Posterior Semicircular Canal Approach for Inner Ear Gene Delivery in Neonatal Mouse.

Inner ear gene therapy offers great promise as a potential treatment for hearing loss and dizziness. One of the critical determinants of the success of inner ear gene therapy is to find a delivery method which results in consistent transduction efficiency of targeted cell types while minimizing hearing loss. In this study, we describe the posterior semicircular canal approach as a viable method for inner ear gene delivery in neonatal mice. We show that gene delivery through the posterior semicircular canal is able to perfuse the entire inner ear. The easy anatomic identification of the posterior semicircular canal, as well as minimal manipulation of the temporal bone required, make this surgical approach an attractive option for inner ear gene delivery.

The influence of the subarcuate artery in the superior semicircular canal dehiscence and its frequency on stillbirths: illustrative cases and systematic review.

Literature describes that on the 25th gestational week the labyrinth is fully formed and with adult size. However, recent studies have shown that the cranial and labyrinth development continues until 3 years of age. OBJECTIVES: To demonstrate through tomographic study the frequency of semicircular canal dehiscence on nine specimens of stillbirths between 32 and 40 weeks and, through literature review, present another possible etiology for its cause. METHODS: Tomographic study of the temporal bone of 9 specimens of stillbirths between 32 and 40 weeks. RESULTS: A frequency of 88.89% of alterations were found in our study, with 44% presenting bilateral alterations and 44% unilateral alteration; 11.11% had no dehiscence. CONCLUSION: The tomographic study showed superior semicircular canal dehiscence (SSCD) in 88% of the specimens studied, protrusion of the superior semicircular canal (SSC) in all fetuses, and an enlarged SSC that may be caused by the expansion process provoked by the subarcuate artery entering the subarcuate canaliculus, leading to SSCD.

Vestibular tributaries to the vein of the vestibular aqueduct.

CONCLUSION: The vein of the vestibular aqueduct drains blood from areas extensively lined by vestibular dark cells (VDCs). A possible involvement in the pathogenesis of an impaired endolymphatic homeostasis can be envisioned at the level of the dark cells area. OBJECTIVES: The aim of this study was to investigate the vascular relationship between the vein of the vestibular aqueduct and the vestibular apparatus, with focus on the VDCs. METHODS: Sixteen male Wistar rats were divided into groups of 6 and 10. In the first group, 2 µm thick sections including the vein of the vestibular aqueduct, utricle, and crista ampullaris of the lateral ampulla were examined by light microscopy and computer-generated three-dimensional imaging. In the second group, ultrathin sections including venules and VDCs were examined by transmission electron microscopy. RESULTS: A microvascular network was observed in close relation to the VDCs in the utricle and the crista ampullaris of the lateral semicircular canal in the vestibular apparatus. One major vein emanated from these networks, which emptied into the vein of the vestibular aqueduct. Veins draining the saccule and the common crus of the superior and posterior semicircular canals were likewise observed to merge with the vein of the vestibular aqueduct.

Subarcuate venous malformation causing audio-vestibular symptoms similar to those in superior canal dehiscence syndrome.

OBJECTIVE: To present a patient with symptoms similar to those of superior canal dehiscence syndrome due to another cause. STUDY DESIGN: Case report. SETTING: University hospital, tertiary referral center. PATIENT: The 65-year-old woman had suffered for 4 years from hearing loss, tinnitus, and pressure-induced vertigo. INTERVENTION: Audio-vestibular testing, high-resolution computed tomography, and magnetic resonance angiography. MAIN OUTCOME MEASURE: The superior canal dehiscence syndrome is caused by failure of normal postnatal bone development in the middle cranial fossa leading to absence of bone at the most superior part of the superior semicircular canal. The typical features for this syndrome are sound and pressure-induced vertigo with torsional eye movements, pulse synchronous tinnitus and apparent conductive hearing loss in spite of normal middle ear function. We present a patient with very similar symptoms and findings, who instead had a superior canal dehiscence close to the common crus. Neuroradiologic findings suggested that the dehiscence was related to a venous malformation. CONCLUSIONS: Symptoms and findings suggesting superior canal dehiscence syndrome can have a different cause.

Local vestibular blood flow and systemic vascular responses to natural vestibular stimulation in the Mongolian gerbil.

HYPOTHESIS: Natural stimulation of the vestibular end organs will produce alterations in the local vestibular microvascular blood flow. BACKGROUND: The vestibular and cardiovascular systems require a coordinated interaction to maintain organ perfusion during rapid positional and postural changes. However, the detailed relationship of these systems is not well understood. There have been no previous descriptions of local vestibular blood flow (VBF) during natural stimulation (NS) conditions. METHODS: In vivo VBF and systemic blood pressure (BP) in the Mongolian gerbil during natural stimulation. Using laser Doppler flowmetry, the authors obtained continuous measures of local VBF in both anesthetized and alert gerbils during sinusoidal rotational stimuli. Simultaneous recordings of systemic BP were collected from the contralateral common carotid artery. RESULTS: The anesthetized gerbils showed stable VBF and BP during all vestibular stimuli. By contrast, alert subjects demonstrated a significant response to natural stimulation. The VBF increased 28% over baseline, and systemic BP increased 8% during a 45-second, 0.133-Hz sinusoid. Decreases in BP of 8% and 5%, respectively, were seen with a 0.10 and 0.20 Hz, 360-second stimulus. A corresponding determination of VBF during the extended stimulus conditions was not technically possible. CONCLUSIONS: To the authors' knowledge, these are the first in vivo descriptions of vestibular blood flow during natural stimulation. In the alert animals, VBF increased in response to NS. This increase in flow does not appear to be directly dependent on systemic blood pressure changes and indicates that the vestibular microvasculature is closely regulated.

Development of blood-labyrinth barrier in the semicircular canal ampulla of the rat.

Cationic polyethyleneimine (PEI) administered intravenously was transported to anionic sites on the capillary and subepithelial basal laminae (BL) in the vestibular labyrinth. Therefore, changes in the PEI distribution on the BL reflect changes in the transport system in the vestibular labyrinth. A 0.1% PEI solution was administered intravenously (7.5 ml/kg) to developing (1, 4, 7, 14 days after birth) and adult rats in order to investigate the development of the macromolecular transport in the ampulla of the semicircular canal as a function of age. After 1 h, the bony labyrinth was removed and embedded in Epoxy resin. Ultrathin sections of the ampulla were then examined with a transmission electron microscope. In the subepithelial BL in the dark cell area and capillary BL in the crista ampullaris, the PEI distribution in both 1- and 4-day-old rats was markedly increased compared to that in either 7-, 14-day or adult rats. In the sensory cells in 1-, 4-day or 7-day-old rats, PEI density and area was significantly greater than in the adult rats. These findings suggest that the macromolecular transport system in the developing rat ampulla becomes mature by 14 days after birth and that the maturation of its transport system in the ampulla is strongly associated with that in the stria vascularis.

Inner ear blood flow in the rat after unilateral arterial occlusion in the vertebrobasilar arterial system.

It is generally accepted that certain kinds of vertigo and hearing disturbances are caused by blood flow insufficiency in the vertebrobasilar arterial system. Using the microsphere method we investigated whether unilateral vertebral artery or unilateral posterior inferior cerebellar artery occlusion could cause an imbalance between right and left inner ear blood flow in rats. We also studied the differential vulnerability between blood flow in the cochlea and in the ampullae of the three semicircular canals. We counted the numbers of microspheres distributed to the cochlea (CO) and microspheres distributed to three ampullae of semicircular canals (SC) under a microscope with the surface preparation method. The results were as follows: i) no imbalances were observed between bilateral CO or SC even in animals with arterial occlusion, and ii) the CO/SCs of animals with arterial occlusion were not significantly different from that of the control animals. These findings suggest that total inner ear blood flow over a certain period of time was even between the ears bilaterally even in animals with arterial occlusion. The blood flow in the ampullae of the three semicircular canals was not more or less affected by arterial occlusion than the blood flow in the cochlea.

Anionic sites of charge barrier in the guinea pig crista ampullaris.

In present studies we obtained anionic sites in the epithelial and capillary basement membranes in the dark cell area of the crista ampullaris in the guinea pig. The immersion method with cationic tracer polyethyleneimine (PEI) was applied. Electronmicroscopically, the arrangement of PEI particles was observed as two strata along the basement membrane. The number of particles could be counted and compared in each portion. The control test with protamine sulfate showed that the number of PEI particles decreased in both the epithelium and capillaries of the dark cell area. In the experiment using furosemide, the stria vascularis and the dark cells had changed, with pathological findings of interstitial edema and PEI particles reduced in number. It is suggested that the PEI particles reflect different conditions of charge in the basement membrane, which influences the production or absorption of the inner ear fluid.

ABR findings, electrocochleograms and caloric tests in vertebrobasilar ischemic rats.

In rats with ischemia induced by occlusion of the anterior inferior cerebellar artery (AICA) or vertebral artery (VA), we investigated the auditory brainstem response (ABR), electrocochleogram and caloric test result. Upon occlusion of the VA, there was no change of the ABR, whereas in the caloric test the duration of nystagmus upon stimulation of both ears shortened. Upon occlusion of the AICA, the cochlear blood flow (CoBF) showed one of three patterns of change no change: n = 5; decrease: n = 10; and transient decrease with recovery: n = 5. The cochlear potentials were dependent on the residual CoBF. In the caloric test, when the left AICA was occluded, the duration of nystagmus induced by stimulation of the left (ipsilateral) ear was shorter than that induced by the right (contralateral) ear. Based on the functional test results, we conclude that in this model of ischemia the function of the vestibular structures including the semicircular canals is more severely affected than is the hearing function.

Local effects of nitric oxide on vestibular blood flow in the Mongolian gerbil.

There is a paucity of studies regarding the regulation of vestibular blood flow (VBF), despite the possibility that vascular alterations may contribute to specific vestibulopathies. The current experiments used the Mongolian gerbil as an animal model since it provides easy surgical access to the vestibular end-organs and has been previously used for physiologic studies involving inner ear function. VBF changes were measured in the posterior semicircular canal using laser Doppler flowmetry following round window membrane (RWM) application of the nitric oxide donor 1, 3-propanediamine-N-[4-1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazi no] butyl (spermine NONOate; SPNO) as a vasodilator. The specificity of the responses induced was tested via pretreatment with an NO scavenger, 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazonline-1-oxyl-3-oxide (carboxy-PTIO; cPTIO). cPTIO, SPNO, vehicle (control) or cPTIO/SPNO were applied to the RWM, during which blood pressure and VBF were monitored for baseline, treatment, and recovery conditions. Results showed concentration-dependent increases in flow, probably resulting from NO's vasodilatory action on local vasculature. cPTIO pretreatment was found to attenuate SPNO-induced VBF increases. These findings support a role of NO in maintaining the vestibular microcirculation.

[Observation of cristae of posterior ampullae with laser Doppler].

UNLABELLED: To set up the methodology of measuring vestibular blood flow was the key to the study of vestibular microcirculation. 10 guinea pigs' posterior ampullae cristae blood flow were measured with Laser Doppler Flowmetry. RESULTS: cochlear flow was 318.39 +/- 91.66mV. Cristae of posterior ampullae was 194.00 +/- 45.26mV. The arterial blood pressure was stable in 9.99 approximately 10.27kPa. The present results showed cochlear and vestibular blood flow were 62.14% and 37.86% in total inner ear blood circulation. The latter appeared to be about one half of cochlear blood flow. These suggested that the blood flow of posterior ampullae can reflect the blood flow of vestibular to some degree. Laser Doppler was technically simple, non-invasive, highly stable, reproducible and sensitive.

Anatomic variations and anomalies involving the facial canal.

Congenital bony dehiscences in the facial canal result from incomplete closure during development and are observed in approximately 55% of temporal bones. Anomalies involving the facial canal frequently are encountered in malformations of the temporal bone. These anomalies include aberrations of the course of one or all of the segments of the canal; abnormal relation to the oval and round window; bifurcations and trifurcations of the nerve; and associations with dysplasia of the stapes, oval window, external ear canal, and auricle. Rarely, the facial nerve may be hypoplastic or totally absent. Two abnormal vessels occasionally may accompany the facial nerve in the Fallopian canal: a persistent stapedial artery and a persistent lateral capital vein.

Blood flow and capillary surface area of rat posterior canal ampulla.

Vascular disorders have often been proposed to explain disorders of the inner ear, in both the cochlear and vestibular systems. While the cochlea has been extensively studied, little work has been done on vestibular blood flow. Existing studies have reported only total vestibular blood flow, using microspheres. By combining the physiologic technique of microsphere injection with new developments in morphologic stereology studies, data on end-organ blood flow (excluding nerve; 0.074 +/- 0.027 microliters/min; 5.99 microliters/min/mm3), capillary surface area (10.87 mm2/mm3), mean capillary diameter (9.64 microns), and end-organ volume (0.013 mm3) was determined for the posterior canal ampulla of young Fischer 344 rats. Results indicate an anatomic basis for increases in blood flow with CO2 breathing, and provide an assessment of appropriate microsphere size for vestibular blood flow studies. By allowing comparison of blood flow and capillary parameters related to surface area and volume, this new method of blood flow study will allow more meaningful data to be collected on the vestibular system.

The vascular anatomy of the vestibular labyrinth in man.

1. A survey of the literature on the vascular anatomy of the vestibular labyrinth in Man is presented, and the methods of investigation used to visualize the vessels are evaluated. A generally correct picture of the subject is provided by the various studies published since Siebenmann's monograph. There are, however, some conflicting points as well as some lack of data with regard to the course and relationships of the large vessels and the capillary areas of the cristae and maculae. 2. This study presents a systematic description of the vascular anatomy of the vestibular labyrinth in Man, from the main arterial and venous stems to the capillary areas, with particular attention to the relationships between the vessels and the osseous walls, neural, and membranous structures. The vessels were visualized by a composite method including the selective injection of the internal auditory artery with coloured silicone or India ink; the counterstaining of the labyrinth with osmic acid; the cutting of the petrous bone in 1-mm thick, serial sections that were cleared with methylsalicylate. The sections were studied by stereomicroscopy, using mainly reflected light. Photos and drawings were made to illustrate the findings. New names were introduced for vessels hitherto unnamed, and some traditional names were modified in order to give a more precise and descriptive terminology. 3. The description followed the two main arteries, the capillary areas and the three main veins. The vestibular labyrinth is supplied by the superior vestibular artery and by the inferior vestibular artery which is a branch of the vestibulo-cochlear artery. The superior vestibular artery runs along the anterior aspect of the vestibule from the utricular nerve up to the cristae of the superior and lateral canals. It supplies the macula of the utricle, the cristae and ampullar crures of the superior and lateral canals. The inferior vestibular artery runs mainly along the medial wall of the vestibule. It supplies the last tract of the scala media and the vestibular caecum with a peculiar pattern which appears to be an adaptation of the common cochlear arrangement to the different spatial condition. It also supplies the macula of the saccule, the crista and ampullar crus of the posterior canal as well as the simple crures of the three canals. The vascular arrangement of the maculae and cristae has a similar three-layered architecture.(ABSTRACT TRUNCATED AT 400 WORDS)

Vasculature of the crista ampullaris of the rat as seen in microcorrosion casts.

A scanning electron microscope study of corrosion cast preparations of the vessels of the crista ampullaris was carried out in adult rats. This method shows the microvasculature of the cristae in the three-dimensional model. As a result of this technique we have been able to demonstrate on microscopical level a particular microvasculature in the septum cruciatum of the crista in rat.

Morphological study of blood-labyrinth barrier in the vestibular organs under normal and experimental acute hypertensive and acute hypotensive conditions.

In order to examine a blood-labyrinth barrier in the vestibular region, capillary permeability of the vestibular organs, i.e. the sacculus, the utriculus and the ampullae of semicircular canals, were studied light and electron microscopically by the horseradish peroxidase (HRP) tracer method. Intravenously infused HRP was not observed outside capillaries because of the tightness of endothelial tight junctions and the paucity of pinocytotic vesicles. Furthermore, the effect of drug-induced acute hypertension and acute hypotension on the capillaries of the vestibular organs was studied morphologically using the tracer technique. In each experiment, there was no extravasation of HRP from capillaries, thus agreeing with the results of the experiment made under normal conditions. These findings mean that capillaries of the vestibular region are of ordinary brain capillary type and contribute to the blood-labyrinth barrier to macromolecules such as HRP both under normal conditions and following abrupt changes in blood pressure.

Vein of the vestibular aqueduct.

The vein of the vestibular aqueduct (VVA) was investigated in a series of 40 human temporal bones. The processing included vascular injection with a colored medium, decalcification and cutting in serial, thick sections, which were put in a clear fluid and studied with a stereo-microscope. The labyrinthine roots of the VVA are the single veins of the ampulla and simple limbs of the semicircular canals and of the posterior wall of the utricle. They drain the rich capillary bed of the simple endolymphatic walls of the canals and the utricle, as well as a small peripheral area of the cristae and the utricular macula. The VVA leaves the vestibule through an individual bone canal running parallel to the vestibular aqueduct up to the dura of the posterior side of the petrosa in the area of the endolymphatic sac. It then opens in the inferior petrosal sinus or the jugular bulb. The vein receives other branches from the bone, dura and sac. Correct information on the course of this vein appears to be lacking in contemporary textbooks and articles, although it has been correctly described since the last century.

[The venous drainage of the vestibular labyrinth in man (author's transl)]. / Le drainage veineux du labyrinthe vestibulaire chez l'homme.

The venous drainage of the vestibular division of the inner ear presents two different and separated routes. One, draining the central part of the sensorial areas (maculae and cristae), ends up into the vein of the cochlear aqueduct. The other drains the perypheral part of the sensorial areas as well as the simple endolymphatic walls and ends into the vein of the vestibular aqueduct. The latter vein shows close relationships to the endolymphatic sac.