[Fortuitous discovery of a voluminous mandibular cyst in a child]. / Découverte fortuite d'un volumineux kyste mandibulaire chez un enfant.

In a five and a half year-old child, a voluminous mandibular cyst was discovered by a dental check-up. The originality of this case consisted in the great volume of this asymptomatic lesion and the anterior localization in the mandible. Treatment was surgical, conserving the deciduous teeth and the underlying germs. The histopathological examination of the lesion confirmed the clinical and radiological aspects of follicular cyst. A regular clinical and radiologic surveillance was necessary until bone regeneration was complete, the risk of per and post-operative fracture being major.

CD1 hearing-impaired mice. II. Group latencies and optimal f2/f1 ratios of distortion product otoacoustic emissions, and scanning electron microscopy.

In our companion paper (Le Calvez et al., 1998), the levels of distortion product otoacoustic emissions (DPOAE) were collected in the ears of CD1 mice with progressive degeneration of cochlear outer hair cells (OHC). Their comparison to standard functional measurements such as auditory-evoked brainstem responses (ABR) showed that CD1 ears could be classified as normal or impaired in a frequency-specific manner using DPOAE levels. The present work reports how DPOAE phases and levels of young CD1 mice were affected by varying the frequency ratio of eliciting stimuli at frequencies f1 and f2. Normally hearing CBA/J mice served as controls. The rate of phase change of DPOAE when f1 was varied and f2 was fixed allowed the group delay of DPOAE to be derived. The changes of DPOAE levels during this procedure disclosed bandpass characteristics that several reports (Fahey and Allen, 1986; Brown and Gaskill, 1990) assumed to be the reflection of important features of cochlear micromechanics, possibly in relation to the coupling of OHCs to the tectorial membrane. Group delays became significantly shorter when ABR thresholds exceeded 40 dB elevation. The bandpass filter characteristics strikingly depended on auditory function so that the optimal ratio f2/f1 progressively shifted from 1.24 to 1.50 or more when hearing loss increased. A difference was also noted between CD1 ears whose ABR thresholds were not yet increased and control CBA/J (optimal ratio 1.20). Scanning electron microscopy disclosed a variety of often minor OHC lesions that were only roughly correlated with cochlear function. However, the presence of abnormalities in the reticular lamina associated with early changes of DPOAE fine structure as a function of f2/f1 supported the hypothesis of some involvement of micromechanical features in the bandpass filter characteristics of DPOAE. The sensitivity of their measurement in pathological situations is potentially interesting.

[Decalcified, lyophilized, sterile heterotopic porcine ossicular xenografts. Experimental evaluation in the guinea pig]. / Les xéno-implants ossiculaires hétérotopiques porcins décalcifiés, lyophilisés et stérilisés. Evaluation expérimentale chez le cobaye.

Using the guinea pig middle ear model, we assessed decalcified, lyophylized, sterile heterotopic porcine ossicular xeno-implants based on a histology (optic and electron scan microscope) and immunologic (immunofluorscence) methods. Implants were placed in the middle ear and others in the dorsal subcutaneous area. Allo-implants were compared as controls. Implants were placed in the middle ear in 54 animals and skin implants in 14. Under the influence of BMP, the implant ossified in all cases in the middle ear. Intense immune recruitment was not observed. Inversely, there was a mononuclear infiltration reaction to the skin implants with formation of a fibrous capsule, immunoglobulin and complement influx and consequently sequestration. The allo-implants were partially reossified. These findings confirm the value of decalcification with hydrochloric acid for BMP induction, independent of species and the failure of attempted immune despecification. Implant outcome is not dependent on its antigen load, which is high compared with its weight, but on the site of implantation. The middle ear appears to be a privileged site of implantation.

Ultrastructural changes in the hydropic cochlea of the guinea-pig.

Transmission electron microscopy of the cochlear organ of Corti in experimental endolymphatic hydrops revealed two principal features. Starting 1 month after induction of hydrops, osmiophilic inclusions thought to represent lipofuscin accumulation were frequently observed in the subcuticular cytoplasm of the outer hair cells along the length of the cochlea. Starting 3 months after induction of hydrops the efferent terminals on the outer hair cells appeared to be vacuolated. These data suggest that oxidative insult is likely to contribute to the pathology associated with endolymphatic hydrops and thus that free radical scavengers might be useful in the treatment of Menière's disease patients. In addition the early modification of the efferent innervation of the hydropic cochlea might underlie the known hypersensitivity to various insults, including noise stimulation, glycerol administration and hypoxia.

Neuronal degeneration of primary cochlear and vestibular innervations after local injection of sisomicin in the guinea pig.

This paper reports on a dynamic study of the morphological changes within the cochlear and vestibular ganglia of the guinea pig after local application of Sisomicin in the inner ear. The treatment leads to a rapid, complete and irreversible destruction of the sensory cells in the cochlear and vestibular neuroepithelia. A progressive degeneration of the type I and type II afferent neurons, presenting a decreasing gradient from the base towards the apex of the cochlea, is rapidly observed and becomes almost complete as early as 15 days after the peripheral injury. Five months after the treatment the spiral ganglion cells have almost completely disappeared. At this time the vestibular ganglion cell density appears normal but the neurons exhibit important signs of alteration. Such damage to the cochlear and vestibular afferent neurons may result from either retrograde neuronal degeneration and/or direct neurotoxic effect of the drug. Thus the combination of the two mechanisms could lead to neuronal losses in spiral and Scarpa's ganglia after the local aminoglycoside intoxication of the inner ear. The difference in the time course of degeneration for these two afferent ganglia could be due to their specific susceptibilities or to their different anatomical locations.

Degeneration and reorganization of vestibular epithelia after local aminoglycoside application in the mammalian inner ear.

The development of degeneration of vestibular end organs and their possible reorganization have been observed over a 2 year period after local application of sisomicin in the inner ear using scanning electron microscopy (SEM). Degeneration of stereocilia took place as early as 5 days after the treatment in the utricule, the saccule and the cristae. At 10 days, almost the entire surface of these sensory epithelia presented a smooth aspect without specific structure. However, after 15 days, an epithelial reorganization developed with clear limits between cells. At 25 days, systematic kinociliary structures were observed at the apical surface of the cells. Five months after the treatment, the new kinocilium was still present and sometimes stereociliary-like structures appeared in the three types of vestibular organs. Two years after treatment, the kinocilium persisted and the embryonic-like ciliary tufts had disappeared. These SEM observations suggest that in mammals some vestibular epithelial regeneration is possible but stops at a stage which could correspond to an early developmental level.

Differences in hair bundles associated with type I and type II vestibular hair cells of the guinea pig saccule.

Several studies have reported variations in shape and size of stereociliary bundles and in a limited number of observations have associated them to type I and type II hair cells. A systematic study has been undertaken for which a technique was developed in order to identify both cell types and their corresponding hair bundles. Numerous fissures were obtained in saccular epithelia and observed in scanning electron microscopy. Saccular type I and type II hair cells in the guinea pig were found to have distinctive hair bundles. The tallest stereocilia of almost all type I cells were longer than 6 microns, and were shorter in the striola compared to the periphery. In contrast, the tallest stereocilia of almost all type II cells were shorter than 6 microns and were not found to vary notably in size from the striola to the periphery. Hair bundles with stereocilia organized in straight or in staggered rows were found for both types of cells across the whole saccular epithelium, with no apparent particular distribution. Possible physiological significance of differences in hair bundles is discussed.

Dynamic changes following combined treatment with gentamicin and ethacrynic acid with and without acoustic stimulation. Cellular uptake and functional correlates.

Regional selectivity of gentamicin (GM) ototoxicity was studied in guinea pigs (GPs) using electrophysiological, morphological, autoradiographic and immunohistological observations following combined treatment with GM (150 mg/kg i.m.) and ethacrynic acid (EA) (30 mg/kg i.c. or i.v., 1.5 h after GM injection). The GPs were either continuously stimulated every 5 min with a series of 256 clicks (70 dB peSPL, 10/s) during 3 h for monitoring fast changes in VIII nerve compound action potential (CAP) after the EA injection, and thereafter kept in the animal quarters (background noise of 60 dB SPL) (group I), or similarly monitored for only 10 min after the EA injection and thereafter kept in a soundproof room (around 0 dB SPL) (group II). Whenever GM labelling was observed it was localized only in the sensory hair cells. From 3 h after EA injection, the GPs in group I presented threshold elevations in the high-frequency region, which progressed to 60-80 dB at all frequencies at and after 48 h. Parallel to the threshold pattern, GM uptake in outer hair cells (OHCs) was seen with an increasing concentration from apex toward base from 3 to 24 h, while after 48 h almost all OHCs were destroyed and inner hair cells (IHCs) were marked by GM. In group II no changes in CAP thresholds were observed until more than 24 h, although GM was detected in the hair cells from 6 h on. At this early stage, the distribution of GM lacked a clear pattern, particularly without a clear apex-base gradient, and GM deposits were found only around the basal body. However in both groups, in late stage (greater than 24 h), the base-apex gradient was more pronounced and GM was found throughout the cell body, with a marked concentration below the cuticular plate. These results suggest that GM may penetrate hair cells around the basal body and that activating the cells by sound potentiates both GM uptake and its intracellular toxicity.

[Wake-sleep rhythm and school rhythm]. / Rhythme veille-sommeil et rythme scolaire.

Recent studies, and notably 24 hour polygraphic recordings, have provided accurate data on the qualitative and quantitative changes in the organization of sleep and wake periods which occur during childhood and adolescence. These studies explain the lack of adaptation of some subjects, notably young children and teenagers, to school hours. It is hoped that this knowledge of changes in circadian rhythms will be taken into account by those who decide on working hours in schools.

Atrophy of middle and short stereocilia on outer hair cells of guinea pig cochleas with experimentally induced hydrops.

Scanning electron microscopy was employed to investigate hair cell morphology at different stages in the development of experimentally induced hydrops in the guinea pig. A particular form of morpho-pathology, never before described, was identified as characteristic of hydropic cochleas. The pathology was characteristically identified as atrophy of the short and middle stereocilia on the outer hair cells while the inner hair cell stereocilia did not have such a pathology. The atrophy was restricted to the upper cochlear turns in remarkable correspondence with the low/middle frequency sensitivity loss and was detected only at the end of the period of fluctuating thresholds. These stereocilia perturbations appear therefore to be linked with the threshold fluctuations and represent the first evidence for a clear correlation between hair cell morphology and physiology in the experimental model of endolymphatic hydrops. Such a morphopathology might also be expected to occur in cochleas of Menière's patients but may have been overlooked in the past because of the discrete nature of the pathology.

Experimental and clinical aspects of carbon as a middle ear prosthesis.

The biocompatibility of vitreous carbon and carbon fibre reinforced carbon (CFRC) as middle ear implants was investigated. In separate animal model systems, vitreous carbon was implanted in the middle ear of 20 DA rats for up to 6 months, whilst 3 varieties of CFRC (basic or crude, ultrasonically cleaned, glazed) were implanted in 98 guinea-pig middle ears for up to 4 months. Tissue reactions to implantation were assessed by means of stereoscopic and standard light microscopy, and scanning electron microscopy with chemical analysis facilities (EDAX, WDAX). Vitreous carbon and glazed CFRC were considered suitable for human implantation and a trial of the latter was started in 23 patients (14 partial, 9 total ossicular implants). At 9 months, only 52% of the implants were still in situ; 40% had been extruded and 8% had elicited inflammatory responses which would undoubtedly result in extrusion. Carbon particle dissemination with carbon fibre destruction and exposure as a result of peroperative prosthesis drilling were considered the likely causes for the failure of this implant.

Otoconia and neural junctions of type I hair cells in amikacin-treated guinea pigs presenting saccular acoustic responses.

Using the experimental guinea pig model, in which total and selective destruction of the cochlear receptor revealed saccular acoustic responses, ultrastructural observations were made on otolithic organs using electron microscopy. Scanning electron microscope studies of otoconia from the saccule and utricle of experimental animals did not show any differences with control animals. Quantitative and qualitative observations of sensory neural junctions of Type I cells also did not show any abnormality. These results confirm the extremely selective toxicity of amikacin for the cochlea, and thus strongly suggest that an acoustic reception by the saccule is a normal feature of the guinea pig inner ear.

[Ovarian insufficiency in congenital galactosemia]. / L'insuffisance ovarienne de la galactosémie congénitale.

Primary ovarian failure was observed in 2 sisters aged 17 and 4 years respectively presenting with congenital galactosaemia. The diagnosis of ovarian failure, clinically suggested in the older girl by the absence of puberty, was confirmed in both cases by a massive increase of baseline and post-stimulation plasma gonadotrophins. The elder sister had extremely low plasma oestradiol levels, and her ovaries were reduced to two strips of fibrous stroma almost devoid of follicles. In both cases the other endocrine glands seemed to be normal. Since the younger girl had received a galactose-free diet from birth, exogenous galactose toxicity could be ruled out. It appears from an analysis of the other 5 published reports that a metabolite of endogenous galactose is responsible for the ovarian lesions. The toxic effects of this metabolite may begin during intra-uterine life or after-birth.

Nocturnal sleep organization in infants "at risk" for sudden infant death syndrome.

Nocturnal sleep organization was compared in normal infants and those "at risk" for sudden infant death syndrome (SIDS) (siblings and near-miss infants). Before 12 weeks of age, sleep modifications were observed in "at risk" infants. During their sleep they had a smaller percentage of intervening wakefulness with a higher amount of active sleep. Quiet and active sleep episodes had longer durations resulting in a longer sleep cycle. After 12 weeks, sleep organization tended to normalize. This fact is discussed as a possible factor for a SIDS event: a higher arousal threshold could play a critical role if homeostasy is disturbed during sleep, mainly at an age when the homeostatic control is not fully established.

[Sarcoidosis in a child disclosed by blindness with major hypercalcemia]. / Sarcoïdose de l'enfant révélée par une cécité avec hypercalcémie majeure.

We report here a case of sarcoidosis, observed in a 12 year-old algerian girl. When the child was examined, at an advanced stage of the disease, her clinical condition was very critical, associating blindness, cachexia, hepatic and splenic enlargement, and major hypercalcaemia. Though chest roentgenograms were normal, the results of both functional pulmonary tests and broncho-alveolar lavage were pathologic. The diagnosis of sarcoidosis was confirmed by the finding of an elevated level of Angiotensin-converting enzyme, and by histologic lesions observed in liver, kidney and conjunctiva biopsies. The corticosteroid treatment improved the general condition, but it failed to better the visual state.

Vestibular acoustic reception in the guinea pig: a saccular function?

After complete destruction of cochlear but preservation of vestibular hair cells in the guinea pig acoustically evoked responses can still be recorded from the round window up to the auditory cortex. At all levels these responses differ from those observed in normal animals but their frequency sensitivity and selectivity make them akin to responses from auditory organs. In a series of experiments a complete cochlear destruction was combined with a total or partial destruction of the vestibule. After complete cochlear and vestibular hair cell destruction no acoustic response could be recorded. But in cases of total cochlear and drastic ampullar and utricular destruction together with an almost undamaged saccular sensory epithelium the same peculiar acoustic responses could be observed. These results support the hypothesis of a functional acoustic reception by the saccule in a mammal.

Spiral ganglion changes after massive aminoglycoside treatment in the guinea pig. Counts and ultrastructure.

Morphological changes of the eighth nerve were observed in the guinea pig between 1 month and 1 year after treatment with large doses of the antibiotic amikacin which resulted in complete cochlear hair cell destruction. The neural retrograde degeneration was found to be relatively fast, with a considerable loss (30 to 55%) of ganglion cells one month after treatment, continuously increasing (up to 85) after one year. Gross changes in the habenula perforata and in the spiral ganglion are described, together with ultrastructural alterations of organelles important for the cell metabolism and axonal transport. The rapid degeneration and the morphological findings suggest a direct influence of toxic substances on the ganglion cells.