Extradural tumors and metastases
Most spinal mass lesions are extradural (Extradural Tumours) and originate from the vertebrae themselves. Age and exact localization serve as important diagnostic landmarks: in patients under 18 years of age, lesions are more often benign, whereas in adults, malignant processes predominate. Additionally, up to 75% of vertebral body tumors are malignant, while 70% of posterior element lesions are benign.
The most frequent spinal pathology is metastases. Multiple lesions are usually localized in the thoracic (70%), lumbar (20%), and cervical (10%) spine.
- Osteolytic metastases (with irregular margins and no sclerosis on CT) are characteristic of lung, breast, kidney, colon, thyroid cancer, and neuroblastoma in children.
- Osteoblastic metastases (presenting with a sclerotic and "ivory vertebra" appearance) are typical of prostate and breast cancer. On MRI, they demonstrate hypointense signals on both T1- and T2-weighted images.
Spinal nerve and root tumors
Pathologies can originate directly from neural structures. A classic example is hemangioblastoma, which can develop in the setting of von Hippel-Lindau disease. Such a tumor may originate from a proximal spinal nerve root (e.g., at the C6 level), have an intradural-extradural extension, and widen the intervertebral foramen (neuroforamen), showing intense contrast enhancement on MRI.
Along the nerve roots of the cauda equina (cauda equina), intradural extramedullary metastases can spread (e.g., in cervical cancer). On MR myelography and post-contrast T1-weighted images, they appear as intensely enhancing nodules. It is important to remember that without knowledge of the clinical picture, such metastases are visually indistinguishable from multiple schwannomas characteristic of neurofibromatosis type 2.
Spinal meningiomas
Meningiomas most commonly present as ovoid intradural extramedullary masses. They are usually located along the anterior surface of the spinal canal and have a broad base attached to the dura mater.
MRI semiotics of meningiomas:
- On non-contrast T1-weighted images, the tumor is slightly hypointense or isointense relative to the spinal cord.
- Following administration of gadolinium, pronounced and homogeneous contrast enhancement is noted with the presence of the "dural tail" sign (dural tail).
- On T2-weighted images, secondary changes in the spinal cord tissue due to compression can be assessed—the appearance of hyperintense signal areas indicates edema or the development of compressive myelomalacia.
Epidural extension and the draped curtain sign
Extension of a tumor (metastases, chordoma) into the epidural space threatens serious complications: spinal cord compression, clinically manifested by progressive paraplegia, saddle anesthesia, pelvic organ dysfunction, and sexual dysfunction.
An interesting radiological phenomenon is the draped curtain sign (draped curtain sign). When the process (e.g., destruction of the posterior vertebral wall in chordoma) extends into the anterior epidural space, it displaces the lateral parts of the posterior longitudinal ligament. However, along the midline, the ligament remains fixed thanks to the strong ventral meningovertebral ligament (at the level of the conus medullaris—the sacrodural ligaments of Trolard and Hoffman). Consequently, on axial MRI slices, the intraspinal component acquires a characteristic bilobed appearance. This sign is not strictly specific to tumors and can occur with epidural hematomas or abscesses.
Briefly: answers to topical questions
What are the most common primary spinal nerve tumors?
The most frequent primary spinal nerve tumors are nerve sheath tumors, among which schwannomas predominate.
- Schwannoma (schwannoma) is the most common intradural extramedullary tumor, usually solitary, originating from dorsal sensory roots.
- Neurofibroma (neurofibroma) is a nerve sheath tumor that can be solitary or multiple.
How do schwannomas differ from neurofibromas on MRI?
On MRI, schwannomas and neurofibromas differ in their location relative to the nerve and specific structural features.
| Sign | Schwannoma (schwannoma) | Neurofibroma (neurofibroma) |
|---|---|---|
| Location | Eccentric location of the nerve relative to the mass | Intramuscular mass |
| Structure | Fascicular structure | Target sign (target sign) |
| MR signal | - | High peripherally and low centrally |
For differential diagnosis of bone lesions: "Body — more often malignant (75%), arch — more often benign (70%)" (regarding the statistics of extradural tumor localization in the vertebra).
Class and exam questions
Why is radiography ineffective in the early stages of metastases?
Metastases primarily affect trabecular (cancellous) bone, whereas radiography better visualizes cortical bone. For destruction to become visible on a radiograph, 50% to 75% of the bone tissue must be destroyed.
What diagnostic imaging method is the gold standard when spinal metastases are suspected?
Magnetic resonance imaging (MRI). It has the highest sensitivity, best demonstrates bone marrow lesions (usually hypointense on T1-weighted images), and clearly outlines tumor extension into paraspinal and epidural soft tissues.
What must intradural nodular metastases along the cauda equina be differentiated from?
Solely based on the MRI picture, they are impossible to distinguish from multiple schwannomas, which are a typical manifestation of neurofibromatosis type 2. Clinical history plays a key role.
What else to study on this topic
- Radiological signs of compressive myelomalacia on MRI
- Specifics of MRI semiotics in neurofibromatosis type 2 (schwannomas)
- Inflammatory nerve root diseases: Guillain-Barré syndrome and CIDP
- Infectious granulomatous processes of the spinal canal (sarcoidosis, Lyme disease)
- Differential diagnosis of the draped curtain sign: tumor, hematoma, abscess
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