CT and MR findings of Michel anomaly: Inner ear aplasia

In 1863, Michel described a condition characterized by a total absence of d ifferentiated inner ear structures associated with other skull base anomali es, including an abnormal course of the facial nerve and jugular veins. Mic hel aplasia clearly differs from Michel dysplasia, in which arrest of embry ologic development occurs later. Recently, the role of otic capsule formati on on mesenchymal differentiation was reported as well as the impact of the genetic deletion of the homeobox gene on the development of the ear, crani al nerves, and hindbrain, We report two patients with a total absence of in ner ear structures bilaterally, illustrating the characteristic appearance of Michel aplasia and associated skull base anomalies.