Immunotherapy has revolutionized cancer treatment over the past decade. As it is increasingly introduced into routine clinical practice, immune-related complications have become more frequent. Accurate diagnosis and treatment are essential, with the goal of reduced patient morbidity. This review aims to discuss the various clinical manifestations, diagnosis, treatments, and prognosis of neurologic complications associated with the use of immune checkpoint inhibitors, adoptive T-cell therapies, and T-cell redirecting therapies. We also outline a suggested clinical approach related to the clinical use of these agents.

A 72-year-old woman presented with rapidly progressive hearing loss and neuropsychiatric symptoms without other focal neurological symptoms. Progressive sequential sensorineural hearing loss (SNHL) was demonstrated on serial audiology. A diagnostic approach to SNHL is reviewed. Lumbar puncture revealed elevated protein, low glucose, and pleocytosis with poorly differentiated cells, and a differential diagnosis is discussed. MRI brain revealed gadolinium enhancement within the internal auditory canals bilaterally as well as the left cochlea. A malignancy workup revealed right axillary lymphadenopathy. Biopsy revealed poorly differentiated breast adenocarcinoma, with identical cells to those in the cerebrospinal fluid. The patient was treated with intrathecal methotrexate with no effect on the patient's hearing. In this case, rapidly progressive SNHL was the presenting feature of widely metastatic breast adenocarcinoma with leptomeningeal carcinomatosis, highlighting the need to search for a central cause for this presentation.