The characteristics of the four major vestibular nuclei and accessory cell groups in the rat have been studied in serially cut horizontal sections. Camera lucida drawings of the vestibular nuclei and their neurons were made in these sections and subjected to a computerized image analysis. The dimensions (volume and length) and the number of cells of each vestibular nucleus were obtained, as well as morphometric parameters of their neurons (cross-sectional area, maximum and minimum diameter, and shape). These parameters were statistically analyzed by comparing the cell population from different nuclei and different parts of each nucleus. Of the major nuclei, the medial, which is the largest, has the greatest number of cells, its neurons being the smallest of all the nuclei, with the size of cells decreasing in a rostrocaudal direction. In contrast, the lateral nucleus contains the fewest cells but also the largest ones. Neurons of the superior and descending nuclei are of an intermediate size and number, with a rostrocaudal decrease in the size of the descending nucleus cells. In addition, minor nuclei are identified and described in their relationship to the other structures in the brain stem. The relevant aspects of the anatomical information in regard to functional roles are reviewed.

A quantitative study was made of the number of fibers, their diameters, and distribution in the nerves innervating individual vestibular receptor organs of three human temporal bones. The specimens were obtained from autopsies conducted within 4 hours postmortem. The temporal bones containing the nerves were fixed in 3% glutaraldehyde and decalcified with EDTA until they were soft enough to allow dissection of the nerve branches to the individual receptors. The nerve branches were processed for osmium staining, embedded in plastic, and cut serially in 1-micron-thick sections for light-microscopic histologic evaluation of their fiber composition. Quantitative evaluation of nerve-fiber characteristics was made with the aid of a laboratory computer and programs for graphic representation and statistical analysis. In the nerves to the individual cristae the number of fibers ranged between 1416 and 2335. Fibers with diameters between 2.5 microns and 3 microns were the most numerous. The number of fibers decreased exponentially with increased size. The thickest fibers had diameters up to 11.5 microns. The distribution of fibers in the nerve of each crista was different for the central and intermediate areas of the crista than it was for the ends. Thin fibers with diameters less than 2.5 microns, which represented 36% of the population, projected to the ends of the receptor area. Thick fibers with diameters greater than 4.5 microns, which represented 8% of the fibers, were distributed relatively uniformly except for the extreme ends of the crista, where they were nearly absent. Fibers with intermediate diameters were distributed throughout the crista, although they were more concentrated at the ends. In the nerves to three maculae, the number of fibers ranged from 3744 to 5538. The percentage of fibers of each size, however, was similar to that in the cristae. The greater portion of fibers had diameters between 3.0 microns and 3.5 microns. Because of the anatomical configuration of the maculae, it was not possible to compare fiber diameters from one area to another. The composition and differential projection of fibers to the crista in the human labyrinth were similar to those found earlier in squirrel monkeys and bullfrogs. On the basis of these similarities in the pattern of innervation, it is suggested that the physiological properties in humans must be similar to those in animals.

IntroductionMany ocular diseases require intravitreal injections of pharmacological agents. Optimizing patients’ experiences during injections is important to ensure compliance and maintenance of quality of life. The objective of this study was to identify strategies to help alleviate discomfort during intravitreal injections.MethodsA cross-sectional study surveying 128 patients during clinic visits between 2014 and 2015 in two outpatient Retina Clinics (one academic and one private). Patients receiving an intravitreal injection(s) for any retinal disorder were given a questionnaire with 10-yes/no responses for various potential strategies. Responses were stratified by sex, age (<30 years, 30–60 years, and >60 years) and total number of prior injections (0–9 injections, 10–20 injections and >20 injections).ResultsA total of 128 patients were surveyed: 59 males, 41 females and 28 with no sex specified. Our results identified four favorable strategies as those receiving more than 50% “yes” votes. These included the presence of technician/staff during the procedure, the use of a neck pillow, a verbal warning before the injection and performing injections in both eyes on the same day. Other specific strategies were identified for females, younger patients and those with greatest experience. These included: females preferred having their hand held during injections (P = 0.001) and using a stress ball (P = 0.000) when compared to males. Stratifying by age, patients 30–60 years old preferred having their hand held (P = 0.008) and background music (P = 0.007). Stratifying by prior injections, patients with >20 prior injections preferred having their hand held (P = 0.001), using a stress ball (P = 0.021) and, if necessary, having bilateral injections performed the same day to improve comfort (P = 0.037).ConclusionsHaving an extra staff member present during the injection, having a neck pillow, having a verbal warning prior to injection and having both eyes injected on the same day were indicated as favorable strategies by over half of those surveyed. Further, specific strategies were identified for females, younger patients (30–60 years old) and those with greatest experience (>20 injections).

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