Abstract
Preoperative radiographic imaging of the temporal bone is well accepted in otology for both the diagnosis of disease and the delineation of anatomic structure for surgical planning. Until recently radiographic techniques have unfortunately failed to demonstrate fibrous or bony obstruction of the basal turn of the cochlea, which may cause difficulties during cochlear implantation. Intraoperative findings have been correlated with preoperative imaging in a consecutive group of six cochlear implant recipients and a series of consistent radiographic signs that may indicate the presence of obstruction of the scala tympani have been identified. A classification system has been developed. Based on thin-section high-resolution computerized tomography (HRCT), the system has been used preoperatively on six cochlear implant recipients. In addition, a systematic evaluation of the temporal bone has been developed for precochlear implant evaluation. This includes (1) the thickness of the parietal bone for seating of the receiving device, (2) the degree of pneumatization of the mastoid, (3) the measurement of the size of the facial recess, (4) the description of the size and orientation of the round window niche, and (5) the patency of the basal turn of the cochlea.
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