The effect of the evanescent wave upon acoustic measurements in the human ear canal.

When making acoustic measurements in a human ear canal, it is often necessary to monitor the output of a sound source with a microphone positioned within a few millimeters of that sound source. This microphone will not only measure the pressure due to the propagated acoustic wave, which we wish to measure, but also the pressure due to the evanescent wave. The pressure due to the evanescent wave can be viewed as a source of error in the measurement of the propagating acoustic wave.

A retrospective study of the role of the argon laser in the management of epistaxis secondary to hereditary haemorrhagic telangiectasia.

Epistaxis is a common symptom in patients with hereditary haemorrhagic telangiectasia. It may vary in severity from infrequent mild bleeds to regular severe bleeding, the latter requiring multiple blood transfusions. Laser, which can be used to coagulate the telangiectasia without destroying the overlying nasal mucosa, would theoretically seem to be the ideal mode of treatment.

Closure of the nasal cavities in the treatment of refractory hereditary haemorrhagic telangiectasia.

From a cohort of 35 patients with hereditary haemorrhagic telangiectasia (HHT), 12 patients have undergone closure of the one or both nasal cavities during the last three years for refractory epistaxis. All had failed other forms of treatment including hormone therapy, laser coagulation and septodermoplasty. All patients were available for follow-up at six months or longer.

Medical examiner variability.

There are undoubtedly many factors that contribute to inter-examiner variability relevant to the use of medical practitioners in justiciable matters. One source of variability with regard to claims relating to hearing disorders could well be the training and 'calibration' of medical examiners. A tentative analysis of the examination papers and of the declared roles of the specialties that provide these examiners lends support to such a thesis.

Tele-education: the virtual medical laboratory.

The virtual medical laboratory (VML) was conceived to provide an Internet-accessible resource, offering access for clinicians and scientists to an invaluable data archive at the institute of Laryngology and Otology, London. The Institute is home to the largest collection of temporal bone, laryngeal, skull and sinus sections in Europe. The skull and sinus collections include an extensive section consisting of animal material.

Osteoma of the internal auditory canal.

We present a case of an osteoma of the internal auditory canal, which was surgically removed with symptomatic improvement. We describe CT, MRI, histological and operative findings, with a review of the proposed aetiology. The implications for imaging in the investigation of retrocochlear lesions are discussed.

Multicomponent acoustic distortion product otoacoustic emission phase in humans. I. General characteristics.

Phase characteristics and latency of 2f1-f2, 3f1-2f2, and 2f2-f1 acoustic distortion product otoacoustic emissions (DPOAEs) have been analyzed in 12 adults with normal hearing. Phase-versus-frequency functions (PFF) have been recorded at each of ten pairs of primary frequencies, by two methods, depending on which one of the primary frequencies f1 or f2 was swept in frequency. Whichever sweep method was used, local phase irregularities were found in the PFF and were shown to be independent of the phase variability due to the measured noise, to be reproducible and frequency specific.

Nasal physiology: neurochemical receptors, nasal cycle, and ciliary action.

The complex interaction of neurotransmitters, vascular supply, and mucociliary function constitute one of the main defense mechanisms of the respiratory tract, modulating airflow and response to noxious assault. One of the main controls of airflow relies upon the modulation of vasodilation and vasoconstriction via the autonomic control of a sinusoid system. In addition to noradrenaline and acetylcholine, an ever-increasing number of neurotransmitters are involved, including neuropeptide Y, vasoactive intestinal peptide, peptide histidine leucine, substance P, and calcitonin gene-related peptide.

The influence of evoking stimulus level on the neural suppression of transient evoked otoacoustic emissions.

This study concerns the suppression of transient evoked otoacoustic emissions (TEOAEs) by contralateral noise. The suppression is interpreted as neurally induced changes in cochlear mechanics. The magnitude of TEOAE suppression is explored in response to a single level of contralateral noise, in 20 normal subjects, and as a function of TEOAE evoking stimulus power in 6 subjects.

Enhanced magnetic resonance imaging and subtraction techniques in postoperative evaluation of craniofacial resection for sinonasal malignancy.

The use of magnetic resonance imaging (MRI) enhanced with gadolinium. and diethylenetriamine pentaacetic acid (DTPA) in the preoperative evaluation of sinonasal malignancy is well established and has an accuracy of over 98%. Since 1979, 208 patients have undergone craniofacial resection at London's Institute of Laryngology & Otology, primarily for sinonasal neoplasia affecting the anterior skull base.

Postnatal development of membrane specialisations of gerbil outer hair cells.

Using a combination of freeze-fracture and thin sections, this study examines the maturation of the membrane specialisations of the gerbil outer hair cells (OHC) between 2 and 16 days after birth (DAB). The apical membrane, the junctional region around the neck of the cell, and the lateral and basal membranes are described. The results suggest a sequential development of the different components of the lateral wall.

Suppression of stimulus frequency otoacoustic emissions by contralateral noise.

The effect of different bands of contralaterally presented noise at low and moderate intensities on stimulus frequency otoacoustic emissions (SFOAE) from human ears is examined. A SFOAE evoked by a continuous stimulus tone and suppressed by a second tone to produce an SFOAE residual was chosen as the probe to determine the effect of the efferent input. At low levels of contralateral noise, a band centred on the ipsilateral stimulus frequency was the most effective suppressor of the SFOAE residual.

Stimulus frequency otoacoustic emissions from guinea pig and human subjects.

Stimulus frequency otoacoustic emissions (SFOAEs) have previously been recorded from human subjects by the suppression of a continuous stimulus tone generated OAE by a second tone (Kemp et al., 1990). This study presents comparative data from guinea pig and human subjects using a similar method.

Dystrophin expression in the hair cells of the cochlea.

Dystrophin is normally expressed in a number of tissues including muscle, brain and the outer plexiform layer of the retina. In Duchenne and Becker muscular dystrophy abnormal or deficient dystrophin expression leads to muscle degeneration and has been implicated in mental retardation and a form of night blindness. We have examined the expression of dystrophin immunoreactivity in cochlear tissues of normal guinea-pig and mouse, and whether expression is perturbed in the cochlea of the dystrophic MDX mouse.

The treatment of chronic sinusitis: a controversial issue.

The persistence of sinusitis after upper respiratory tract infection is influenced by a range of aetiological factors such as anatomical variation which may be surgically corrected, mucociliary abnormalities and immune deficiency. The latter is more common than previously realised, encompassing IgG subclass deficiency, reduced opsonization and Fc gamma receptor polymorphism. This has therapeutic implications, with the possibility of IgG replacement therapy and vaccination.

Two modes of hair cell loss from the vestibular sensory epithelia of the guinea pig inner ear.

In the vestibular and auditory neurosensory epithelia of poikilothermic vertebrates and of birds, damaged sensory "hair" cells are often deleted by extrusion from the apical surface. In contrast, in the adult mammalian auditory epithelium (the organ of Corti), the bodies of damaged hair cells degenerate within the epithelium. To determine whether this apparent difference is species related or is associated with the differing structural organisation of the epithelia, hair cell deletion in the mammalian vestibular end-organs was examined.

An evaluation of mucus glycoproteins in the larynges of victims of sudden infant death syndrome.

Larynges from 24 victims of Sudden Infant Death Syndrome (S.I.D.

Mechanisms of hearing loss in acoustic neuroma: an otoacoustic emission study.

Evoked otoacoustic emissions (EOAE) are active mechanical responses from the cochlea which provide information about the integrity of the preneural cochlear receptor mechanisms. It may be hypothesised, therefore, that if a hearing impairment is neural in origin, normal EOAEs may be obtained from the cochlea, which, although dissociated, is functioning normally. This study examined the status of the cochlea with EOAE in patients with cochlear (Meniere's disease) and neural (surgically proven acoustic neuroma) disease.

Comparison of assessment of caloric nystagmus by observation of duration and by electronystagmographic measurement of slow-phase velocity.

The 'duration' of induced nystagmus was the first parameter used to quantify vestibular function during caloric testing. However, later work suggested that there was a poor correlation between this measure and the physiological events occurring during caloric testing. This, coupled with the development of electronystagmography and the value of a permanent record of the caloric responses, led to the widespread use of the 'slow-phase velocity' measurement of induced nystagmus, as the most commonly used parameter for assessment of the caloric test.

Differential effect of adaptation on the ipsi- and contralateral auditory brainstem pathways.

Auditory brainstem potential components II and V are delayed in the contralateral recording in comparison with that ipsilateral to the stimulus. Wave III is recorded earlier contralaterally. The effect of increasing stimulus repetition rate on the ipsilateral/contralateral latency differences in these components was examined.

Assessment of an implementation of a narrow band, neonatal otoacoustic emission screening method.

Objective: To validate a narrow band method for the detection of transient evoked otoacoustic emissions (TEOAEs) in neonates.

Design: A method for the assessment of TEOAEs was implemented. The method was based upon assessing the estimated signal to noise ratio of a narrow band of TEOAEs from 1.