast
Pneumoencephalography cont’d
Pt turned upside down in special chair that can rotate vertically 360 degrees to get air to fill ventricals
Extremely painful, very dangerous
Headaches and severe vomiting common side effects
Replacement of spinal fluid was by natural generation- took as long as 2-3 months