CT Procedure Of Myelogram

1. CT MYELOGRAPHY
Subodh Dhungana
Chitwan Medical College

2. Meninges
• Membranes that enclose the brain
and spinal cord
• Dura Mater- outer layer
• Arachnoid = middle layer
• Pia mater = innermost layer
• Subarachnoid space = wide space
between arachnoid and pia mater

3. Subarachnoid Space
• Wide space between arachnoid and pia mater
• Filled with CSF
• Bathes brain & spinal cord with nutrients Cushions against shocks
• Where contrast is injected for myelograms

4. CSF Information
• Total adult CSF volume is 150 ml
• 50% intracranial
• 50% spinal
• Adult opening pressure is normally 7-15 cm fluid
• >18 abnormal
• Young adults slightly higher <18-20

5. Indications
1. Demonstration of the site of a cerebrospinal fluid leak i.e.rhinorrhea or otorrhea.
2. Symptoms or signs of spontaneous intracranial hypotension.
3. Surgical planning, especially in regard to the nerve roots.
4. Evaluation of the bony and soft tissue components of spinal degenerative changes.
5. Radiation therapy planning.
6. Diagnostic evaluation of spinal or basal cisternal disease.
7. Non diagnostic MRI studies of the spine or skull base.
8. Poor correlation of physical findings with MRI studies.
9. Use of MRI precluded because of:
a. Claustrophobia.
b. Technical issues, e.g., patient size.
c. Safety reasons, e.g., pacemaker.
d. Surgical hardware.
10. Delineation of congenital anomalies (when MRI is insufficient)

6. Contraindications
1. Known space-occupying intracranial process with increased intracranial pressure.
2. Historical or laboratory evidence of bleeding disorder or coagulopathy.
3. Recent myelography performed within 1 week.
4.Previous surgical procedure in anticipated puncture site (can choose alternative
puncture site).
5. Generalized septicemia.
6.History of adverse reaction to iodinated contrast media and/or gadolinium based
MR contrast agents.
7. History of seizures (patient may be premedicated).
8. Grossly bloody spinal tap (may proceed when benefit outweighs risk).
9. Hematoma or localized infection at region of puncture site.
10. Pregnancy

7. Contrast Media
• Earlier - oil-based, air-contrast. Ionic contrast media
• Current - Non ionic, water soluble iodine-based media.
• WHY??
•(1). Oil-based agents (e.g., iophendylate) lack of fine image detail (due to cohesiveness) and the
need to remove the dye (to prevent arachnoiditis and post-spinal headaches) made these agents
suboptimal
•(2) ionic water-soluble media (e.g., iothalamate meglumine), they are unsuitable for direct contact
with neural tissue, as such contact could lead to severe muscle spasms, seizures, cerebral edema
and hemorrhage,, hypotension, hyperthermia, rhabdomylolysis, multi-system organ failure, and
death. Also cause disruption of Blood Brain Barrier(BBB0.
• nonionic water-soluble agents (e.g., metrizamide, iohexol OMNIPAQUE 300), which are
significantly less neurotoxic than the ionic water-soluble agents are been used instead for last
two decades.
• Many radiological contrast agents are neurotoxic and should not be administered intrathecally

8. Procedure
• The patient is placed prone or lateral decubitus on
the tabletop, and the skin of the midlumbar back
is prepped and draped in standard sterile
technique.
• L2-L3 or L3-L4 interlaminar or interspinous space
is localized.
• Subcutaneous and intramuscular local anesthetic is
administered.
• spinal needle is introduced through the
anesthetized region and directed toward the
midline. Smaller needles are associated with
lower risk of bleeding.
• A nonionic iodinated contrast medium is slowly
administered intrathecally through the lumbar
needle under intermittent imaging. Dose varies
(usually 6- 17ml) depends upon manufacture
label.

9. • Prior to removing the needle, imaging may be obtained to document the needle
position
• The needle is then removed from the back, and the patient is secured to the
tabletop by a support device prior to being tilted into Trendelenburg or reverse
Trendelenburg position.
• Using intermittent imaging, table tilting, and patient rotation, anteroposterior,
oblique, and cross-table lateral images of the region in question are documented
on film or digital media.
• For cervical myelography, and in some instances, thoracic myelography with
the patient prone, the head is hyperextended on the neck, thus creating a
lordotic “trough,” and the table is then gradually and slowly tilted head
downward until the opacified
• cerebrospinal fluid “column” flows through the area of interest

10. Syringes and Spinal Needles
Syringes
More Spinal Needles (uncovered)
Spinal
Needles
(covered)

11. Puncture made at L2-L3 or L3-L4 space

12. Spinal needle Injection

13. CT Myelogram Images

14. Comments
• Multiple slices taken (1.5 – 3mm)
• Gantry is tilted
• Windowing allows for density and contrast changes
• Can obtain images with small amounts of contrast
• Can be done 4 hours after initial injection

15. Comments
• Intrathecal injection un the lumbar region is sufficient in the majority
of the cases but in cases where complete block is suspected in the
region of the cervical or upper dorsal spine, and if that is the
anatomic region of interest, cisternal puncture is prefereable.
• Wait for 10-20 minutes after injection of the contrast of the contrast
in to the thecal sac for uniform distribution of contrast. During this
period the patient should lie prone in case of cervical and lumbar
study is to be performed and supine, if dorsal spine is the region of
interest.

16. Questions
• What is the shape of vertebral foramen of cervical spine?
• What are the indication for the contrast enhanced image of spine?
• Why Coronal MPR images are important as the sagittal image in
craniovertebral region?
• What is the slice thickness for the MPR images of disc lesions?
• What is the function of CSF?
• What do you mean by rhinorrhea or otorrhea?
• Why oil based and ionic contrast media are not used in Myelography?
• What are the best Lumber Puncture sites?
• Why L3-L4 is best for the Lumbar puncture site?

17. Thank You!!!!