Presenting as Intractable Trigeminal Neuralgia

Introduction: CAlcifying PseudoNeoplasms Of the Neuraxis (CAPNON) are rare, usually asymptomatic, non-neoplastic lesions arising within the central nervous system. We present a case of CAPNON involving the mandibular division of the trigeminal nerve, and presenting as intractable trigeminal neuralgia.

Methods: The clinical, radiographic, and pathological findings associated with this case were analyzed, and a review of the English literature was performed.

Results: A 44-year-old African American female presented with a 14-year history of intractable trigeminal neuralgia affecting her entire right face, but most severe in the V3 distribution. She had undergone two microvascular decompressions and a radiofrequency ablation at other institutions, with no improvement in her symptoms. The patient had a known right middle fossa heterogeneously enhancing mass with a densely calcified core abutting the trigeminal ganglion. Previous transsphenoidal biopsy of the lesion was reported as “endodermal cyst with squamous metaplasia.” Repeat imaging on presentation showed enlargement of the lesion, now measuring 18 mm. We performed a right pterional craniotomy with zygomatic osteotomy for a gross total resection of the lesion. Intra-operatively, the mass appeared to be arising from V3 and the adjacent ganglion, splaying its fascicles. Frozen path was consistent with a meningothelial lesion. Final pathology disclosed a discrete, lobulated mass with variably calcified chondroid matrix, peripheral “ropey” cords, central ossification, and a variable surface layer of meningothelial cells, consistent with CAPNON. Post-operatively, the patient experienced complete resolution of her trigeminal neuralgia symptoms, but had some deterioration in her V3 function, which improved on follow-up. A review of the literature revealed one other case of trigeminal neuralgia associated with CAPNON, in which the lesion involved the gasserian ganglion. We could not identify another case of CAPNON involving V3.

Conclusion: CAPNON can present as a diagnostic challenge, and should be included in the differential diagnosis of trigeminal neuralgia as an etiology amenable to surgical treatment.