Recording of Cranio-Labyrinthine Pressure Transmission in Man by Acoustic Impedance Method

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Abstract
This investigation shows that an increase in intracranial pressure produced by compression of the cervical veins regularly produces changes of the acoustic impedance of the middle ear. Observations in man and experiments on the cat and guinea pig indicate that these impedance changes are caused by transmission of hydrostatic pressure to the labyrinthine fluids, and a consequent increase in the mechanical load on the stapedial footplate. Preliminary attempts to use the method for diagnostic purposes in five unilateral cases of Meniere's disease and in one case of acoustic neurinoma were negative, the impedance responses to the increase in intracranial pressure being equal bilaterally and of the same magnitude as in normal subjects. The anatomical background of cranio-labyrinthine pressure transmission is discussed with particular reference to cases of excessive cerebrospinal fluid leakage occasionally observed in stapes surgery and rare' cases of spontaneous fluctuations of the acoustic impedance of the middle ear. The phenomenon reported may partly explain the difficulties encountered in demonstrating significant pathological values when absolute acoustic impedance measurement is applied in the diagnosis of middle ear disease.