Inner Ear Volume in Craniosynostotic Mice

Abstract

Craniosynostosis is a congenital defect causing premature fusion of cranial sutures. These skull abnormalities can cause developmental delays, cranial venous hypertension, raised intracranial pressure, hearing impairments, and facial deformities. The temporal bone, specifically, plays a crucial role in the development in many of the features affected by craniosynostosis. The jugular foramen is an interosseous foramen formed by the temporal and occipital bones. Stenosis of the jugular foramen has been reported in individuals suffering from both syndromic and non‐syndromic complex (multi‐suture) craniosynostosis. Children with complex craniosynostosis also exhibit anomalous basicranial venous drainage in the form of persistent condylar and mastoid emissary veins uniting the sigmoid dural venous sinus with the suboccipital venous plexus and posterior auricular vein, respectively. The otic capsule is crucial for proper establishment of the sigmoid dural venous sinus during development. The petrous portion of the temporal bone is a significant branch point for dural venous sinuses and is altered in children with craniosynostosis syndromes. This study aimed to compare the volume of the otic capsule in syndromic craniosynostotic mice and their wild‐type littermates for possible effects on basicranial venous drainage. Using the otic capsule as a proxy for temporal bone volume and symmetry, we hypothesize that craniosynostosis causes a change in otic capsule volume throughout ontogeny that may also alter dural venous drainage pathways.The Fgfr2+/C342Y mouse model of Crouzon's syndrome along with wild‐type littermates were analyzed using serial micro‐computed tomography sections of whole heads at embryonic day 17.5 (E17.5), postnatal day 14 (P14), and postnatal day 42 (P42). Further, a subset of mouse crania were immersed in potassium iodine solution (Lugol's solution) to stain soft tissue structures. Immersion was performed to enable measurement of the unossified otic capsule of the earliest stages. Amira 3D analysis software was used to reconstruct three dimensional isosurface structures and compute volumes from complete two‐dimensional CT image stacks.While we did not find evidence of otic capsule volumetric differences in the earliest stages examined, significant differences between Fgfr2+/C342Y and WT littermates did emerge in the sub adult population (P42; p = 0.0455). Further investigations will examine the surface area of the jugular foramen, as well as, emissary foramina.