What is Myelography? Radiographic examination of: spinal canal, spinal cord, and nerve roots using...

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