A 31-year-old woman presented with headaches, dizziness, tinnitus, and syncope. She also experienced difficulty swallowing and impaired balance and coordination. Imaging revealed a 4 mm mass lesion at the right aspect of the foramen magnum on computed tomography, and subsequent magnetic resonance imaging confirmed that extra-axial lesion (Figure 1). Surgical resection was performed, and histology confirmed the presence of a calcifying pseudoneoplasm of the neuraxis (CAPNON) (Figure 2). Following surgery, the patient’s condition improved, and she was discharged with recommendations for outpatient follow-up.

CAPNON is a benign, rare entity characterized by slow-growing non-neoplastic fibro-osseous lesions and is distinguished by the presence of calcium deposits within the tumor tissue.^1,2 The calcified material has a unique fibrillated quality at least focally and can become ossified. Reactive macrophages and inflammation are frequently present. The pathogenesis, clinical presentation, and outcomes are poorly understood.¹ With only approximately 150 cases reported, diagnosis and management pose a challenge.² CAPNONs frequently resemble meningiomas, cavernomas, chordomas, foreign body reactions, or low-grade astrocytomas.^3,4 CAPNONs located at the skull base may resemble intra-axial calcified lesions such as low-grade glial neoplasms (e.g., oligodendroglioma and ependymoma), mixed neuronal-glial tumors (e.g., ganglioglioma), vascular malformations (e.g., cavernous malformation), and granulomatous or infectious processes (e.g., tuberculosis).²

CAPNONs can occur at any location along the neuraxis and affect individuals aged 2-90 years, with a peak incidence between the age of 40 and 60 years.⁵ The most common presenting symptoms include headache and seizures, although some cases are discovered incidentally.³ Management depends on factors such as location, size, and presenting symptoms. Asymptomatic lesions may be monitored without intervention, whereas surgical resection is typically indicated for superficial lesions.³

Informed Consent: We obtained informed consent from the patient described in this report.

Authorship Contributions: Concept- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Design- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Supervision- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Fundings- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Materials- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Data Collection and/or Processing- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Analysis and/or Interpretation- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Literature Search- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Writing- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.; Critical Review- M.S., O.L.A.N., B.A.P., M.L.D., L.F.F.

Conflict of Interest: No conflict of interest was declared by the authors.

REFERENCES

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2. Sassi F, Zehani A, Ghedira K, Chelly I, Bellil K, Haouet S. Calcifying pseudoneoplasm of the neuraxis (CAPNON): Unraveling a rare non-neoplastic calcified central nervous system lesion. Int J Surg Case Rep. 2023;109:108588.
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