MRI of pituitary abscess: two cases and review of the literature.

Pituitary abscesses, rare lesions, may be divided into primary and secondary types. Primary pituitary abscesses occur within a previously healthy gland, while secondary abscesses arise within an existing lesion, such as an adenoma, craniopharyngioma, or Rathke's cleft cyst. Secondary abscesses share radiologic characteristics with the lesions from which they arise. There has been no review of the MRI characteristics of primary pituitary abscesses. We report two cases and review the literature. The typical primary pituitary abscess gives the same or slightly lower signal than brain on T1-weighted images, and could be mistaken for a solid mass or presumed to represent a pituitary adenoma. Contrast-enhanced images are useful, demonstrating absence of central enhancement, suggesting a fluid or necrotic center. In one of our cases, meningeal enhancement was obvious; this has not been reported previously and may be diagnostic, when associated with a rim-enhancing pituitary mass.

Optic chiasmal compression by venous aneurysm: magnetic resonance imaging diagnosis.

The overwhelming majority of traumatic carotid cavernous fistulas present with a bruit, arterialization of conjunctival vessels, or an elevated intraocular pressure. Described herein is a patient who presented with progressive deterioration of vision, without any of the above signs. Magnetic resonance imaging demonstrated compression of the optic ch asm by a venous aneurysm arising from a carotid cavernous fistula. This entity should be considered in patients who present with progressive visual loss.

Fast inversion recovery for myelin suppression (FIRMS). A new MRI pulse sequence for highlighting cerebral gray matter.

The purpose of this study is to test a new pulse sequence, fast inversion recovery for myelin suppression (FIRMS) for its ability to improve the conspicuity of gray matter. Twenty-six seizure patients were scanned with FIRMS as well as standard sequences. Gray matter conspicuity was evaluated objectively using region-of-interest calculations, including image contrast, contrast ratios, and contrast:noise (C/N). In evaluation of the hippocampus and cortex, all objective measurements of conspicuity were highest for FIRMS. In five clinical cases of suspected cortical dysplasia, FIRMS improved delineation of pathology in positive cases and ruled out the diagnosis in negative cases. In a case of hippocampal sclerosis, FIRMS was able to demonstrate atrophy of the alveus. Fast inversion recovery for myelin suppression holds promise for its ability to highlight the cerebral cortex and hippocampus.