Low-artifact intravascular devices: MR imaging evaluation

Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible.     

Electromyographic evaluation of a novel surgical preparation to enhance nerve-muscle specificity that follows mammalian peripheral nerve trunk transection

Previous studies indicated that axons from proximal stumps of transected peripheral nerves "prefer" to grow through Silastic tubes attached to their native (originally associated) rather than foreign (not originally associated) distal stumps. We determined whether or not this specificity is expressed at the level of the neuromuscular junction. Proximal stumps of transected rat sciatic nerves (peroneal and tibial branches) were attached to single inlet ends of 6-mm-long, Y-shape Silastic implants. One outlet was attached to the distal peroneal and the other to the distal tibial stump. Ten weeks later, innervation of the anterior tibialis and interosseous muscles (normally innervated predominantly by peroneal and tibial nerve fibers, respectively) was assessed by measuring compound muscle action potential amplitudes and latencies that follow supramaximal peroneal and tibial nerve stimulation. Results showed higher amplitudes in anterior tibialis muscle, induced by "native" peroneal (vs. tibial) stimulation in four of five animals, and higher amplitudes in interosseous muscles after "native" tibial (vs. peroneal) stimulation in all cases examined. Preparations in which bridges between proximal and distal nerve stumps were bridged with unbranched tubes showed random patterns of muscle innervation. The results suggest that if allowed to express "specificity" at the level of nerve trunk transection, regenerating mammalian peripheral axons can grow into, and form functional connection with, native (vs. foreign) muscle groups. This finding has possible clinical significance.     

ESWL: stone-free efficacy based upon stone size and location

Summary Extracorporeal shock wave lithotripsy was used for the treatment of 1060 patients or 1128 kidneys with solitary stones. There were 528 pelvic stones, 82 upper caliceal stones, 120 middle caliceal stones and 398 lower caliceal stones. These groups were divided into two subgroups of large (>15 mm) and small (15 mm) stones. A total of 1232 treatments were carried out (1.16/patient or 1.09/kidney) and 91% of the patients underwent a single treatment. Auxiliary procedures were required in 5% of the patients and the complication rate was 3%. Overall, 74% of the patients were stone-free after 3 months of follow-up. Of the 26% with residual stones, 18% had sand (2 mm fragments) or match-heads (4 mm), 6% had fragments (5 mm) and 2% had no fragmentation at all. A stone-free result occurred in approximately 87% with small pelvic and upper caliceal stones, whereas large stones in these locations became stone-free in approximately 70% of cases. Both large and small stones in the lower half of the kidney (mid and lower calices) become stone-free less frequently (to a statistically significant degree) than do similar stones located in the pelvis or upper calices.     

Osteopetrosis: MR characteristics at 1.5 T

Four patients with proved osteopetrosis (three with the infantile malignant form and one with the benign form) were examined with magnetic resonance imaging at 1.5 T. All patients were studied in the coronal and sagittal planes using both short and long repetition time/echo time sequences. The infantile malignant form was characterized by a complete lack of signal from the marrow alternating with a signal intensity equivalent to that of the intervertebral disks, resulting in a "stepladder" appearance. In the benign form or after successful marrow transplantation in the infantile malignant form, intermediate or high signal intensity in the vertebrae was noted, suggesting the presence of some marrow elements.