Radiological evaluation of temporal bone surgical landmarks for a transcanal transpromontorial approach to the internal auditory canal using three-dimensional computed tomography.

OBJECTIVE: This study aimed to analyse a three-dimensional transcanal transpromontorial approach to the internal auditory canal using three-dimensional computed tomography. METHOD: This study was a retrospective investigation of 48 ears of 24 patients using three-dimensional reconstruction data from normal temporal bone computed tomography. The inner structures of the temporal bone were three-dimensionally reconstructed. Eight points were marked in the three-dimensional object with reference to the axial, coronal and sagittal plane images of the computed tomography scans. Distances and angles to each point were measured from the oval and round windows. RESULTS: The point of the facial nerve from the internal auditory canal to the labyrinthine segment could be traced between the cochlear apex and the geniculate ganglion based on the oval window. CONCLUSION: This technique helps with identifying the locations of important surgical landmarks using three-dimensional reconstructions of pre-operative computed tomography scans and to identify the facial nerve from the internal auditory canal during surgery.

Clinical features and radiological evaluation of otic capsule sparing temporal bone fractures.

OBJECTIVE: To evaluate the clinical and radiological aspects of otic capsule sparing temporal bone fractures. METHODS: Using medical records, 188 temporal bones of 173 patients with otic capsule sparing temporal bone fractures were evaluated. Otoscopic findings and symptoms, facial paralysis, and hearing loss were assessed. RESULTS: Using regional analysis, 7 fractures were classified as type I, 85 as type II, 169 as type III and 114 as type IV. Fourteen of the 17 facial paralysis cases improved to House-Brackmann grade II or lower at an average of 57.6 days after the initial evaluation. Thirty-one patients underwent initial and follow-up pure tone audiometry examinations. The air-bone gap closed significantly from 27.2 dB at an average of 21.8 days post-trauma to 19.6 dB at an average of 79.9 days post-trauma, without the need for surgical intervention. CONCLUSION: Initial conservative treatment for facial paralysis or conductive hearing loss is possible in otic capsule sparing fracture cases after careful evaluation of the patient.

Analysis of the coplanarity of functional pairs of semicircular canals using three-dimensional images reconstructed from temporal bone magnetic resonance imaging.

OBJECTIVES: This study was conducted to investigate the angles and orientation of semicircular canals, and the coplanarity of functional canal pairs. METHODS: Fluid signals in semicircular canals were reconstructed with three-dimensional reconstruction software using 20 temporal bone magnetic resonance images of normal subjects. The angles between each pair of semicircular canals were measured. RESULTS: The mean angles between the anterior and horizontal semicircular canal plane, the horizontal and posterior semicircular canal plane, and the anterior and posterior semicircular canal plane were 83.7°, 82.5° and 88.4°, respectively. Pairs of contralateral synergistic canal planes were formed 15.1° between the right and left horizontal semicircular canal planes, 21.2° between the right anterior and left posterior semicircular canal, and 21.7° between the left anterior and right posterior semicircular canal. CONCLUSION: Each semicircular canal makes an almost right angle with other canals, but synergistically acting functional canal pairs of both ears do not lie in exactly the same plane.

Clinical Feasibility of Multiplanar Reconstruction Images of Temporal Bone CT in the Diagnosis of Temporal Bone Fracture with Otic-Capsule-Sparing Facial Nerve Paralysis.

The aim of this study is to evaluate the feasibility of multiplanar reconstructive (MPR) imaging of temporal bone CT in the diagnosis of temporal bone fracture with oticcapsule-sparing facial nerve paralysis. Twelve patients with traumatic facial nerve paralysis with otic-capsule sparing and temporal bone fractures were selected. Multiplanar reconstruction images were obtained with the V-works 4.0 software program (Cybermed, Seoul, Korea) using axial scanning of high-resolution temporal bone CT of the fracture line. The clinical profiles of the patients displaying temporal bone fractures were examined in relation to the findings. Multiplanar images of the fracture line provided information regarding the direction of the external force that fractured the temporal bone. The fracture line was more continuous in the MPR images than in the axial view. All patients showed an imaginary extended fracture line directed toward the otic capsule. The direction of the fracture line toward the middle ear cavity is important, as it may suggest insult to the otic capsule. The MPR image parallel to the fracture line of the temporal bone provides a guideline for the vector of the force that induced the fracture. Thorough investigation of the critical organs during surgical exploration is recommended if the direction of the fracture in the MPR image points toward the otic capsule in the middle ear even if the fracture line relative to the otic capsule is not well defined in the axial or CT view.

Clinical feasibility of temporal bone magnetic resonance imaging as a prognostic tool in idiopathic acute facial palsy.

OBJECTIVE: To assess the feasibility of temporal bone magnetic resonance imaging for evaluating the severity and prognosis of idiopathic acute facial nerve palsy. METHODS: Forty-four patients with idiopathic acute facial nerve palsy who had undergone gadolinium-enhanced magnetic resonance imaging were selected retrospectively. The degree of radiological facial nerve enhancement was determined using quantitative analysis (with region-of-interest measurements for separate facial nerve segments) and using subjective visual analysis. The clinical severity of facial nerve palsy was then correlated with the degree of facial nerve enhancement. RESULTS: The visually determined degree of facial nerve enhancement did not correlate significantly with the House-Brackmann grade at either the early or late stages (p > 0.05). Results using the region-of-interest system were similar (p > 0.05). CONCLUSION: Temporal bone magnetic resonance imaging is not essential for patients with acute facial nerve palsy.

Volume variation of mastoid pneumatization in different age groups: a study by three-dimensional reconstruction based on computed tomography images.

Although there have been some reports that measured the size of mastoid pneumatization, only a few studies have reported the age-related variations in the mastoid air cell system using three-dimensional (3D) reconstruction techniques of computed tomography (CT) images. We performed a retrospective, cross-sectional study. A 3D reconstruction based on CT images was performed on 199 ears of 102 patients (age range 6-84 years) without otologic disease by a surface-rendering algorithm. The results showed that mastoid pneumatization continued to grow until the third decade. Thereafter, it declined slowly, and then rapidly after the seventh decade. No statistically significant difference was found between male and female or between right and left sides. There was a significant difference between the larger and smaller sides of individuals. The volume measurement technique based on the 3D reconstruction technique reported here is widely available, highly accurate and easy to perform.