Ellis Douek

EFFECTS OF INCUBATOR NOISE ON THE COCHLEA OF THE NEWBORN

The possible effects of incubator noise on the hearing of premature babies have long been debated. The type of hearing loss found in 12 low-birthweight children was examined; and the variable noise level in regularly used incubators was measured. This noise, applied to guinea pigs continuously during their second week after birth, was shown histologically to destroy a proportion of the sensory cells in the cochlea. Adult guinea pigs, however, were not vulnerable in this way. The conclusion is that there is definite circumstantial evidence of the damaging effect of many incubators on the hearing of premature infants.

The Effects of Combined Gentamicin and White Noise on the Spiral Organ of Young Guinea Pigs

The present work describes the effects on the spiral organ of very young guinea pigs, of continuous white noise (76 dB SPL, 7 days) combined with gentamicin, using surface preparations and both transmission and scanning electron microscopy to analyse structural changes. Gentamicin only, at 80 mg/kg/day for 5 days did not cause any perceptible loss of hair cells, and only minimal structural changes. When combined with 7 days of white noise, there was a widespread effect on outer hair cells throughout the cochlea, some changes being similar to those induced by sound alone, others being seen only in the combined experiments. Outer hair cell losses with sound and gentamicin treatment were highly variable, but in addition to apical damage, also seen in sound-treated animals, a more basal area of cell loss appeared in the spiral organ.

Extra-Tympanic Electrocochleography

A non-invasive technique for recording the cochlear action potential in adults without recourse to sedation or local anaesthesia is presented. This technique has been assessed in two ways: (1) A group of normal subjects was tested to obtain distributions of response amplitude and latency as functions of stimulus intensity. (2) A group of patients with Menieres disease was tested with trans- and extra-tympanic electrocochleography to compare the intensity amplitude functions and wave-forms obtained from the two methods. On the basis of this study the use of extra-tympanic electrocochleography as a replacement for the trans-tympanic method is discussed.

The Crossed Acoustic Response and Objective Tests of Hearing

Objective tests of hearing now have a recognised rôle in the assessment of children. Three types of responses can be used for this purpose, the cortical responses (evoked response audiometry), the brain‐stem responses (crossed acoustic responses) and the cochlear responses (electrocochleography). The crossed acoustic test is a new development, and its main virtues are that it can be easily and simply applied to all children, even when there is some active resistance, without recourse to sedation or anaesthesia. The preliminary results have been encouraging and suggest that it can be used as a screening test during the clinic.

Scintigraphic evaluation of glomus tumours.

The current investigations of choice for a suspected glomus tumour are either direct or indirect angiography to include digital subtraction followed by computerized tomography (CT) or magnetic resonance imaging (MRI) or, if available, CT and MRI with gadolinium alone. Although these modalities confirm the diagnosis and give anatomical information to facilitate accurate staging, they do not provide functional data. The use of radionuclide scintigraphy can add an extra physiological dimension to glomus tumour imaging. Iodine-131/123 metaiodobenzylguanidine (MIBG) is a tumour imaging agent which has been used to diagnose head and neck neuroendocrine tumours to include paragangliomata and medullary carcinoma of the thyroid (MCT). However, it is expensive and the new head and neck tumour imaging agent technetium-99 m (Tc99m) (v) dimercaptosuccinic acid (DMSA) has superceded it as the imaging agent of choice to evaluate MCT. We report a patient with a glomus jugulare tumour which was evaluated with I131/I123-MIBG and Tc99m (v) DMSA. The tumour was functional and is the first reported case exhibiting positive accumulation of both I131-MIBG and Tc99m (v) DMSA. The patient was subsequently treated with a therapeutic dose of I131-MIBG. The significance of these results is discussed.

Clinical aspects of extracochlear electrical stimulation.

The history of attempts to help the totally deaf by electrical stimulation of the cochlea is well known.l-La Our own interest in this question stems from a new approach reported in 1977.: The principle therein is that by using singlechannel electrical stimulation applied externally to the cochlea, useful speech communication may be obtained. The reasons for using an external stimulus rather than one applied by an intracochlear electrode were the following:

A single average crossed acoustic response.

Although the Crossed Acoustic Response is the simplest objective test of hearing acuity, as it can be used without an anaesthetic in the mobile child, a serious obstacle to its wide use has been cost. This was because two averagers have been necessary. This paper describes a modification of the equipment which is not only cheap but which can be used to adapt any existing electrocochleograph or cortical evoked response recorder.