Case History: A 36-year-old Asian male presented with complaints of a first episode of generalized tonic-clonic convulsions.
No associated history of fever, focal neurological deficit, or cranial nerve involvement. Patient was vegetarian with negative diabetes, hypertension, and HIV status.
Figure 1. Contrast-enhanced axial CT image showing non-enhancing hyperdense calcified nodular appearing mass lesion (arrow) is noted in left superior cerebellar peduncle. No evidence of intraparenchymal hemorrhage is noted.
Figure 2. Contrast-enhanced coronal CT image showing calcified mass lesion (arrow). The lesion shows no evident enhancement with normally passing left posterior communicating artery in relation to lesion.
Figure 3. T2 weighted (5120/105) non-contrast axial image showing uniform hypointense lesion (arrow) in superior cerebellar peduncle on left side near left perimesencephalic cistern. There is no evidence of surrounding vasogenic edema is noted.
Figure 4. T1 weighted (700/50) non-contrast axial image showing linear hypointensities (arrow) in corresponding areas of T2 hypointensity.
Figure 5. T2 weighted gradient image (938/15) shows blooming effect in the lesion suggestive of calcified matrix of the lesion (arrow).
Figure 6. Post-contrast T1 weighted (11/7) fat suppressed shows no evident contrast-enhancement (arrow) or any slow filling/draining vascular channels even on 10-minute delayed scan.
Diagnosis: Calcifying pseudo-neoplasm of the neuroaxis in left superior cerebellar peduncle (CAPNON).
Absence of typical popcorn “T2 hyperintensity” and hemosiderin ring differentiate CAPNON from calcified cavernous hemangioma.
