Vacuum phenomenon in the temporomandibular joint: A clinical, computed tomography and magnetic resonance case report

A 28-year-old woman presented with a history of clicking and mandibular clenching. She was studied clinically and with axial and coronal CT. The patient was going through a tense emotional period and reported tightening of her teeth (clenching); she was under psychological and neurological treatment for depression including pharmacological therapy. She presented slight pain only at maximum mouth opening at the right temporomandibular joint (TMJ) and in the lateral pole on palpation; there was no coincidence between initial and maximal interocclusal contacts because of premature dental contacts. She showed occlusal group function in the right side and canine guidance in the left side with a right contact of balance, local muscular pain in the right deep masseter muscle and in the superior and middle portion of the right trapezium on palpation. On CT, a spherical area of 3 mm diameter with an average density of -647 HU (SD±4.7) was found in the upper and posterior area of the lower space of the right TMJ, together with a thicker lower synovial tissue. This observation was confirmed by MRI. Like other joints, the TMJ could present vacuum phenomenon images inside synovial tissue in the presence of degenerative disease. It is important for radiologists to recognize this rare entity.