Isolated Primary Central Nervous System Lymphoma of the Optic Nerve: A Case Report and Review of the Literature.

Introduction: Optic nerve involvement in primary central nervous system lymphoma (PCNSL) has been reported only a few times in the literature, with generally dismal outcomes. We focused on an extremely rare presentation of PCNSL in an immunocompetent patient with isolated manifestations of the optic nerve.

Case report: A 72-year-old man presented with subacute vision loss in his left eye and optic disc swelling. Initial magnetic resonance imaging (MRI) of the orbits revealed a T2 hyperintense signal with enhancement of the left prechiasmatic optic nerve, suggestive of optic neuritis. He experienced visual improvement after 6 weeks of prednisone. However, 2 months after steroid tapering, he presented with worsening left-eye vision loss and new right-eye vision loss with imaging showing a peripherally enhancing chiasm lesion. A biopsy of the left optic nerve confirmed diffuse large B-cell lymphoma and negative systemic imaging was consistent with PCNSL. He was treated with high-dose methotrexate, rituximab, procarbazine vincristine (R-MVP), and cytarabine (AraC) with some visual improvement in the right eye and resolution of previously seen enhancement on MRI. The patient is in remission with no further deterioration of his vision.

Conclusion: This is the first reported case of isolated optic nerve involvement with a durable response to chemotherapy. This case emphasizes the importance of considering malignancy and maintaining a low threshold for optic nerve biopsy in patients with atypical cases of severe steroid-refractory vision loss with enhancement or enlargement of the optic nerve on MRI. Standard chemotherapy regimens for PCNSL can potentially achieve a curative response in these patients.