Pupil sparing oculomotor nerve palsy with concomitant Horner syndrome as a presentation of mantle cell lymphoma relapse

A woman in her 70s, with a background of mantle cell lymphoma (MCL), presented with headache and diplopia. Neuro-ophthalmic examination revealed a combination of Horner syndrome and ipsilateral pupil sparing oculomotor nerve palsy (ONP). Cerebrospinal fluid immunophenotyping demonstrated CD5 positive clonal B lymphocytes, consistent with neurological involvement by MCL. Imaging of the brain and orbits was normal, but a cervical mass was seen along the course of the sympathetic chain accounting for the Horner syndrome. She was treated with intrathecal chemotherapy with improvement in symptoms and resolution of ophthalmoplegia but was left with residual anisocoria and mild ptosis. This presentation (concomitant Horner and ipsilateral ONP) is rare and typically localises to the ipsilateral cavernous sinus, which appeared radiologically normal in this case.