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Objective. Evoked tympanic membrane displacement (TMD) measurements show a correlation with intracranial pressure (ICP). Attempts to use these measurements for non-invasive monitoring of ICP in patients have been limited by high measurement variability. Pulsing of the tympanic membrane at the cardiac frequency has been shown to be a significant source of the variability. In this study we describe a post processing method to remove the cardiac pulse waveform and assess the impact of this on the measurement and its repeatability. Approach. Three-hundred and sixteen healthy volunteers were recruited for evoked TMD measurements. The measurements were quantified by V m, defined as the mean displacement between the point of maximum inward displacement and the end of the stimulus. A sample of spontaneously pulsing TMDs was measured immediately before the evoked measurements. Simultaneous recording of the ECG allowed a heartbeat template to be extracted from the spontaneous data and subtracted from the evoked data. Intra-subject repeatability of V m was assessed from 20 repeats of the evoked measurement. Results with and without subtraction of the heartbeat template were compared. The difference was tested for significance using the Wilcoxon sign rank test. Main results. In left and right ears, both sitting and supine, application of the pulse correction significantly reduced the intra-subject variability of V m (p value range 4.0 × 10−27 to 2.0 × 10−31). The average improvement was from 98 ± 6 nl to 56 ± 4 nl. Significance. The pulse subtraction technique substantially improves the repeatability of evoked TMD measurements. This justifies further investigations to assess the use of TMD measurements in clinical applications where non-invasive tracking of changes in ICP would be useful.

Objective: Although previous studies have shown associations between patient symptoms/outcomes and the spontaneous tympanic membrane displacement (spTMD) pulse amplitude, the contribution of the underlying intracranial pressure (ICP) signal to the spTMD pulse remains largely unknown. We have assessed the relative contributions of ICP and arterial blood pressure (ABP) on spTMD at different frequencies in order to determine whether spTMD contains information about the ICP above and beyond that contained in the ABP. Approach: Eleven patients, who all had invasive ICP and ABP measurements in situ, were recruited from our intensive care unit. Their spTMD was recorded and the power spectral densities of the three signals, as well as coherences between the signals, were calculated in the range 0.1–5 Hz. Simple and multiple coherences, coupled with statistical tests using surrogate data, were carried out to quantify the relative contributions of ABP and ICP to spTMD. Main results: Most power of the signals was found to predominate at respiration rate, heart rate, and their harmonics, with little outside of these frequencies. Analysis of the simple coherences found a slight preference for ICP transmission, beyond that from ABP, to the spTMD at lower frequencies (7/11 patients at respiration, 7/10 patients at respiration 1st harmonic) which is reversed at the higher frequencies (2/11 patients at heart rate and its 1st harmonic). Both ICP and ABP were found to independently contribute to the spTMD. The multiple coherence reinforced that ICP is preferentially being transmitted at respiration and respiration 1st harmonic. Significance: Both ABP and ICP contribute independently to the spTMD signal, with most power occurring at clear physiological frequencies—respiration and harmonics and heart rate and harmonics. There is information shared between the ICP and spTMD that is not present in ABP. This analysis has indicated that lower frequencies appear to favour ICP as the driver for spTMD.

Evoked tympanic membrane displacement (TMD) measurements, quantified by VSpontaneous and evoked TMD data from each ear in the sitting and supine position were recorded from 100 healthy volunteers using the MMS-14 CCFP analyser. ECG was also recorded to identify each heartbeat. Using bespoke software written in Matlab, spontaneous data were analysed to produce average pulse amplitude (PA) waveforms and evoked data were analysed to calculate average VThere was a strong positive correlation between PA and VThis study shows that large V

OBJECTIVE Tympanic membrane displacements (TMDs) are used to non-invasively gauge inner-ear fluid pressure. Inner-ear fluid pressure equalizes with intracranial pressure (ICP) via the cochlear aqueduct and therefore TMDs can indirectly evaluate ICP. We studied the relationship between two TMD modalities, evoked and spontaneous. Evoked TMD is a reflex response to an auditory stimulus and the established stapes-footplate mechanism explains how evoked TMDs change with ICP. Spontaneous TMD refers to a pulsatile TMD waveform expressed in the form of pulse amplitudes (TMD-PAs), the origins of which are poorly understood. We investigated whether both modalities respond similarly to an ICP change, suggesting a common mechanism. APPROACH ICP was manipulated in 20 healthy volunteers by a postural change from sitting (lower ICP) to supine (higher ICP). Differences between paired sitting and supine TMD results generated ΔEvoked and ΔSpontaneous values. MAIN RESULTS Evoked TMDs became more inward on lying supine while spontaneous TMDs became more outward. There was no evidence of a correlation between ΔEvoked and ΔSpontaneous (Right ears: r = -0.38, p = 0.10, 95% CI -0.75 to 0.21; Left ears: r = 0.34, p = 0.16, 95% CI -0.17 to 0.75). SIGNIFICANCE This suggests the stapes-footplate mechanism is not the primary mechanism explaining how spontaneous TMDs respond to changing ICP.

Objectives: Evoked tympanic membrane displacement (TMD) measurements, quantified by Vm, record small volume changes in the ear canal following stimulation of the acoustic reflex. Vm shows a correlation with intracranial pressure (ICP) and has been proposed as an option to non-invasively measure ICP. The spontaneous pulsing of the tympanic membrane, driven by the cardiovascular pulse, may contaminate the recordings and contribute to high measurement variability in some subjects. This study hypothesised that the larger the spontaneous vascular pulse, the larger the variability in Vm.

OBJECTIVE Evoked tympanic membrane displacement (TMD) is a non-invasive technique for assessing intracranial pressure (ICP). The aim of this study was to define reference intervals (RIs) in the healthy population. APPROACH Measurements were made in 154 healthy adults. Results were quantified by V m, which is the most frequently described TMD measurement. Distributions were determined for sitting and supine posture. Differences between right and left ears were explored using a Wilcoxon signed-rank test. Postural changes were used to assess pressure transfer between the cerebral spinal fluid (CSF) and the perilymph. MAIN RESULTS The range in which 95% of scores fall is -283 to 722 nl (M = 132 nl) left sitting, -232 to 623 nl (M = 97 nl) right sitting, -543 to 717 nl (M = 37 nl) left supine and -584 to 504 nl (M = -15 nl) right supine. No significant difference was seen between the left and right ears in the sitting position; a significant difference was seen in the supine position. A significant effect of posture was seen for both the left and right ears. Postural changes indicated pressure transfer between the CSF and perilymph more often in the right ear (75.3%) than the left (61.9%). Pressure transfer could not be assumed in either ear for 13.4% of participants. SIGNIFICANCE We present the largest dataset of evoked TMD in healthy individuals and the first set of RIs for V m. A patient cohort with both invasive ICP and evoked TMD measurements is needed to validate the technique for clinical use.

Object. The authors assessed the accuracy and repeatability of the tympanic membrane displacement (TMD) test, an audiometric technique that is used to evaluate changes in intracranial pressure (ICP) in children with shunted hydrocephalus. Methods. A prospective comparative evaluation of 31 clinical episodes of shunt malfunction was made by using the serial TMD test and direct ICP measurement in eight children with shunted hydrocephalus between January 1995 and February 1996. The volume displacement of the tympanic membrane (Vm) on stapedial contraction was inward for raised ICP in 11 instances and ranged from −120 to −539 nl (mean −263.5 nl). This was confirmed by direct ICP monitoring, which showed values ranging from 20 to 30 mm Hg (mean 26 mm Hg). The TMD test measurement (Vm) in 18 instances of low ICP ranged from 263 to 717 nl (mean 431.3 nl); this was corroborated by direct ICP measurement, which ranged from 3 to 7 mm Hg (mean 4.2 mm Hg). The normal baseline Vm values obtained when patients were asymptomatic ranged from −98 to 197 nl (mean 110 nl). As a noninvasive diagnostic tool used in predicting changes in ICP, the TMD test had a sensitivity of 83% and specificity of 100%. The positive predictive value of the test was 100% and the negative predictive value was 29%. Conclusions. The TMD test can be used on a regular basis as a reproducible investigative tool in the assessment of ICP in children with shunted hydrocephalus, thereby reducing the need for invasive ICP monitoring. The equipment necessary to perform this testing is mobile. It will provide a useful serial guide to ICP abnormalities in children with shunted hydrocephalus.

Purpose: Raised intracranial pressure (ICP) is a potentially treatable cause of morbidity and mortality but tools for monitoring are invasive. We sought to investigate the utility of the tympanic membrane displacement (TMD) analyser for non-invasive measurement of ICP in children. Methods: We made TMD observations on normal and acutely comatose children presenting to Kilifi District Hospital (KDH) at the rural coast of Kenya and on children on follow-up for idiopathic intracranial hypertension at Evelina Children's Hospital (ECH), in London, UK. Results: We recruited 63 patients (median age 3.3 (inter-quartile range (IQR) 2.0-4.3) years) at KDH and 14 children (median age 10 (IQR 5-11) years) at ECH. We observed significantly higher (more negative) TMD measurements in KDH children presenting with coma compared to normal children seen at the hospital's outpatient department, in both semi-recumbent [mean -61.3 (95 % confidence interval (95 % CI) -93.5 to 29.1) nl versus mean -7.1 (95 % CI -54.0 to 68.3) nl, respectively; P = 0.03] and recumbent postures [mean -61.4 (95 % CI -93.4 to -29.3) nl, n = 59) versus mean -25.9 (95 % CI -71.4 to 123.2) nl, respectively; P = 0.03]. We also observed higher TMD measurements in ECH children with raised ICP measurements, as indicated by lumbar puncture manometry, compared to those with normal ICP, in both semi-recumbent [mean -259.3 (95 % CI -363.8 to -154.8) nl versus mean 26.7 (95 % CI -52.3 to 105.7) nl, respectively; P < 0.01] and recumbent postures [mean -137.5 (95 % CI -260.6 to -14.4) nl versus mean 96.6 (95 % CI 6.5 to 186.6) nl, respectively; P < 0.01]. Conclusion: The TMD analyser has a potential utility in monitoring ICP in a variety of clinical circumstances. © 2013 The Author(s).

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.

This study investigated the prevalence of perilymphatic hypertension (raised perilymphatic pressure) in a population of subjects with tinnitus. A review of the literature showed how changes in perilymphatic pressure could affect tympanic membrane displacement measurements. This review also revealed that perilymphatic hypertension was more likely to occur in young females (less than 45 years) than in other subjects. An experiment was designed to test 32 subjects, who were divided into four groups according to their age and sex. These subjects underwent several routine audiological tests and were then tested with the tympanic membrane measurement system to determine the perilymphatic pressure of both ears. Statistical analysis of the experimental results showed that the young females had raised perilymphatic pressure. This was significantly higher than the perilymphatic pressure of the other test groups and of that of a normal population. The young females also exhibited other symptoms indicative of raised perilymphatic pressure. The raised pressure was thought to be due to an increase in fluid pressure which is more likely to occur in females due to variations in the levels of circulating hormones with menstrual irregularities, pregnancy and the menopause.