Temporal bone histopathologic findings in partial trisomy 13 and partial trisomy 14

Objective: To describe temporal bone histopathology in an infant with partial trisomies of chromosomes 13 and 14. Methods: Temporal bones were taken at autopsy from a 7-day-old neonate who has both partial trisomy 13 and partial trisomy 14. The right temporal bone was embedded in celloidin and sections were cut for microscopic examination. The left temporal bone was studied by microdissection. The middle ear was examined and the inner ear sensory organs dissected for study by light microscopy. Results: The external auditory canal was stenotic in both ears. Remnants of mesenchymal tissue were present in the middle ear cavity. The middle ear ossicles were normal except that both stapes were malformed with a single crus and a small footplate. Both facial nerve canals were dehiscent in the region of the oval window. The cochlea was malformed bilaterally; a scala communis was present and the basilar membrane was abnormally short. No loss of sensory cells was observed in either cochlea. Blood vessels were found traversing scala vestibuli and there were cystic lesions in the stria vascularis and spiral ligament. In the middle cochlear turn, the bony wall of scala vestibuli and the osseous spiral lamina were covered by a substantial layer of connective tissue which appeared to be an extension of the spiral ligament. This is an unusual finding which, to the authors' knowledge, has not been previously reported. In the vestibular apparatus a wide communication was present between the saccule and utricle. Conclusions: As this study demonstrates, abnormalities of the external, middle, and inner ear may occur in cases of partial trisomy 13 and partial trisomy 14. Both temporal bone findings and clinical features in partial trisomy 13 and partial trisomy 14 to some degree overlap with those of trisomy 13, partial trisomy 13 and partial trisomy 14.