A Unique Presentation of Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS) Presenting as Foot Drop in B-cell Acute Lymphoblastic Leukemia: A Case Report.

Central nervous system (CNS) involvement in adult B-cell acute lymphoblastic leukemia (B-ALL) continues to pose treatment challenges, even with advancements in chemotherapy and targeted immunotherapy. Blinatumomab, a bispecific T-cell engager, has been shown to improve outcomes for patients with relapsed or refractory B-ALL; however, it can lead to immune-related neurotoxic effects, including immune effector cell-associated neurotoxicity syndrome (ICANS). We present an unusual case of a 38-year-old man with refractory B-ALL who experienced a parenchymal CNS relapse that manifested as foot drop during treatment with blinatumomab, likely as a result of ICANS. Initially, the patient achieved a remission with no minimal residual disease after undergoing R-HyperCVAD (rituximab, cyclophosphamide, vincristine, doxorubicin, and dexamethasone) and intrathecal chemotherapy. Unfortunately, he later relapsed with CNS involvement confirmed by imaging and biopsy. Following salvage therapy that included blinatumomab, he developed acute neurotoxic symptoms and peripheral neuropathy, which did not improve despite treatment. This case illustrates the complexities of CNS relapse in B-ALL and highlights a rare occurrence of neurotoxicity associated with blinatumomab, stressing the importance of awareness and prompt management of such complications.