Calcifying pseudoneoplasm of the neuraxis: A rare case involving the oculomotor nerve

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare entity which can occur at intracranial and spinal locations. Clinical presentation is due to local mass effect rather than tissue infiltration. Lesions causing significant symptoms or are showing radiological progression require surgical resection. Maximal surgical resection is considered curative for this non-neoplastic entity with only two cases of recurrence reported in the literature. Cranial nerve involvement is extremely rare and the presenting neurological deficit is unlikely to improve even with surgical intervention.

We describe a case of CAPNON at the right posterior clinoid process with involvement of the right oculomotor nerve in a 38-year-old male. Computed tomography demonstrated an amorphous mass which had intermediate to low T1 and T2 signal on magnetic resonance imaging. The oculomotor nerve was compressed with sign of atrophy. The patient underwent maximal surgical debulking for progressive symptoms of worsening pain and ophthalmoplegia. Postoperatively, the patient's symptoms were stable but did not improve.

Preoperative diagnosis of CAPNON is difficult due to its rarity and nonspecific clinical and radiological findings. Surgical resection is considered in cases with worsening symptoms, progression on serial imaging, or uncertain diagnosis. Relatively inaccessible lesions with little or no clinical symptoms can be observed.