[Pressure relations between endocranial and intracochlear fluid spaces in patients with inner ear diseases]

Relationship of vestibular aqueduct and inner ear pressure in Ménière's disease and the normal population

OBJECTIVE

Etiopathogenesis of Ménière's disease has not been resolved. The principal histopathologic finding in this disease is endolymphatic hydrops. The majority of radiologic and histopathologic studies demonstrated a narrow vestibular aqueduct in Ménière's disease. There is no study in the literature investigating the relationship between inner ear pressure and vestibular aqueduct dimensions. Static acoustic compliance is a noninvasive procedure that is thought to measure perilymphatic pressure at the footplate. An increase in mechanical fluid pressure in the inner ear is transmitted to the footplate of the stapes. This causes a reduction in the compliance at the drum. The aim of this study is to investigate the relationship between vestibular aqueduct dimensions and static acoustic compliance in Ménière's disease and the normal population.

STUDY DESIGN

Prospective study.

METHODS

Forty patients with Ménière's disease and 40 healthy individuals with no otolaryngologic disorders were the subjects of this study. Each group was further divided into two according to static compliance value (normal and low static compliance). In these four groups dimensions of vestibular aqueduct were determined radiologically by high-resolution computerized tomography and correlated with normal and low static acoustic compliance values (normal and high perilymphatic pressure).

RESULTS

The results demonstrated that vestibular aqueduct is narrower in patients with Ménière's disease than the normal population. However, there is no relationship between vestibular aqueduct dimensions and inner ear pressure obtained by static acoustic compliance measurements.

Relationship of the cochlear aqueduct and inner ear pressure in Ménière's disease and in a normal population

OBJECTIVE

The aim of this study was to determine the dimensions of cochlear aqueduct radiologically in patients with Ménière's disease and in normal subjects, and to correlate these findings with normal and low static acoustic compliance (SAC) (high and normal perilymphatic pressure) to see whether the dimensions of the cochlear aqueduct play any role in the perilymphatic pressure in normal individuals and patients with Ménière's disease.

STUDY DESIGN

Prospective double-blind study.

SETTING

The study was conducted at Hacettepe University Medical Faculty, a tertiary care center.

PATIENTS

Forty patients with Ménière's disease with bilateral involvement, diagnosed by vertigo attacks, fluctuating hearing loss, tinnitus, fullness in the ear, and cochlear sensitivity constituted the patient group. Forty healthy individuals with no otolaryngologic symptoms constituted the control group.

INTERVENTIONS

All individuals underwent SAC measurement in terms of equivalent volume in milliliters, based on two volume measurements. To measure the dimensions of the cochlear aqueduct, high-resolution computed tomography of the temporal bone in the axial plane was performed.

RESULTS

There was no statistically significant difference in the width of the cochlear aqueduct between patients with Ménière's disease and normal subjects. When SAC measurements were also taken into account, there was no difference in cochlear aqueduct dimensions between individuals with normal and low SAC values in the two groups.

CONCLUSION

The dimensions of cochlear aqueduct are not significantly different in Méniére's disease patients and normal individuals. Also, the cochlear aqueduct does not appear to play a significant role in normal and low SAC values in the two groups of individuals.

Pressure transfer between intracranial and cochlear fluids in patients with Meniere's disease

OBJECTIVES

To elucidate the pressure transfer between intracranial and labyrinthine fluids in patients with well-defined unilateral Meniere's disease.

STUDY DESIGN

Eleven patients previously exposed to hypobaric pressure agreed to be investigated further with the tympanic membrane displacement (TMD) technique. TMD was used to indirectly analyze perilymph pressure changes as the result of changes in body position.

METHODS

Repeated measurements for both the diseased and the healthy ears were made with the patients supine and then in a sitting position. The TMD parameters for the maximum inward displacement, the Vi, and the mean volume displacement, the Vm, were calculated and compared.

RESULTS

The paired comparison showed statistically significant larger Vi values for both ears in the supine position. A similar tendency was observed for the Vm value. This difference of the Vi was significantly larger for the diseased ear compared with the currently healthy ear. The results were compared to the audiometric and electrocochleographic results previously obtained on the same patients when they were subjected to hypobaric pressure. Patients who experienced the largest differences in hearing level thresholds in the lower frequencies also showed the greatest differences in TMD values as the result of postural changes.

CONCLUSIONS

Despite the limited number, the statistically supported results suggest a relation between the efficiency of the routes of pressure transfer and the observed effect of hypobaric exposure. The results also indicate that for the patients tested, the routes of communication are more effective in the diseased ear than in the healthy ear--a condition that may relate to the pathogeneses of Meniere's disease.

Why monitor perilymphatic pressure in Menière's disease?

A cohort of 39 patients with confirmed raised intracranial pressure was investigated. Of these patients, 24 (62%) complained of tinnitus and 11 (28%) suffered from paroxysmal rotary vertigo. Intracranial hypertension can occur without the usual headache and visual symptoms. In such cases, the patient may be referred to the otolaryngological clinic and the condition may be mistaken for Menière's disease or a labyrinthine disorder. The Tympanic Membrane Displacement (TMD) technique now provides a non-invasive method of monitoring the intracranial and perilymphatic pressures. This study provides recommendations for the use of TMD techniques in the otolaryngological clinic for screening, diagnosing and monitoring treatment of patients presenting with raised perilymphatic pressure.