Shinya Fukuse

Autoregulation of cochlear blood flow

SummaryThe cochlear blood flow of healthy adult guinea pigs was measured with a laser Doppler flowmeter and flow dynamics were anaylzed on the basis of autoregulation. Angiotensin Il infusion was used to raise blood pressure, while phlebotomy was done to lower blood pressure. The characteristics of autoregulation of cerebral blood flow and muscular blood flow were also investigated. Cochlear blood flow was considered to have some autoregulation but was less than brain blood flow, which showed significant regulation. Muscular blood flow seemed to have no similar regulatory mechanism.

Effects of Prostaglandins on Perilymphatic Oxygenation: Enhancement of Cochlear Autoregulation by Prostacyclin

Effects of prostaglandin E1, prostacyclin, a prostacyclin analogue (OP-2507), and an inhibitor of thromboxane A2 synthetase (OKY-046) on the perilymphatic oxygen tension were measured in the feline tympanic perilymph under various respiratory conditions and blood pressure ranges. Factors influencing the capacity of the autoregulative properties of the inner ear vessels to accommodate changes in systemic blood pressure were also examined. Intravenous administration of prostacyclin, OP-2507, and OKY-046 prevented a decrease in perilymphatic oxygen tension when the systemic blood pressure decreased. Even a negative correlation of the differential coefficients between the perilymphatic oxygen tension and the systemic blood pressure was noticed during the administration of prostacyclin. Thus, prostacyclin enhanced the autoregulative property of the inner ear vessels. Furthermore, correlation studies between perilymphatic oxygen tension and cochlear blood flow demonstrated a partial dissociation, indicating the presence of autoregulation in the mean systemic blood pressure range under 80 mmHg.

Effects of a Depressor on Cochlear Blood Flow and Perilymphatic Oxygen Tension

To clarify the characteristics of the blood circulation in the cochlea, we investigated the relationship between cochlear blood flow and perilymphatic oxygen tension in guinea pigs with trimetaphan camsilate induced hypotension. Cochlear blood flow was measured by laser Doppler flowmetry, and perilymphatic oxygen tension by a polarographic method. Cochlear blood flow generally paralleled systemic blood pressure, while perilymphatic oxygen tension showed a slower response to the decrease of systemic blood pressure. Although there were individual differences in the changes of systemic blood pressure, cochlear blood flow and perilymphatic oxygen tension, they were found to be dose dependent. Since hypotension induced by trimetaphan camsilate is fairly reproducible in the dose range of this experiment, this drug can be used as a ganglion blocking agent in experiments on cochlear blood flow and perilymphatic oxygen tension during systemic hypotension. The change of perilymphatic oxygen tension with a slower response could be considered to be a factor in the homeostasis in the inner ear fluid.

Hearing Impairment in a Patient with Mumps Complicated by Vestibular Dysfunction and Meningitis.

A 6-year-old girl complained of difficulty hearing four days after the onset of parotid swelling. Four days later she developed vertigo and vomiting, and was brought to our outpatient clinic. Audiograms showed total deafness of the right ear. Rotatory and horizontal nystagmus was also noted. Caloric testing revealed canal paresis (CP) on the right. Neurological examination revealed nuchal rigidity. Lumbar puncture was done, and the findings led to the diagnosis of aseptic meningitis. Various therapeutic agents including vasodilators, vitamin B, gamma globulin and steroid hormone were administered for two weeks. Although her general condition and equilibrium recovered, her hearing impairment did not improve. It was probable that meningitis following mumps infection preceded the inner ear lesion in this case and affected the inner ear by spreading through the cochlear aqueduct or internal acoustic meatus.

Lipoma in the deep lobe of the parotid gland; A case report.

60-year-old male had a tumor which originated in the deep lobe of the parotid gland and extended to the parapharyngeal space. CT-sialography revealed tumor extension to the parapharyngeal space with clear imaging. The CT number of this tumor was lower (-104 to -128) than that of lipoma tissue (-80 to -90).Ga-scintigraphy showed RI accumulation, probably because of the sialography performed 35 days before scintigraphy.Under general anesthesia, the patient was operated on. The tumor was a parotid tumor with a dumbell-like shape.