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Baby Yoda: Pareidolia and Patternicity in Sacral MRI and CT Scans

Pareidolia is the human tendency to “see,” imagine, or perceive an alternative image that resembles the image that is actually displayed. Examples include “seeing” faces and other familiar images when looking at clouds or other stimuli. Pareidolia is a form of patternicity, which is the brain’s tendency to perceive patterns within stimuli, whether the pattern is truly there or not. In medical education, we sometimes use these phenomena to teach medical trainees to recognize patterns when looking at medical imaging studies. Examples include “seeing” a Scotty Dog when looking at a lateral oblique view radiograph of the vertebral spine. The appearance of a collar or break in the neck of the Scotty Dog helps us to diagnose a par interarticularis fracture in the human patient. Now we present a new example of pareidolia/ patternicity in medical imaging, which is the face-like appearance seen in magnetic resonance imaging (MRI) and computed tomography (CT) scans of the sacrum on axial views. The “face” resembles that of the fictional character often unofficially referred to as “Baby Yoda,” from the Disney Plus subscription television series The Mandalorian (see Figure 1). The bilateral sacral foramina resemble the large, bilateral eyes on Baby Yoda’s face. The bilateral sacral ala resembles Baby Yoda’s long ears. The sacral canal in the midline resembles the face’s mouth. The bilateral sacroiliac joints resemble the outer borders of the face and ears. We propose that these comparisons can help clinicians (especially trainees) learn to recognize the actual human anatomic structures when viewing MRI and CTscan images. Using the Baby Yoda face to recognize sacral anatomic structures is clinically relevant for many medical conditions. If the outer borders of Baby Yoda’s ears show irregularities and adjacent signal changes this could denote sacroiliac joint erosions and subchondral bone edema, respectively. Such findings could signify sacroiliitis (as seen in spondyloarthopathies such as ankylosing spondylitis, psoriatic arthritis, Reiter’s syndrome, and so on). Conversely, the absence of the outer borders of Baby