Mitsuo Tominaga

Disorders of cochlear blood flow

The cochlea is principally supplied from the inner ear artery (labyrinthine artery), which is usually a branch of the anterior inferior cerebellar artery. Cochlear blood flow is a function of cochlear perfusion pressure, which is calculated as the difference between mean arterial blood pressure and inner ear fluid pressure. Many otologic disorders such as noise-induced hearing loss, endolymphatic hydrops and presbycusis are suspected of being related to alterations in cochlear blood flow. However, the human cochlea is not easily accessible for investigation because this delicate sensory organ is hidden deep in the temporal bone. In patients with sensorineural hearing loss, magnetic resonance imaging, laser-Doppler flowmetry and ultrasonography have been used to investigate the status of cochlear blood flow. There have been many reports of hearing loss that were considered to be caused by blood flow disturbance in the cochlea. However, direct evidence of blood flow disturbance in the cochlea is still lacking in most of the cases.

Thirty-year trends in sudden deafness from four nationwide epidemiological surveys in Japan.

Conclusions. The estimated annual number of patients with sudden deafness treated in Japan has increased during the last 30 years, especially in the elderly population. Hypertension and diabetes mellitus could contribute to the etiology of this disorder. Objectives. To investigate the epidemiological trends of sudden deafness in Japan over the past 30 years by analyzing data from national surveys. Materials and methods. Nationwide epidemiological surveys on sudden deafness were conducted four times by the Research Committee of the Ministry of Health and Welfare in Japan. The first, second, third, and fourth surveys were performed in 1972, 1987, 1993, and 2001, respectively. Results. The estimated annual numbers of patients with sudden deafness treated in Japan were 4000 in 1972; 16 700 in 1987; 24 000 in 1993, and 35 000 in 2001.The average ages of patients at onset were 39.1, 45.4, 49.3, and 51.3 years, respectively. Thus, both the number of patients and the average age of patients with sudden deafness have increased during the past 30 years. Patients with sudden deafness in the fourth survey exhibited hypertension and diabetes mellitus more frequently than did patients in the first survey; this trend was particularly noticeable among elderly patients.

Transmeatal low-power laser irradiation for tinnitus.

Objective To evaluate effectiveness of 60-mW laser irradiation in the treatment of tinnitus. Study Design Prospective, randomized double-blind study. Methods This investigation included 68 ears in 45 patients with disabling unilateral or bilateral tinnitus. The active or placebo laser treatment was administered transmeatally once a week for 6 minutes. Laser irradiation was performed four times during a 4-week period. A questionnaire was administered to evaluate the loudness, duration, quality, and annoyance of tinnitus before and after irradiation. The loudness and pitch match for tinnitus were obtained, and distortion product otoacoustic emissions were also examined. Results No significant difference was observed between the active and placebo laser groups with regard to outcome of loudness, duration, quality, and annoyance of tinnitus. In one patient who received active laser treatment, acute hearing deterioration occurred after the third irradiation. Conclusion Transmeatal low-power laser irradiation with 60 mW is not effective for the treatment of tinnitus.

Contribution of stapedial artery to blood flow in the cochlea and its surrounding bone

This study was performed to elucidate the contribution of the stapedial artery (SA)--which has been considered to be independent of the vertebrobasilar system--to blood flow in the ear by observing ear blood flow in Sprague-Dawley rats. A laser-Doppler (LD) probe was positioned on the bony wall of the cochlear basal turn after removal of the middle ear mucosa. The LD output was measured while either or both the SA and the anterior inferior cerebellar artery (AICA) were occluded. The LD output decreased to 70.6+/-2.5% (mean+/-S.D.) of the baseline value following SA occlusion, and to 58.0+/-7.8% following AICA occlusion in 12 animals. The rebound phenomenon of blood flow, which is a type of autoregulation, was only observed after releasing AICA occlusion. Simultaneous occlusion of the SA and AICA decreased the LD output to 27.0+/-5.5% of the baseline value. The role of the contribution of the SA and AICA to the LD output is discussed.

Blood Flow Measurements in the Ears of Patients Receiving Cochlear Implants

We measured cochlear blood flow in 12 patients who received cochlear implants, using a laser-Doppler probe with an outer diameter of 0.8 mm. The subjects had congenital deafness, idiopathic progressive sensorineural hearing loss, Waardenburgs syndrome, narrow internal auditory canal, or sudden deafness. Putting the probe tip to the site of drilling for cochlear implantation, we measured blood flow before, during, and after the cochlear bony wall was opened. The laser-Doppler output was confirmed even after the tip of the probe was inserted into the perilymphatic space in all cases. Our results revealed that blood flow was maintained in all cochleas, although there was a probability of reduction in blood flow volume. We conclude that laser-Doppler flowmetry is both relatively safe and useful for measuring blood flow in the ears during cochlear implantation procedures.

Response of cochlear blood flow to prostaglandin E1 applied topically to the round window.

Conclusions. The increase in cochlear blood flow (CBF) after administration of prostaglandin E1 (PGE1) to the round window depends on increased blood flow through the anterior inferior cerebellar artery (AICA). Objectives. To evaluate the response of CBF to PGE1 applied topically to the round window, and to investigate the origin of blood flow changes after this topical application. Material and methods. The response of CBF to topically applied PGE1 was measured by placing the tip of a laser Doppler probe on the bony wall of the basal turn of the cochlea after the middle ear mucosa over the cochlea had been removed in guinea pigs and rats. In rats, the CBF response to PGE1 administration was investigated after occlusion of the AICA or stapedial artery. Results. CBF increased following PGE1 administration in both guinea pigs and rats. In rats, CBF increased from 100% to 132%±10% (mean±SD) after the topical application of 0.5 µl of a 0.014% PGE1 solution. CBF decreased after occlusion of the AICA or stapedial artery but did not increase after PGE1 administration during occlusion of the AICA. The CBF response to PGE1 administration was similar before and after occlusion of the stapedial artery.

Blood Flow in the Ears of Patients Receiving Cochlear Implants

We measured cochlear blood flow (CBF) in 55 patients who received cochlear implants, using a laser-Doppler probe placed over the site of drilling in the cochlear bony wall. The subjects included 29 patients with congenital deafness of unknown cause, 8 with idiopathic progressive sensorineural hearing loss, 4 with postmeningitic deafness, 3 with Waardenburgs syndrome, 3 with congenital cytomegalovirus infection, and 8 whose deafness had other causes. There was a wide range of CBF values in patients with congenital deafness of unknown cause. In the patients with idiopathic progressive sensorineural hearing loss, the CBF was significantly lower in patients more than 40 years old. Intracochlear calcification following meningitis appears to be associated with a reduced CBF.

Imaging of a congenital perilymphatic fistula

A 7-year-old boy with a history of purulent meningitis and watery rhinorrhea was studied using computed tomography (CT) and magnetic resonance imaging (MRI). He had a common cavity in the left inner ear. With high-resolution heavily T2-weighted MRI, leakage of the inner ear fluid into the middle ear at the oval window area through a congenital perilymphatic fistula could be visualized. Surgery to close the fistula showed a perforation in the stapes footplate.

Changes in Cochlear Blood Flow Due to Endotoxin-Induced Otitis Media

The purpose of this study was to elucidate the influence of otitis media on blood flow in the lateral wall of the cochlea by means of a model of endotoxin-induced otitis media. The cochlear blood flow (CBF) following lipopolysaccharide inoculation into the middle ear cavities of rats was measured by laser-Doppler flowmetry and compared with that of untreated ears. After this evaluation, the influence on CBF of concomitant use of a nitric oxide synthase inhibitor was also investigated. The first day after inoculation, the CBF of treated ears decreased significantly. This decrease recovered gradually between the 7th and 14th days. With concomitant use of a nitric oxide synthase inhibitor, the decrease in CBF was prevented to some extent. The results showed a functional influence upon CBF by endotoxin-induced otitis media. The significance of prophylactic use of the drug is also discussed in regard to the effect on CBF following otitis media.

A Clinical Study on the Prognosis of Sudden Deafness Treated at Nagoya University.

名古屋大学では1972年から今日まで, 発症から2週間以内に来院し, 固定時まで聴力の経過が追えた突発性難聴症例のデータをコンピュータに入力してきた。患者数は男994人, 女845人のあわせて1839人であった。年齢分布に有意な男女差はなかった。聴力の回復は, 10～19歳が最もよく加齢するごとに乏しくなる傾向がみられたが, 9歳未満の症例においても悪い傾向を認めた。めまいは, 男26.3%, 女33.9%に伴っており, 有意に女にその合併が多かったが, 聴力の回復に男女差はなかった。初診時聴力レベルや治療中の聴力レベルと固定時聴力レベルの相関係数を求めたところ, 高周波音域では, 全般的にその相関係数が高く, 4000Hz, 8000Hzでは第21病日で相関係数0.95であった。1～4病日の聴力レベルと5～7病日の聴力レベルが同様であれば, 固定時聴力レベルに有意な差は認められなかった。