To determine the frequency and characteristics of small cerebral aneurysms with atypical appearances on magnetic resonance (MR) images.MR imaging studies (n = 117) obtained at 1.5 T of small aneurysms (< 1 cm diameter) were prospectively and retrospectively analyzed. Signal intensity characteristics and gadolinium-enhancement patterns in 84 aneurysms (62 patients) were evaluated. The patency of all aneurysms was confirmed at angiography or at the time of surgery.A characteristic signal void was seen on 62 (53%) of 117 studies. On the remaining 55 (47%) studies, aneurysms had atypical signal intensity that was isointense, heterogeneous, or hyperintense. Contrast-enhanced aneurysms were seen on 27 (53%) of 51 gadolinium-enhanced studies.Atypical MR imaging characteristics were seen in roughly half of cases. These atypical-appearing aneurysms may erroneously be considered to be thrombosed or be mistaken for other common lesions such as small tumors and be dismissed as nonvascular.
Twenty-eight patients with intradural inflammatory disease of the spine were studied in order to characterize the MR imaging findings of infectious and inflammatory conditions. Patients were categorized according to the spinal compartment involved. Among the 12 patients in the intradural extramedullary group, unenhanced scans were either normal or nonspecific while contrast-enhanced scans were helpful in visualizing and localizing the lesion. Nevertheless, contrast-enhanced MR studies were unable to differentiate infection and inflammation from tumor in this compartment. Among 16 patients with intramedullary lesions, four had granulomatous disease and 12 had nongranulomatous disease. The granulomatous lesions resembled tumors and displayed MR characteristics of a focal lesion with large nodular enhancement. The patients with nongranulomatous intramedullary lesions exhibited two subsets of MR findings. In the first subset of nine patients, diffuse cord swelling and high signal were seen on long TR images, combined with either no enhancement or peripheral, diffuse, or speckled enhancement of the spinal cord on contrast-enhanced short TR images. In the second subset of three patients, minimal or no spinal cord swelling was displayed despite the visualization of high signal on long TR scans and nodular enhancement with contrast administration on short TR scans. Both subsets were sufficiently unique that nongranulomatous myelitis could usually be differentiated from spinal cord tumors.
Summary: Purpose : Vigabatrin (Sabril, Hoechst Marion Roussel) is an antiepilepsy drug (AED) presently marketed in 64 countries for the treatment of partial and secondarily generalized seizures. Vigabatrin (VGB) is marketed in a subset of these countries for the treatment of infantile spasms. Clinical experience in humans has shown that VGB provides effective seizure control with a wide margin of safety. However, animal toxicity studies raised concern when prolonged administration of VGB was shown to induce intramyelinic edema (IME) in some laboratory animal species. Methods : Animal and human data were reviewed with respect to the potential for VGB‐induced IME. Surveillance of patients receiving VGB in clinical trials or by prescription has been conducted for <15 years to identify patients developing clinical abnormalities that might be IME related. Results : The histologic lesions of VGB‐induced IME in animals are reliably reproduced and correlate with changes in multimodality evoked potentials (EPs) and magnetic resonance imaging (MRI). Numerous studies of the effects of VGB on EP and MRI in epilepsy patients have demonstrated no clear‐cut IME‐related changes in these modalities. Additionally, autopsy and surgical brain samples from VGB‐treated patients have been scrutinized for potential IME histopathology. In an estimated 350,000 patient‐years of VGB exposure (‐175,000 patients exposed for 2 years at an average dose of 2 g/day), no definite case of VGB‐induced IME has been identified. Conclusions : Comprehensive review of a variety of sources of data failed to identify any definite case of IME in humans treated with VGB.
MR imaging was performed in 13 patients with benign lumbar arachnoiditis both before and after IV injection of gadopentetate dimeglumine. The arachnoiditis was proved by previous myelography in 12 patients and by noncontrast MR imaging in one patient. The disease was presumably the result of previous myelography and/or surgery. It was characterized as mild in two patients, moderate in two patients, and severe in nine patients. Imaging was performed on a 1.5-T unit, and both short and long TR images were obtained before and after contrast administration. Noncontrast MR images demonstrated changes consistent with arachnoiditis in all patients. After contrast, three patients had no enhancement, three patients had minimal enhancement, three patients had mild enhancement, and four patients had moderate enhancement. In no case did contrast enhancement alter the diagnosis or reveal additional findings that could not be seen on the noncontrast images. Gadopentetate dimeglumine enhancement plays little role in the diagnosis of lumbar arachnoiditis. If used for another reason, however, short TR scans may show enhancement of adherent roots in some cases. In addition, administration of gadopentetate dimeglumine will not cause sufficient enhancement to hinder the detection of arachnoiditis on long TR images and may aid in recognition of adherent roots on short TR images.
Magnetic resonance imaging (MRI), which has recently begun to replace myelography, postmyelography computed tomography (CT), and to some extent, bone scans, has become the procedure of choice in the evaluation of spinal tumors; the applications of MRI in this role are reviewed.In the extradural space, MRI is the most sensitive technique for the detection of tumors in the vertebral bodies.At the same time, it provides superb delineation of suspected thecal sac impingement.In the intradural extramedullary space, MRI is generally as accurate as myelography and postmyelography CT while being noninvasive.Finally, in the intramedullary space, MRI is unquestionably the procedure of choice in the evaluation of suspected cord tumors.In general, MRI has become the best initial procedure in the evaluation of suspected tumors of the spine, regardless of the space in which they may lie; frequently, it is the only required examination.
MRI appearance of adult polyglucosan body disease is described. A 67-year-old man presenting with a chronic progressive degenerative neurologic disorder was found to have marked atrophy of the entire cord, without signal abnormalities on long TR images. Autopsy revealed atrophy of the cord, diffuse gliosis, and numerous corpora amylacea.
