Radial collagen fibers in the tympanic membrane play an important role in the conduction of sound above 4 kHz.

Objective-Optical coherence tomography (OCT) is a diagnostic imaging modality that combines low coherence light with inter ferometry to produce high-resolution cross-sectional images of living tissues. Using this technology, we have imaged in vivo the human tympanic membrane (TM) in the office clinic setting and characterized TM microstructure in normal and pathologic conditions. Study Design-Prospective clinical trial.Materials and Methods-The normal and diseased TMs in 10 adult subjects were examined. Each subject underwent direct microscopic examination before OCT imaging to provide visual coregistration of associated subsites including the anulus fibrosus, pars tensa, pars flaccida, and umbo. The probe from the imaging system (1,310-nm central wavelength, 15-μm coherence length, Niris; Imalux, Cleveland, OH, USA) was introduced into the ear canal to obtain lateral cross-sectional images.Results-Systematic imaging of the TM was performed with characterization of the epithelial and collagenous layers. The overall TM thickness was clearly demonstrated and quantified.Conclusion-The ability to noninvasively study middle ear microstructures in vivo is essential in the treatment of diseases of the ear. OCT may provide the otologist/neurotologist with the ability to 1) image pathology such as cholesteatoma, dimeric TMs, and chronic otitis media; 2) gauge the response to pharmacological therapy; and 3) monitor postsurgical changes after tympanoplasty and other procedures. OCT may provide a means to optimize the diagnosis and management of patients with middle ear disease. (1). It uses light to discern differences in tissue microstructure and uses coherence gating to localize the origin of the reflected optic signal. OCT is analogous to B-mode ultrasonography but uses broadband near-infrared light to produce images with a resolution approaching that of light microscopy (10-15 μm) (1,2). OCT relies on differences in tissue optical properties to generate contrast, with axial resolution on the order of 10 μm and of a depth of penetration of approximately 1 to 2 mm, depending on turbidity. Axial resolution is inversely proportional to the coherence length of the sources. Lateral resolution is diffraction limited and therefore dependent on the optical design of each device. Although OCT has been used as a measurement tool in ossiculoplasties and stapedectomies (3), in vivo use of OCT in the human tympanic membrane (TM) has not previously been reported. KeywordsIn the head and neck, OCT applications have primarily focused on characterizing cancer and other disease processes in the larynx (4), because OCT is ideal for imaging the thin, layered structures of the vocal fold epithelium and lamina propria. Most OCT applications in the study of the middle and inner ear have focused on either animal investigations or human temporal bone studies (5-10). In this study, we use OCT to image and characterize the TM in both normal and pathologic conditions. Successful OCT imaging of the TM will allow the clinician to obtain stru...

The central nervous system depends critically on a regular supply of oxygen and glucose for the formation of adenosine triphosphate (ATP) and the sustenance of its energy metabolism. Consequently, a significant reduction in the supply of oxygen and glucose to neuronal tissue causes an imbalance between the energy supply and demand, inducing the onset of neuronal ischemia and triggering many metabolic cascades leading to irreversible injury and cell death. Nicotinamide (NAm), an essential precursor to nicotinamide adenine dinucleotide (NAD+), which raises brain ATP levels, may improve cerebral blood flow and is neuroprotective against ischemia‐induced injury. We therefore chose to examine the metabolic and electrophysiologic/functional effects of NAm (0.1 mM, 1.0 mM, 10.0 mM) under normal, control, and ischemic conditions, as well as following the early stages of reperfusion (“return‐to‐control” conditions) using an in vitro rabbit retina model where blood flow effects are excluded. Under nonischemic, control conditions, the protective concentration of NAm (10.0 mM) increased glucose utilization (34%, P < 0.01) and decreased lactate production (44%, P < 0.01), but had no significant effect on electrophysiologic function. After 2 h of ischemia, glucose utilization was significantly decreased (41%, P < 0.01) and lactate production was unaffected by NAm (10 mM). Following 3 h of “reperfusion”, NAm (10 mM) significantly improved glucose utilization (217%, P < 0.01), lactate production (40%, P < 0.01), and electrophysiologic function (264%, P < 0.01) relative to controls. Thus, the functional neuroprotective effects of NAm may be independent of blood flow effects, but related, at least in part, to its improvement of tissue glucose utilization and lactate production.

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