THE ANATOMY OF THE HUMAN PROMONTORY FOR LASER-DOPPLER FLOWMETRY

Studies of the dynamic characteristics of cochlear blood flow (CBF) ut ilizing laser Doppler flowmetry (LDF) in laboratory animals have provi ded a new approach to the understanding of control mechanisms of CBF a nd the role of the CBF in cochlear disorders. However, few studies exi st indicating that LDF of human CBF may be possible. Since bone thickn ess, density, structure characteristics, and blood flow all greatly af fect LDF recording, we examined the anatomy of the human promontory fo r inter-individual variations in thickness, quality and vascularity of the bone and mucosa and recorded middle ear topographic relationships to the underlying cochlear lateral wall vasculature. Temporal bones f rom 21 cadavers without known premortem histories of ear disease were obtained. India ink was infused selectively via the vertebral or carot id system to study the origin of bone/mucosa circulation to the otic c apsule. Light microscopy revealed that the human promontory was charac terized as cortical bone having few blood vessels. The thickness of th e bone measured at four horizontal levels and mucosa at the top of pro montory and anteriorly around the tympanic plexus varied from 1.67 +/- 0.64 to 1.13 +/- 0.26 mm for bone and 0.06-0.13 mm for mucosa. The th innest bone was found around the tympanic plexus, where the bone thick ness varied from 0.6 to 1.2 mm. Previous data indicate that current LD F instruments can provide a linear measure of blood flow through bone thicknesses of 1-3 mm or more (depending on the type of bone). Data fr om the current study indicate that direct valid dynamic measures of CB F are possible in humans. Since the optimal area available is small, t he topography of the middle ear should be well known and the recording site well defined to obtain valid results.