Imaging features of meningiomas
When evaluating MRI scans, it is important to remember that spinal meningiomas do not always demonstrate the classic radiological features characteristic of their cerebral variants. The main consequence of the growth of such a lesion is mechanical compression of the spinal canal structures.
As a result of tissue growth, the spinal cord is displaced. Interestingly, despite direct pressure, secondary changes in the MR signal intensity within the spinal cord parenchyma itself are infrequently recorded. This means that even with marked mass effect, the brain parenchyma may appear relatively intact.
Differential diagnosis: leptomeningeal metastases
When detecting space-occupying lesions in the spinal canal, secondary involvement of the meninges must be ruled out. Metastases can originate either from distant organs (lung or breast carcinomas — usually in elderly patients) or present as "drop metastases" (drop metastasis) from primary CNS tumors (in young patients). The latter include medulloblastomas, ependymomas, high-grade gliomas, as well as choroid plexus carcinomas and papillomas.
Metastasis enhancement patterns:
- "Sugar coating" sign (sugar coating pattern): diffuse contrast enhancement along the pia mater (pia mater) and nerve roots.
- Nodular form: the appearance of multiple small enhancing foci.
- Solitary form: the formation of a single mass lesion.
Please note: sometimes secondary lesions do not enhance with paramagnetic contrast agents. In such non-obvious situations, careful evaluation of T2-weighted images or the use of myelographic sequences plays a key role.
Rare tumors and pseudolesions
Spinal meningiomas must be differentiated from a number of other, less common extramedullary pathologies located beneath the dura mater (intradural).
True rare neoplasms in this zone include:
- Lipomas.
- Paragangliomas.
- Dermoid and epidermoid cysts.
- Hemangioblastomas (especially in carriers of von Hippel-Lindau syndrome, in whom they may grow directly from the proximal segments of nerve roots).
Tumor mimics: Pathologies of a completely different nature can frequently be mistaken for a neoplasm:
- Degenerative changes: intervertebral disc extrusions, disc or juxtafaceted cysts.
- Cystic lesions: arachnoid, neuroenteric cysts, or teratomas.
- Inflammatory processes.
Clinical case review: neurofibromatosis
Multiple nerve root lesions require the exclusion of genetic syndromes.
- Neurofibromatosis type 2 (NF2): In young adults, an MRI of the lumbar spine (on T2 and contrast-enhanced T1-weighted images) may reveal a scattering of small, intensely enhancing nodules attached to the roots of the cauda equina (cauda equina). Pathognomonic confirmation of the diagnosis is provided by the detection of bilateral vestibular schwannomas in the internal auditory canals, as well as bilateral trigeminal schwannomas in Meckel's cave (Meckel cave) on brain MRI.
- Neurofibromatosis type 1 (NF1): Characterized by the growth of multiple large nodules arising from the spinal nerve roots. On T2-weighted scans, they appear iso- or hyperintense, and after contrast administration, they demonstrate robust and homogeneous enhancement.
Briefly: answers to topical questions
From which cells and membranes of the spinal cord does a spinal meningioma originate?
A spinal meningioma originates from meningocytes or arachnoid cell rests.
- Meningothelial arachnoid cells are the main source for the development of primary extra-axial neoplasms.
- Arachnoid granulations are structures of the dura mater from whose remnants these tumors can also form.
Meningiomas are typically characterized by a broad base attached to the dura mater.
Clinical rule for NF: If multiple root tumors are found, be sure to scan the entire neuraxis (complete neuraxis).
Class and exam questions
What is better at detecting subarachnoid spread of primary CNS tumors?
Magnetic resonance imaging has a higher sensitivity compared to cerebrospinal fluid cytology (CSF cytology).
In which cases is CSF cytology superior to MRI?
Cerebrospinal fluid cytology is more sensitive when detecting the spread of lymphomas and leukemias along the CSF pathways.
Do leptomeningeal metastases always enhance with contrast?
No, not always. In the absence of contrast enhancement, T2-weighted images and myelographic sequences help establish the diagnosis.
What else to study on this topic
- Growth and imaging features of cauda equina schwannomas
- Specifics of drop metastases in high-grade gliomas
- Differential diagnosis of juxtafaceted and disc cysts on MRI
- Manifestations of von Hippel-Lindau syndrome (VHLs) in the spinal canal
- Sugar coating pattern: physical principles of the MR signal
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