Accessory salivary tissue in the mylohyoid boutonnière: a clinical and radiologic pseudolesion of the oral cavity.

BACKGROUND AND PURPOSE Though classically depicted as a continuous muscular barrier between the sublingual and submandibular spaces, the mylohyoid muscle is often discontinuous. These areas of discontinuity may contain fat, blood vessels, salivary tissue, or combinations thereof that may be mistaken both clinically and radiologically for pathologic abnormalities. We sought to demonstrate the prevalence and radiologic appearance of dehiscence of the mylohyoid muscle. METHODS One hundred axial, contrast-enhanced CT studies of the neck, obtained over a 10-month period, were retrospectively reviewed. Inclusion criteria included 3-mm-thick slices and absence of pathologic abnormalities or surgical changes in the oral cavity. Scans were assessed for the presence and contents of mylohyoid defects such as accessory salivary tissue, defined as nonlymphoid tissue within defects in the mylohyoid, having attenuation and enhancement characteristics similar to those of orthotopic sublingual and submandibular salivary tissue. RESULTS Mylohyoid defects were identified in 77 of 100 individuals. The deficiencies were bilateral in 67% and unilateral in 33%. Accessory salivary tissue was identified in 37 of 100. Fat and blood vessels were commonly identified within the mylohyoid defects. Sixty-one percent of the defects contained only fat. Thirty-five percent of the defects contained blood vessels. CONCLUSION Deficiencies in the mylohyoid muscle were visible in 77% of individuals who underwent scanning. The defects may contain fat, blood vessels, salivary tissue, or all three characteristics. Accessory salivary tissue was identified in 37% of individuals who underwent scanning. Recognition of mylohyoid deficiencies and the typical appearance of accessory salivary tissue will allow accurate diagnosis of this benign, anatomic variant.