Perilesional edema associated with an intracranial calcifying pseudoneoplasm of the neuraxis in a child: case report and review of imaging features.

Calcifying pseudoneoplasms of the neuraxis (CAPNONs) are rare, nonneoplastic lesions of the CNS. Their radiographic features have been well described, with prominent calcifications seen on CT imaging and generally uniform hypointensity on T1- and T2-weighted MRI sequences, with variable patterns of contrast enhancement. They are not associated with significant perilesional edema. The authors present an unusual case of an 8-year-old boy who was found to have a 2.5-cm right frontal mass that demonstrated reduced signal on T2-weighted sequences, heterogeneous contrast enhancement, and extensive perilesional edema on MRI sequences. The differential diagnoses included a chronic infection or neoplasm. He underwent gross-total resection of a firm, calcified mass that had clear boundaries between it and the surrounding gliotic brain. Pathological analysis demonstrated a well-circumscribed lesion with islands of lamellar calcifications and intervening spindle cells, consistent with a CAPNON. At 8 months after surgery the patient remained seizure free, and MRI revealed no evidence of residual lesion and significant improvement in perilesional edema. This particular case highlights the potential for unusual presentation of CAPNON and the rare presence of perilesional edema.