Toru Sekitani

Vestibular Neuronitis: Epidemiological Survey by Questionnaire in Japan

An epidemiological survey on vestibular neuronitis in Japan was conducted by means of a questionnaire filled in by major neuro-otology clinics (otolaryngologists) during 1988-1990 (3 years). The diagnostic criteria of vestibular neuronitis settled on in 1986 by the Standardization Committee of the Japan Society of Equilibrium Research were applied. Gross analysis of questionnaire answers showed that i) there was no sexual difference, ii) the peak of age distribution was between 40-50 years, iii) about 30% of all cases had had common colds prior to the disease, the rate being highest among children below 10 years, iv) disappearance of positional and positioning nystagmus appeared in about 60% of all cases within 3 months, and that v) caloric CP was observed in about half of the cases at the follow-up test. Progress was not as favorable when compared to previous studies.

Progress of caloric response of vestibular neuronitis

Progress of caloric response and subjective symptoms of 60 patients with vestibular neuronitis was evaluated by a long term follow-up study. Normalization of caloric responses was confirmed in 25 (41.7%) out of 60 patients, 20 of whom had recovered within 2 years of the onset of vertigo. The rate of the patients with canal paresis was about 90% after 1 month of the onset, and 80% after 6 months, while 50% of them still showed canal paresis after 5 or 10 years had passed. Complete relief from subjective symptoms was recognized in 34 (56.7%) cases during the follow-up period. We conclude that the prognosis of vestibular neuronitis is not always good, because vestibular function did not recover within normal levels in about half of the patients in spite of complete relief from subjective symptoms in many of them.

Vestibular Compensation in Vestibular Neuronitis. Long-term Follow-up Evaluation

We evaluated vestibular function, especially for positional, head shaking and caloric nystagmus, in 43 patients with vestibular neuronitis, for long periods from the onset. The results suggested that in these cases of vestibular neuronitis, which were studied for more than 10 years after onset of the disease, the disease may still be in the uncompensated stage or may have worsened in the partially compensated stage.

Fine Structures of Utricle of Developing Chick Embryo Exposed to 2G Gravity

Utricular otoconia of the chick embryos incubated under continuous 2G load were examined under a scanning electron microscope. Morphological changes were confined to the process of otoconial formation and the otoconial size. Otoconial formation was remarkably delayed in the utricle of 2G centrifuged chick embryo. Giant otoconia, which sometimes amounted to over 100 microM in length, existed along the marginal zone of the utricular otolithic membrane. These results indicate that the 2G state influences the otoconical formation.

Serovirological Study of Vestibular Neuronitis

A serovirological study to clarify the pathogenesis of vestibular neuronitis was made on 44 patients. The diagnosis of vestibular neuronitis was made under the diagnostic criteria. Sera from all 44 cases were collected twice or more at defined intervals. Of these, 36 cases were treated as paired sera. Seventeen out of 36 paired cases showed significant change in serum viral antibody titer (HSV, 2 cases; CMV, 1 case; EBV, 7 cases; rubella, 2 cases; adeno., 2 cases; influ. A, 1 case; influ. B, 2 cases). It was assumed that infection caused by these detected viruses played an important role in the onset of vertigo in each case.

Vestibular neuronitis in children.

Seventeen cases of vestibular neuronitis in children, including 11 cases from the questionnaires of an epidemiological survey in Japan and 6 patients in our clinic, were examined. Sex and age distribution was 11 males and 6 females, ranging in age from 3 to 15 years. Bilateral and recurrent cases were not encountered. Fifty-three percent of children had had a preceding episode of an upper respiratory tract infection and this ratio was higher than that in adults. The etiology of vestibular neuronitis is probably many-faceted, but it is thought that upper respiratory tract infections play an important role especially in children. Vertiginous symptoms had almost subsided among children at the last visit. However, among adults, 24% of patients felt persisting unsteadiness. The disappearance of positional and positioning nystagmus was observed in 71% of children at the last visit. Caloric CP failed to recover in only 14% of all cases who were re-examined. As shown in this study, the prognosis in children is better than in adults for nystagmus and caloric response. The results of this study thus indicate that not only central compensation but also recovery of the peripheral vestibular function is more effective for bringing recovery from the vestibular disorder in children than in adults.

Glycoconjugates in the Otholithic Organ of the Developing Chick Embryo

The presence of glycoconjugates in the otolithic organ of developing chick embryos was investigated histochemically using lectins. On the 6-day-old chick embryo, intense labelling with lectins was observed in the sensory epithelium, on the surface of the epithelium and on the immature otoconia. The otoconia were intensely labelled with lectins at every stage of the chick embryos, while the labelling with lectins in the sensory epithelium became weaker with the maturing of the otoconia. In TEM observation, the secretory granules of the supporting cells of the sensory epithelium were labelled with lectin. The reaction of lectin was more intense in the electronic dense zone of the otoconium than in the electronic lucent zone at every stage of the chick embryos. These findings indicate that the precursors of the otoconia are secreted by the supporting cells of the sensory epithelium and that glycoconjugates play an important role in otoconial formation.

Effects of carbonic anhydrase inhibitor on the otolithic organs of developing chick embryos

Carbonic anhydrase appears to be involved in the process of otoconial formation. The purpose of this investigation was to observe the morphologic change in the surface structure of the otolithic organ in developing chick embryos after injection of the carbonic anhydrase inhibitor, acetazolamide. Acetazolamide (1.5, 3, or 6 mg/0.06 mL/egg) was injected into the yolk sac of the embryo of the fifth day of incubation. Embryo specimens were collected on the 11th, 13th, and 18th days of incubation. The chicks were killed on the third day posthatching, and the surfaces of the otolithic organs were observed under a scanning electron microscope. A marked disturbance in otoconial formation was noted in both utricle and saccule, marked by a decrease or absence of otoconia. A widely exposed meshwork structure of otolithic membrane was observed, with sensory cilia penetrating the meshwork small holes in many instances. There were also several otoconial abnormalities, such as the appearance of only a single giant otoconium, or from several to dozens of giant otoconia, and rough, spongy-surfaced global substances entirely covering the maculae. Clearly, carbonic anhydrase inhibitor (acetazolamide) injected into the yolk sac of developing chick embryos alters and inhibits normal otoconial morphogenesis.

Differential Diagnosis of Vertigo— Combined Galvanic Test and MRI

Differential diagnosis of the disease entities of vertigo are important in clinical investigations. Many concepts and procedures have been proposed for available diagnostic tests. Recent basic and clinical studies proved the efficacy and reliability of galvanic tests, including galvanic nystagmus test (GNT) and galvanic body sway test (GBST), emphasizing that the effects of galvanization are: 1) on the action potential in vestibular nerve and 2) on the resting discharge of the vestibular nerve. These suggest further that galvanic nystagmus reaction (GNT) is mainly a manifested reaction of the semicircular canal system, while galvanic body sway such as spinal reflexes (includ. GBST) are mainly a reaction of the otolithic system. The purpose of this paper is to review briefly the previous results of GBST in our laboratory; and to introduce a newly devised combined galvanic test, simultaneous recording of both GBST and GNT; and also introduce magnetic resonance imaging (MRI) of the brain including the cerebrum, cerebellum with brainstem relating the central vestibular system, both of which help us to make a more defined diagnosis of the central origin vertigo. On CGT of a normal subject, galvanic eye movements are constantly induced showing the initial eye deviation and the following main deviation during galvanization, on both eyes, which are almost similar and occur synchronously. Galvanic body sway is also induced well with individual components, as described in the previous papers. CGT of the cases with vertigo revealed abnormal response patterns in each disease.

The otolithic organ in the developing chick embryo. Scanning electron microscopic study on the utricular macula.

The long and short axes of utricular maculae were measured to calculate growth curves using an ocular micrometer under stereomicroscope. The mean lengths of the long and short axes on the 6th incubation day were 0.06 mm and 0.05 mm, respectively. Thereafter: 1.00 mm and 0.74 mm on the 11th incubation day; 1.34 mm and 1.03 mm on the 15th incubation day; and on hatching 1.51 mm and 1.07 mm, respectively. The surface structure, particularly the otoconia and the sensory hairs of the utricular maculae, on the 4.5th incubation day to the 7th post-hatching day of White Leghorn chicks were observed with a scanning electron microscope (SEM). A number of microvilli and primary cilium on the inner surface of the otocyst were found between the 4.5th and the 5th incubation day. Immature sensory hairs appeared on the 5th incubation day. The polarity of the sensory hairs became evident on and after the 9th incubation day. Mature sensory hairs were seen all over the utricular maculae between the 1st and the 3rd post-hatching day. Mature sensory hairs were mainly seen near the striola, and immature ones peripherally. Then, the various forms in the maturation phase of sensory hairs were seen between the striola and the periphery. These arrangements suggest some process of maturity from the peripheral region to the central striola region. Immature otoconia were first seen on the 6th incubation day. Mature otoconia were recognized on and after the 11th incubation day, and they were observed on the whole surface of the utricular maculae. Global substances on the macula with a rough surface and spongy structure were observed suggesting otoconial precursors transforming themselves into otoconial crystals.