ABSTRACT
F-18 FDG is a tracer of glucose metabolism, which is commonly used in PET/CT for oncological diagnosis and staging. F-18 FDG uptake represents the glycolytic activity in the cell. Physiological FDG concentration may be noted often in the muscles of head and neck, tongue, muscles on mastication, extra ocular muscles due to eye movements, cricopharyngeus and posterior cricoarytenoid muscles on phonation, etc. Here we report a case of Awake Bruxism, who came for F-18 FDG PET/CT for evaluation of Pyrexia of unknown origin (PUO), showing intense F-18 FDG uptake symmetrically in masticator muscles. Bruxism is a habit of involuntary spasmodic grinding or clenching of teeth. Many factors like psychosocial, genetic, certain medications and sleep disorders are known to be associated with bruxism. Therefore knowledge of physiological F-18 FDG uptake as well as artifactual uptake is essential for nuclear medicine physicians, to avoid ambiguity in diagnosis.