The purpose of this retrospective study was to evaluate the possible leakage of intra-articular contrast solution into the cerebrospinal fluid (CSF) through dehiscence of the roof of the glenoid fossa (RGF-dehiscence) in patients with temporomandibular joint osteoarthritis (TMJ-OA) and RGF-dehiscence by magnetic resonance arthrography (MRA). 25 joints of 22 patients (mean age, 44.28 ± 17.09 years) were evaluated, and RGF dehiscence and protruded sac sizes were measured on sagittal and coronal sections. The intact dura mater and the leakage of contrast agent into CSF were also evaluated. The protruded sac was observed in four joints (16 %) (average size, 0.25 × 0.20 mm). Contrast agent leakage into the cerebrospinal fluid was visualized in three joints (12%) (one with protruded sac formation and two without sac formation). Numbness in the head, neck, and arm, tremors, and loss of strength in the arm were observed in the side, ipsilateral to the joint after MRAr shots, in patients with contrast agent leakage. The same complications were observed in the other two patients with protruded sacs, but no contrast material leakage into the CSF. Patients with TMJ-OA and RGF-dehiscence are prone to contrast material leakage into the CSF, and this risk increases in joints with protruded sacs.