Facial diplegia as the presenting manifestation of acute lymphoblastic leukemia

A 36-year-old man with recent onset of unilateral peripheral 7th nerve paresis presented ten days later with involvement of the other side of his face. Physical examination was otherwise normal, and since blood tests and imaging were also normal, he was considered to have bilateral Bell's palsy. However, unexpected headaches and worsening of the paresis led to a gallium-67 scan which revealed uptake in the mediastinum. A repeat lumbar puncture revealed cells which were identified as lymphoblasts. T-cell acute lymphoblastic leukemia (T-ALL) was diagnosed, although the peripheral blood smear was normal. The differential diagnosis of bilateral 7th nerve palsy and of mononuclear cerebrospinal fluid pleocytosis is discussed, as well as this rare central nervous system presentation of acute leukemia.