Temporal bone and cranial nerve findings in pontine tegmental cap dysplasia

Pontine tegmental cap dysplasia (PTCD) is a recently described brain malformation associated with multiple cranial neuropathies, most commonly congenital sensorineural hearing loss. The purpose of this study is to systematically characterize the cranial nerve and temporal bone findings in a cohort of children with this rare condition.

Sixteen patients with PTCD and diagnostic quality imaging were retrospectively reviewed. All patients had high-resolution MR of the brain and/or internal auditory canals, and seven patients had additional high-resolution CT of the temporal bones. Studies were evaluated by two pediatric neuroradiologists for cranial nerve and temporal bone anomalies.

Fifteen of 16 patients (94 %) had duplication of one or both internal auditory canals. Of the 24 total duplicated internal auditory canals, all 24 (100 %) demonstrated stenosis or atresia of the vestibulocochlear nerve canal, as well as ipsilateral vestibulocochlear nerve aplasia. Of the non-duplicated internal auditory canals, 63 % (5/8) were atretic or stenotic. Thirty-eight percent (3/8) were associated with absent vestibulocochlear nerve, and 38 % (3/8) demonstrated isolated cochlear nerve aplasia. Twenty-five percent (2/8) demonstrated normal vestibulocochlear nerves, both in the same patient. Fifteen of 16 patients overall (94 %) demonstrated bilateral cochlear nerve aplasia. Of the 32 total temporal bones, 4 (13 %) demonstrated facial nerve aplasia. Seventy-nine percent (22/28) of facial nerves that were present demonstrated an aberrant origin or course.

Patients with PTCD have highly characteristic temporal bone and cranial nerve findings on both CT and MR. Recognition of these findings is important for improved diagnosis of this rare disorder, particularly by CT.