Case of the Month
Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO
July 2022
Next Case of the Month Coming August 2...
Spinal Calcifying Pseudoneoplasm of the Neuraxis (CAPNON)
- Background:
- Calcifying pseudoneoplasms of the neuraxis (CAPNON) are nonneoplastic, calcified lesions occurring anywhere in the central nervous system.
- These lesions can be intra-axial or extra-axial and have been reported in the brain and spine with similar frequency.
- They are usually slow-growing and commonly exhibit an indolent course with a generally good prognosis, although CAPNON recurrence is occasionally reported.
- They are rare lesions with unclear etiology. It has been proposed that they may arise from a reactive proliferative process, metaplastic transformation, or neoplasm.
- The trigger factors are unknown, but a response to possible trauma, infection, or inflammation has been proposed.
- Clinical Presentation:
- The range of symptomatology in these rare lesions is heterogeneous and depends on the location, which can be anywhere around the central nervous system.
- Intracranial lesions may produce focal neurologic deficits, seizures, headache, vomiting, or papilledema.
- Spinal lesions cause radiculomyelopathy and manifest as subacute areflexic paraparesis, root pain, paresthesias, and cauda equina syndromes. Asymptomatic lesions may be discovered incidentally.
- Key Diagnostic Features:
- CT and MRI are the primary imaging modalities to diagnose a lumbar CAPNON and assess overall tissue features and spatial relationships.
- CT: Typically shows solid, high-attenuated calcifications; in the spinal canal, as shown in our case, it is a nodular structure that is heavily calcified, sharply delineated, and usually located in the midline.
- MRI: Often shows a well-defined lesion uniformly hypointense on both T1- and T2-weighted images without surrounding edema; high susceptibility artifact is seen in T2*-weighted images; after IV contrast administration, there are various patterns of enhancement: minimal linear internal or rim enhancement and more serpiginous internal enhancement in more extensive lesions; MR myelography pictures the nodule and the displacement of the cauda equina roots within the thecal sac.
- Differential Diagnoses:
- Intra-axial:
- Ganglioglioma and oligodendroglioma, cavernous malformation, and tuberculosis: They can also manifest as calcified intra-axial lesions, but with different morphology, signal intensity, and patterns of enhancement.
- Intraventricular choroid plexus tumors, meningioma, or ependymal tumors: They can also manifest as calcified intra-axial lesions, but the morphology, signal intensity, and pattern of enhancement are different.
- Extra-axial and skull base:
- Calcified meningioma: Very common; a broad-based dural attachment should raise the suspicion of this diagnosis.
- Vestibular schwannoma, chordoma, and chondrosarcoma: The uniform T2 hypointensity without enhancement would be unusual in these entities.
- Spine:
- Calcified spinal meningioma: Spinal meningiomas are 1 of the 2 most common intradural extramedullary spinal tumors, but the lumbar location is uncommon. Spinal calcified meningiomas are rare (5%). They are typically well shaped, showing prominent and homogeneous enhancement and a broad-based dural attachment with the typical dural tail sign.
- Less frequent, spinal granulomatous diseases such as tuberculosis
- Intra-axial:
- Treatment
- Excisional biopsy or total resection can be curative and should be considered the treatment of choice when CAPNON is symptomatic.
- The decision to proceed with surgical intervention must be influenced by the clinical presentation. The type of approach should be discussed at a multidisciplinary level to mitigate the inherent risks of surgical intervention.
- Prognosis of this entity is generally favorable.
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