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PubMed1989

Calcitonin-gene-related-peptide-immunoreactive innervation of the rat head with emphasis on specialized sensory structures.

The distribution of calcitonin-gene-related peptide-like immunoreactivity (CGRP-IR) was studied in sections of decalcified rat head and selected whole-mount preparations in order to address the complex peptidergic innervation patterns in peripheral cephalic specialized zones and to examine neuronal ganglia in situ. Labeled neuron somata in trigeminal, glossopharyngeal, and vagal ganglia comprised a large proportion of small to medium size type B ganglion cells. Parasympathetic ganglia (ciliary, otic, sphenopalatine, submandibular) revealed a small population of labeled somata and numerous perisomatic IR axons, whereas sympathetic ganglion cells (superior cervical) were devoid of label though richly innervated by perisomatic IR axons. The gustatory geniculate ganglion contained only a few labeled neurons and axons. Coarse peripheral CGRP-IR axons were traced to skeletal muscle motor end plates (e.g., lingual, tensor tympani, etc.), and thin sensory axons most densely innervated the cornea, iris, general integument, all mucosal epithelia lining the tympanic, nasal, sinus and oropharyngeal cavities, and the cerebral meninges. Blood vessels, glands, ducts, and their orifices were often heavily innervated, and specific specializations and exceptions are discussed. Distinctive patterns of IR innervation characterized the various specialized sensory systems, including 1) cochlear and vestibular hair cells; 2) lingual, palatal, oropharyngeal, and laryngoepiglottal taste buds; 3) main olfactory epithelium and axons projecting to glomeruli in specific sectors of main olfactory bulb; 4) septal-olfactory organ; 5) vomeronasal organ; and 6) the nervus terminalis system. Secretory epithelia (ciliary body, choroid plexus, and stria vascularis) were notably lacking in CGRP-IR. Despite the multiplicity of functionally distinct CGRP neuronal and axonal populations, certain generalizations merit consideration. The extensive innervation of chemosensory nasal and oral epithelia may contribute to specific chemical sensitivities (e.g., relating to olfactory and gustatory senses) as well as evoking "nociceptive" responses to chemical irritants as part of a "common chemical sense." An efferent role for some of these peptidergic afferent axons may also be inferred from their specific distributions. Sites involved in regulating access to and sensitivity of sense organs to external stimuli (e.g., cochlear and vestibular hair cells, taste bud orifices, and main olfactory epithelium) are heavily innervated. Other IR axons are in position to exert control over airflow through nasal turbinates, glandular secretion, blood circulation, and duct transport systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1995

Premotor neurons for trigeminal motor nucleus neurons innervating the jaw-closing and jaw-opening muscles: differential distribution in the lower brainstem of the rat.

The distribution of premotor neurons for trigeminal motor nucleus neurons innervating the jaw-closing and jaw-opening muscles was examined in the lower brainstem of the rat by using retrograde and anterograde labeling techniques. First, Fluorogold, a fluorescent retrograde tracer, was injected into the dorsolateral or ventromedial division of the trigeminal motor nucleus, each of which contains motoneurons innervating the jaw-closing or jaw-opening muscles, respectively. Second, Phaseolus vulgaris-leucoagglutinin, an anterograde tracer, was injected into each of the lower brainstem sites, where clusters of retrogradely labeled premotor neurons had been seen in the first set of experiments. Third, after injection of the anterograde tracer into a lower brainstem site, followed by injection of the retrograde tracer cholera toxin B subunit into a masticatory muscle, termination of anterogradely labeled axons onto retrogradely labeled motoneurons was confirmed with the aid of a confocal laser-scanning microscope. It was found that the premotor neurons distributed in the mesencephalic trigeminal nucleus, medial part of the parabrachial region, supratrigeminal region, and dorsal parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei project preferentially to the dorsolateral division of the trigeminal motor nucleus, whereas those in the lateral part of the parabrachial region, intermediate parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei, and alpha part of the gigantocellular reticular nucleus project preferentially to the ventromedial division of the trigeminal motor nucleus. The dorsal and lateral parts of the medullary reticular formation and the medullary raphe nuclei contain premotor neurons of both types. Group k motoneurons, a cluster of trigeminal motoneurons that innervate the tensor tympani muscle, receive projection fibers predominantly from the dorsolateral part of the oral pontine reticular formation.

Animals↗
PubMed2002

Ontogenetic and phylogenetic transformations of the ear ossicles in marsupial mammals.

This study is based on the examination of histological sections of specimens of different ages and of adult ossicles from macerated skulls representing a wide range of taxa and aims at addressing several issues concerning the evolution of the ear ossicles in marsupials. Three-dimensional reconstructions of the ear ossicles based on histological series were done for one or more stages of Monodelphis domestica, Caluromys philander, Sminthopsis virginiae, Trichosurus vulpecula, and Macropus rufogriseus. Several common trends were found. Portions of the ossicles that are phylogenetically older develop earlier than portions representing more recent evolutionary inventions (manubrium of the malleus, crus longum of the incus). The onset of endochondral ossification in the taxa in which this was examined followed the sequence; first malleus, then incus, and finally stapes. In M. domestica and C. philander at birth the yet precartilaginous ossicles form a supportive strut between the lower jaw and the braincase. The cartilage of Paauw develops relatively late in comparison with the ear ossicles and in close association to the tendon of the stapedial muscle. A feeble artery traverses the stapedial foramen of the stapes in the youngest stages of M. domestica, C. philander, and Sminthopsis virginiae examined. Presence of a large stapedial foramen is reconstructed in the groundplan of the Didelphidae and of Marsupialia. The stapedial foramen is absent in all adult caenolestids, dasyurids, Myrmecobius, Notoryctes, peramelids, vombatids, and phascolarctids. Pouch young of Perameles sp. and Dasyurus viverrinus show a bicrurate stapes with a sizeable stapedial foramen. Some didelphids examined to date show a double insertion of the Tensor tympani muscle. Some differences exist between M. domestica and C. philander in adult ossicle form, including the relative length of the incudal crus breve and of the stapes. Several differences exist between the malleus of didelphids and that of some phalangeriforms, the latter showing a short neck, absence of the lamina, and a ventrally directed manubrium. Hearing starts in M. domestica at an age in which the external auditory meatus has not yet fully developed, the ossicles are not fully ossified, and the middle ear space is partially filled with loose mesenchyme. The ontogenetic changes in hearing abilities in M. domestica between postnatal days 30 and 40 may be at least partially related to changes in middle ear structures.

Animals↗
PubMed1987

Abnormalities of the ear associated with exencephaly in mouse fetuses induced by maternal exposure to cadmium.

Exencephaly was induced in mouse fetuses by maternal injection of cadmium chloride (CdCl2) on day 7 of gestation. The heads of exencephalic, nonexencephalic experimental, and control fetuses were embedded in paraffin and sections were stained with hematoxylin and eosin. Compared to those of controls, the ears of the exencephalic fetuses were smaller (microtia) and low set. The meatal plug representing the external auditory canal was thick, variously branched, and often directed inferiorly. Usually, there were just two ossicles. The stapedial artery, facial nerve, and stapedius muscle were hypoplastic; the tensor tympani was small or absent. There were 1.0 to 2.0 turns of the cochlea in contrast to 2.5 turns in the controls. The organ of Corti was underdifferentiated; the spiral ganglion had fewer cells. In the control, the long axes of the anterior and posterior semicircular ducts were at right angles to each other and in vertical planes, but in the exencephalics, they tended more laterally towards the horizontal plane. The differentiation of the cristae ampullares and maculae was also severely affected. In several specimens, the entire membranous labyrinth had been distended; these labyrinths also had unusual epithelial infoldings. In cadmium-treated nonexencephalic fetuses, the external ears were normal and appropriate to the body size; five of them were examined histologically; in all, the five middle ear contents were hypoplastic; in three, the cochlea had a maximum of two turns and the organ of Corti, crista ampullaris, and macula were hypoplastic. By an analogy to abnormalities of mutants with neural tube defects, it is suggested that the exencephaly induced by cadmium might affect the differentiation of the ear. Partial involvement of the ear in nonexencephalic experimental embryos may be the result of direct action of cadmium during critical stages of development.

Abnormalities, Drug-Induced↗
PubMed1998

Descriptive anatomy of the human auditory tube.

The aim of this study was to correlate current morphologic data relating to the lumen of the auditory tube. Four methods were used: dissection under the operating microscope; microendoscopy of the tubal lumen; optical and electron microscope histology; and MR or CT imaging. The auditory tube consists of two unequal cones, a small posterior third, fixed and osseous (protympanum), and a mobile fibrocartilaginous anterior two-thirds, both joined by the tubal isthmus, a short constriction which is pseudosphincteric at endoscopy. The tensor veli palatini muscle (TVPM) and the levator veli palatini muscle (LVPM) are the chief muscles that vary the tubal lumen of the fibrocartilaginous portion, which is collapsed at rest. CT and especially MR imaging allows their observation in static conditions. Serial histologic sections reveal the continuity between the TVPM and the tensor tympani muscle. The main cartilage framing the lumen varies in shape according to the level surveyed. The tubal mucosa is lined with an epithelium combining ciliated and mucus cells, involved in mucociliary drainage and gas exchanges in the auditory tube. These morphologic elements represent a basis for study of tubal physiology and for planning treatment in dysfunctions of the auditory tube.

Adolescent↗
PubMed2004

[Function tests for the Eustachian tube. Current knowledge].

The Eustachian tube regulates the homeostasis of the middle ear. Problems with its function are predominantly found in childhood. As a consequence, otitis and hearing impairment occur. The most important muscle is the tensor tympani muscle. The complexity of the functional anatomy and physiology are reasons why no function test alone is capable of fulfilling all diagnostic needs. The predictive value of the various Eustachian tube function tests for the outcome of a tympanoplasty is not yet clear. An overview of clinically and scientifically relevant tests for the Eustachian tube function is provided.

Eustachian Tube↗
PubMed1995

Evidence of a medial olivocochlear involvement in contralateral suppression of otoacoustic emissions in humans.

Otoacoustic emissions (OAEs) evoked by click stimuli were recorded in both ears of 20 normal human subjects, in the presence and absence of a contralateral masking broad band noise. No difference in the amplitude of OAE suppression was noted between the first tested ear and the second one. In addition, 20 pathological subjects were tested according to the same protocol. Ten of them belonged to a group of patients whose vestibular nerve was sectioned on one side to relieve incapacitating vertigo and thus represented a group in whom olivocochlear efferents were severed. A great reduction of suppression observed in the operated ear suggested that olivocochlear efferent fibers are necessary to obtain a full suppressive effect. Three of the pathological subjects were patients who had undergone a decompression of the facial nerve which necessitated the same surgical approach as vestibular neurotomy, but without any section of vestibular fibers. This surgical control group demonstrated that the surgical act by itself cannot explain the difference observed in the neurotomized group. Finally, seven of the pathological subjects were patients with Bell's palsy, which paralyses the facial nerve and abolishes the stapedial reflex. No suppression difference was observed between healthy ears and ears without stapedial reflex. Therefore, it appeared that the stapedial reflex was not involved in the contralateral suppression of EOAEs. However, as the tensor tympani muscle remained functional in these patients, its involvement in the suppressive effect cannot be excluded.

Adult↗
PubMed1987

Asymmetries in the acoustic reflexes of the cat stapedius muscle.

Electromyographic activity (EMG) was used to monitor contractions of the stapedius muscle evoked by both ipsilateral and contralateral sound in ketamine-anesthetized or decerebrate cats. After the onset of a continuing tone, stapedius EMG often had bursts of activity at regular intervals; similar bursts were also observed in the EMG from the tensor tympani muscle. Plots of the r.m.s. amplitude of stapedius-EMG versus sound level usually had a steep rising phase (small dynamic range) and a plateau at high sound levels. For sound stimulation at 1 kHz, the crossed stapedius reflex had a lower maximum amplitude (ave. amplitude ratio: 0.37) and a higher threshold (ave. 8 dB) than the uncrossed reflex. Since the uncrossed reflex evokes considerably more stapedius EMG than does the crossed reflex, it probably produces correspondingly greater changes in middle-ear sound transmission.

Acoustic Stimulation↗
PubMed1992

Cochlear IgG in the C3H/lpr autoimmune strain mouse.

The inner ear of the C3H/lpr autoimmune strain mouse was evaluated to identify potential mechanisms by which systemic autoimmune disease interferes with auditory function. The inner ears were immunohistochemically stained for IgG at ages before (2 months) and after (6-10 months) autoimmune disease onset and compared to age-matched nonautoimmune C3H/HeJ controls. Immunoreactivity for IgG was not seen in the 2 month C3H/lpr autoimmune mice or in either age group of the C3H/HeJ controls. On the other hand, all older C3H/lpr mice showed reaction product in the vessels of the cochlea, particularly the stria vascularis and bony capsule. Less frequent sites of staining were the geniculate ganglion, marrow cavities of the bony capsule, tensor tympani muscle, and on one occasion, a hair cell of the organ of Corti. These findings indicate that IgG is widespread within the cochlea and its vessels during systemic autoimmune disease and not directed against any specific sensorineural structure. This suggests a generalized or indirect mechanism whereby such systemic disease affects the inner ear.

Animals↗
PubMed1993

Inner ear basic fibroblast growth factor in CBA/J, C3H/HeJ, and autoimmune Palmerston north mice.

Basic fibroblast growth factor (bFGF) has a mitogenic effect on fibroblasts and osteoblasts for matrix proliferation and on endothelial cells for neovascularization. Because otic capsule osteogenesis in autoimmune disease subjects often involves abnormal matrix and vascular changes, bFGF may serve as a potential mediator for such bone disorders. To investigate this relationship, bFGF was evaluated in the Palmerston North autoimmune strain mouse, which develops otic capsule sclerotic lesions during the progression of its systemic disease. Inner ears from PN mice, along with control CBA/J and C3H/HeJ mice, were immunohistochemically stained with antibodies against bFGF to identify its presence and possible role in otic capsule disease. Although cells reactive for bFGF were observed along the lining of the otic capsule in all three strains, a significantly higher frequency was observed in the PN mice. Other sites of staining included connective tissue around the tensor tympani muscle and the geniculate ganglion. This identification of bFGF in the otic capsule raises the possibility that it may play some role in normal bone maintenance, as well as abnormal bone or connective tissue remodeling in autoimmune disease.

Animals↗
PubMed1993

Displacement of the gerbil tympanic membrane under static pressure variations measured with a real-time differential moire interferometer.

It is thought that chronic middle ear disease ultimately causes changes in the stiffness and elasticity of the tympanic membrane, but it is unknown whether such changes occur early in the course of the disease. In order to analyze mechanical changes in different parts of the tympanic membrane, a full field moire interferometry technique was utilized to measure the shape and real-time displacement in response to positive and negative pressure gradients applied across the tympanic membrane. The measurements were performed on fresh isolated temporal bones from the Mongolian gerbil. In order to gain sufficient visual access to the pars tensa for the moire measurements, the tympanic bulla was opened, the tensor tympani muscle and the incudo-stapedial joint were cut, and part of the medial wall of the tympanic cavity was removed. The malleus and incus and their ligaments were kept intact. The specimens were kept continuously humidified with an evaporator or in a humid chamber, since otherwise the tympanic membrane dries out in a few minutes when its medial surface is exposed. This desiccation reduces the elasticity and cause shrinkage which results in a reduction of the height of the cone constituted by the pars tensa. Profiles of the tympanic membrane at rest and under different pressure conditions were extracted from the moire interferograms. The tympanic membrane and ossicular complex exhibit a hysteresis effect as differences in the displacement patterns under identical pressure gradients during the loading and the unloading phase; a residual displacement of the pars tensa was for instance seen after the pressure gradient across the tympanic membrane was eliminated.

Animals↗
PubMed1983

Appearance of effusion material in the attic space correlated to an impaired Eustachian tube function.

In adult Sprague-Dawley rats a dysfunction or a total blockade of the Eustachian tube was established by various experimental procedures. The appearance of effusion material in the attic was subsequently considered to be evidence of incomplete ventilation of the middle ear cavity. Though the salpingopharyngeus muscle (SPM) seemed to be the muscle which could open the Eustachian tube maximally, splitting of the soft palate and consequent interference with the tensor veli palatini muscle (TVPM) and the levator veli palatini muscle (LVPM)--but obviously not with the salpingopharyngeus muscle (SPM)--caused the effusion material to be produced in the middle ear cavity. Neither blockade by about 80% of the tympanal orifice nor severing of the tendon of the tensor tympani muscle (TTM) close to the malleus produced any signs of effusion material whatsoever. Our findings strongly suggest that the most important part of the Eustachian tube, as regards ventilation, is the nasopharyngeal portion, as a normally functioning TVPM and LVPM seems to be an absolute prerequisite to prevent effusion material from developing in the attic.

Animals↗
PubMed1999

Malleus-to-footplate prosthetic interposition: experience with 265 patients.

Absence of the long process of the incus with or without absence of the stapes head accounts for more than 80% of ossicular discontinuities. Total or partial replacement prostheses, made of various materials, are interposed to restore the transfer function of the middle ear. To simplify ossicular reconstruction, reduce operative times and costs, improve functional outcomes, and avoid the risk of infections, we have adopted, during the past 10 years, a technique that makes use of a personally designed alloplastic prosthetic device. The prosthesis connects the malleus to the footplate, even in the presence of the stapes superstructure. This malleus-to-footplate prosthesis consists in a plastipore-coated steel piston and hydroxyapatite head, complete with a groove. The groove is placed beneath the malleus neck after dissection of the tensor tympani tendon and the shaft of the piston on the footplate. Two hundred ninety primary ossiculoplasties with the malleus-to-footplate prostheses were performed in 265 patients from 1986 to 1995 in the ENT Department of the University of Verona. The average postoperative air-bone gap at 0.5 to 3 kHz was 11 dB at 1 year and 14 dB at 5 years. These outcomes are significantly better than those personally obtained previously with ossicular or alloplastic prostheses. No extrusions occurred. The structural characteristics of the malleus-to-foot-plate prosthesis endow the prosthesis with a high degree of biocompatibility and stability and optimal sound-transfer function. The rationale for this particular ossiculoplasty procedure is discussed.

Adolescent↗
PubMedDate not supplied

Middle ear sound transmission: a field of early interest to Merle Lawrence.

Merle Lawrence, together with his teacher, E.G. Wever, made early contributions to the problem of middle ear sound transmission. Experiments were mostly done in cats and studied the effects of stepwise destruction of the middle ear on cochlear input and the effects of changes in middle ear air pressure on sound transmission. Their experiments provided the first physiologic evidence that the origin of auditory distortion lies in the inner ear, not in the middle ear. Lawrence also demonstrated a dual innervation of the tensor tympani muscle. With the aid of newer instrumentation, the authors studied the effects of alterations of the middle ear cavity configuration, stepwise removal of the middle ear structures, restriction of ossicular mobility, and ossicular mass loading. Our experiments caused partial decoupling of the tympanic membrane and distortion of the axis ligaments, the apparent weak elements of the middle ear system in cats. The placement of the prosthesis along the mallear handle did not affect sound transmission, as long as the connection between malleus and prosthesis was made inflexible.

Animals↗
PubMed1999

Nature of the tympanic membrane insertion into the tympanic bone of the rat.

The nature of the insertion of the tympanic membrane into the tympanic bone was studied in the rat during the developmental period ranging from 18 days post conception (dpc) to 40 days after birth (dab). Techniques applied were light microscopy, electron microscopy and immunohistochemistry with antibodies to cytoskeletal proteins: vimentin, desmin and alpha-smooth muscle actin (sma) as fibroblast differentiation markers. It was established that the cartilaginous annulus of the pars tensa was connected to the tympanic bone by an interface of specialised connective tissue. Both the fibrocartilage and the interface were derived from the embryonal mesenchyme between the tympanic ring and meatal plate. Electron microscopy showed that the interface was composed of two types of fibroblast. The majority of these cells were myofibroblasts, which were interconnected by junctions and had intimate contact with the collagenous fibres. A small number were identified as genuine fibroblasts. Cytoskeletal characterisation revealed the presence of three types of cell: V cells which expressed vimentin, VA cells which expressed vimentin and alpha-sma and VAD cells which expressed vimentin, alpha-sma and desmin. The myofibroblasts expressed antigens of both smooth muscle cells (alpha-sma, desmin) and connective tissue cells (vimentin). It is suggested that the pars tensa is connected to the tympanic bone by a network of contractile cells and fibres. Contraction will move the membrane in an outward direction and antagonise the inward retraction by the tensor tympani.

Actins↗
PubMed2001

Metastasis of cervical esophageal carcinoma to the temporal bone--a study of the temporal bone histology.

A 49-year-old male developed left abducens nerve palsy as a result of metastatic spread of carcinoma of the cervical esophagus to Rouviere's node and infiltration of the petrous portion of the left temporal bone. Postmortem temporal bone histology revealed that cancer cells had invaded the greater superficial petrosal nerve (GPN), lesser superficial petrosal nerve, tensor tympani muscle (TTM) and the skin covering the anterior wall of the left external auditory meatus. These findings suggest that the carcinoma metastasized from the cervical esophagus to Rouviere's node and directly invaded the middle cranial fossa and then the temporal bone, and further infiltrated the middle ear via perineural invasion.

Carcinoma, Squamous Cell↗
PubMed1989

Pathogenesis of cholesteatoma based on clinical results of anterior tympanotomy.

A new conception of the pathogenesis of cholesteatoma is proposed based on clinical results of anterior tympanotomy, a procedure developed in order to prevent recurrence of cholesteatoma following retraction pocket formation after canal-up operation. In the cholesteatomatous ear, there is always a long, thick bony septum between the epitympanum and the supratubal recess. This septum is called the anterior attic bony plate, forming the tympanic diaphragm together with the tensor tympani mucosal fold. In anterior tympanotomy, this bony plate is removed finishing intact canal wall mastoidectomy, making a new ventilating route to the eustachian tube. With this technique, the rate of recurrence was reduced from 17 to 5%. Based on these results it is proposed that the real pathogenesis of cholesteatoma is not tubal dysfunction, but the osseous tympanic diaphragm.

Cholesteatoma↗
PubMed2001

Accessory oval foramen.

We describe an opening with smooth walls in front and medial to foramen ovale which leads to an oblique canal directed towards the fossa pterygoidea. The canal was up to 2.3 mm long and opened near the root of the pterygoid process. We called this opening "foramen ovale accessorium", and found it in 48 of 124 anatomical specimens. The foramen was present in newborns and in those aged over 80 years old on one side but rarely on both sides of the sphenoid bone. Only in a single specimen were there two foramina side by side in front of the foramen ovale. In another case, the foramen ovale accessorium was present in the anterior wall of the canalis ovalis and pointed to the fossa pterygoidea. The localization and direction of the foramen ovale accessorium led us to the conclusion that it housed some of the separate rootlets for the chewing muscles, in this case for mm pterygoidei, mm tensor veli palatini and tensor tympani. The existence and contents of the foramen ovale accessorium is important in surgical interventions on the trigeminal nerve and/or ganglion Gasseri.

Adult↗