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Contrast angiography is the standard means of diagnosing spinal dural arteriovenous fistulas. We present a patient in whom a spinal dural arteriovenous fistula was demonstrated on phase contrast MR angiography.

We report a case with a paraophthalmic aneurysm that was wrapped with muslin because it was unclippable. Six months after wrapping, the patient developed gradual vision loss involving the ipsilateral eye. Both CT and MR studies demonstrated a loculated fluid collection with marked surrounding enhancement in the region of the previous surgery. Craniotomy revealed an abscess centered in the region of the aneurysmal wrapping. Pathological diagnosis was consistent with a foreign-body reaction with acute and chronic inflammation. Postoperatively the patient showed improvement in vision. We describe the MR findings in this case of muslin-induced optic arachnoiditis ("gauzoma").

Gangliocytomas are rare CNS tumors that occur in children and young adults. We present a case of a cerebellar gangliocytoma with invasion of the cervical spinal cord demonstrated on MR. Radiographic differentiation of gangliocytomas from other ganglion cell tumors--ganglioglioma, dysplastic gangliocytoma of Lhermitte-Duclos, and desmoplastic infantile ganglioglioma--is discussed.

Mycosis fungoides (MF) is a malignant T-cell lymphoma that primarily involves the skin, but may, in its advanced stages, metastasize to internal organs. From autopsy series, CNS involvement of MF can be seen in 14% of patients. We describe the CT and MR findings in three patients with CNS metastases. The images showed various manifestations of CNS MF, including parenchymal homogeneously intensely enhancing masses and ependymal enhancement. The CSF and biopsy results were eventually diagnostic in all three cases. One patient was treated prior to pathologic diagnosis, the other two were treated after diagnosis. The tumor improved following treatment in two patients. Although the imaging findings of CNS MF are nonspecific, they can be the first evidence of the disease.

Meningioangiomatosis (MA) is a rare hamartomatous lesion of the cerebral cortex; to date only 18 cases with imaging findings have been reported in the English literature. The origin of MA is probably malformative, with possible association with neurofibromatosis. These lesions frequently cause seizures in young patients. We report two new cases seen at our institution and present their CT and MR findings clearly illustrating MA cortex infiltration. Gd-DTPA used in one of the two cases failed to cause enhancement.

AIDS-related polyradiculopathy is a syndrome associated with cytomegalovirus infection. We report two cases of AIDS-related polyradiculopathy in which spinal T1-weighted MRI with gadolinium-DTPA showed enhancement of the pial lining of the conus medullaris, cauda equina, and lumbar nerve roots. Both patients clinically improved with ganciclovir treatment.

A fat suppression MR technique used in combination with Gd-DTPA enhancement was investigated to determine its value in cases of inflammatory optic nerve lesions. This technique, the so-called hybrid method, is a derivative of the chopper fat suppression technique and provides water-only images without increasing the imaging or postprocessing time. The study group consisted of four patients with acute visual loss, all of whom received Gd-DTPA. Conventional T2-weighted and fat suppression post-Gd-DTPA T1-weighted images were obtained in all patients; in addition, in one patient a post-Gd-DTPA T1-weighted image without fat suppression was obtained. In three patients, the conventional T2-weighted images failed to reveal any abnormality. In contrast, the enhanced optic nerve and enhanced perineural inflammatory infiltrate were easily identified on T1-weighted images after administration of Gd-DTPA and application of fat suppression technique. The lesions in inflammatory optic neuritis or perineuritis were easily distinguished from the surrounding fat, which had been suppressed. This combined technique resulted in significantly improved definition of normal anatomic structures and made the enhancing lesions more conspicuous, especially in areas with large amounts of fat such as the retrobulbar orbit.

Somewhat conflicting reports have appeared about the significance of linear meningeal thickening and enhancement adjacent to peripherally located cranial mass lesions on contrast enhanced magnetic resonance images. Some authors consider this finding nearly diagnostic of meningioma. In an attempt to determine the specificity of this so-called tail sign, particularly with respect to meningioma, we retrospectively reviewed 16 cases from institutional records. From our results, the tail sign appears to be highly suggestive but not specific for meningioma.

A case of Ramsay Hunt syndrome (herpes zoster oticus) was studied with Gd diethylenetriamine pentaacetic acid enhanced magnetic resonance imaging using a surface coil rather than a conventional head coil. This allowed us to demonstrate in detail the inflammatory changes of the multiple structures, involved.