Anatomic features of the fetal round and oval windows, and their relations with the tympanic nerve.

OBJECTIVE: The study aimed to examine morphometric properties of the round window (RW) and oval window (OW) and to show their relation with the tympanic nerve (the Jacobson's nerve, JN) in human fetuses from the otologic surgeon's perspective. METHODS: Thirty temporal bones of 15 fetal cadavers (8 males, 7 females) aged with 24.40 ± 3.71 weeks were included in the study. The height, width and surface area of the RW and OW and also distance from the JN to the OW and RW were measured. RESULTS: The height, width and surface area of the RW in this work were measured as 1.48 ± 0.25 mm, 1.57 ± 0.37 mm, and 2.05 ± 0.69 mm2, respectively. The RW was detected as round-shaped (8 cases, 26.7%), oval-shaped (15 cases, 50%), and dome-shaped (7 cases, 23.3%). The height, width and surface area of the OW were measured as 1.42 ± 0.26 mm, 2.90 ± 0.44 mm, and 3.63 ± 0.74 mm2, respectively. The OW was observed as oval-shaped (15 cases, 50%), kidney-shaped (10 cases, 33.3%), D-shaped (4 cases, 13.3%), and trapezoid-shaped (1 case, 3.3%). The JN was found 1.21 ± 0.60 and 1.18 ± 0.54 mm away from the RW and OW, respectively. CONCLUSION: This study containing morphological data about the shapes, diameters and area of the RW and OW may be useful to predict surgical difficulty, and to select implants of suitable size preoperatively for the windows. Knowing the relationship between the JN and the windows can be helpful to avoid iatrogenic injuries of the nerve.

Tympanic-mastoid and parotid schwannomas of the facial nerve: clinical presentation related to the anatomic site of origin.

Objective: To describe the clinical presentation of the facial nerve schwannomas according to the anatomical site of origin. Method: A retrospective study in which the clinical presentation, diagnostic protocol and treatment of facial nerve tumors in adults was evaluated. Results: We found 6 cases, 4 cases of tympanic-mastoid location at the spectrum of its possible clinical presentation: from symptomatic cases with facial paralysis, to an asymptomatic case in the tympanic portion found as intraoperative finding; and also found two cases located at the parotid gland, one with complete facial paralysis and one without facial palsy. Conclusions: For the diagnosis of intratemporal and parotid schwannomas of the facial nerve, a high clinical suspicion is required given its heterogeneous presentation; its clinical course depends on the segment of origin and expansion: more frequently asymptomatic at the tympanic horizontal portion and symptomatic at the mastoid vertical portion. These tumors must be assessed with imaging studies, incisional biopsy is not recommended. The treatment is surgical resection in symptomatic patients with facial paralysis greater than grade III of House-Brackmann, with immediate reconstruction of the nerve.

Objetivo: Describir la presentación clínica de los schwannomas del nervio facial de acuerdo con el sitio anatómico de origen. Método: Se realizó un estudio retrospectivo en el que se evaluó la presentación clínica, el protocolo diagnóstico y el tratamiento de tumores del nervio facial en adultos. Resultados: Se encontraron seis casos, cuatro de ellos de localización tímpano-mastoidea en los extremos de su posible presentación clínica: desde casos sintomáticos con parálisis facial, hasta un caso asintomático de la porción timpánica encontrado como hallazgo transoperatorio; y se encontraron dos casos de localización parotídea, uno con parálisis facial completa y otro sin parálisis facial. Conclusiones: Para el diagnóstico de tumores intratemporales y parotídeos del nervio facial se requiere una elevada sospecha clínica dado lo heterogéneo de su presentación; su curso clínico depende del segmento de origen y de su extensión: más frecuentemente son asintomáticos los de la porción timpánica y son sintomáticos los de la porción mastoidea. Estos tumores deben evaluarse con estudios de imagen; no se recomienda realizar biopsia incisional. El tratamiento es la resección quirúrgica en los casos sintomáticos con parálisis facial de grado IV o mayor de House-Brackmann, con reconstrucción inmediata del nervio.

Chronic Conductive Hearing Loss Leads to Cochlear Degeneration.

Synapses between cochlear nerve terminals and hair cells are the most vulnerable elements in the inner ear in both noise-induced and age-related hearing loss, and this neuropathy is exacerbated in the absence of efferent feedback from the olivocochlear bundle. If age-related loss is dominated by a lifetime of exposure to environmental sounds, reduction of acoustic drive to the inner ear might improve cochlear preservation throughout life. To test this, we removed the tympanic membrane unilaterally in one group of young adult mice, removed the olivocochlear bundle in another group and compared their cochlear function and innervation to age-matched controls one year later. Results showed that tympanic membrane removal, and the associated threshold elevation, was counterproductive: cochlear efferent innervation was dramatically reduced, especially the lateral olivocochlear terminals to the inner hair cell area, and there was a corresponding reduction in the number of cochlear nerve synapses. This loss led to a decrease in the amplitude of the suprathreshold cochlear neural responses. Similar results were seen in two cases with conductive hearing loss due to chronic otitis media. Outer hair cell death was increased only in ears lacking medial olivocochlear innervation following olivocochlear bundle cuts. Results suggest the novel ideas that 1) the olivocochlear efferent pathway has a dramatic use-dependent plasticity even in the adult ear and 2) a component of the lingering auditory processing disorder seen in humans after persistent middle-ear infections is cochlear in origin.

The paratympanic organ: a barometer and altimeter in the middle ear of birds?

A century has passed since the discovery of the paratympanic organ (PTO), a mechanoreceptive sense organ in the middle ear of birds and other tetrapods. This luminal organ contains a sensory epithelium with typical mechanosensory hair cells and may function as a barometer and altimeter. The organ is arguably the most neglected sense organ in living tetrapods. The PTO is believed to be homologous to a lateral line sense organ, the spiracular sense organ of nonteleostean fishes. Our review summarizes the current state of knowledge of the PTO and draws attention to the astounding lack of information about the unique and largely unexplored sensory modality of barometric perception.

Cortical representation of tympanic membrane movements due to pressure variation: an fMRI study.

Middle ear sensory information has never been localized in the homunculus of the somatosensory cortex (S1). We investigated the somatosensory representation of the middle ear in 15 normal hearing subjects. We applied small air pressure variations to the tympanic membrane while performing a 3T-fMRI study. Unilateral stimulations of the right ear triggered bilateral activations in the caudal part of the postcentral gyrus in Brodmann area 43 (BA 43) and in the auditory associative areas 42 (BA 42) and 22 (BA 22). BA 43 has been found to be involved in activities accompanying oral intake and could be more largely involved in pressure activities in the oropharynx area. The tympanic membrane is indirectly related to the pharynx area through the action of tensor tympani, which is a Eustachian tube muscle. The Eustachian tube muscles have a role in pressure equalization in the middle ear and also have a role in the pharyngeal phase of swallowing. Activation of BA 42 and BA 22 could reflect activations associated with the bilateral acoustic reflex triggered prior to self-vocalization to adjust air pressure in the oropharynx during speech. We propose that BA 43, 42, and 22 are the cortical areas associated with middle ear function. We did not find representation of tympanic membrane movements due to pressure in S1, but its representation in the postcentral gyrus in BA 43 seems to suggest that at least part of this area conveys pure somatosensory information.

Neural control of eustachian tube function.

OBJECTIVES/HYPOTHESIS: It has been hypothesized that middle ear pressure can be controlled by the Eustachian tube through a neuronal reflex arc in animal models. We aimed to define the role of the neuronal control mechanisms in regulating middle ear pressure in humans. STUDY DESIGN: Prospective study. METHODS: The study population consisted of 95 ears of 95 volunteers. The mechanoreceptors on the tympanic membrane and the baroreceptors in the middle ear, which are assumed to form the afferent plexus of the neuronal reflex arc, were blocked by topical administration of lidocaine hydrochloride, in various patient groups. The Eustachian tube functions forming the efferent plexus of the neuronal reflex arc were evaluated by manometric tests both before and after blocking the possible afferent plexus in each study group. RESULTS: The baroreceptors established in the tympanic plexus might possibly have an effective role in this mechanism where the mechanoreceptors on the tympanic membrane seem to have a minor effect. CONCLUSIONS: Neuronal control mechanism could play an important role in regulating Eustachian tube function in humans. Laryngoscope, 2009.

Vascular findings in the facial nerve canal in human temporal bones with diabetes mellitus.

OBJECTIVE: To identify pathological changes to vessels in the facial nerve canal among patients with diabetes mellitus. DESIGN: Histopathologic human temporal bone study. SUBJECT: This study examined 26 temporal bones from 13 patients with type 1 diabetes mellitus and 40 temporal bones from 20 patients with type 2 diabetes mellitus. Temporal bones from patients with type 2 diabetes mellitus were divided into 2 groups according to the method of diabetes management: insulin (n = 11) and oral hypoglycemic agents (n = 9). For the control groups, 16 age-matched normal temporal bones from 11 subjects were recruited for type 1 diabetes mellitus and 11 age-matched normal temporal bones from 8 subjects were recruited for type 2 diabetes mellitus. MAIN OUTCOME MEASURES: Thicknesses of vessel walls in the labyrinthine, tympanic, and mastoid portions of the facial nerve canal were examined under light microscopy. RESULTS: Vessel walls for all portions of the facial nerve canal were significantly thicker in diabetic patients than in normal controls for both types 1 and 2 diabetes. In type 2 diabetic patients, vessel wall thickness was significantly greater in patients treated with insulin therapy than in patients treated via oral hypoglycemic agents. CONCLUSION: The facial nerve in patients with diabetes mellitus is ischemic compared with normal controls. These findings suggest a histologic basis for the high incidence and difficulty in achieving improvement of facial nerve palsy in patients with diabetes mellitus.

The tympanic segment of the facial nerve: anatomical study.

There is a conroversy in the literature about the length of the proximal tympanic segment of the facial nerve (PTSFN). The objective of the current study is to measure the length of the tympanic segment of the facial nerve (TSFN) and of its proximal (PTSFN) and distal (DTSFN) segments, in normal human temporal bones. Moreover, we will explore if these lengths are correlated. If a form of a functional relationship can be established, it could offer insights in partially predicting or estimating the length of the TSFN as well as of its proximal and distal portions. Direct measurements were obtained in 40 normal human temporal bones, which were examined by surgical dissection. Relationships between these measurements were established using Pearson's correlation method (two-tailed). The length of the TSFN was on average 10.97 mm. The length of the PTSFN was on average 5.25 mm and of the DTSFN was 5.72 mm. No significant statistical differences according to gender or side (right or left) were detected. It was determined that the length of the TSFN was in linear correlation with positive direction with its proximal (PTSFN) and distal (DTSFN) segments. Also the PTSFN length was in linear correlation with positive direction with the DTSFN length. The length of the PTSFN comprises about one-half of the TSFN length. The existence of a definite correlation between the lengths of the TSFN, PTSFN, and DTSFN implies the existence of a form of functional interrelationship. This could facilitate prediction and identification of the TSFN and PTSFN lengths from the easily identifiable DTSFN length during surgery.

Cognition is cool: Can hemispheric activation be assessed by tympanic membrane thermometry?

Hemispheric activation during cognitive tasks using functional magnetic resonance imaging (fMRI) can be difficult to interpret, uncomfortable, and is not widely available. This study investigated whether tympanic membrane thermometry could be used as a broad measure of hemispheric activation. Infrared probes measured ear temperature continuously while subjects performed left or right hemisphere tasks. Temperature decreased in the left ear as activation increased in the left hemisphere during a verbal task, and in the right ear during a visuo-spatial task. When compared to a baseline, ear temperature measurements appeared to reflect relative changes in activation of the left and right hemispheres. Tympanic membrane thermometry therefore may be used as a broad marker of hemispheric activation. Its ability to demonstrate relative involvement of the two hemispheres during cognitive processes makes it especially useful in studies of hemispheric interaction. Its low cost, rapid set-up, and non-invasive nature also make it particularly attractive.

A microdissection study of the facial nerve at the labyrinthine and tympanic segments in adults.

OBJECTIVES: To determine the relationship in detail between the tympanic and the labyrinthine segments of the facial nerve and the relationship between the bony structures and the neighboring nerve. MATERIALS AND METHODS: Measurement of the length of the segment of the facial nerve within the internal auditory canal and the lengths of the labyrinthine and tympanic segments were made on fourteen temporal bones collected from eight fresh cadavers. RESULTS: The minimum distance between the point where the facial nerve leaves the internal auditory canal and the tympanic segment was measured as 4.71+/-0.54 mm. The angle between the labyrinthine and the tympanic segments at the geniculate ganglion was measured as 73 degrees 85' +/-10 degrees 89'. The angle between the labyrinthine and the superior vestibular nerve were measured as 34 degrees 35' +/-5 degrees 51'. CONCLUSION: We believe that the results of our measurements will help the surgeons to minimize the complications who work in this particular anatomic area.

Long-term results of tympanic neurectomy for chronic parotid sialectasis.

BACKGROUND: Chronic parotid sialectasis presents as troublesome recurrent swellings of the parotid salivary gland during swallowing and mastication. The main treatment options are parotidectomy with its associated high morbidity and tympanic neurectomy. AIM: The aim of this study is to present the long-term results of our experience about tympanic neurectomy for chronic parotid sialectasis. PATIENTS AND METHODS: Twenty two patients underwent tympanic neurectomy (14 males; 8 females) between 1983 and 1999 with an mean follow up of over six years. The hallmark of our surgery is to interrupt as many branches of the tympanic nerve as possible by extensively drilling in the hypotympanum and below the basal turn of cochlea, with removal of the anterior and posterior branches. RESULTS: 17 of the 22 patients had a marked to total reduction in symptoms on follow-up. Four patients were troubled enough to go on to undergo a superficial parotidectomy. There was no significant morbidity associated with the procedure. CONCLUSION: Tympanic neurectomy performed by an experienced otologist should be the preferred surgical option for chronic parotid sialectasis, with parotidectomy being reserved for those patients who fail to improve.

Somatic (craniocervical) tinnitus and the dorsal cochlear nucleus hypothesis.

PURPOSE: Of all nonauditory sensory systems, only the somatosensory system seems to be related to tinnitus (eg, temporomandibular joint syndrome and whiplash). The purpose of this study is to describe the distinguishing characteristics of tinnitus associated with somatic events and to use these characteristics to develop a neurological model of somatic tinnitus. MATERIALS AND METHODS: Case series. RESULTS: Some patients with tinnitus, but no other hearing complaints, share several clinical features including (1) an associated somatic disorder of the head or upper neck, (2) localization of the tinnitus to the ear ipsilateral to the somatic disorder, (3) no vestibular complaints, and (4) no abnormalities on neurological examination. Pure tone and speech audiometry of the 2 ears is always symmetric and usually within normal limits. Based on these clinical features, it is proposed that somatic (craniocervical) tinnitus, like otic tinnitus, is caused by disinhibition of the ipsilateral dorsal cochlear nucleus. Nerve fibers whose cell bodies lie in the ipsilateral medullary somatosensory nuclei mediate this effect. These neurons receive inputs from nearby spinal trigeminal tract, fasciculus cuneatus, and facial, vagal, and glossopharyngeal nerve fibers innervating the middle and external ear. CONCLUSIONS: Somatic (craniocervical) modulation of the dorsal cochlear nucleus may account for many previously poorly understood aspects of tinnitus and suggests novel tinnitus treatments.

Gustatory otalgia and wet ear syndrome: a possible cross-innervation after ear surgery.

HYPOTHESIS: The chorda tympani and Arnold's nerves have close approximation to each other and their cross-innervation is possible after ear surgery. STUDY DESIGN: A retrospective study was performed with a temporal bone pathology case and two clinical cases as representatives of such a possibility. Patients had severe otalgia and wet ear during gustatory stimulation. METHODS: A temporal bone pathology case was studied under a light microscope. Earache and/or wet ear were provoked during gustatory stimulation. Wet ear was tested with iodine-starch reaction after the subject tasted lemon juice. RESULTS: The temporal bone specimen has clusters of regenerated fibers in the tympanic cavity in the area of the chorda tympani and Arnold's nerves, suggesting a possibility of mixing. There are regenerated fibers in the iter chordae anterius, showing successful bridging of the chorda tympani nerves across a long gap. Detachment of the skin over the operated mastoid bowl obscured signs in one clinical case. Another clinical case of gustatory wet ear showed objective evidence of cross-innervation with iodine-starch reaction. CONCLUSION: The detachment procedure and iodine-starch reaction were the proofs that the signs were related to regenerated fibers. This is the first report of gustatory otalgia and wet ear after ear surgery.

Head-related transfer functions of the barn owl: measurement and neural responses.

Sounds arriving at the eardrum are filtered by the external ear and associated structures in a frequency and direction specific manner. When convolved with the appropriate filters and presented to human listeners through headphones, broadband noises can be precisely localized to the corresponding position outside of the head (reviewed in Blauert, 1997). Such a 'virtual auditory space' can be a potentially powerful tool for neurophysiological and behavioral work in other species as well. We are developing a virtual auditory space for the barn owl, Tyto alba, a highly successful auditory predator that has become a well-established model for hearing research. We recorded catalogues of head-related transfer functions (HRTFs) from the frontal hemisphere of 12 barn owls and compared virtual and free sound fields acoustically and by their evoked neuronal responses. The inner ca. 1 cm of the ear canal was found to contribute little to the directionality of the HRTFs. HRTFs were recorded by inserting probetube microphones to within about 1 or 2 mm of the eardrum. We recorded HRTFs at frequencies between 2 and 11 kHz, which includes the frequencies most useful to the owl for sound localization (3-9 kHz; Konishi, 1973). Spectra of virtual sounds were within +/- 1 dB of amplitude and +/- 10 degrees of phase of the spectra of free field sounds measured near to the eardrum. The spatial pattern of responses obtained from neurons in the inferior colliculus were almost indistinguishable in response to virtual and to free field stimulation.

Overlay versus underlay tympanoplasty. Part I: historical review of the literature.

The history of otology is the history of the successful treatment of infections of the middle ear and the eardrum. Otologists have sought to restore hearing lost to infections of the eardrum since the 1600s. The development of instruments, techniques, and materials to treat infection is fascinating because of the serendipitous nature of the discoveries and the insight of the discoverers. This historical review describes the history of the treatment of infections of the ear and the development of modern techniques of ear surgery. Two contemporary methods of tympanic membrane repair are then described.

Anatomy and orientation of the human external ear.

A knowledge of the external ear and tympanic membrane is essential to practicing audiologists. This article provides an introduction to the anatomy of this area including dimensions, orientation, vasculature, innervation, and relations to other structures. Traditional diagrams are often inadequate in describing these structures. For example, typical frontal and sagittal views of the external auditory meatus do not adequately describe its anteroposterior course. Axial (transverse) views provide easier visualization of these areas. A nomenclature is also provided for areas and angles of the external auditory meatus.

Structure and function of the tympanic membrane: a review.

Advances made in the last three decades of research on morphological, cell biological, and immunobiological aspects of the tympanic membrane of laboratory animals and humans are reviewed. The tympanic membrane is composed of the pars flaccida and pars tensa with considerable variations in their size and thickness. Both pars flaccida and pars tensa consist of an epidermal layer, a lamina propria, and a mucosal epithelial layer. The fibrils of the fibrous layer contain a large amount of type II and type III collagen, and a small amount of type I collagen. It has been suggested that such an unusual collagen composition is the underlying reason for the unique physical feature of the pars tensa of the tympanic membrane. A large number of mast cells are found in the Shrapnell's membrane and these cells are suggested to be responsible for the production of middle ear effusion. The cellular basis for the epidermal migration and the role of epidermal and fibroblast growth factors in epidermal cell proliferation and in wound healing are also reviewed. Future research directions on tympanic membrane biology and pathobiology are discussed.