Tumor-mimicking sarcoid-like reaction with lymphoid infiltration showing intracranial extension from the left jugular foramen: illustrative case.

backgroundAccumulation of normal lymphocytes within the intradural extramedullary space is rare. To the best of the authors' knowledge, no prior reports have described a sarcoid-like reaction with lymphoid infiltration arising around the jugular foramen and adhering to cranial nerves. Here, the authors present the case of a tumor-mimicking sarcoid-like reaction with intracranial extension from the left jugular foramen, adherent to the cerebellum, medulla oblongata, and lower cranial nerves. OBSERVATIONS: A 64-year-old woman with a history of serous otitis media and presumed tuberculous meningitis presented with persistent headache, left-sided tinnitus, hearing loss, hoarseness, and progressive vertigo. Imaging revealed a 2-cm enhancing mass around the left jugular foramen, extending intracranially and adhering to the cerebellum and medulla oblongata. The preoperative differential diagnoses included schwannoma, glomus tumor, meningioma, lymphoma, and granuloma. A retrosigmoid approach was used for biopsy and partial resection. Intraoperative pathology revealed lymphocytic infiltration without malignancy. Definitive pathology confirmed sarcoid-like lymphoid infiltration without evidence of neoplastic or infectious etiology. The patient showed a remarkable response to corticosteroid therapy, with both clinical and radiographic improvement and no recurrence at 20 months. LESSONS: Recognition of this rare entity and intraoperative identification of lymphocytic infiltration may support the use of corticosteroids and influence surgical decision-making. https://thejns.org/doi/10.3171/CASE25316.