Inflammatory Pseudotumor of the Skull Base Mimicking Neoplasm: A Rare Case of Trigeminal Neuropathy.

Trigeminal neuropathy is a rare presenting symptom of inflammatory pseudotumor (IPT), a benign yet locally aggressive lesion with significant diagnostic challenges. A 55-year-old woman presented with right-sided facial pain and numbness. Magnetic resonance imaging (MRI) revealed a T2-hypointense, enhancing lesion in the right parasellar region involving Meckel's cave and the trigeminal ganglion, mimicking schwannoma or meningioma. Surgical resection and histopathology confirmed IPT, characterized by polyclonal lymphoplasmacytic infiltration and absence of neoplastic or infectious etiology. Central nervous system (CNS) involvement of IPT is rare, and its radiologic mimicry of neoplasms complicates diagnosis, with definitive identification requiring histopathologic and immunohistochemical analysis. In this case, anaplastic lymphoma kinase (ALK) and immunoglobulin G4 (IgG4) negativity ruled out inflammatory myofibroblastic tumor (IMT) and IgG4-related disease. The patient responded well to corticosteroid therapy. IPT should be considered in the differential diagnosis of skull base lesions, and a combination of surgical and corticosteroid therapy can achieve symptom resolution and minimize recurrence.