Time-resolved spinal MR angiography: initial clinical experience in the evaluation of spinal arteriovenous shunts

BACKGROUND AND PURPOSE: Spinal arteriovenous shunts usually require digital subtraction angiography (DSA) for evaluation. We report a unique time-resolved spinal MR angiographic (TRSMRA) technique with a temporal resolution of 3-6 seconds and spatial resolution of approximately 1 mm(3) that has the potential to noninvasively detect, localize, and follow-up these cases. MATERIALS AND METHODS: Eleven patients with clinical presentation and/or MR findings suspicious for a spinal arteriovenous shunt were referred for TRSMRA. Patients subsequently underwent spinal DSA to confirm the presence or absence of a shunt or were followed clinically until an alternative diagnosis was found. TRSMRA was also used to predict the level of the shunt in the positive cases. In addition, 2 of these patients as well as a 12th patient referred to us posttreatment received a follow-up TRSMRA to assess treatment outcome. RESULTS: Early venous shunting was identified by using TRSMRA in 6 cases. All 6 were confirmed to have an AV shunt on subsequent spinal DSA. The shunt level predicted by TRSMRA consistently correlated with DSA to within 1 vertebral level. In the 5 patients with a negative screening TRSMRA, DSA or clinical outcome confirmed the absence of an arteriovenous shunt in all of the cases. Posttreatment TRSMRA in 3 patients accurately assessed the success or failure of treatment. CONCLUSION: Combining acceleration techniques to achieve high frame rate TRSMRA provides sufficient temporal and spatial resolution to identify, localize, and follow patients suspected of having a spinal arteriovenous shunt. Further study in a larger population is warranted to assess the accuracy of this technique.     

Animal models of arthritis: relevance to human disease.

Animal models of arthritis are used to evaluate potential antiarthritis drugs for clinical use. Therefore capacity of the model to predict efficacy in human disease is one of the most important criteria in model selection. Animal models of rheumatoid arthritis (RA) with a proven track record of predictability include rat adjuvant arthritis, rat type II collagen arthritis, mouse type II collagen arthritis, and antigen-induced arthritis in several species. Agents currently in clinical use (or trials) that are active in these models include corticosteroids, methotrexate, nonsteroidal anti-inflammatory drugs, cyclosporin A, leflunomide, interleukin-1 receptor antagonist, and soluble tumor necrosis factor receptors. For some of these agents, the models also predict that toxicities seen at higher doses for prolonged periods would preclude dosing in humans at levels that might provide disease-modifying effects. Animal models of osteoarthritis (OA) include mouse and guinea pig spontaneous OA, meniscectomy and ligament transection in guinea pigs, meniscectomy in rabbits, and meniscectomy and cruciate transection in dogs. None of these models have a proven track record of predictability in human disease because there are no agents that have been proven to provide anything other than symptomatic relief in human OA. Efficacy data and features of the various models of RA and OA are discussed with emphasis on their proven relevance to human disease.     

Differentiation between cortical atrophy and hydrocephalus using 1H MRS

Quantitative ¹H MRS to determine cerebral metabolite patterns and MRI to determine CSF flow were applied to 12 patients with ventricular dilation—Group A, cortical atrophy (N = 5); or Group B, hydrocephalus (N = 7)—and in 9 normal controls. While mean brain water (Group A = 80% ± 6; Group B = 86% ± 5; normal = 85% ± 4) did not differ between the two groups of patients and controls, ¹H MRS distinguished those patients with cortical atrophy (Group A) (N-acetylaspartate/creatine (NAA/Cr) = 0.69 ± 0.17, versus normal = 1.06 ± 0.16; P < 0.002; [NAA] = 5.9 ± 1.3 mmoles/kg, versus normal 8.0 ± 1.4; P < 0.02) from those with hydrocephalus (Group B) (NAA/Cr = 1.16 ± 0.11; [NAA] = 9.2 ± 1.2; P > 0.13 and P > 0.07). Lactate levels were elevated in 3/5 patients with cortical atrophy, but in 0/7 of those with hydrocephalus. Mean absolute concentrations (mmoles/kg) of the five major cerebral osmolytes were 41 ± 4 (Group A), 43 ± 6 (Group B), and 42 ± 4 (normal), so that despite massive brain deformation, constant osmolality was maintained. ¹H MRS may directly benefit surgical planning in hydrocephalus infants by clearly identifying those with cortical atrophy who do not require CSF diversion. Thinning of the cortical mantle in hydrocephalus may result from osmotically driven reduction in individual cell volumes, (shrinkage), rather than brain-compression.