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At least 19 recordsLinked to original sources
PubMed1986

Thalamic projections to the posterior sylvian and posterior ectosylvian gyri of the sheep brain, revealed with the retrograde transport of horseradish peroxidase.

The auditory area of the sheep cerebral cortex was studied on the basis of its afferents from the medial geniculate nucleus, traced with the horseradish peroxidase retrograde transport method. The results show that the medial geniculate nucleus projects only to the anterior parts of the posterior ectosylvian gyrus and the posterior sylvian gyrus. A small area of the posterior ectosylvian gyrus receives afferents exclusively from the ventral part of the medial geniculate nucleus, while the anterior part of the posterior sylvian gyrus receives also afferents from the posterior nucleus of the thalamus and the pulvinar. In addition, it was found that the medial part of the medial geniculate nucleus projects in a sparse way to the auditory cortex. The middle part of the posterior ectosylvian gyrus receives afferents from the posterior nucleus of the thalamus, the suprageniculate nucleus and the pulvinar, while the posterior part of the posterior ectosylvian gyrus together with the posteriormost part of the posterior sylvian gyrus receive afferents from the pulvinar. Finally, the area located between the anterior and the posteriormost part of the posterior sylvian gyrus receives afferents from both the posterior nucleus of the thalamus and the pulvinar.

Animals↗
PubMedDate not supplied

Pathomechanics of posterior sag of the tibia in posterior cruciate deficient knees. An experimental study.

This study was an investigation of the pathomechanics of posterior sag of the tibia in knees with posterior knee instability caused by PCL deficiency. By using fresh cadaver knees, the authors hoped to define the relationship of the posterior joint capsule and the medial and lateral collateral ligaments (MCL, LCL) with posterior knee instability in the PCL deficient knee. Thirty newtons of posterior stress were applied to the knees to simulate postoperative conditions. Roentgenographic methods were then used to evaluate posterior sag and change in the distance between the origin and insertion of the PCL. Strain gauges were used to measure the actual strain of the PCL and the collateral ligaments. The PCL, the posterior capsule, and the medial and lateral collateral ligaments were sequentially divided and the above measurements were then repeated in the same way, using 30 N of applied posterior stress. When only the PCL was cut, posterior sag and medial rotation of the tibia occurred with increasing severity as flexion increased. No sagging or rotation of the tibia was observed at full extension in the knees that had isolated PCL "injury". When the posterior capsule was sectioned, no significant changes were noted in the severity of the sag or the rotation. When the MCL or LCL was divided in a PCL deficient knee, greater sag occurred with flexion and a significant sag was observed even at full extension. The MCL "injury" was associated with increased medial rotation, whereas LCL "injuries" were associated with lateral rotation of the tibia.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMedDate not supplied

Dynamic posterior shift test. An adjuvant in evaluation of posterior tibial subluxation.

The dynamic posterior shift test, a clinical method for evaluating both straight posterior instability and posterolateral rotatory instability, (PLRI), is a simple, dynamic, and reliable (reproducible) test that serves as an adjuvant to other clinical tests designed to evaluate an injury or insufficiency of posterior structures in the knee. The examiner maintains the hip at near 90 degrees of flexion to control rotation of the femur while slowly extending the knee passively. The hamstrings should be stretched to maintain their tightness. The tightened hamstrings assist gravity in subluxating the tibia posteriorly; they also provide dynamic axial loading to the joint as the knee is extended. In knees with posterior instability, the posteriorly subluxated tibia suddenly reduces as the knee joint nears full extension, and a jerk or "clunk" is felt by both the patient and the examiner. Thus, the patient's feeling of instability is reproduced by the test. We have used the dynamic posterior shift test for 5 years (as an adjuvant in our physical examination) to evaluate signs of posterior instability of the knee. Not only is the test reliable, but it is more definitive than other tests in evaluating straight posterior instability and PLRI. It is easy to perform and the results are reproducible. Because this test is dynamic rather than passive, it enhances the accuracy of evaluating posterior instability of the knee.

Biomechanical Phenomena↗
PubMed1987

Posterior commissural connections of area pretectalis and neighboring structures in cat, with special reference to pupilloconstrictory pathway via posterior commissure.

The overall distribution of posterior commissural connections of the area pretectalis and the neighboring structures was studied in the cat, by the methods of anterograde fiber degeneration and retrograde axonal transport of horseradish peroxidase (HRP). After a localized lesion was made within the posterior commissure, dense degenerated terminals were distributed in the most rostral part of the nucleus pretectalis posterior, the nucleus of posterior commissure, the interstitial nucleus of Cajal, and the central tegmental field. A medium amount of degenerated terminals were observed in the nucleus pretectalis anterior (pars reticularis), the dorsal part of the periaqueductal grey at its most rostral levels, the caudolateral parts of the nucleus pretectalis posterior and the nucleus of optic tract, the H field of Forel, parts of the somatic cell columns of the oculomotor nucleus and the trochlear nucleus. A small amount of degenerated terminals were seen in the ventromedial part of the caudal periaqueductal grey, the ventral lateral geniculate nucleus and the zona incerta. However, the amount of degenerated terminals was very small in the nucleus pretectalis medialis and the nucleus pretectalis olivaris. Following an HRP (dissolved in 5% alkyl-phenol ethylene oxide) injection into the unilateral area pretectalis where fibers of the posterior commissure fan out, retrogradely labeled cells were observed in all of the above described (posterior commissural fiber recipient) regions of the pretectal and neighboring structures, with the exception of the somatic cell columns of the oculomotor nucleus and the trochlear nucleus. The number of labeled cells appeared roughly proportional to the amount of degenerated terminals of the posterior commissural fibers described above with the apparent exception of the nucleus pretectalis anterior, pars reticularis, where only a few labeled cells were identified. The findings were discussed with special reference to the pupilloconstrictory pathway via the posterior commissure.

Animals↗
PubMed1988

Study of axonal dystrophy. III. Posterior funiculus and posterior column of ageing and old rats.

Axonal dystrophy in normal ageing can be studied in experimental animals. Primary sensory neurones show two different kinds of change with ageing, i.e. axonal dystrophy and axonal atrophy (degeneration). This paper reports the chronology and topography of these two processes in relation to growth and involution of these neurones throughout the lifespan of the rats used in this study. Axonal spheroids preferentially form at presynaptic terminal regions in many of the collaterals of central branches of the axons, i.e. in the posterior funiculus nuclei, posterior column and posterior funiculus. Axonal dystrophy in normal ageing is essentially a morbid process restricted to the terminal parts of the axon. It shows little tendency to expand retrogradely along the axon. Evidence is presented that spheroids in posterior funiculus also derive from terminal axons. Preference is also noted in the lumbosacral rather than cervical neurons, and in longer (posterior funiculus nuclei) rather than shorter (posterior column) collaterals. Quantitative study of myelinated fibres in posterior funiculus shows that they increase in number until middle age (400 days) of the animals, before beginning to decline. On the other hand, axonal atrophy begins to appear early in small numbers, and increases in numbers with age. Atrophy involves the whole length of the axon within the posterior funiculus from the start, suggesting, therefore, that it does not belong to a dying-back process. It is noteworthy that the main development of axonal dystrophy lies in the earlier half of the animals' life, while that of axonal atrophy lies in the latter half. This fact adds to the evidence that axonal dystrophy, as far as in normal ageing is concerned, is more related to the positive side of neuronal activity, e.g. one form of growth abnormality of axon.

Aging↗
PubMed1989

Electrocardiographic diagnosis of remote posterior wall myocardial infarction using unipolar posterior lead V9.

The accuracy of four electrocardiographic criteria for diagnosing remote posterior myocardial infarction was assessed prospectively in 369 patients undergoing exercise treadmill testing with thallium scintigraphy. Criteria included the following: 1) R-wave width greater than or equal to 0.04 s and R-wave greater than or equal to S-wave in V1; 2) R-wave greater than or equal to S-wave in V2; 3) T-wave voltage in V2 minus V6 greater than or equal to 0.38 mV (T-wave index); 4) Q-wave greater than or equal to 0.04 s in left paraspinal lead V9. Twenty-seven patients (7.3 percent) met thallium criteria for posterior myocardial infarction, defined as a persistent perfusion defect in the posterobase of the left ventricle. Sensitivities for the four criteria ranged from 4 to 56 percent, and specificities ranged from 64 to 99 percent. Posterior paraspinal lead V9 provided the best overall predictive accuracy (94 percent), positive predictive value (58 percent), and ability to differentiate patients with and without posterior myocardial infarction of any single criterion (p less than .0001). Combining the T-wave index with lead V9 further enhanced the diagnostic yield: the sensitivity for detecting posterior infarction by at least one of these criteria was 78 percent, and when both criteria were positive, specificity was 98.5 percent. It is concluded that a single, unipolar posterior lead in the V9 position is superior to standard 12-lead electrocardiographic criteria in diagnosing remote posterior myocardial infarction, and that combining V9 with the T-wave index maximizes the diagnostic yield.

Electrocardiography↗
PubMed1975

Mitral stenosis with posterior diastolic movement of posterior leaflet.

The echocardiographic diagnosis of mitral stenosis depends in part on the demonstration of abnormal posterior leaflet movement to distinguish it from other conditions that similarly affect anterior leaflet motion. In mitral stenosis the posterior leaflet has been shown to move anteriorly in diastole rather than in the normal posterior direction. A patient presented with clinical evidence of moderate mitral stenosis. The anterior leaflet echo was typical but the posterior leaflet showed posterior diastolic movement. At catheterization moderate mitral stenosis was confirmed. To our knowledge this is the first report of the echocardiographic demonstration of posterior diastolic movement of the posterior mitral leaflet in documented mitral stenosis.

Angiocardiography↗
PubMed1992

Improved detection of accessory pathways that bridge posterior septal and left posterior regions in the Wolff-Parkinson-White syndrome.

To improve the detection of accessory pathways that bridge the posterior septum and left posterior free wall, catheter maps of the coronary sinus from 21 patients (group I) who needed dissection of both these anatomic regions were compared with data from 23 (group II) with pathways confined to the posterior septum and from 9 (group III) with left posterior pathways. A decapolar catheter was used to map the coronary sinus in 0.5 to 1 cm steps. Intraoperative mapping was performed with a 16-electrode band. Catheter maps during atrial pacing and orthodromic supraventricular tachycardia were analyzed for the site of earliest activation and for differences in a new directional measure of conduction time between adjacent mapping sites. The site of earliest activation alone did not distinguish accessory pathways that bridged both anatomic regions, because 14 of 21 patients (66%) in group I would have been misclassified to either group II or III. In contrast, anterograde and retrograde directional conduction times distinguished patients in group I from those in groups II (p less than 0.01 to less than 0.0003) and III (p less than 0.04 to less than 0.0001). A multivariate model that incorporated the observed differences in directional interelectrode conduction times improved the identification of group I patients, with a sensitivity of 87% and a specificity of 90%. The results define new features in activation patterns measurable during catheter mapping that identify accessory pathways that bridge the posterior septum and left posterior free wall.

Adolescent↗
PubMed1990

Vaulted posterior chamber lenses and the posterior capsule.

Sixty-eight patients who had extracapsular cataract surgery with intraocular lens implantation in the bag received one of two types of lenses that had been designed to create a gap between the posterior surface of the optic and the posterior capsule. Two to four months after surgery, we found that the central spacing between the posterior lens surface and the posterior capsule measured by optical pachymetry averaged 0.25 mm. The mean of the spacing for the Pharmacia LSP laser ridge was 0.25 mm (range 0.1 to 0.6) and that of the 3M LE meniscus lens was 0.24 mm (range 0 to 0.8). The amount of adherence of the posterior capsule to the posterior lens surface was less with the laser ridge design than with the meniscus lens.

Aged↗
PubMed1990

Posterior polar cataracts: a predisposition to intraoperative posterior capsular rupture.

We performed phacoemulsification or planned extracapsular cataract extraction on posterior polar cataracts in 31 eyes of 22 patients and experienced eight cases of posterior capsular rupture (26%). Capsular rupture occurred during removal of the posterior polar opacity or during cleaning of the posterior capsule after the opacity had been removed. We believe that excessive adherence of the opacity to the posterior capsule and unusual thinness of the capsule predisposed these eyes to posterior capsular rupture.

Adult↗
PubMed1990

Posterior instability of the knee near extension. A clinical and stress radiographic analysis of acute injuries of the posterior cruciate ligament.

We evaluated the accuracy of six clinical tests for posterior instability in 24 knees with acute surgically-proven posterior cruciate ligament injuries and intact anterior cruciate ligaments. We also performed stress radiography under anaesthesia. The gravity sign and the posterior drawer test in near extension and its passive reduction were diagnostic in 20 of the 24 knees, and the active reduction of posterior subluxation was diagnostic in 18. The reversed pivot shift sign helped to diagnose severe posterior and posterolateral subluxations, but the external rotation recurvatum test was negative in all 24 knees. Stress radiography in near extension revealed a highly significant increase in posterior tibial subluxation in the injured knees.

Acute Disease↗
PubMed1992

Assessment of the posterior malleolus as a restraint to posterior subluxation of the ankle.

We assessed the function of the posterior malleolus, the anterior tibiofibular ligament, and the fibula with regard to posterior stability of the talus in ten ankles of cadavera. Posteriorly directed loads of as much as 200 newtons were applied. Two groups of ankles were tested; in the first group, three ankles in which the ligamentous and osseous structures were intact were tested after transection of the posterior capsule and after removal of 10, 20, 30, and 40 per cent of the articular surface of the distal end of the tibia from the posterolateral corner. In the second group, seven ankles were tested in the same sequence, but the anterior tibiofibular ligament and the fibula were transected before sectioning of the articular surface. Compared with the results for the intact ankle, the experiments on the first group demonstrated less than one millimeter of additional posterior translation of the talus after removal of as much as 40 per cent of the articular surface. In the second group, in which the anterior tibiofibular ligament and the fibula had been transected, significant posterior translation of the talus (more than three millimeters) occurred after removal of 30 per cent of the articular surface (p < 0.01). This represented a 160 per cent increase in translation compared with that in the intact ankle.

Aged↗
PubMed1977

[Diagnosis of posterior infarction. Value of vectorcardiography. Apropos of 108 cases, 31 of which had exclusively posterior necrosis].

An analysis of the vectorcardiogram results (VCG) in 77 cases with a posterior extension of an infarct and 31 cases with an exclusively posterior infarction (EPI) has allowed us to distinguish some diagnostic criteria relative to the extension, or localisation, of an infarct in the posterior segment. The maximum anterior vector (MAV) appears late (36.5 ms +/- 5), and the amplitude of its projection onto Z is increased; the maximum vector (V max) appears early (41.5 ms +/- 4.5), and its orientation is anterior (+ 24 degrees +/- 11); the interval separating MAV from V max is reduced to 5 ms; the transition from before backwards is late (50 ms +/- 6); the ratio of anterior surface to posterior surface is increased (1.45); there is a terminal delay, most frequently occuring in the right posterior quadrant in 78 percent of cases; and finally, the T loop approaches the Z axis. Repeat electrocardiograms in patients with EPI show the most frequent changes to be represented (in 25 cases out of 31) by the following formula: AQRS " 0 degrees, R/S greater than or equal to 1 in V2, RV2 greater than RV6. The diagnosis of an exclusively posterior infarction can therefore be made with a high degree of certainty when these electrocardiographic abnormalities are associated with the clinical picture of coronary insufficiency.

Computers↗
PubMed1979

Blood supply of the rat hypothalamus. VI. Posterior region of the hypothalamus (nucleus hypothalamicus posterior, nuclei praemammillares, nucleus supramammilaris, mammilary body).

It was shown by the double ink-filling technique that the arteries of the rat premammillary region and mammillary body arise from the a. communicans posterior while these areas are drained by the anterior interpeduncular vein. Disregarding some minor overlaps and anastomoses, the blood supplies of the two territories are independent of each other and from the neighbouring areas of the hypothalamus, diencephalon and mesencephalon. Arteries of the premammillary region arise from the premammillary artery, except for some branches of the posterior tuberal and interpeduncular arteries. The mammillary body is supplied by three mammillary arteries (anterior, posterior and lateral). The premammillary region drains into the anterior and posterior premammillary veins. Venous blood of the mammillary body is collected by the anterior and posterior mammillary veins which end in the anterior interpeduncular vein. The circulation of individual premammillary and mammillary nuclei is described in detail.

Animals↗
PubMed1986

Long-term discission rate after placing posterior chamber lenses with the convex surface posterior.

The incidence of secondary capsulotomy was studied in a group of 757 posterior chamber intraocular lenses placed with the convex surface posterior within the capsular bag. Minimum follow-up was 12 months and ranged up to 61 months, with a mean of 33 months. In the first year, only 2.9% of cases required discission, but this rose to 15.7% at five years. The need for capsulotomy with angled-haptic lenses was 7.9% at three years; it was 15.0% with uniplanar lenses (P = .04). This difference appeared to be due to better apposition of the optic to the posterior capsule in the angled lenses, creating a more effective barrier to epithelial pearl migration. Capsulotomy carries significant risks and lens designs that minimize the long-term need for capsulotomy should be sought. Convex posterior lenses with angled haptics have a low incidence of posterior capsule opacification.

Cataract↗
PubMed1986

Incidence of posterior capsule opacification in eyes with and without posterior chamber intraocular lenses.

The incidence of posterior capsule opacification after extracapsular cataract extraction was significantly lower in eyes implanted with posterior chamber intraocular lenses than in nonimplanted eyes. The number of loops fixated in the bag was significantly smaller in the eyes that became opacified than in those that did not. These findings suggest that the posterior chamber lens suppresses the two processes that lead to opacification: the development of a ring-shaped opacity at the site of contact between the anterior capsule rim and the posterior capsule and the migration of lens epithelial cells toward the center of the capsule. These suppressive effects were greater when the posterior chamber lens was fixated in the bag.

Aged↗