Ex-PRESS glaucoma filter: an MRI compatible metallic orbital foreign body imaged at 1.5 and 3T.

AIM: To report on the MRI compatibility of the Ex-PRESS glaucoma filtration device, a tiny metallic implant placed into the anterior chamber of the eye that is much smaller than traditional glaucoma shunts, and to educate the radiology community regarding its appearance. MATERIALS AND METHODS: Seven patients with Ex-PRESS glaucoma filtration devices were identified that had undergone MRI at San Francisco General Hospital/University of California San Francisco Medical Center by searching and cross-referencing the radiology reporting system and the electronic medical record. MRI images were reviewed for artefact interfering with interpretation. Ophthalmology examinations were reviewed for evidence of complications. RESULTS: Eighteen individual MRI examinations were performed during 12 unique MRI events on these 7 patients. 13/18 individual MRI examinations and 7/12 MRI events were performed at 3 T with the others performed at 1.5 T. Mean time from Ex-PRESS implantation to MRI was 17.5 months. Mean time from MRI to first ophthalmology examination was 1.1 months and from MRI to latest ophthalmology examination was 6.6 months. Susceptibility artefact did not interfere with image interpretation and no complications related to MRI were encountered. CONCLUSION: The Ex-PRESS glaucoma filtration device appears to be safe for MRI at 1.5 and 3 T and does not produce significant susceptibility artefact to affect diagnostic interpretation adversely.

Interobserver variability in the assessment of CT imaging features of traumatic brain injury.

The goal of our study was to determine the interobserver variability between observers with different backgrounds and experience when interpreting computed tomography (CT) imaging features of traumatic brain injury (TBI). We retrospectively identified a consecutive series of 50 adult patients admitted at our institution with a suspicion of TBI, and displaying a Glasgow Coma Scale score < or =12. Noncontrast CT (NCT) studies were anonymized and sent to five reviewers with different backgrounds and levels of experience, who independently reviewed each NCT scan. Each reviewer assessed multiple CT imaging features of TBI and assigned every NCT scan a Marshall and a Rotterdam grading score. The interobserver agreement and coefficient of variation were calculated for individual CT imaging features of TBI as well as for the two scores. Our results indicated that the imaging review by both neuroradiologists and neurosurgeons were consistent with each other. The kappa coefficient of agreement for all CT characteristics showed no significant difference in interpretation between the neurosurgeons and neuroradiologists. The average Bland and Altman coefficients of variation for the Marshall and Rotterdam classification systems were 12.7% and 21.9%, respectively, which indicates acceptable agreement among all five reviewers. In conclusion, there is good interobserver reproducibility between neuroradiologists and neurosurgeons in the interpretation of CT imaging features of TBI and calculation of Marshall and Rotterdam scores.

MRI findings in Susac's syndrome.

BACKGROUND: Susac syndrome (SS) is a self-limited syndrome, presumably autoimmune, consisting of a clinical triad of encephalopathy, branch retinal artery occlusions, and hearing loss. All three elements of the triad may not be present or recognized, and MR imaging is often necessary to establish the diagnosis. OBJECTIVE: To determine the spectrum of abnormalities on MRI in SS. METHODS: The authors reviewed the MR images of 27 previously unreported patients with the clinical SS triad, and 51 patients from published articles in which the MR images were depicted or reported. RESULTS: All 27 patients had multifocal supratentorial white matter lesions including the corpus callosum. The deep gray nuclei (basal ganglia and thalamus) were involved in 19 (70%). Nineteen (70%) also had parenchymal enhancement and 9 (33%) had leptomeningeal enhancement. Of the 51 cases from the literature, at least 32 had callosal lesions. The authors could not determine the presence of callosal lesions in 18 of these patients, and only one was reported to have a normal MRI at the onset of encephalopathy. CONCLUSIONS: The MR scans in SS show a rather distinctive pattern of supratentorial white matter lesions that always involve the corpus callosum. There is often deep gray matter, posterior fossa involvement, and frequent parenchymal with occasional leptomeningeal enhancement. The central callosal lesions differ from those in demyelinating disease, and should support the diagnosis of SS in patients with at least two of the three features of the clinical triad.

Neuroimaging of AIDS. I. Central nervous system toxoplasmosis.

Toxoplasmosis is the most common cerebral mass lesion encountered in HIV-positive patients. Previously uncommon, this disease has increased markedly since the AIDS epidemic. There are occasionally unusual appearances of central nervous system toxoplasmosis that make diagnosis by standard imaging techniques difficult or impossible. More recently, MR spectroscopy has increased the ability to differentiate between various central nervous system lesions.

Imaging of acute head injury.

This article reviews the neuroradiological evaluation of acute head injury with an emphasis on CT and MR imaging. Subacute and chronic head injury are not discussed. CT remains the modality of choice in the emergency setting, permitting rapid, comprehensive assessment of the great majority of head injuries. MR is most useful in patients in whom there is a discrepancy between clinical symptoms and CT findings. In addition, MR is the imaging modality of choice in the subacute and chronic setting. The superior contrast resolution of MR permits optimal evaluation of nonhemorrhagic (and hemorrhagic) white matter shearing injuries, and the lack of beam-hardening artifact permits a more thorough evaluation of the brain stem, posterior fossa, and cortical surface.

Intraocular silicone oil for retinal detachment in AIDS: CT and MR appearances.

AIM: To describe the CT and MR features of intraocular silicone oil which is used to treat complex retinal detachments in patients with acquired immune deficiency syndrome (AIDS). PATIENTS AND METHODS: Seven male patients with AIDS were treated by pars plana vitrectomy and intraocular silicone oil injection for complex retinal detachments due to biopsy proven cytomegalovirus retinitis. Two patients had bilateral therapy. RESULTS: Silicone oil was hyperdense to muscle on CT with attenuation values of 106-139 HU (mean 115, SD 4.5). On MR, when compared with normal vitreous, intraocular silicone oil appeared hyperintense on T1-, proton density, and T2-weighted spin-echo sequences. A chemical shift artifact was seen on all MR images, being most marked on the T2-weighted images. CONCLUSION: The high attenuation value of silicone oil on CT and its hyperintensity on T1 weighted MR images my cause diagnostic confusion with haemorrhage. These entities can be distinguished at CT by directly measuring the attenuation number (silicone oil > 100 HU; blood < 90 HU), and at MR by the presence of a chemical shift artifact.

Neuroimaging in head injury.

This article reviews the neuroradiologic manifestations of acute nonpenetrating head injury. The pathophysiology of the various types of neurotrauma is correlated with the imaging features. Computed tomography (CT) remains the initial imaging modality of choice, allowing rapid diagnosis of the majority of injuries. Magnetic resonance imaging is useful in the subacute and chronic stages (particularly in a patient whose initial CT scan is unremarkable) to assess brainstem and white matter shearing injuries.

Clinical and radiographic findings in disseminated tuberculosis of the brain.

We report clinical and radiographic findings in a patient with disseminated tuberculosis (TB) of the brain. A Burmese man developed a left hemiparesis and mild cognitive difficulty 1 month into therapy for miliary TB. A head MRI showed numerous (> 100) contrast-enhancing supratentorial and infratentorial lesions. Following 9 months of treatment with isoniazid, ethambutol, rifampin, and pyrazinamide, most lesions resolved; however, one cortical tuberculoma enlarged significantly. The patient was continued on isoniazid and rifampin, with radiographic resolution of the tuberculoma 4 months later.

A pneumatized anterior clinoid mimicking an aneurysm on MR imaging. Report of two cases.

The advent of magnetic resonance (MR) imaging has marked a new era in neuroimaging--particularly in terms of diminishing the need for more invasive diagnostic procedures. A cautionary note should be sounded, however, about an important limitation of standard spin-echo MR studies. Two patients were referred for angiography because MR imaging indicated the presence of a "paraclinoid aneurysm." In retrospect, these findings were due instead to a pneumatized anterior clinoid. Angiography could have been avoided had this pitfall been recognized, and had a gradient-echo flow-imaging protocol been utilized. This latter approach (which does not replace spin-echo imaging) is more sensitive to flowing blood and thus allows differentiation of an air space from a nonthrombosed aneurysm.

The spinal tap: a new look at an old test.

The spinal tap, or lumbar puncture, has indisputable value; opinions differ, however, on the amount of that value. The procedure has variable utility depending on the clinical indications and the results of tests on the cerebrospinal fluid. Its greatest value is in the evaluation of infectious or malignant meningitis; for most other diseases, it provides additional, but not essential, information. Because of the potential risk of the spinal tap, decisions about when to do the procedure must be made carefully. A probability analysis is provided to elucidate the usefulness of data from cerebrospinal fluid tests.