MRI artifact masquerading as orbital disease.

OBJECTIVES: To describe the diagnostic challenge associated with magnetic resonance imaging (MRI) artifact and to describe methods of minimizing this artifact. METHODS: Gadolinium enhancement was demonstrated to be artifact by using an inversion recovery pulse sequence technique. RESULTS: A patient with complaints of painless loss of vision also had radiologic abnormalities that led to subsequent referral to a tertiary care facility. Increased signals on the fat-suppressed contrast enhanced MRI was demonstrated to be artifact by using an inversion recovery technique which produced a normal MRI of the orbit. CONCLUSIONS: Clinical confusion leading to unnecessary and costly evaluation may be avoided if one considers the possibility of artifact when reviewing magnetic resonance studies. When magnetic susceptibility is suspected, the use of an inversion recovery sequence can better delineate the true nature of the abnormality.

Incidental detection of hippocampal sclerosis on MR images: is it significant?

BACKGROUND AND PURPOSE: The prevalence of hippocampal sclerosis in the general nonepileptic patient population is not well described. While reports of its association with partial complex seizures are abundant, its absence in nonafflicted patients is generally presumed but not well documented. To test the hypothesis that hippocampal sclerosis is specific for epilepsy, we reviewed the MR imaging studies of 207 patients referred for hearing loss to determine whether high-resolution MR imaging could detect unsuspected hippocampal sclerosis in nonepileptic patients. METHODS: Our institution screens patients with hearing loss by using high-resolution coronal and axial temporal bone MR imaging that includes the hippocampus within the imaging volume. We retrospectively reviewed 207 studies randomly selected from this database. RESULTS: The hippocampus was normal in 205 patients; in the remaining two patients we identified one or more primary determinants for hippocampal sclerosis. Subsequent retrospective chart review revealed that both patients had had previously diagnosed seizure disorders. CONCLUSION: The imaging determinants of hippocampal sclerosis are not prevalent in nonepileptic patients. Incidental identification of hippocampal sclerosis on MR images is uncommon and significant, and should prompt further clinical investigation to exclude a seizure disorder.

Imaging of sella and parasellar disease.

The sella and parasellar region may be affected by a variety of disease states. Diseases of this region often result in visual disturbances because of the proximity of the sella to the optic pathways and cranial nerves. Knowledge of the pathological conditions affecting the sella and surrounding structures is important for the orbital imager.

Terson syndrome: CT evaluation in 12 patients.

PURPOSE: Terson syndrome may be overlooked in the acute setting and often requires ophthalmologic intervention to prevent long-term visual loss. In this syndrome, vitreous or retinal hemorrhage results from an abrupt rise in intracranial pressure, leading to retinal venous hypertension and intraocular hemorrhage. Our objective was to determine whether imaging findings could be discovered that might facilitate an earlier diagnosis. METHODS: Our inpatient medical record data base for 1991-1996 listed 11 patients with Terson syndrome. The medical records of these 11 patients were reviewed retrospectively and compared with their noncontrast head CT scans and with scans of 10 control subjects. One additional case was discovered prospectively, for a total of 12 patients. Three radiologists unaware of the patients' history evaluated CT scans of the orbits for evidence of intraocular hemorrhage. RESULTS: CT findings in eight patients were suggestive of retinal hemorrhage manifested by a retinal crescent or nodule that was slightly hyperdense relative to the vitreous humor. There was a high degree of concordance between the retrospective and independent reviews. CONCLUSION: Retinal nodularity and crescentic hyperdensities are evident on CT scans in the majority of patients with Terson syndrome. Although findings are subtle and not present in all cases, in the setting of subarachnoid hemorrhage they suggest retinal hemorrhage and warrant detailed fundoscopic evaluation.

Magnetization transfer contrast imaging of the human leg at 0.1 T: a preliminary study.

Magnetization transfer contrast imaging is an MR technique that capitalizes on interactions between the protons of mobile and macromolecularly bound water molecules. Studies to date, conducted primarily on 4.7 T and 1.5 T MR systems, have yielded results unique from conventional T1- and T2-weighted imaging studies. In this study, performed on a 0.1 T device, a section of lower leg was imaged in 20 normal human subjects and one patient with muscular dystrophy, using both a standard 500/22 gradient-echo sequence and a 500/22 gradient-echo sequence combined with off-resonance radio frequency irradiation designed to elicit magnetization transfer contrast. Results of the two techniques were compared. Our findings suggest that magnetization transfer contrast imaging is feasible at 0.1 T, and that this technique allows reproducible tissue characterization and improves contrast between certain tissues.