Abstract
Calcifying pseudoneoplasm of the neuroaxis (CAPNON) is a rare, non-neoplastic, calcified mass lesion that may occur anywhere along the neuroaxis and which often demonstrates an unusual but distinctive radiographic signature.1-6 A man in his early 60s presented with headache and a left cerebellar lesion of unclear etiology. The patient deferred treatment and was followed-up with serial MRI. After 5 years, the patient presented with new dysphagia, progressive gait imbalance, and left sided ataxia, which prompted diagnosis of an expanding posterior fossa CAPNON. After patient consent was obtained, the lesion was approached by a left far lateral craniotomy and C1 laminectomy, including subtotal condylectomy for maximal expansion of the surgical corridor. After the cisterna magna was opened, a branch of the posterior inferior cerebellar artery was mobilized away from the tumor. The mass was debulked centrally by breaking up the calcifications, which allowed for near-total resection of the mass in a piecemeal fashion. The tumor was tightly adherent to the hypoglossal nerve and the spinal rootlets of the accessory nerve; therefore, a very small tumor remnant was left in place to preserve cranial nerve function. An associated cyst in the left cerebellopontine angle was also resected. The patient recovered well from surgery, with no new neurological deficit. Postoperative MRI findings confirmed near-total resection of the mass. This video demonstrates microsurgical resection of a CAPNON, with attention to distinctive radiographic characteristics and intraoperative visualization. CAPNON is a rare but important neurosurgical disease that may be underrecognized in practice.