Motomichi Sakata

Vascular Compressive Abducens Nerve Palsy Disclosed by Magnetic Resonance Imaging

PURPOSE To assess magnetic resonance imaging as a diagnostic tool of neurovascular compression in a patient with abducens nerve palsy. METHODS We performed magnetic resonance imaging of the brainstem of a 46-year-old patient with left abducens nerve palsy using spoiled gradient recalled acquisition in the steady state (SPGR), which allows high-resolution T1-weighted imaging and detection of the arteries across the plane of slices as a high-signal-intensity area. RESULTS Computed tomography of the brain was unremarkable except for leftward shifting of the basilar artery. As disclosed by magnetic resonance imaging with the SPGR, the right vertebral artery was shifted to the left and joined with the left vertebral artery, and the left abducens nerve was compressed by the vertebral artery. No other abnormal signals were seen in the brainstem. CONCLUSIONS These findings suggest that the abducens nerve palsy in this patient was caused by vascular compression at the root exit zone. Magnetic resonance imaging with the SPGR is useful for the diagnosis of vascular compressive neuropathy.

Three-Dimensional Imaging of the Temporal Bone Using a Helical CT Scan and Its Application in Patients with Cochlear Implantation

Recent advanced techniques for the reconstruction of three-dimensional (3D) images allow further visual recognition of the fine structures of the temporal bone. We demonstrate the advantages of reconstruction 3D imaging in helical CT scans of the normal temporal bone and in patients who have received cochlear implants. After the temporal bone was scanned in the axial plane in the helical scan mode, the data were transferred to a workstation and 3D reconstruction was performed. The normal temporal bone structures were well recognized on these 3D images. The spatial relationship between the lymphatic space of the inner ear and the electrode array is visible. This method provides a detailed anatomy of the insertion of the electrodes into the cochlea and provides precise images of electrode routes by means of varying the angles of view on the computer display. Individual electrodes could not be distinguished. The information from 3D images may be useful not only for pre-but also postoperative investigations in cochlear implantation.

Middle Ear Imaging Using Virtual Endoscopy and Its Application in Patients with Ossicular Chain Anomaly

Virtual endoscopy (VE) is a recently developed technique to provide a realistic surface rendering of various organs, which can be applied to the use of three-dimensional (3D) studies of several lesions. However, its advantages in otological disease have not been well investigated. In this study, we evaluated the application of VE in patients with ossicular chain anomalies. Virtual middle ear endoscopy was a time-saving method, however, we needed the appropriate technical procedures of algorithm and reconstruction spacing to generate accurate 3D images of ossicles. We obtained virtual surgical views of middle ear structures and related anomalies, and confirmed by intraoperative findings that these images were mostly compatible with the actual lesions of ossicles. VE allowed an identification of the anatomy of the ossicles and adjacent structures simultaneously. The elements of the stapedial crura were clearly visualized with VE images in 93.3% of normal ears. Pathological ossicular chain findings such as malleus or incus fixation, dislocation and disruption, except footplate fixation were investigated successfully. One possible procedure, using alterable CT value in the obtained VE images on the monitor, is proposed for further detection of fine lesions of the ossicles. These observations suggest that virtual middle ear simulations accurately represent major intraoperative findings. This technique may have an important role in preoperative planning, surgical training, and/or postoperative evaluation in otology.

Radiographic features of an aneurysmal bone cyst of the orbit

Aneurysmal bone cyst is an unusual benign solitary lesion of bone occurring rarely in the orbit. In this report, we present computed tomography and magnetic resonance images of an orbital aneurysmal bone cyst involving the frontal bone in a 16-month-old boy. The aneurysmal bone cyst exhibited bone destruction, new bone formation of the orbital roof and fluid-fluid levels in the lesion following hemorrhage. These radiographic features may be useful for diagnosing orbital aneurysmal bone cysts.

Anomalous Vessels in the Middle Ear Associated with Congenital Anomalies of the Internal Carotid Artery

A case with unilateral hypoplasia of the internal carotid artery was reported. The rerouting of anomalous vessels in the middle ear, visualized by otoscopy, was demonstrated with CT and MRI. Associations with internal carotid hypoplasia, the intercarotid collaterals, both anomalous middle ear arteries and the enlarged internal maxillary artery were confirmed with MRI. MR images were helpful to diagnose not only the anomalous vessels but also the multiple anastomoses.