ABSTRACT
BACKGROUND: Anatomical variants such as an overhanging facial nerve or promontory can impede access to the footplate during stapedectomy. Drilling away bone from the cochlear promontory may be required. In the case of a floating or depressed footplate, it has been recommended that a "pothole" be drilled in the inferior margin of the oval window. There is little published information on the anatomy of the promontory with respect to these maneuvers. MATERIALS AND METHODS: Twenty temporal bones were studied. A series of measurements was made to assess how much bone may safely be removed without risking damage to the underlying cochlear endosteum and, hence, spiral ligament and stria vascularis. RESULTS: The bony promontory is thickest posteriorly, and here, the endosteum has least lateral projection. The promontory becomes thinner closer to the oval window. Moving anteriorly, the bone becomes thinner and the underlying endo steum more closely follows the bony contour. The stria vascularis and spiral ligament may be less than 0.2 mm inferior to the inferior margin of the oval window posteriorly. This distance is at least 0.3 mm at the midpoint of the footplate (range, 0.3-0.5 mm). CONCLUSION: Bone may be removed inferiorly to the posterior one-third of the footplate from lateral to a line that makes an angle of 35 degrees with the superoinferior axis of the footplate. In creating a "pothole" in the case of a floating or depressed footplate, the authors recommend that it be created at the midpoint of the inferior margin of the oval window and should not exceed 0.3 mm in diameter.
Subject(s)
Stapes Surgery/methods , Stapes/anatomy & histology , Facial Nerve/anatomy & histology , Humans , Organ of Corti/anatomy & histology , Oval Window, Ear/anatomy & histology , Stapes Surgery/standards , Temporal BoneSubject(s)
Carcinoma, Squamous Cell/pathology , Carcinoma, Squamous Cell/secondary , Ear Neoplasms/secondary , Endolymphatic Sac/diagnostic imaging , Tomography, X-Ray Computed/methods , Carcinoma, Squamous Cell/diagnostic imaging , Ear Neoplasms/diagnostic imaging , Endolymphatic Sac/pathology , Humans , Lung Neoplasms/pathologyABSTRACT
Mycobacterium tuberculosis is a rare cause of mastoiditis, but diagnosis is often delayed, with potentially serious results. We present the case of a 7-year-old child who failed to improve even once the diagnosis was made and appropriate medical treatment initiated. At mastoidectomy, a bony sequestrum was found which had not been evident on CT scanning. We review the diagnosis and management of this condition and suggest that failure to respond to drug therapy even in the absence of demonstrable complications be added to the list of indications for surgical intervention.
