Standard Radiography
Normal evaluation of the lumbar spine is based on three main radiographs:
- Posteroanterior (posteroanterior) projection.
- Lateral (lateral) projection.
- Targeted lateral view at the L5-S1 segment level. To perform this view correctly, the X-ray beam must be directed strictly parallel to the plane of the intervertebral disc.
MR myelography and X-ray myelography
MR myelography is advantageous because it does not require intrathecal contrast administration, but its drawback is a lower signal-to-noise ratio (SNR), which creates a risk of missing minor pathological changes.
X-ray myelography is used to a limited extent today. Its strict indications include:
- Presence of contraindications to MRI (e.g., pacemakers incompatible with a magnetic field) or unavailability of the machine, as well as severe claustrophobia.
- Need for dynamic assessment of the spinal canal in spondylolisthesis.
- Diagnosis of the condition of the dural sac (thecal sac) and nerve roots (e.g., in cases of arachnoiditis).
- Detection of active cerebrospinal fluid (CSF) leakage.
- Assessment of the postoperative spine when metallic implants create pronounced artifacts on MRI images.
Preparation and technique for myelography
The procedure requires careful preparation:
- Ruling out contrast allergy (medication pre-treatment is prescribed if necessary).
- Discontinuation of medications that lower the seizure threshold (48 hours before and 24 hours after the procedure), as iodinated contrast can provoke seizures.
- Coagulation profile monitoring — the INR (INR) value must be < 1.5.
- Ruling out pregnancy in women of childbearing potential.
For the puncture, the patient is placed in the prone position (prone), arms overhead, left knee drawn up. This stabilizes the position and widens the interspinous spaces. The puncture is performed using a 22-G to 26-G Quincke needle (Quincke-type) under fluoroscopic guidance (fluoroscopy), most often at the L2-L3 level.
After placing the needle, 1-2 ml of a non-ionic contrast agent approved for intrathecal use is injected. The "wisp of smoke" sign (wisp of smoke) confirms that the needle is in the subarachnoid space. The table is then tilted foot-down (reverse Trendelenburg / reverse Trendelenburg) so that the contrast fills the lumbar dural sac.
Spinal angiography
Imaging of the spinal cord vessels is difficult due to their small caliber, complex anatomy, and the presence of multiple feeding vessels (feeders).
Digital subtraction angiography (DSA) remains the gold standard due to its high spatial resolution. In practice, to reduce radiation exposure and contrast volume, CT angiography (CTA) or MR angiography (MRA) is performed beforehand. This allows mapping of vascular malformations and determination of the level of feeding vessels before performing DSA. Contrast-enhanced MRA has been noted to successfully visualize the artery of Adamkiewicz (Adamkiewicz artery) in the majority of cases.
Briefly: answers to topical questions
What complications can occur after X-ray myelography?
After X-ray myelography, seizures and post-lumbar puncture cerebrospinal fluid leakage may occur. The main adverse events associated with the procedure include:
- Seizures — the risk of developing them is posed by the intrathecal administration of iodinated contrast.
- Post-lumbar puncture CSF leak — the probability of this complication is reduced by using smaller-diameter puncture needles (from 22-G to 26-G).
At what anatomical level does the artery of Adamkiewicz typically originate?
The artery of Adamkiewicz (artery of Adamkiewicz) typically arises from the aorta at the level of the ninth thoracic to second lumbar vertebra (T9–L2). In most cases, this large vessel, also called the greater radicular artery (a. radicularis magna), originates on the left side. It is the primary source of blood supply to the lower thoracic, lumbar, and sacral segments of the spinal cord.
Which anatomical structures are evaluated in detail on the lateral lumbar radiograph?
On the lateral lumbar radiograph, a lateral projection is obtained. For targeted assessment of the L5–S1 level, a lateral view is used with the X-ray beam directed parallel to the intervertebral disc. In osteoporosis, vertical striation of the vertebral bodies may be detected on lateral spondylograms.
Class and exam questions
In what clinical scenarios is X-ray myelography ordered instead of MRI?
It is ordered when there are contraindications to MRI (e.g., cardiac pacemaker), severe claustrophobia, for dynamic assessment in spondylolisthesis, to search for cerebrospinal fluid leaks, or when metal artifact interference precludes adequate MRI evaluation.
How to confirm that the needle is in the subarachnoid space?
Under fluoroscopic guidance, 1-2 ml of contrast is injected; the appearance of the "wisp of smoke" sign confirms the correct placement of the needle.
Why are certain medications discontinued before myelography?
Intrathecal iodinated contrast carries a risk of seizures; therefore, seizure-provoking medications are discontinued 48 hours before and not resumed for 24 hours after the procedure.
What else to study on this topic
- Features of visualization of the artery of Adamkiewicz
- Specifics of thoracic and cervical myelography
- Artifacts from surgical materials in MRI
- The "wisp of smoke" sign in diagnostic imaging
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