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Until now, shunt catheters used in endolymphatic sac (ELS) and duct surgery have not been visible at computed tomography (CT) imaging. This report summarizes findings at postoperative CT in 50 patients who underwent endolymphatic system decompressive surgery with a new opaque shunt catheter placed at or into the endolymphatic duct (ELD). The catheter was visible in all 50 cases, and the best projection for visualization was the semicoronal view. The postoperative visualization of the opaque shunt catheter allows determination of the exact placement of the catheter (a) in the bony vestibular aqueduct (within the membranous ELD); (b) at the external aperture of the bony vestibular aqueduct (within or at the membranous ELD at its junction with the ELS); or (c) outside the bony vestibular aqueduct system or aperture but presumably within the membranous ELS. These objective findings may be used as a marker to help predict outcomes from this type of nondestructive inner ear surgery, as well as to determine exactly where the surgeon placed the shunt-tube catheter tip.

The abducens nerve, the sixth cranial nerve, innervates the lateral rectus muscle of the eye and is responsible for lateral horizontal ocular movement. A wide variety of abnormalities, both primary to the nerve itself and secondarily involving the nerve, can paralyze the abducens nerve. MR imaging offers the best opportunity to detect the underlying abnormality causing abducens nerve palsy. In this pictorial essay, we illustrate the MR imaging features of numerous conditions that cause isolated abducens nerve palsy.

We performed a retrospective study of symptomatic peripheral vascular malformations to determine if MR imaging can be used to distinguish slow-flow venous malformations from high-flow arteriovenous malformations and arteriovenous fistulas. Twenty-seven MR examinations in 25 patients with malformations outside the CNS were reviewed. Sixteen venous malformations, nine arteriovenous malformations, and two arteriovenous fistulas were included. In all cases, the MR findings were correlated with the results of angiography. The distinction between slow-flow venous malformations and high-flow arteriovenous malformations and arteriovenous fistulas was made primarily on T2-weighted MR images, which showed high signal intensity in venous malformations and flow voids in high-flow lesions. In addition to the previously described MR features of venous malformations (serpentine pattern with septations, associated muscle atrophy, and typical T1 and T2 signal intensities), several new MR features were apparent. Venous malformations had a propensity for multifocal involvement (37%), orientation along the long axis of extremities or affected muscles (78%), and adherence to neurovascular distributions (64%). Prominent subcutaneous fat was commonly seen adjacent to the malformation. MR images of arteriovenous malformations and arteriovenous fistulas also commonly showed muscle atrophy and subcutaneous fatty prominence. Our results show that slow-flow venous malformations can be distinguished from high-flow arteriovenous malformations and fistulas on the basis of spin-echo MR signal characteristics. The associated imaging characteristics help in the differential diagnosis in problematic cases.

A 5 1/2-year-old boy developed a huge cyst in his chiasmal glioma 4 years after radiation therapy. The cyst produced obtundation but was successfully treated.

Absolute ethanol was used to treat 20 patients with symptomatic vascular malformations (SVMs) (ie, venous malformations, arteriovenous malformations, and congenital and posttraumatic arteriovenous fistulas) in whom previous surgery or standard embolotherapy had failed or who were not candidates for surgery. All large complex lesions required multiple embolizations as staged procedures. Immediate thrombosis was achieved in all patients; complications (13% of cases) were generally minor and were treated conservatively. Follow-up studies, performed in 19 of 20 patients, showed persistent occlusion of the SVM in all cases. Ethanol embolization of SVMs, performed according to strict techniques, has proved efficacious in SVM management and is emerging as a definitive form of therapy.

Comprehensive efficacious neuroimaging of the vestibular pathways requires cooperation and coordinated efforts between the otologist and the neuroradiologist to avoid duplication of expensive and sometimes invasive study. For peripheral lesions, for example, those of the labyrinthine organ, thin-section CT is optimum as a first examination. For retrolabyrinthine lesions along nerve tracts or in the central pathway, MRI is preferred. When bone erosion occurs, CT can also be helpful in evaluation of the base of the skull to detect and define the extent of these lesions, for example, cholesterol granuloma and glomus tumor.

Between 1965 and 1985, 47 cases of glottic and/or tracheal stenosis were diagnosed at the Rocky Mountain Regional Spinal Cord Injury System. A retrospective review of medical records identified associated injuries, pulmonary and other medical complications in this patient population. Radiographic and endoscopic reviews utilised a grading system to classify the severity of stenosis. The clinical symptoms of stenosis were multiple, including dysphonia, aspiration, dysphagia, odynophagia, dyspnea and excessive secretions. The wide spectrum of treatment modalities included endoscopy with excision and/or dilation, general medical management, steroids, radiation therapy, intubation, stent insertion and surgical repair of the stenotic area. Outcome status was reviewed and suggestions provided for the early diagnosis and treatment of this potentially life-threatening condition.

The authors summarise their findings in use of computerised tomography (C.T.) in she initial evaluation of 119 spinal cord injured patients admitted to the Rocky Mountain Regional Spinal Cord Injury System from May, 1979 through to October, 1983. Of the 119 patients, 47 (40%) had CT during the initial evaluation of their injury. (32 of 67 paraplegics and 11 of 52 tetraplegics had high resolution CT scans). Prior to August, 1981, EMI-5005 scanners were available but were used sporadically because of factors discussed below. In 1981, the GE 8800 CT became available for use and subsequently largely replaced tomography in the evaluation of thoracic lumbar injury and was used frequently in cervical injury. Technical requirements for useful CT were found to be: sagittal and coronal reformatting capability; rapid scanning; thin sections of 1-5 mm for cervical studies and 5 mm for lumbar thoracic studies with overlapping for reformatting; extended bone window; and digital radiographic views. Advantages of CT over tomography included not having to turn the patient for the lateral examination, thus increased safety; diminished X-ray exposure dose for CT as compared with tomography: CT: approximately 2-4 r/examination tomography: approximately 75-100 r/examination. Additionally, CT was advantageous for the visualization of the C7, Tl level; for display of the posterior vertebral elements and arch: for evaluation of canal integrity; unsuspected fractures and fracture fragments and tracking of missile paths. Orthopaedic surgeons found thoracic lumbar CT helpful for planning spine stabilisation, and for the approach for reduction of canal fragments. The authors conclude that following plain X-ray films, CT is the radiographic procedure of choice in the evaluation of the vertebral column in spinal cord injury.

Computerised tomography (CT) scanning has become an accepted diagnostic method in evaluation of patients with spinal cord injury and has become increasingly important in the assessment of the vertebral column, spinal cord, and brain. Since CT images are graphic representations of generated computer mathematical data viewed with variable window and level selections (display factors), various image representatations are possible and potentially erroneous objective and subjective conclusions from viewing and measuring anatomical findings can result if an appreciation of this potential variability is not understood. Additionally, the CT image can be reconstructed from a variety of mathematical algorithm selections, which can enhance or diminish aspects of tissue contrast (smoothing or edge enhancement). Optimization of these factors, (window and level selection for viewing, and image generation algorithm), is especially important if detection and measurement of objective structures are to be reliable. The authors studied otpimization of algorithm selection and display factors (window and level selection), with a phantom designed to mimic spinal column, spinal cord and subarachnoid space. Varying concentrations of metrizamide in the phantom were scanned. With the G.E. 8800 Scanner, the bone algorithm was found to be the optimum algorithm for optimum spinal cord images if the measured metrizamide CT attenuation number was greater than 150-200. With a metrizamide CT attentua-tion number less than 150 the soft tissue algorithm was optimum. Window centre (level) selection greatly influenced the measurement of cord size, whereas window width did not. The appropriate window centre (level) selection is the mean between the metrizamide CT attenuation number and the cord CT attenuation number. The clinical application of these findings is summarized, and includes: Patients with metrizamide CT studies that require accurate measurement of spinal cord size or measurement of spinal cord cyst size (post-traumatic cystic myelopathy). Significant errors are possible if the formula for appropriate window centre selection is not followed. Additionally, the use of the bone algorithm requires higher contrast for accuracy, thus if metrizamide concentrations are weak, erroneous interpretations are possible. The authors also found that in the presence of metal (rods, screws or plates) the bone algorithm increased artifacts in CT, thus should not be used in this situation but rather the soft tissue algorithm must be used when metal is present to minimize artifacts.