Numb chin syndrome by precursor B acute lymphoblastic leukemia
Authors: Carlos G. Romo, Preetesh Jain, Jorge E. Cortes
Journal: American Journal of Hematology (2014)

A 22-year-old man was diagnosed with CD-20 positive precursor B acute lymphoblastic leukemia (pre B-ALL) in 2007. He achieved complete remission (CR) after therapy with Rituximab and Hyper-CVAD and maintenance with a regimen of 6-mercaptopurine, vincristine, methotrexate, and prednisone regimen. After a 5-year remission, he presented in July 2012 with lower back pain and paresthesias in the left lower extremity. MRI scan showed abnormal enhancement at the L2, L3, and S2 levels with epidural extension of soft tissue encasing the left L2 and L3 nerve roots and ganglia. A bone marrow (BM) biopsy confirmed relapse of pre B-ALL while the CSF was uninvolved with leukemia. He did not have any evidence of Philadelphia chromosome or any other molecular abnormality. He was treated with radiation to paravertebral mass and augmented hyper-CVAD with pegylated asparaginase and rituximab in addition to intrathecal chemoprophylaxis. He achieved morphological and cytogenetic remission with this therapy. In September 2012, he was presented with gradually progressive altered mentation, slurring of speech, and chin paresthesias over a period of 72 hr. His physical exam revealed poor concentration, dysarthria, diminished sensation over the mental area, and sialorrhea; rest of the examination was unremarkable. Investigations showed WBC 14.1 × 109/L with 1% circulating blasts, hemoglobin 9 g/dL, platelet count 84 × 109/L, and LDH 2670 IU/L [range 313–618]. CT scan of the brain was normal. CSF analysis including opening pressure, cytology, biochemistry, and cultures were unremarkable. Empirical intrathecal cytarabine was administered twice in a week due to a high clinical suspicion of CNS involvement by leukemia. MRI scan of the head and neck revealed hypointense BM signal involving the calvarium, skull base, and the mandible. Abnormal enhancement and T2 signal hyperintensity within the body and ramus of the left mandible and to a lesser degree within the right mandible was also observed (see arrows Images A–D). Diffusion-weighted images of the brain were normal. Intrathecal cytarabine was continued for 2 weeks with significant improvement of symptoms by day 9. The patient continued on Hyper-CVAD/Rituximab therapy and maintained CR and subsequently received matched unrelated donor transplant in January 2013. One year after transplant he has stable graft function without evidence of disease. Neuroleukemiosis is the infiltration of the peripheral nervous system by leukemic cells 1, 2. Neuroleukemiosis is most commonly observed in patients with relapsed leukemia but can also be seen as the initial presentation 2, 3. Mental nerve neuropathy, also known as numb chin syndrome, is a rare form of neuroleukemiosis in which pain or paresthesias occur in the distribution of the mental nerve. Bilateral involvement, as seen in this case, is more frequently reported in cases of leukemia than with metastasis from a solid primary tumor 3. Present image demonstrates the clinical significance of performing MR imaging in patients with suspected nerve infiltration with leukemia1. Pre- and post-contrast (Panel A and Panels B, C, D, respectively) MRI. A & B. Axial T2 and T1 sections with enhancement of left greater than right mandibular ramus (arrows). C. Sagittal T1 showing enhancement of the left mandibular nerve along the mandibular body. D. Coronal T1 demonstrating bilateral enhancement in the mental foramen.