Anterior commissure: anatomic-MR correlation and use as a landmark in three orthogonal planes

Correlation of cryomicrotomic and myelin-stained sections of human cadaver heads with spin-echo magnetic resonance (MR) images documents that MR imaging routinely displays the anterior commissure in three orthogonal planes as a distinct white-matter tract that resembles bicycle handlebars. The anterior commissure crosses the midline at the upper end of the lamina terminalis, just anterior to the anterior columns of the fornices. To each side of midline, it curves antero-inferolaterally and then postero-inferolaterally through the lateral nucleus of the globus pallidus to course with the white matter of the external and extreme capsules toward the middle and inferior temporal gyri. Because the anterior commissure is easily recognizable in all three planes at differing pulse sequences, the commissure has proved to be a major landmark for identification of the complex anatomy of this region, especially in sagittal sections.     

Effect of chymopapain on the meninges studied in an experimental model

The effect of chymopapain and contrast media in the epidural space on meninges has not been studied conclusively. The authors injected chymopapain into the epidural space of monkeys and measured the degree of arachnoid fibrosis that resulted. Animals were given injections of 1.2 mL of diatrizoate (280 mg iodine per milliliter), chymopapain (100 IU/mL), kaolin (100 mg/mL) (as a positive control), or saline (0.9%) (as a negative control). Three months later the animals were killed; the dural sac was removed intact and was fixed, sectioned, stained, and examined with light microscopy. Kaolin-treated animals developed mild to marked fibrosis of the dura. The saline- and diatrizoate-treated animals developed little or no evidence of fibrosis. One of four chymopapain-treated animals developed degenerative changes in dorsal nerve roots and fibrosis in the adjacent arachnoid. The other chymopapain-treated animals had little or no evidence of fibrosis. The studies suggest that neither diatrizoate nor chymopapain causes arachnoid fibrosis.     

T1 and T2 measurements on a 1.5-T commercial MR imager

In order for relaxation times to be used in clinical diagnosis, the precision of the measurement must be determined. The authors measured T1, T2, and proton density in a phantom and in human volunteers to determine the reproducibility of the method. The coefficient of variance of T1 measurements in the phantom during a 15-month period with two software upgrades was 5%. Variance of T2 measurements with any given software was 4% or less, and overall in the 15-month period, with two software changes, the T2 reproducibility was between 6% and 9%. The reproducibility is sufficiently high that precise clinical measurements of T1, T2, and proton density are feasible.     

Effect of axial loading on neural foramina and nerve roots in the lumbar spine

The hypothesis that the neural foramina in some patients are critically narrowed by axial compression of the spine has not been studied with direct imaging techniques. Frozen cadaveric motion segments of the lumbar spine (intervertebral disk and contiguous vertebrae) were imaged with computed tomography (CT). The segments were thawed and compressed in a hydrostatic press to simulate axial loading, and then the segments were frozen and imaged again. The motion segments were subsequently sectioned with a cryomicrotome, and the chronic degenerative changes present in the disks were classified. Pre- and post-compression CT images were compared, and anatomic relationships were studied. In 41 randomly selected segments (some with preexisting radial, transverse, and concentric annular tears), compression diminished the diameters and cross-sectional areas of the spinal canal and neural foramina. In no cases were nerve roots displaced, distorted, or compressed by axial loading. This study suggests that axial loading, such as that produced by ordinary weight bearing, does not critically compromise the neural foramina even in the presence of chronic degenerative disk changes.     

What role should the intra-aortic balloon have in cardiac surgery.

Intra-aortic balloon pumping (IABP) to assist the failing circulation has become widely applied and accepted since its introduction in 1968. The elective, preoperative use of IABP for patients undergoing cardiac surgery has now become the controversy. The purposes of this report are to examine our experience with IABP and to determine its appropriate role in high-risk patients. IABP was utilized in 75 of 2333 (3.2%) adult cardiac surgical patients at Emory University Hospital from January 1976 through June 1978. IABP was required for refractory shock following cardiopulmonary bypass (CB) in 53 patients, for preoperative cardiogenic shock after acute myocardial infarction (CSMI) in nine and was electively placed prior to CB in 13. Sixty-two patients (81%) were able to separate from CB with IABP and pharmacologic support and were assisted 24-432 hours (median 64 hours). Fifty-five (73%) were weaned from IABP. Fifty (67%) are hospital survivors; late deaths have occurred in six patients (8%). Hemodynamic effect of IABP was demonstrated by comparison of pumping 1:1 to 1:8 mode in five balloon-dependent patients after CB. IABP was found to decrease systolic blood pressure, left ventricular filling pressure and peripheral resistance (p < .05). It increased diastolic and mean blood pressure, cardiac index and the endocardial viability ratio (p < .05). The post-CB use of IABP resulted in highest salvage when utilized to support failing hearts that required surgery despite recent preoperative infarction or when intraoperative ischemic injury had occurred. Poorest results were in patients with extensive chronic myocardial damage. Except in the case of preoperative cardiogenic shock, it was impossible to establish statistically reliable criteria for patients in whom elective preoperative insertion was found to be necessary. Careful surgical and anesthesia management with good monitoring can be used instead of preoperative IABP in the majority of (if not all) hemodynamically stable patients regardless of risk classification.