Diffuse cranial nerve infiltration in acute lymphoblastic leukemia: MRI diagnosis.

Cranial nerve involvement in acute lymphoblastic leukemia (ALL) is a rare manifestation of central nervous system infiltration and may present diagnostic challenges, particularly when cerebrospinal fluid (CSF) cytology is negative. We report the case of a 21-year-old male with known acute T-lymphoblastic leukemia undergoing chemotherapy, who presented with acute bilateral facial weakness consistent with seventh cranial nerve palsy and dysphagia suggestive of glossopharyngeal nerve involvement. Initial laboratory studies were unremarkable. Brain MRI revealed diffuse thickening and intense enhancement of multiple cranial nerves, including the facial and glossopharyngeal nerves, consistent with leukemic infiltration. CSF cytologic analysis did not demonstrate malignant cells, but further immunophenotypic assessment (flow cytometry) was not available. Given the clinical and radiologic findings, intrathecal chemotherapy was initiated, resulting in progressive improvement of neurologic symptoms. This case illustrates the critical role of MRI in diagnosing leukemic cranial nerve infiltration, particularly when CSF analysis is inconclusive. Early recognition is essential to guide prompt treatment and improve neurologic outcomes.