Tympanic Membrane Displacement Analyser Tracing Modifications Induced by Glycerol in Menièrés Disease: El Analizador de Desplazamiento de la Membrana Timpánica: Seguimiento de las Modificaciones inducidas por el Glicerol en la Enfermedad de Ménière

Clinical comparison of tympanic membrane displacement with invasive intracranial pressure measurements

A non-invasive method of assessing intracranial pressure (ICP) would be of benefit to patients with abnormal cerebral pathology that could give rise to changes in ICP. In particular, it would assist the regular monitoring of hydrocephalus patients. This study evaluated a technique using tympanic membrane displacement (TMD) measurements, which has been reported to provide a reliable, non-invasive measure of ICP. A group of 135 hydrocephalus patients was studied, as well as 13 patients with benign intracranial hypertension and a control group of 77 volunteers. TMD measurements were carried out using the Marchbanks measurement system analyser and compared between the groups. In 36 patients, invasive measurements of ICP carried out at the same time were compared with the TMD values. A highly significant relationship was found between TMD and ICP but intersubject variability was high and the predictive value of the technique low. Taking the normal range of ICP to be 10-15 mmHg, the predictive limits of the regression are an order of magnitude wider than this and therefore Vm cannot be used as a surrogate for ICP. In conclusion, TMD measurements do not provide a reliable non-invasive measure of ICP in patients with shunted hydrocephalus.

The prognostic value of the otoacoustic emission test in low frequency sudden hearing loss

Low frequency sudden hearing loss (LFSHL) is a frequent finding in the otological practice. Several prognostic indicators have been suggested concerning the prediction of the outcome of sudden hearing loss, but so far there are no proven factors to establish the prognosis. The aim of this study was to assess whether OAEs could be considered as a reliable prognostic test in LFSHL. The study group consisted of 20 patients presenting with a unilateral LFSHL. Each patient was submitted to spontaneous otoacoustic emissions (SOAEs), transient otoacoustic emissions (TEOAEs) and distortion products (DPOAEs) recording and then treated with glycerol administrated intravenously in 3-h intervals for 4 days. Pure tone audiometry (PTA) threshold was evaluated again 1 h after the last administration of glycerol. After osmotic therapy 12 patients (60%) showed a significant PTA improvement with a mean improvement of 11 dB; modifications were significant at the Student's t test for paired data (P<0.0001). The relationship between the pretherapy presence or absence of SOAEs, TEOAEs and DPOAEs and PTA modification was not significant at the exact Fisher's test. In conclusion, even if our study supports that OAEs could be an indicator of the inner ear functional state, they cannot be utilized as a prognostic test in LFSHL in relation to the efficacy of osmotic therapy. Among the other parameters evaluated, only the precocity of therapy seems to be related to prognosis in LFSHL.