Calcifying pseudoneoplasms of the neuraxis (CAPNON) are very rare, non-neoplastic, calcified lesions of the central nervous system of poorly understood etiology.
Given the rarity of these lesions, detailed epidemiological data is not available. Since their first description, less than 50 cases have been reported in the literature.
The clinical presentation of patients with CAPNON is heterogeneous and generally depends on the location and size of the lesion. Symptoms are related to local compression or irritation of the adjacent tissue. In spinal affections, the predominant presentation is local or back pain 2. In contrast, intracranial CAPNON may present with not only headache but also seizures, cranial neuropathy, or motor deficits 2. In few cases, it was an incidental finding 2.
CAPNONs are usually solitary extra-axial masses 3,4. An understanding of etiology remains elusive with reactive, metaplastic and even neoplastic processes having been proposed 3,5.
They demonstrate extensive calcifications and a nodular chondromyxoid matrix with an amorphous quality and fibrovascular stroma. The spindle and epithelioid cells surrounding the matrix showed positive staining with antibodies against epithelial membrane antigen (EMA) 1-3. They are S100 and GFAP negative 3.
Although the typical histopathologic features can be observed in most cases, some may be unusual and may be confused with calcified meningioma or tumoral calcinosis.
Can be seen a heavily calcified well-defined leptomeningeal or parenchymal mass.
Typical signal characteristics are those of calcium:
- T1: iso to hypointense
- T2: low signal on FLAIR and T2
- T1 C+ (Gd): varies from none to moderate enhancement
- T2*: mild blooming
Treatment and prognosis
If resection is required then it is usually curative. Morbidity relates to operative complications and damage to structures adjacent to the mass 3,4.
History and etymology
The entity was first described by Rhodes and Davis in 1978 6.
CAPNON should be considered in the imaging differential diagnosis of a heavily calcified lesion in neuroaxis and the differential will depend on the location. It is worth considering this entity to avoid aggressive surgical intervention in a lesion that is difficult to resect, as the natural history of CAPNON is generally indolent.
- 1. Aiken AH, Akgun H, Tihan T et-al. Calcifying pseudoneoplasms of the neuraxis: CT, MR imaging, and histologic features. AJNR Am J Neuroradiol. 2009;30 (6): 1256-60. doi:10.3174/ajnr.A1505 - Pubmed citation
- 2. Stienen MN, Abdulazim A, Gautschi OP et-al. Calcifying pseudoneoplasms of the neuraxis (CAPNON): clinical features and therapeutic options. Acta Neurochir (Wien). 2013;155 (1): 9-17. doi:10.1007/s00701-012-1502-2 - Pubmed citation
- 3. Brasiliense L B, Dickson D W, Nakhleh R E, Tawk R G, Wharen R. Multiple Calcifying Pseudoneoplasms of the Neuraxis. (2017) Cureus. 9 (2): e1044. doi:10.7759/cureus.1044 - Pubmed
- 4. Ghaemi J, et al Calcifying pseudoneoplasm of the neuraxis (CaPNoN): an unusual cause of third nerve palsy in a teenager DOI 10.1259/bjrcr.20150494
- 5. Mohapatra I, Manish R, Mahadevan A, Prasad C, Sampath S, Shankar SK. Calcifying pseudoneoplasm (fibro osseous lesion) of neuraxis (CAPNON) - a case report. (2010) Clinical neuropathology. 29 (4): 223-6. Pubmed
- 6. Rhodes RH, Davis RL. An unusual fibro-osseous component in intracranial lesions. (1978) Human pathology. 9 (3): 309-19. doi:10.1016/s0046-8177(78)80088-4 - Pubmed