A blurry orthopantomogram (OPG) is obtained for a Down syndrome patient. What is the most likely cause of the blur?

Blurring (motion artifact) on an OPG is most commonly caused by patient movement during the exposure, which typically takes 14-20 seconds. Patients with Down syndrome may have difficulty maintaining stillness due to intellectual disability, hypotonia, or anxiety. Other OPG errors include: chin too low (anterior teeth appear out of focus, spine may superimpose), chin too high (flattened smile curve, condyles out of frame), improper focal trough positioning (teeth blurred), and patient not biting the bite peg properly. Motion artifact produces indistinct, blurry cortical bone outlines throughout the image.