Calcifying Pseudoneoplasm of the Neuraxis with Vasogenic Edema and Post-surgical Regrowth: A Case Report

Introduction: Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare, benign central nervous system (CNS) lesion, first described in 1978. With approximately 150 reported cases, it remains poorly understood due to its rarity, variable presentation, and nonspecific features, often leading to misdiagnosis. Calcifying pseudoneoplasm of the neuraxis can occur anywhere along the neuraxis, with a slight predilection for intracranial sites. Surgical resection is the primary treatment, typically curative with low recurrence rates. This case report presents a unique instance of CAPNON, contributing to the understanding of its clinical spectrum and management challenges. Case Presentation: A 54-year-old female presented with urinary incontinence, bilateral arm weakness, and depressed mood. She had a medical history of a hysterectomy and a vertebral fracture. Initial magnetic resonance imaging (MRI) revealed a 35 × 27 × 33 mm left frontal lobe mass with mixed solid and cystic components, central calcification, heterogeneous enhancement of the solid portion, and surrounding vasogenic edema — an atypical finding for CAPNON. Surgical resection confirmed CAPNON histopathologically, showing a chondromyxoid matrix with calcifications and inflammatory infiltrate. Post-surgery, the patient’s symptoms improved, but follow-up MRIs at 8 and 12 months showed residual tumor growth from 18 × 15 × 13 mm to 21 × 24 × 26 mm. Consequently, the patient underwent intensity-modulated radiation therapy (IMRT) with 54 Gy in 27 fractions. Conclusions: This case of CAPNON is notable for its atypical presentation with vasogenic edema, post-surgical tumor regrowth, and the subsequent use of radiotherapy — features that challenge the conventional perception of CAPNON as uniformly benign and surgically curable. It underscores the potential for unexpected behaviors in CAPNON and the necessity for tailored management strategies beyond standard surgical resection.