Teaching NeuroImage: Calcifying Pseudoneoplasm of the Neuraxis in the Setting of Hereditary Hemorrhagic Telangiectasia and Seizures

We report a 50-year-old man presenting with grand-mal seizures. Workup included MRI of the brain demonstrating a heterogeneously enhancing focus, likely hemorrhagic, in the left occipital region (Figure 1). A vascular etiology was presumed due to the patient's history of Hereditary Hemorrhagic Telangiectasia. Furthermore, digital subtraction angiography revealed an irregular blush with the absence of early venous drainage to suggest an arteriovenous malformation (AVM). On surgical resection, the specimen showed substantial calcifications (Figure 2). Final pathology diagnosed a calcifying pseudoneoplasm of the neuraxis (CAPNON), presumably arising from an AVM remnant.1 They are rare, slow-growing lesions believed to form secondary to tissue insult. The benefits of this finding over an AVM are 2-fold; cerebral autoregulation is maintained, and future surveillance angiograms are avoidable. CAPNONs have been observed after trauma, infections, neoplasms, and inflammation.2 Complete resection was confirmed by intraoperative angiogram and postoperative MRI. The patient had no complications and returned to his seizure-free neurologic baseline.