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

Abstract

Background: 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.

Case description: 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.

Conclusion: 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.

Keywords: Calcified pseudotumor; Calcifying pseudoneoplasm of the neuraxis; Cranial nerve palsy; Skull base tumor.

Figure 1:

(a): Computed tomography (bone window, axial view) showing amorphous calcification of the right posterior clinoid process, (b): magnetic resonance imaging (MRI) susceptibility weighted imaging showing low signal within the lesion, (c): MRI T2-weighted image (axial view) showing low intensity of the lesion with oculomotor nerve entering posteriorly.

Figure 2:

(a): Magnetic resonance imaging (MRI) noncontrast T1-weighted image (axial view) demonstrating heterogeneous intermediate to low intensity, (b): MRI postcontrast T1-weighted image (axial view) demonstrating minimal enhancement, (c): MRI postcontrast T1-weighted image (sagittal view) demonstrating minimal contrast enhancement, (d): MRI T2-weighted image (coronal view) showing low signal intensity and its relationship with the oculomotor nerve.

Figure 3:

(a): Hematoxylin and eosin (H&E) stain showing characteristic calcified chondromyxoid nodules with surrounding fibrovascular tissue and chronic inflammation, (b): H&E staining in higher power showing edge of calcified nodule with epithelioid cells and patchy chronic inflammation.

Figure 4:

(a): Epithelial membrane antigen (EMA) immunostain showing peripheral EMA-positive meningothelial cells, (b): CD163 immunostain showing prominent macrophage infiltration in the surrounding fibrovascular tissue.