Non-invasive perilymphatic pressure measurement in normal hearing subjects and in patients with Meniere’s disease using the MMS-10 Tympanic Displacement Analyser

Abstract

Hydrostatic pressure in the endolymphatic and perilymphatic compartments of the inner ear in animals can be detected invasively by means of (micro)pipettes and pressure transducers (Angelborg and Agerup 1975; Bohmer 1993). For obvious reasons these direct invasive methods are not suitable for human inner ears. The MMS-10 Tympanic Displacement Analyser (TDA) is a commercially available device to measure variations of perilymphatic pressure non-invasively. The TDA is based on the principle that movements of the tympanic membrane, induced by the stapedial reflex, produce small volume displacements in the external auditory canal (Marchbanks 1991; Reid et al. 1989; Marchbanks and Reid 1990; Reid et al. 1990; Moss et al. 1990). These variations in nanolitres can be measured by the TDA. The displacement of the tympanic membrane depends on the resting position of the stapes footplate within the oval window. A high perilymphatic pressure displaces the resting position of the stapes footplate laterally and allows a higher degree of freedom for motion in a medial direction and correspondingly a more inward displacement of the tympanic membrane. Conversely a low perilymphatic pressure displaces the footplate more medially, resulting in more motion laterally and a more outward displacement of the tympanic membrane. The intracranial pressure is related to the perilymphatic pressure and thus to tympanic membrane displacement. First, TDA measurements were used in intracranial hypertension (Ernst and Lenarz 1993) and peri-operative monitoring of ventricular shunt surgery (Murthy et al. 1992). Later, the TDA was employed also in otological disorders, such as Meniere’s disease (Palva and Dammert 1969; Beentjes 1972). In our studies the perilymphatic pressure of normal hearing subjects was measured by means of the TDA in three different conditions with special attention to external factors that could possibly influence the perilymphatic pressure: 1) body position, 2) diurnal variation, 3) physical exertion. Results were compared with measurements in patients with Meniere’s disease.