Isolated Diplopia as the Sole Manifestation of Solitary Clival Plasmacytoma

Background: Plasmacytomas are monoclonal proliferations of plasma cells occurring in bone or soft tissue without systemic involvement.Solitary bone plasmacytoma (SBP) is a localized tumor without other skeletal lesions or bone marrow infiltration.Clival involvement is extremely rare, with few cases reported.Case Report: A 47-year-old male presented with a 3-month history of diplopia.MRI revealed a T1-and T2-isointense clival lesion with bone destruction.Endoscopic transnasal transsphenoidal biopsy confirmed plasmacytoma.Systemic workup ruled out multiple myeloma.The patient received 50 Gy radiotherapy in 25 fractions.At 14-month follow-up, he showed complete clinical recovery and reduction in tumor size.Conclusion: Solitary clival plasmacytoma is a rare but treatable cause of isolated diplopia.It should be considered in the differential diagnosis of clival lesions, with radiotherapy offering favourable outcomes.