FIGURE 5.

MicroCT of human inner ears: different preparations and voxel resolutions. (A) Midmodiolar view at the level of the round window (asterisk) of an ossified OsO₄-post-fixed human temporal bone presenting the bony structure and low contrast of main nerve trunks of the cochlear (cn) and vestibular nerve (vn) in the inner ear canal. The singular nerve (sn) innervating the posterior ampulla (pa) lightly accentuated from the fluid filled bony canal; 15 μm voxel size. (B) Registered dataset of the same specimen after decalcification demonstrating the increased contrast of soft tissue. Note the fibrous connective tissue at the round window (asterisk)! The membranous labyrinth is clearly silhouetted against the perilymphatic compartment, Reissner’s membrane (arrowhead) allowed to clearly identify scala vestibuli (sv) and scala tympani (st); 15 μm voxel size. (C) I₂KI contrasted ossified temporal bone depicts highest contrast in the central cochlear nerve (cn) but impeded to outline most other soft tissues; 15 μm voxel size. (D) 3 μm voxel sized scan of an ossified OsO₄-post-fixed human inner ear embedded in epoxy resin. Reissner’s membrane (arrowheads) revealed high contrast, such as the stria vascularis (asterisk) and cochlear nerve (cn). Inset figure shows a magnified view of the sensory epithelium of the basal turn. The delicate osseous spirallamina lamelle (arrowheads) are clearly visible. (E–G) Registered datasets imaged at different voxel resolutions [(E) 15 μm, (F) 10 μm, and (G) 5.5 μm]. Insets show magnified views of cochlear nerve fibers traveling through the fundus region (fu) and display the increase of the level of detail. (H,I) Maximum intensity projection of sub volumes of the dataset shown in (G); 5.5 μm voxel size. (H) Horizontal view of cochlear basal and middle turn displays the ramification of the peripheral nerve fiber bundles (pf) spreading towards the sensory epithelium (se). Central fibers (cf) coalesce to the cochlear nerve; facial nerve (fn) shows highest contrast. Single bundles of the nerve fiber meshwork extend into the vestibular end organs of the utricle (ut) and anterior ampulla (aa). (I) View perpendicular to the modiolar plane illustrates nerve bundles of the singular nerve and innervation of the macula sacculi (sa). The spiral nerve coil in the cochlea reveals darker areas (arrowheads) that correspond to unmyelinated somata of the spiral ganglion. Legends: aa, anterior ampulla; cn, cochlear nerve; fn, facial nerve; fu, fundus region; pa, posterior ampulla; pf, peripheral nerve fibers; sa, macula sacculi; se, sensory epithelium; sl, spiral ligament; sn, singular nerve; st, scala tympani; sv, scala vestibule; ut, utricle; vn, vestibular nerve.