Partial Pupil-Sparing Third Nerve Palsy as a Manifestation of Cerebral Toxoplasmosis in an HIV-Positive Patient: A Case Report

Purpose Neuro-ophthalmic manifestations are common in patients with advanced human immunodeficiency virus (HIV) infection and may result from opportunistic intracranial infections. However, partial pupil-sparing third cranial nerve palsy is an uncommon presentation in this population and may be misleading, as it is often presumed to be ischemic. We report an atypical presentation of cerebral toxoplasmosis manifesting as partial pupil-sparing third nerve palsy. Observations We report the case of a 37-year-old HIV-positive male with advanced human immunodeficiency virus infection who presented with headache, seizures, and binocular diplopia and was found to have a partial pupil-sparing third nerve palsy. Neuroimaging revealed multiple intracranial enhancing lesions with surrounding vasogenic edema. Cerebrospinal fluid analysis demonstrated varicella zoster virus positivity, and stereotactic brain biopsy ultimately confirmed cerebral toxoplasmosis. The patient was managed with antimicrobial therapy and showed clinical improvement. Conclusions and Importance In patients with human immunodeficiency virus infection, pupil-sparing third nerve palsy should not be presumed to be exclusively ischemic, as infectious and other opportunistic etiologies may underlie its presentation. Careful clinical assessment, detailed examination, and appropriate neuroimaging are essential for accurate diagnosis and timely management.