M. Ikeda’s research while affiliated with Nihon University and other places

Only a few benign tumours of the middle ear have been reported to lead to the development of facial palsy. Here, we describe a patient with middle-ear cavernous lymphangioma and facial palsy. Single case study. A 61-year-old man presented with left-sided hearing impairment and incomplete left facial palsy. A tumour was confirmed to be occupying the epi- to mesotympanum and to be joined to the facial nerve. The tumour was removed along with facial nerve tissue, which was resected at its horizontal portion, and the remaining facial nerve was fixed by end-to-end anastomosis. Complete facial paralysis occurred after the operation, but the patient's House-Brackmann grade gradually improved to grade III. Post-operative histopathological examination revealed infiltration of the lymphangioma into the facial nerve tissue, together with mild neural atrophy of the facial nerve. These findings suggested that tumour invasion was the cause of facial palsy in this patient.

Otological diseases sometimes occur during the taking off or the landing of airplanes. We experienced a case which occurred during the landing of the domestic airline. A 36 y.o. male suffered vertigo, deafness and ear ringing when his domestic flight landed. He was referred the next day and still showed positional nystagmus and sensorineural hearing loss. We considered it to be an aero-alternobaric barotraumas perilymph fistula and had him admitted. His condition improved to normal by the conservative treatment except high frequency hearing loss. The cause of his symptom was probably the relatively negative pressure pattern of the mechanisms of alternobaric barotraumas which occur in airplanes. There are not many case reports so far about perilymph fistulas caused by aero-alternobaric barotraumas, but the occurrence during descending is more commonly reported than during ascending. It seemed to be important to ensure prevention method especially when the patient is suffering from upper airway infection and the Eustachian tube dysfunction. This kind of disease is rare but we need to regard aero-alternobaric barotraumas as one of the differential diagnosis when the patient suffered vertigo, deafness and ear ringing during air flights.

We analyzed the time-dependent change of optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN), during the 7 days of 6-degree head-down bedrest experiment in which the same subjects were examined a variety of biomedical changes due to a long time alteration of the direction of gravity. At Tsukuba Space Center of National Space Development Agency of Japan (JAXA; Japan Aerospace Exploration Agency as present), 6 healthy adult male subjects were assigned. We collected OKN and OKAN (both right and left directions) data 6 times; sitting position on the previous day of bedrest, spine position on the 1st, 3rd and 5th day of bedrest, and sitting position again immediately after bedrest on the 7th day and on the next day after bedrest. The OKN gain (OKN slow-phase-velocity/stimulus speed) tended to decrease on the 1st day during bedrest, recovered gradually by the 5th day, and exceeded the pre-bedrest level after bedrest. The gain was higher when the OKN slow phase directed rightward than leftward throughout the 6 times. The appearance rate of OKAN first-phase decreased throughout the bedrest and it recovered to the pre-bedrest level with the end of bedrest. In contrast, the appearance rate of OKAN second-phase increased on the 1st day and the increase was maintained thereafter, suggesting that an OKAN generator might be different between the first and the second phase. The maximum slow-phase-velocity of OKAN decreased markedly on the 1st day, but the recovery was unclear during and after bedrest. No clear tendency was found in the time-dependency of the OKAN duration. We considered that these time-dependent changes observed in the optokinetic-oculomotor system might be mainly based on the alternation in gravity information to the otolith organ, and that the method of bedrest must be useful for a long-term adaptation study in the vestibular system under microgravity.

To determine the characteristics of causative factors of taste disorders amongst the elderly, and to examine the therapeutic effect of a zinc agent, taking into account age-related factors. A total of 408 patients with taste disorders were divided into three groups by age: 49 years or younger, 50 to 64 years old, and 65 years or older. The incidence of taste disorders caused by drug administration and systemic disease were significantly higher in the elderly group. A serum zinc concentration of 69 microg/dl or lower was found in 33 per cent of the elderly group, significantly more (p < 0.001) than the 19 per cent of the 49 years or younger group with such a concentration. Zinc administration was therapeutically effective in 70 per cent of the whole population studied, and in 74 per cent of the elderly population. In the elderly, the incidence of taste disorders caused by drug administration or systemic disease was significantly greater compared with other age groups. The curative effects of zinc administration were not observed to be influenced by age.