Facial Nerve Abnormalities in Congenital Middle Ear Malformations With Comments on Preoperative Detectability: A Report of Two Cases

Facial nerve abnormalities and congenital middle ear malformations originate in similar developmental stages and are often concomitant. Preoperative recognition of such a condition is desirable to prevent any damage, but it is often difficult. Here, we report two cases of middle ear malformations associated with facial nerve abnormalities, describe the computed tomography (CT) appearance, and discuss its preoperative detectability. Case 1 was a 40-year-old female with a facial nerve abnormality associated with stapes ankylosis. She underwent stapes surgery. The facial nerve was hanging over the footplate of the stapes. Case 2 was a 32-year-old female with a facial nerve abnormality associated with stapes ankylosis. She underwent an exploratory tympanotomy. The facial nerve was branched. The branches emerged from the incudo-malleolar joint, ran between the chorda tympani nerve and the incus, and ran into the temporal bone inside the canaliculus chorda tympani. For both cases, the facial nerve branches were detectable with high-resolution CT (HRCT) in the mastoid segment and were confirmed during surgery. For Case 2, the facial nerve was also visible with HRCT as soft tissue shadows in the tympanic portion on the lateral side of the stapes. These two cases highlighted the critical role of preoperative CT imaging in detecting subtle features of facial nerve anomalies, such as nerve branching in the mastoid segment or soft tissue shadows around ossicles.