[The vascular pattern of the endolymphatic duct, endolymphatic sac and its anatomic differences in guinea pigs].

In order to study the vascular pattern of the endolymphatic duct and sac, endolymphatic duct and sac were examined with vascular Indian ink injection and image analysis. The Results were as follows: 1. In the 20 temporal bones, 17 (85%) had posterior meningeal artery (PMA) and posterior vestibular artery (PVA) supply and the rest (3 specimens, 15%) had no PVA supply; 2. The distribution frequency of PMA in the endolymphatic sac was much higher than that of PVA(P < 0.01), but the distribution of PMA and PVA in the endolympatic duct were not different (P > 0.05). The conclusions is that there are anatomic differences in vascular supply and pattern of the endolymphatic duct and sac, PMA is the main vascular structure in the endolymphatic sac.

The endolymphatic duct and sac of the rat: a histological, ultrastructural, and immunocytochemical investigation.

A study of the ultrastructure, vascularization, and innervation of the endolymphatic duct and sac of the rat has been performed by means of light- and electron-microscopic and immunocytochemical methods. Two different types of epithelial cells have been identified: the ribosome-rich cell and the mitochondria-rich cell. These two cell types make up the epithelium of the complete endolymphatic duct and sac, although differences in their quantitative distribution exist. The morphology of the ribosome-rich cells varies between the different parts of the endolymphatic duct and sac; the morphology of the mitochondria-rich cells remains constant. According to the epithelial composition, vascularization, and structural organization of the lamina propria, both duct and sac are subdivided into three different parts. A graphic reconstruction of the vascular network supplying the endolymphatic duct and sac shows that the vascular pattern varies among the different parts. In addition, the capillaries of the duct are of the continuous types, whereas those supplying the sac are of the fenestrated type. Nerve fibers do not occur within the epithelium of the endolymphatic duct and sac. A few nerve fibers regularly occur in the subepithelial compartment close to the blood vessels; these fibers have been demonstrated in whole-mount preparations by the application of the neuronal marker protein gene product 9.5. Single beaded fibers immunoreactive to substance P and calcitonin-gene related peptide are observed within the same compartment. Dopamine-beta-hydroxylase-immunoreactive axons are restricted to the walls of arterioles. Morphological differences between the different portions of the endolymphatic duct and sac are discussed with regard to possible roles in fluid absorption and immunocompetence.

Degeneration of vestibular sensory cells caused by ablation of the vestibular aqueduct in the gerbil ear.

The vestibular aqueduct of the gerbil has a unique anatomic feature that makes it possible to selectively obliterate the endolymphatic sac with or without interfering with its venous drainage. In animals in which only the endolymphatic sac was ablated, endolymphatic hydrops was slight in the cochlea and was absent in the vestibular labyrinth. The cochlear and vestibular sensory cells were normal. In animals in which both the endolymphatic duct and the vein were obliterated, hydrops was slight, with the exception of a few cochleas that showed moderate hydrops. The sensory cells of the posterior canal cristae had degenerated in all specimens, while varied pathologic changes in cochlear and vestibular sensory cells were present in some specimens. These results suggest that hydrops is primarily due to blockage of the endolymphatic duct and sac and that degeneration of sensory cells occurs when blood flow in the vestibular aqueduct is impeded. Pathologic changes in the endolymphatic sac, including the vascular plexus at the endolymphatic sac, may play an important role in the production of endolymphatic hydrops and vestibular symptoms in Meniere's disease.

Arterial supply of the human endolymphatic duct and sac.

The arterial anatomy of the endolymphatic duct and sac was studied in vascular casts of methyl methacrylate of six human heads. The chief source of arterial blood supply to the endolymphatic duct and sac appeared to be the occipital artery. Arterioles entered the bone of the mastoid process. Arterioles in bone, the walls of the sigmoid sinus, and the posterior fossa dura coursed medially to supply the endolymphatic sac. The orientation of arterioles tended to be along the long axis of the endolymphatic duct and sac, whereas venules were more likely to be circumferentially oriented. Arterioles arising from dural vessels divided into deeper branches, which supplied periductal connective tissue, and superficial branches, which entered canaliculi of the vestibular aqueduct. Gross anatomic findings were confirmed by histologic examination of temporal bones.

Periductal vessels of the endolymphatic duct.

Light microscope was used to examine the rich vascular plexus surrounding the human endolymphatic duct, both in the periductal loose connective tissue and in the bony channels surrounding the bony vestibular aqueduct. We also performed computer-aided three-dimensional reconstruction on one serially sectioned region of the endolymphatic duct. We found an anastomotic and looping network of vessels residing in the loose connective tissue close to the epithelium of the endolymphatic duct. This network often received a vascular contribution from the vessels in the periaqueductal bony channels. These findings were verified by light microscopic examination of 50 temporal bone specimens. Concurrent with this finding, histologic examination also showed different characteristic features of the vascular system of the endolymphatic duct-proximal sac areas and of the more distal parts of the endolymphatic sac. These features include the arrangement, quantity, and contents of the periaqueductal bony channels, as well as the organization of the bone containing these periductal bony channels. Findings from this study help the understanding of the anatomy of the human endolymphatic duct. In addition, they support and supplement earlier observations of the structure of the endolymphatic duct. We suggest the possible existence of a periductal vasculature system, similar in pattern to that in the endolymphatic sac, but specialized to work with the duct to aid its function.

Animal models of inner ear vascular disturbances.

Animal models of vascular disorders are identified or developed for the evaluation of functional deficits and morphologic alterations. This information will serve a useful purpose for a better understanding of sudden deafness, Meniere's disease, and presbycusis. The study of microcirculation of the inner ear vessels reveals that their responses to various stimuli, such as anoxia, sympathetic nerve stimulation, hypothermia, and drugs, are different from those of the middle ear vessels. In sudden occlusion of the major vascular supply to the inner ear, the cochlea is found to be more vulnerable than the vestibular labyrinth; outer and inner hair cells and stria vascularis are most often affected. Animal models for Meniere's disease are also described, and the importance of vascularity at the endolymphatic duct and sac is discussed from an etiologic viewpoint. In presbycusis, animal models show sensory cell and spiral ganglion cell atrophies in different locations than in human cochleas, and the relationship between these atrophies and vascular impairments is not clear at the present time.

The microvascular architecture of the vestibule and the endolymphatic duct and sac of the rat in vascular corrosion casts.

The blood vessels of the vestibule and the endolymphatic duct and sac (ES) of the rat were reproduced with methacrylate casting medium and observed under a scanning electron microscope. Dense capillary networks of the macula utriculi and the macula sacculi were observed. The collecting venules from the vestibule emptied into the vein of the vestibular aqueduct (VVAQ). The plexus of the vessels in the ES was triangular in shape and had anastomoses with vessels of the bone and dura and drained into the VVAQ. The posterior meningeal artery (PMA) gave off two branches to the ES. These findings supported the similarity of the vascularization of the vestibule and the ES between the human and the rat.

Basal lamina pathology of the utricle and endolymphatic duct in Ménière's disease.

Labyrinthectomy was performed in a patient with a 4-year history of Ménière's disease. The utricle and the proximal portion of the endolymphatic duct were studied using light and electron microscopy. The epithelium varied in height from squamous to columnar. The basal lamina lining the columnar epithelial cells showed marked thickening which was visible in the light microscope. Electron microscopy revealed that the basal lamina had a fibrillar structure. The basal lamina of adjacent blood vessels also showed pathologic thickening with similar fibrillar texture. The significance of basal lamina thickening in association with Ménière's disease is discussed.

Reversibility of the endolymphatic potential after transient anoxia.

The effect of transient local anoxia (10 to 120 min) upon the endolymphatic potential (abbr. EP) was observed in 30 normal guinea pigs. The recovery of the EP was complete in the animal subjected to 10 min anoxia and almost complete in 20 min anoxia. When the duration of anoxia was 30 min or longer, the recovery of the potential was incomplete, and the longer the duration of anoxia, the lower the level of the EP after reoxygenation. These results were discussed in relation to the possible role of a transient anoxia upon sudden deafness.

Endolymphatic hydrops with absence of vein in paravestibular canaliculus.

Unilateral endolymphatic hydrops is described associated with absence of the vein in the paravestibular canaliculus (PVC), and with decreased vascularity of the vestibular aqueduct and endolymphatic sac. The venous return from the vestibule was normal as far as the junction of the branches forming the PVC vein. At this junction, a blind venous loop was formed with no continuation of venous drainage through the PVC. This probably represents a developmental anomaly. The decreased vascularity of the endolymphatic sac may be related to the absence of the PVC vein. However, anatomical and functional relationships of these vessels are not clear and need further study. Perisac fibrosis and endosteal bone formation are possibly secondary to the decrease in vascularity. A large chronic rupture of the inferior saccule wall probably accounts for the absence of vertigo and the relatively mild degree of cochlear endolymphatic hydrops.