The vestibular-evoked myogenic potential (VEMP) is expected to be one of the examinations for saccular function. We report a case of dysequilibrium possibly due to a saccular disorder. A 27-year-old female came to our clinic complaining of severe recurrent dysequilibrium spells for few hours on September 21, 1998. The first attack was only vertigo with bilateral tinnitus for 8 days before. She did not show possible vestibular findings on a routine vestibular test. An electrochochleogram showed the dominant negative summating potential (SP) on both sides, and the furosemide test showed negative findings on both sides. A VEMP test indicated a low amplitude in the right ear, which improved to the normal response after furosemide injection. The amplitude was increased by furosemide administration even in the left ear. These findings suggested bilateral endolymphatic hydrops in the cochlea and saccule especially on the right side. The VEMP test may reveal saccular hydrops, which differs from the conventional Ménière type vertigo.

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Relationship between neurological asymptomatic vertigo and the vertebrobasilar system as revealed by magnetic resonance angiography.

Many patients suffering from vertigo have no neurological symptoms except for a positional nystagmus. Vertigo without any neurological findings has not been thought to be a vertebrobasilar (VB) attack. The purpose of this study is to clarify the relationship between vertigo without any neurological symptoms and the VB system using magnetic resonance angiography (MRA). MRAs of the VB system were examined in 31 patients with positional nystagmus of unknown origin (PNU) and in 14 patients with benign paroxysmal positional vertigo (BPPV) as control. MRA was performed with a 1.5-tesla system using the two-dimensional time-of-flight technique. Abnormalities such as elongation, bending, narrowing or obstruction of the artery were detected in 27 patients of the PNU group and 8 patients of the BPPV group. A significant difference in the abnormalities was noticed between the two groups (p < 0.05; chi(2) test). This result is almost similar to those of previous studies using conventional vertebral angiography and digital subtraction angiography. Thus, MRA is useful in examination of the VB system. Moreover, our study suggested that the positional nystagmus might result from VB ischemia, even if there were no other neurological signs.

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Regeneration of adult budgerigar's hair cells following acoustic trauma.

The functional and structural changes of hair cells of the adult budgerigar following acoustic trauma were examined using auditory brainstem response (ABR), and both scanning and transmission electron microscopy. Just after exposure to a 1,500-Hz pure tone at 120 dBSPL for 98 h, severe damages and disappearance of short hair cells were observed in the middle region of the basilar papilla. Fourteen days after the exposure, the threshold of ABR recovered to the level before the exposure, and normal short hair cells, which have synapses with nerve endings, were rearranged all over the damaged region of the basilar papilla. These results indicate that the hair cells of the adult budgerigar have capability to regenerate, and to restore the auditory perceptive function following acoustic trauma.

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Development of melanosomes and cytochemical observation of tyrosinase activity in the inner ear.

The ultrastructure and tyrosinase activity of melanocytes in the inner ear of pigmented guinea pigs were observed. Melanocytes/melanocyte-like cells were seen in the stria vascularis, the vestibular dark cell area and the endolymphatic sac. In the stria vascularis, melanosomes in several stages of maturation were seen in the cytoplasm of the intermediate cells and melanin-laden endosomes existed in the basal cells. Only the intermediate cells contained tyrosinase-positive cytoorganelles; Golgi sacs and neighboring small vesicles. Numerous melanocytes containing many melanosomes were observed under the epithelium of the vestibular dark cell area, and they showed tyrosinase activity. Melanocytes were seen in the endolymphatic sac, and they also showed tyrosinase activity. However, the epithelial cells of the endolymphatic sac, which had vacuoles containing melanin, did not show tyrosinase activity. Based on these findings, it can be said that (1) most of the intermediate cells of the stria vascularis must be melanocytes, (2) melanogenesis is vigorous in melanocytes of the inner ear, and (3) melanin in the epithelial cells of the endolymphatic sac is transferred in from melanocytes and is never synthesized in the epithelial cells.

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Increased capillary permeability of the stria vascularis to HRP, induced by experimental acute hypotension in rats.

Acute hypotension was produced in rats by using two experimental techniques: intravenous infusion of a ganglion-blocking agent (Arfonad), and venesection of a femoral vein. Horseradish peroxidase (HRP) was injected intravenously after each procedure, and subsequently observed in the inner ear by light and electron microscopy. In both experimental models, a large amount of tracer spread into the intercellular spaces, but it was halted by tight junctions bordering the stria vascularis. The endothelium exhibited a high distribution density of labelled vesicles, which suggested increased vesicular transport. There was no extravasation of HRP from capillaries in the spiral ligament in spite of the presence of some labelled pinocytotic vesicles. The present study was concerned with the discovery of enhanced capillary permeability of the stria vascularis under acute hypotension, as in the case of acute hypertension (Sakagami et al., 1984).

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Ultrastructural study of the effect of acute hypertension on the stria vascularis and spiral ligament.

The effect of acute hypertension, induced in rats by intravenous injection of methoxamine chloride (Mexan), on the stria vascularis and spiral ligament was studied electronmicroscopically with the tracer method of horseradish peroxidase (HRP). Considerable extravasation of HRP occurred in the stria vascularis, due to the increased vesicular transport. The leaked HRP spread into intercellular spaces, but was prevented from spreading towards the endolymph by zonulae occludentes between marginal cells and towards the perilymph by zonulae occludentes between basal cells. The reaction product was occasionally found between basal cells. No leakage of HRP from capillaries was observed in the spiral ligament, although some labelled micropinocytotic vesicles were present in the endothelium. It is suggested that, under acute hypertensive conditions, areas of zonulae occludentes bordering the stria vascularis play an important role as a barrier to HRP, whereas capillaries in the spiral ligament themselves act as a barrier to it.

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PubMedDate not supplied

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.

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