PubMed · 5590082
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C Zini. [Indirect microtympanoscopy].. https://pubmed.ncbi.nlm.nih.gov/5590082/
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BACKGROUND: Optical coherence tomography (OCT) is a new medical imaging technology that generates cross-sectional images of tissue microstructure with micron-scale resolution. Optical coherence tomography is analogous to ultrasound, measuring the intensity of infrared light rather than acoustical waves. OBJECTIVE: To demonstrate the feasibility of using OCT for ultra-high-resolution imaging of the middle ear via ex vivo imaging studies of human tissue. DESIGN: Images of the tympanic membrane and middle ear were acquired ex vivo, through the ear canal, without perforating the tympanic membrane. MATERIALS: Four excised intact temporal bones and the auditory apparatus were harvested from cadavers and imaged fresh, without previous fixation. RESULTS: The resulting images were compared with the gross sample and verified the ability of OCT to delineate relevant structures, such as the tympanic membrane and its sublayers, and the middle ear ossicles, nerves, and tendons at higher resolutions than possible with standard clinical imaging technologies. CONCLUSION: The ability of OCT to produce high-resolution images of tissue structure, without contact and in real time, as well as its ability to be integrated with endoscopes, suggests that this technology could become a useful modality for the diagnosis and management of a range of clinical middle ear abnormalities.
Although tympanic-membrane (TM) perforations are common sequelae of middle-ear disease, the hearing losses they cause have not been accurately determined, largely because additional pathological conditions occur in these ears. Our measurements of acoustic transmission before and after making controlled perforations in cadaver ears show that perforations cause frequency-dependent loss that: (1) is largest at low frequencies; (2) increases as perforation size increases; and (3) does not depend on perforation location. The dominant loss mechanism is the reduction in sound-pressure difference across the TM. Measurements of middle-ear air-space sound pressures show that transmission via direct acoustic stimulation of the oval and round windows is generally negligible. A quantitative model predicts the influence of middle-ear air-space volume on loss; with larger volumes, loss is smaller.
We report the use of a self-retaining aural speculum that provides an excellent view of the middle ear through a small endural incision. We have found this instrument of value in tympanoplasty and stapes surgery in particular.