Abstract
Five cases of cerebello-pontine angle and brain-stem tumors with fluctuating hearing loss were reported. They were consisted of two cases of acoustic neurinomas, one of cerebello-pontine angle meningioma, one of hemangioblastoma of brain-stem, and one of supra- and sub-tentorial dumb-bell type astrocytoma.
Their fluctuating hearing losses occurred predominantly on the range of low frequencies. They were observed paroxysmal fluctuation in the hearing losses during their clinical courses. In two cases of them, deafness occurred and improved abruptly, and we found a cyst in a part of these tumors.
The mechanisms of the fluctuating phenomenon were explored from the operative and audiological findings, and following causes were presumed.
The first, in the courses of growths of the tumors, it may act as reversible invasion to acoustic nerve or acoustic tracts in the brain-stem, within a certain period of time. The second, as a result of that cerebello-pontine angle tumor may exert pressure upon the labyrinthine artery, it may cause the reversible of the inner ear function to make change in some instances. The third, the rapid increase or decrease in cerebro-spinal fluid pressure may cause the change of pressure of the tumor on acoustic nerve or brain-stem.
