Myelography is a medical procedure used to examine parts of the central nervous system within the vertebral canal. It is an important radiologic modality for diagnosing disorders of the spinal cord.

What is Myelography?

Myelography is a radiological investigation of the vertebral canal. It usually employs two types of modalities— fluoroscopy and radiologic imaging. Myelography is a form of fluoroscopy because it involves the usage of a contrast dye that is injected into the space within the vertebral column. The dye is usually injected using a lumbar puncture, a medical procedure that includes making a small hole in the lumbar part of your spine. At the same time, it uses a CT scan (occasionally, an X-ray scan) to highlight the dye in white. This way, doctors can visualize structures like your spinal cord in real time.¹

Myelogram vs. Myelography

A myelogram is an image produced by a myelography procedure. It is shown on a radiograph, such as an X-ray or CT scan film. It shows details about the spinal cord, various nerve roots, and their surrounding anatomical parts. On the other hand, myelography is the procedure in which a health professional trained in imaging and nuclear medicine visualizes these body parts. A qualified radiologist interprets the results.

Types of Myelograms

Sometimes, myelograms are classified on the basis of the region being scanned or the type of scans being used, such as:

Cervical myelograms focus on the cervical spine present in your neck
Thoracic myelograms show structures in your thoracic vertebral column or chest
Lumbar myelograms are the most common ones and target the region of your lower back
Conventional X-ray myelograms use X-rays to highlight various anomalies
CT myelograms use computerized tomography (a type of highly concentrated X-ray scan) to visualize your spine
MR myelograms use the safe imaging of an MRI scan²

Indications for Myelography

Given the availability of nonionizing imaging like MRI scans, myelography is usually restricted to situations where other modalities cannot be employed. It is excellent for visualizing pathologies of the thecal sac, a layer of protective sheath or meninges that surrounds the spinal cord.³
In addition, certain populations cannot undergo routine MRI exams, e.g., patients with pacemakers, metallic screws, and wires inserted during surgery, patients who cannot lie still and complete an MRI scan, etc. Myelography is an important diagnostic tool for such patients.
Myelography is often performed when patients show signs and symptoms of neurological and musculoskeletal damage in their backbone, such as:

Back pain
Numbness and tingling in arms or legs
Weakness in one’s arms or legs
Trouble standing or walking
Loss of bladder control
Loss of bowel control
Sharp pain, shooting down the legs
Unexplained muscle weakness⁴

Nerve Damage

The contrast dye used in mylography highlights the nerves within the spinal canal. This way, areas of potential nerve damage or neuropathy become more visible to physicians, who can determine if you have any nerve compression, impingement, or trauma causing your symptoms.

CSF Leaks

Cerebrospinal fluid leaks happen when the fluid that surrounds and protects structures like the brain and spinal cord starts to leak out of its regular pathways. They are often caused by a tear in the dura mater and result in head and neck pain, photophobia, and nausea. Myelography shows the exact location of these leaks with high precision, helping doctors diagnose and treat them in time.

Spinal Abnormalities

Myelograms are an important modality for identifying as well as differentiating between different abnormalities of the spine and the spinal canal:

Spinal stenosis occurs when the spinal canal narrows, putting pressure on the nerves and spinal cord. This compression can cause pain, stiffness, or weakness. Myelography pinpoints the exact locations where the spinal cord is restricted during spinal stenosis.
Herniated discs happen when the nucleus pulposus — the soft inner substance of a disc — bulges out and puts pressure on nerves or the spinal cord nearby. Myelography highlights any such bulging or protruding parts pressing on your nearby nerves or the spinal cord.
Degenerative disc disease, in which the discs in the spine wear away over time. This can change the spinal canal and put pressure on nerves. Myelography outlines these areas of damage, as well as their severity.
Myelography can show various changes associated with spine arthritis, such as the presence of bony spurs or osteophytes and spondylolisthesis, which is the displacement of one vertebra over the other.

Coronal images from a CT myelogram show contrast extravasating along the course of the left L2 nerve root, called a localizing CSF leak. (B) T2-weighted images from a cervical spine MRI myelogram showing a fluid collection in the dorsal spinal canal extending over multiple segments called a non-localizing CSF leak. Image courtesy: Evaluation and treatment of spontaneous intracranial hypotension, Researchgate, 2019. Available at: Researchgate

Tumors & Malignancy

Doctors use myelography to assess how various tumors and types of cancer impact the spinal column for prompt diagnosis and treatment. It can indicate how metastatic lesions affect the spinal canal, particularly leptomeningeal involvement. It helps design targeted treatments like radiation therapy. Myelography can also help identify various primary tumors of the spinal cord, such as:

Schwannomas
Astrocytomas
Ependymomas
Hemangioblastomas
Oligodendrogliomas
Neurofibromas
Gangliogliomas

Infection & Inflammation

Myelography can outline collections of pus and inflammatory fluids in the spinal canal, particularly when these infections lead to swelling and space-occupying lesions in the spinal column. Examples include:

Epidural abscess
Discitis
Spinal osteomyelitis
Tuberculous spondylitis
Pyogenic spondylitis
Fungal spondylitis
Arachnoiditis

Cysts

Cysts are small fluid-filled sacs that develop within the spinal column. They often impact surrounding structures if they are large enough in size, all of which can be determined using myelography. Examples of cysts diagnosed by myelography include:

Arachnoid cysts
Synovial cysts
Epidermoid cysts
Dermoid cysts
Radicular cysts
Neuroenteric cysts

Cervical myelography (prone position). With the patient’s head reclined, there is sufficient time to acquire images that show the cervical nerve roots in detail without losing contrast. Image courtesy: Myelography in the age of MRI: Why we do it, and how we do it, Researchgate, 2011. Available at: Researchgate

What are the Contraindications for Myelography?

Myelography has a few contraindications, which are mainly associated with the use of X-rays, contrast dyes as well as the involvement of lumbar puncture procedure, including:

Allergy to constituents of contrast dye, especially iodinated contrast media
Pregnancy and lactating mothers
Conditions with abnormally raised intracranial pressure
A patient who is unable or unwilling to remain still or follow instructions
Patients with a medical history of connective tissue disorders, e.g., Marfan syndrome, Ehlar Danlos syndrome
Uncontrolled hypertension and diabetes
Infections within the central nervous system, e.g., encephalitis, meningitis⁵

What can I do for Myelography Prep?

Myelography does not involve extensive preparation. The main preparation lies in ensuring the patient is not allergic to contrast or can get harmed by radiation during the process.⁶

History & Examination

Doctors will ask you about your current complaints, past medical history, and any allergies you have to medications. In addition, they will ask you to undergo a neurological exam, a spine exam, a pain assessment, and a nutritional status exam. Lab investigations for myelography include:

Complete blood count
Coagulation profile
Serum electrolytes
Renal function tests
Infection screening

Informed consent for myelography usually involves explaining all the steps, risks, and expected outcomes of a myelogram. It may also require additional consent for a lumbar puncture, which is the procedure through which contrast dye is injected into your spinal canal.

Do’s & Don’ts Before Myelography

Your doctor will ask you to adopt a few practices to make sure you have a comfortable experience during your myelography procedure, such as:

Inform your healthcare team about any allergic reactions you have had to medications. This is even more important if you have a past or family history of reactions to contrast dyes used in fluoroscopic procedures.
Other than blood thinners, you can continue to take your prescribed medications as usual unless advised.
Don’t eat or drink anything for at least 6 hours before your myelography procedure. If absolutely necessary, your doctor might allow you to take your daily medications with a small sip of water.
Arrive at least 60 minutes before your scheduled appointment time to allow for any pre-procedure prep.
Bring all relevant X-ray, CT, or MRI scans of your spine or brain to your myelography procedure.
Leave all valuable items like jewellery at your house to avoid misplacing them.
If you choose to have an outpatient procedure, avoid taking blood thinners like aspirin for at least five days before your appointment. In addition, bring a caregiver with you to drive you back home, as you cannot drive immediately after a myelogram.

Step-by-Step Procedure for Myelography

Myelography is performed in a hospital’s radiology or nuclear medicine department. It involves a team of nurses, radiologists, and radiologic imaging technicians and can be performed as an inpatient or outpatient procedure.

Anesthesia & Premedication

Local anesthesia is the most common type of anesthesia used for myelography. However, general anesthesia might be used, too. A prophylactic antibiotic cover is usually not required. However, different drugs to prevent anxiety and vomiting are now being used to improve patients’s experiences during myelography, such as:

Diazepam
Lorazepam
Ondansetron
Metoclopramide

As far as the contrast dye for myelography is concerned, it is usually a water-soluble, nonionic, and iodinated substance. It should also be visualized easily using radiologic modalities. Examples include:

Iohexol
Iopamidol
Iopanoic acid

During the Myelography Procedure

First of all, you will be asked to change into a hospital gown, lie on your side, and draw your legs and knees up to your chest. This position widens the space in your spinal canal. Your back will be exposed.

Depending on your condition, an antiseptic solution cleans a part of your lumbar (and sometimes cervical) region. The lumbar region constitutes the lower back, where the lumbar puncture occurs.
A sterile needle is inserted into your spinal canal.
The doctor slowly injects a contrast dye into the spinal canal via this needle.
As the dye circulates throughout your spinal column, an X-ray or CT machine takes images of your spinal cord and its surrounding structures.⁷

What happens after a Myelogram?

Once the myelography procedure ends, you will be asked to lie down for at least two hours to prevent accidental CSF leaks. Your doctor will give you extra fluids to flush out the contrast dye, as its accumulation can lead to headaches. They will monitor and discharge you once you are vitally stable. You will also be asked to rest at home and avoid unnecessary movements for the remainder of the day.

What risks are associated with Myelography?

The most significant risk associated with myelography is related to complications of lumbar puncture and an allergic reaction to the contrast dye used to highlight various structures. Allergies can cause anything from milder symptoms like superficial swelling, headache, and hives to multiorgan failure and death during anaphylactic shock. On the other hand, the risks of lumbar puncture associated with myelography are:

Hemorrhage
Infection at the injection site
Rupture of meninges
Severe headache
CSF leakage
Short-term numbness, tingling sensations, or pain in your back and legs

Myelography vs. MRI

Myelography is a relatively older diagnostic modality than MRI. In fact, MRI scans have mostly replaced myelograms for most indications. This is because of the totally noninvasive nature of the MRI, as well as the absence of potentially harmful radiation. However, myelography is still a top choice for patients for whom an MRI is contraindicated or cannot be used.⁸

Conclusion

Myelography is a diagnostic modality that uses X-rays and a contrast dye to visualize various conditions of the spinal cord and its nearby structures. The dye highlights various anomalies, and the results are captured on a machine. After recovery time, patients can be discharged on the same day. It is associated with some pain and minor risks. MRI scans have mostly replaced it.

Refrences

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Patel, D. M., Weinberg, B. D., & Hoch, M. J. (2020). CT Myelography: Clinical Indications and Imaging Findings. RadioGraphics, 40(5), 1353-1365. https://doi.org/10.1148/rg.2020190135
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Myelography: A Key Diagnostic Tool for Spinal Conditions

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