Myelography is a type of

radiographic Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical ("diagnostic" radiography and "therapeu ...

examination that uses a

contrast medium A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiop ...

(e.g. iodised oil) to detect

pathology Pathology is the study of disease. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatme ...

of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

, including the location of a

spinal cord injury A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. It is a destructive neurological and pathological state that causes major motor, sensory and autonomic dysfunctions. Symptoms of ...

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

s, and

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

s. Historically the procedure involved the injection of a

radiocontrast agent Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography (contrast CT), projectional radiography, and fluoroscopy. Radiocontrast agents are typically iod ...

into the cervical or

lumbar spine The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe t ...

, followed by several X-ray projections. Today, myelography has largely been replaced by the use of MRI scans, although the technique is still sometimes used under certain circumstances – though now usually in conjunction with CT rather than X-ray projections.

Types

Cervical myelography

This procedure is used to look for the level of where spinal cord disease occurs or compression of the spinal cord at the neck region for those who are unable or unwilling to undergone MRI scan of the spine.

Lumbar myelography

This procedure is to look for the level of spinal cord disease such as lumbar nerve root compression,

cauda equina syndrome Cauda equina syndrome (CES) is a condition that occurs when the bundle of nerves below the end of the spinal cord known as the cauda equina is damaged. Signs and symptoms include low back pain, sciatica, pain that radiates down the leg, numbness ...

conus medullaris The conus medullaris (Latin for "medullary cone") or conus terminalis is the tapered, lower end of the spinal cord. It occurs near lumbar vertebral levels 1 (L1) and 2 (L2), occasionally lower. The upper end of the conus medullaris is usually no ...

lesions, and

spinal stenosis Spinal stenosis is an abnormal narrowing of the spinal canal or neural foramen that results in pressure on the spinal cord or nerve roots. Symptoms may include pain, numbness, or weakness in the arms or legs. Symptoms are typically gradual in ...

. This is done for those who are unwilling or unable to do MRI scan of the spine. Lumbar puncture is done before injected contrast into the

thecal sac The thecal sac or dural sac is the membranous sheath (theca) or tube of dura mater that surrounds the spinal cord and the cauda equina. The thecal sac contains the cerebrospinal fluid which provides nutrients and buoyancy to the spinal cord. F ...

. However, it is dangerous to do lumbar puncture in those who have raised intracranial pressure (ICP). For those who had recently done lumbar puncture in one week time, there may be some

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

(CSF) accumulates in the

subdural space The subdural space (or subdural cavity) is a potential space that can be opened by the separation of the arachnoid mater from the dura mater as the result of trauma, pathologic process, or the absence of cerebrospinal fluid as seen in a cadaver. ...

. Thus needle maybe mistakenly inserted into subdural space rather than the targeted subarachnoid space. AP, lateral, and oblique radiographic views of the lumbar spine are taken. The oblique view is used to examine the exiting nerve roots from cauda equina.

Thoracic myelography

To image the thoracic spine, lumbar puncture is done and contrast medium is injected into the puncture site. The subject lie down on one side, then head of the table is lowered, with subject's head supported by bolster or pad to prevent the contrast from flowing up into the neck.

CT myelography

Contrast media is injected into the thecal sac. The subject is then rotated longitudinally a few times to ensure even coating of the contrast around spinal cord and reduce the possibility of layering of the contrast media just before CT scan.

Myelography in children

General anesthesia General anaesthesia (UK) or general anesthesia (US) is medically induced loss of consciousness that renders a patient unarousable even by painful stimuli. It is achieved through medications, which can be injected or inhaled, often with an analgesi ...

is required for all children before 6 years old, and most of the children before 12 years old. For those children with spinal cord diseases, lumbar puncture may damage the spinal cord due to possibility of

tethered spinal cord syndrome Tethered cord syndrome (TCS) refers to a group of neurological disorders that relate to malformations of the spinal cord. Therefore, lumbar puncture should be done at the lowest position as possible for such cases. However, spinal cord injury is rare. There is also a possibility of herniation of cerebellar tonsils when C1/C2 puncture is done laterally.

Procedure

Water-soluble non-ionic

iodinated contrast Iodinated contrast is a form of water-soluble, intravenous radiocontrast agent containing iodine, which enhances the visibility of vascular structures and organs during radiography, radiographic procedures. Some pathologies, such as cancer, have p ...

agent is used nowadays and cause very little complication, unlike oil-based dye that was used previously which can cause

arachnoiditis Arachnoiditis is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the central nervous system. The outermost layer of the meninges is the dura mater (Latin for hard ...

. However, history of allergy to iodine is contraindicated for the use of iodinated contrast. A CT scan is typically performed after radiographic contrast media (dye) has been placed with

fluoroscopic Fluoroscopy (), informally referred to as "fluoro", is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object. In its primary application of medical imaging, a fluoroscope () allows a surgeon to see t ...

guidance into a sac-like lining (the first- and hardest and outermost- layer of the spinal meninges, the spinal dura mater) surrounding the spinal cord and nerves. The material is typically water-soluble, which has largely replaced nonsoluble oil-based fluids, while CT has largely replaced the conventional X-ray projections used for image acquisition in the past. The process usually involves lying face down on a table, with the lower extremities secured tightly with straps to the table. After the skin area has been numbed, the dye is injected into the

, then the table is slowly rotated in a circular motion, first down at the head end for approximately 4 to 6 minutes, then rotated up at the head end for the same duration. Several more minutes lying flat and the process is complete. This movement ensures the contrast has sufficiently worked its way through the spinal cord, followed by X-rays or a CT scan. Post-procedure care centers around ensuring that infection (especially skin or subcutaneous infections,

myelitis Myelitis is inflammation of the spinal cord which can disrupt the normal responses from the brain to the rest of the body, and from the rest of the body to the brain. Inflammation in the spinal cord can cause the myelin and axon to be damaged re ...

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...

encephalitis Encephalitis is inflammation of the Human brain, brain. The severity can be variable with symptoms including reduction or alteration in consciousness, aphasia, headache, fever, confusion, a stiff neck, and vomiting. Complications may include se ...

, or

sepsis Sepsis is a potentially life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage of sepsis is followed by suppression of the immune system. Common signs and s ...

) does not set in and that the "plug" at the site of the spinal tap does not become dislodged. Patients are usually instructed to avoid strenuous activity and heavy lifting, for example. Some patients are given instructions to keep their heads elevated at least 30 degrees for a specified number of hours. Complications from the surgery can cause a loss of

(CSF), which could cause severe headaches. This can be corrected by returning to the medical facility and having them perform a blood patch. In this procedure, a small amount of blood is taken from the arm and injected into the exact spinal tap location to stop the leaking of CSF.

Decline in use due to MRI

Nowadays, MRI has all but replaced myelography. MRI is preferable because injection of contrast medium into the spinal canal is infrequently needed for better images. However, a CT myelogram may be useful for patients who cannot undergo MRI (e.g., those with pacemakers or

cochlear implant A cochlear implant (CI) is a surgically implanted Neuroprosthetics, neuroprosthesis that provides a person who has moderate-to-profound sensorineural hearing loss with sound perception. With the help of therapy, cochlear implants may allow for imp ...

s). CT is preferred when MRI images are limited by metallic artifact from titanium disc replacement implants, screws, and other metals reactive with MRI device components.

Contrast agent

Prior to the late 1970s, iofendylate (trade names: Pantopaque, Myodil) was the radio

contrast agent A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiop ...

typically employed in the procedure. It was an iodinated oil-based substance that the physician performing the spinal tap usually attempted to remove at the end of the procedure. This step was both difficult and painful and complete removal could not always be achieved. The process of removing the contrast agent necessitated removing some of the patient's CSF along with it and the resulting deficiency of CSF gave rise to severe headache if the patient was raised from the prone position, requiring bed rest in the laying position. Moreover, iofendylate's persistence in the body might sometimes lead to

, a potentially painful and debilitating lifelong disorder of the spine. This led to extensive litigation around the world since the substance was administered to millions of myelography patients over the course of more than three decades.Myodil litigation
/ref> After water-soluble agents (such as metrizamide) became available it was no longer necessary to remove the contrast agent as it would eventually be absorbed into the body although the water-soluble agent sometimes gave rise to severe headaches if it got into the head, requiring bed rest in the upright position. File:Myelographie Punktion.jpg, Myelography punction File:Myelographie schraeg.jpg, Conventional myelography in oblique projection. You can see the individual nerve root sheaths. File:Post-Myelo-CT.jpg, Computed tomography after conventional myelography. The overlap-free representation often allows a more secure assessment. The high density of contrast material may be troublesome in case of insufficient mixing prior to CT.

Complications

Headache occurs in about 25% of the cases after the procedure and the incidence is more frequent in females. 5% of those who undergone the procedure may experience nausea and vomiting. There is also a risk of contrast medium being injected into the subdural space when part of the bevel of the needle is in the subarachnoid space and another part is in the subdural space. The contrast medium would flow freely in the subdural space, mimicking the flow as if it was in the subarachnoid space. If there is doubt that the needle is in the subdural space, AP and lateral views of the radiograph should be taken and the subject is to be rebook for another date for the same procedure.

References

*Bontranger, Kenneth L. & Lampignano, John P. (2005). ''Radiographic Positioning and Related Anatomy'', St. Louis: Elsevier Mosby. .

External links

U of Maryland
{{Medical imaging Diagnostic neurology Projectional radiography pt:Mielograma