Variations in Microanatomy of the Human Modiolus: Implications for Cochlear Implants

Human cochlear anatomy is highly variable. The phenomenon has been first described qualitatively, followed by a quantitative variability assessment with detailed anatomical models of the human cochlea. However, all previous work focused on lateral cochlear wall. Few information is available on the variability of the modiolar wall. Modiolar variability, likely determined by variability in the spiral ganglion, provides key information on when during ontogenesis the individual cochlear morphology is established: before and/or after neuronal structures are formed. In the present study we analyzed 108 corrosion casts, 95 clinical cone beam computer tomographies and 15 µCTs of human cochleae and observed modiolar variability of similar and larger extent than the lateral wall variability. Lateral wall measures correlated with modiolar wall measures significantly. ~49% of the variability has a common cause, very likely established already during the time when the spiral ganglion is formed. Proximity of other neuronal and vascular structures, defining the remaining variability in scalar spaces, are determined later in ontogenesis, when the scalae are formed. The present data further allows implications for perimodiolar cochlear implants and their tip fold-overs. In particular, the data demonstrate that tip fold-overs of preformed implants likely result from the morphology of the modiolus (with radius changing from base to apex), and that optimal cochlear implantation of perimodiolar arrays cannot be guaranteed without an individualized surgical technique.

Variations and some clinically relevant relations of A. cystica in pigs - a corrosion cast study

The aim of this study was to investigate the variations as well as the length of A. cystica and its branches in pigs using corrosion casting method with the self-polymerising resin Duracryl® Plus. The method included several steps: hepatectomy, precasting treatment, injection of Duracryl, polymerisation of casting medium, corrosive treatment, cleaning of the corrosion casts, air-drying and preservation of casts. The livers were collected from 12 male 6-month-old pigs (crossbred Landrace×Danube White). With regards to the beginning of A. cystica, 4 variations were observed and grouped as follows: variation A  A. cystica detached from R. dexter medialis, together with R. quadratus (variation A1), or alone (variation A2); variation B1 – A. cystica originated from A. gastroduodenalis, or was a branch of the common trunk (R. dexter) (variation B2). The metric data were processed by GraphPad Prism 6 for Windows. Clinically relevant relations between А. сystica, Ductus cysticus, A. celiaca and R. sinister also were described. The new information re-ceived about the blood supply of the gallbladder would contribute to the understanding of the etiology of postoperative complications as a result of surgical interventions in this location and for their prevention.

Study of Renal Posterior Segmental Artery by Corrosion Cast Method

BACKGROUND Variations in origin, course and distribution of renal blood vessels are frequent observations. The aim of this study was to observe the pattern of posterior segmental renal artery by corrosion cast method. METHODS Thirty pairs of kidneys were collected from cadavers in anatomy department of Subharti Medical College, Meerut. Corrosion casts of renal arteries were prepared by infusing cellulose acetate butyrate solution through abdominal aorta. They were macerated in conc. hydrochloric acid. Origin, course and distribution of the posterior segmental artery were studied. RESULTS Renal posterior segmental artery most frequently originated as a continuation of the posterior division (93 %). It has no anastomosis with nearby segmental arteries. CONCLUSIONS Posterior segmental artery supplies posterior segment of kidney and may also frequently give origin to apical segmental artery. This study of origin, course, distribution and variations of renal posterior segmental artery will be useful for surgical and radiological practice. KEYWORDS Kidneys, Renal Artery, Anterior Division, Posterior Division, Posterior Segmental Artery, Abdominal Aorta, Corrosion Casts

Estimating Arterial Cyclic Strain from the Spacing of Endothelial Nuclei

Background The non-uniform distribution of atherosclerosis within the arterial system is widely attributed to variation in haemodynamic wall shear stress. It may also depend on variation in pressure-induced stresses and strains within the arterial wall; these have been less widely investigated, at least in part because of a lack of suitable techniques. Objectives Here we show that local arterial strain can be determined from impressions left by endothelial cells on the surface of vascular corrosion casts made at different pressures, even though only one pressure can be examined in each vessel. The pattern of pits in the cast caused by protruding endothelial nuclei was subject to “retro-deformation” to identify the pattern that would have occurred in the absence of applied stresses. Methods Retaining the nearest-neighbour pairs found under this condition, changes in nearest-neighbour vectors were calculated for the pattern seen in the cast, and the ratio of mean changes at different pressures determined. This approach removes errors in simple nearest-neighbour analyses caused by the nearest neighbour changing as deformation occurs. Results The accuracy, precision and robustness of the approach were validated using simulations. The method was implemented using confocal microscopy of casts of the rabbit aorta made at systolic and diastolic pressures; results agreed well with the ratio of the macroscopic dimensions of the casts. Conclusions Applying the new technique to areas around arterial branches could support or refute the hypothesis that the development of atherosclerosis is influenced by mural strain, and the method may be applicable to other tissues.