ABSTRACT
The numb chin syndrome (NCS) is characterized by chin or lower lip numbness restricted to the distribution of the mental nerve (the distal trigeminal nerve). The authors report a patient whose initial symptom of tumor recurrence was unilateral numbness of the chin. A 65-year-old male was admitted because of paresthesia around the left chin and left lower lip. Neurologic examination revealed hypesthesia on the left side of chin, lower lip and buccal mucous mem-brane. Bone scan (Tc-99m MDP) showed focal hot uptakes on the left mandible and left first rib. Brain CT with bone window setting showed a focal osteolytic lesion in the bone marrow of the left mandibular canal without destruction of bone cortex. Both coronal T1 weighted image and axial T2 weighted image showed focal low signal intensities on the left ramus. The pathophysiologic mechanism could be understood by identification of the pathologic focus.