Radiologic evaluation of the mastoid segment of the facial nerve tract in the intact temporal bone.

PURPOSE: To localize the facial nerve course in the mastoid segment and to measure its distances relative to the tympanic membrane. METHODS: This is a cross-sectional descriptive study. During 2019 in a tertiary hospital, 129 non-contrast and non-pathologic temporal CT images were studied in a tertiary hospital. Facial nerve distances were measured from the planes passing through the annulus in the axial cross-sections at superior, umbo, and inferior levels of the tympanic membrane. It was done in two different dimensions which are anteroposterior (toward the plane of the ear canal wall) and mediolateral (toward the plane of the tympanic membrane). RESULTS: The least mean anteroposterior distance between the facial nerve and the posterior ear canal wall was at the level of umbo (3.66 ± 0.76 mm). The nearest point of the nerve toward the tympanic membrane was the inferior level (- 0.03 ± 0.81 mm). Overall external ear canal lengths were statistically significantly lower in women rather than men. There was a reverse correlation between the age and the ear canal length. CONCLUSION: Posterior canalplasty seems to be safe unless dissection does not cross the plane of annulus. In this study, the safe margin was 1.4 mm in posterior canal wall drilling. It also should be performed carefully if it extends to the inferior side of the canal. Measuring the mediolateral dimension of the nerve toward the annulus in the axial CT images seems to be practically beneficial, especially in the inferior where the ear canal wall turns and might not act as a good landmark. Paying attention to this plane may reduce the risks of nerve injury in any procedures with transcanal approaches, particularly in inferior canaloplasty.

The anatomical and radiological evaluation of the Vidian canal on cone-beam computed tomography images.

INTRODUCTION: The aim of this study is to explore the anatomy of the Vidian nerve to elucidate the appropriate surgical approach based on preoperative cone-beam computed tomography (CBCT) images. MATERIALS AND METHODS: The Vidian canal and its surrounding structures were morphometrically evaluated retrospectively in CBCT images of 400 cases by the Planmeca Romexis program. The types of the Vidian canal were determined and seven parameters were measured from the images. RESULTS: Three types of the Vidian canal according to the relationship with the sphenoid bone were found as follows: the Vidian canal totally protruded into the sphenoid sinus (19.75%), partially protruded into sphenoid sinus (44.37%) and embedded inside bony tissue of the body of sphenoid bone (35.87%). The position of the Vidian canal was medial (34.62%), on the same line (55.12%) and lateral (10.25%) to the medial plate of the pterygoid process. The distance between the Vidian canal and the vomerine crest, the mid-sagittal plane, the round foramen, the palatovaginal canal, and the superior wall of the sphenoid sinus, the length of the Vidian canal and the angle between the Vidian canal and the sagittal plane was found to be 16.69 ± 2.14, 13.80 ± 2.00, 8.88 ± 1.60, 5.83 ± 1.37, 23.98 ± 2.68, 13.29 ± 1.71 mm and 25.78° ± 3.68° in males, 14.62 ± 1.66, 11.43 ± 1.28, 8.51 ± 1.63, 5.78 ± 0.57, 22.37 ± 2.07, 12.91 ± 1.26 mm and 23.43° ± 3.07° in females, respectively. CONCLUSIONS: Our results may assist with proper treatment for surgical procedures around the Vidian canal with a high success rate and minimal complications. Therefore, the results obtained in this study contribute to the literature.

Surgical anatomy of facial nerve for revision transmastoid surgery.

We analyze the relationships of the 3 segments of the facial nerve with respect to constant anatomic structures that can be identified during revision surgery via translabyrinthine approach. This study was conducted on 15 formalin-fixed cadavers whose facial nerves were dissected bilaterally under operative microscope via translabyrinthine approach. The distances between the round window niche and the midpoint of the tympanic segment and the beginning of the mastoid segment were 6.64 ± 1.79 mm and 3.99 ± 0.79 mm, respectively. The distances between the tympanic ostium of the eustachian tube and the first and the second genu were 7.02 ± 0.62 mm and 12.25 ± 1.24 mm, respectively. We used the superior semicircular canal, the tympanic ostium of the eustachian tube, and the round window niche as landmarks to identify the facial nerve during revision surgery. Our study also showed that the auricular branch may also be originated from the posterior surface of the facial nerve.

Arnold Nerve Reflex: Vagal Hypersensitivity in Chronic Cough With Various Causes.

BACKGROUND: A higher incidence of Arnold nerve reflex (ANR) has been observed in patients with chronic cough. However, the different ANR response in various causes of chronic cough remains unclear. Furthermore, it is unknown whether ANR will change after effective treatment. METHODS: Patients with chronic cough were enrolled in the Guangzhou Institute of Respiratory Health. The causes of chronic cough were diagnosed via a validated management algorithm. Patients underwent an assessment of ANR response before and after 1 month of etiologic treatment. RESULTS: A total of 127 patients with chronic cough and 55 healthy control subjects were enrolled. The positive response, defined as cough-only ANR or urge-to-cough (UTC), was present in 14.8% of patients with cough variant asthma (CVA), 11.1% of patients with upper airway cough syndrome, 15.4% of patients with gastroesophageal reflex related cough (GERC), 4.8% of patients with eosinophilic bronchitis, and 26.9% of patients with unexplained cough (UC). No ANR or UTC was found in the healthy control subjects. The incidence of the positive response was higher in subjects with CVA, GERC, and UC compared with healthy control subjects (all P < .05). No difference was observed among the different causes of chronic cough (all P > .05). After 1 month of treatment, 87.5% of patients identified with a positive response changed to a negative response. In a subgroup analysis, an increased cough sensitivity to capsaicin was found in the patients with a positive response compared with the patients with a negative response (P < .05). CONCLUSIONS: A positive ANR appears to be a sign of vagal hypersensitivity and can be reversed after effective treatment of chronic cough. However, although various causes of chronic cough share a similar feature of an elevated ANR response in a minority of patients, there appears to be limited usefulness in assessing ANR because it does not appear to be a valid predictor of etiology of chronic cough or outcome of treatment.

Daily auricular stimulation with capsaicin ointment improved cough reflex sensitivity in elderly patients with dysphagia: a pilot study.

Background: In our previous study, a single auricular application of capsaicin ointment, but not placebo improved cough reflex in elderly patients with dysphagia.Aims/Objectives: In the present study, we examined whether daily auricular application of capsaicin ointment continued to improve cough reflex in similar patients.Material and methods: With a cotton swab, 0.025% capsaicin ointment was applied in each external auditory canal alternately once a day for 2 weeks. The cough reflex sensitivity was evaluated on videoendoscopy using a numerical score and inhalation cough challenge test using citric acid in elderly dysphagic inpatients.Results: After daily auricular application of capsaicin ointment for 2 weeks, the endoscopic score of glottal closure and cough reflexes significantly improved, and the citric acid cough threshold significantly decreased. There was a significant correlation between the endoscopic score and the citric acid cough threshold before and after daily capsaicin application in the patients.Conclusions: Daily auricular stimulation with capsaicin ointment for 2 weeks continued to improve the cough reflex sensitivity in elderly patients with dysphagia.Significance: Daily auricular stimulation with capsaicin ointment would be a safe and effective intervention to prevent pneumonia in elderly with a risk of aspiration.

Prevalence of Arnold Nerve Reflex in Adults and Children With Chronic Cough.

BACKGROUND: Cough originates from stimulation of structures innervated by the vagus nerve, including the airways and distal esophagus. Arnold nerve reflex describes the induction of cough by stimulation of the external auditory canal, which is innervated by the auricular branch of the vagus. Historically, the prevalence of this reflex has been reported in the range of 2% to 3% on the basis of studies of outpatients in otolaryngology practices, but has not been investigated in healthy volunteers or in patients with chronic cough. METHODS: Two hundred adults and 100 children with chronic cough, as well as 100 adult and 100 pediatric volunteers, underwent evaluation consisting of stimulation of the external auditory canal of each ear with a cotton-tipped applicator. Cough occurring within 10 seconds of stimulation was considered induced by the intervention. RESULTS: Arnold nerve reflex was present in 25.5% of adults and 3% of children with chronic cough. The prevalence of the reflex was 2% among healthy adults and children. In adults with chronic cough, Arnold nerve reflex was observed more commonly in women (31.6%) than men (12.5%) and was unilateral in the majority of patients (90.2%). CONCLUSIONS: The greater than 12 fold prevalence of Arnold nerve reflex in adults with chronic cough compared with healthy volunteers supports the concept of cough hypersensitivity syndrome (CHS), in which vagal hypersensitivity is proposed to underlie chronic refractory cough. The absence of increased prevalence among children with chronic cough suggests that cough hypersensitivity syndrome is an acquired condition, perhaps triggered by viral respiratory infection or other environmental factor.

Innervation of the Human Cavum Conchae and Auditory Canal: Anatomical Basis for Transcutaneous Auricular Nerve Stimulation.

The innocuous transcutaneous stimulation of nerves supplying the outer ear has been demonstrated to be as effective as the invasive direct stimulation of the vagus nerve for the treatment of some neurological and nonneurological disturbances. Thus, the precise knowledge of external ear innervation is of maximal interest for the design of transcutaneous auricular nerve stimulation devices. We analyzed eleven outer ears, and the innervation was assessed by Masson's trichrome staining, immunohistochemistry, or immunofluorescence (neurofilaments, S100 protein, and myelin-basic protein). In both the cavum conchae and the auditory canal, nerve profiles were identified between the cartilage and the skin and out of the cartilage. The density of nerves and of myelinated nerve fibers was higher out of the cartilage and in the auditory canal with respect to the cavum conchae. Moreover, the nerves were more numerous in the superior and posterior-inferior than in the anterior-inferior segments of the auditory canal. The present study established a precise nerve map of the human cavum conchae and the cartilaginous segment of the auditory canal demonstrating regional differences in the pattern of innervation of the human outer ear. These results may provide additional neuroanatomical basis for the accurate design of auricular transcutaneous nerve stimulation devices.

Effects of a sensory branch to the posterior external ear canal: coughing, pain, Ramsay Hunt's syndrome and Hitselberger's sign.

BACKGROUND: A distinct nerve innervating the external auditory canal can often be identified in close relation to the facial nerve when gradually thinning the posterior canal wall. This nerve has been attributed to coughing during cerumen removal, neuralgic pain, Hitselberger's sign and vesicular eruptions described in Ramsay Hunt's syndrome. This study aimed to demonstrate the origin and clinical impact of this nerve. METHODS AND RESULTS: In patients with intractable otalgia or severe coughing whilst inserting a hearing aid, who responded temporarily to local anaesthesia, the symptoms could be resolved by sectioning a sensory branch to the posterior canal. In a temporal bone specimen, it was revealed that this nerve is predominantly a continuation of Arnold's nerve, also receiving fibres from the glossopharyngeal nerve and facial nerve. Histologically, the communicating branch from the facial nerve was confirmed. CONCLUSION: Surgeons should be aware of the posterior auricular sensory branch and its clinical implications.

Effects of laserneedle stimulation in the external auditory meatus on brainstem and very early auditory evoked potentials in humans.

OBJECTIVES: For the first time, brainstem auditory evoked potentials (BAEP) and very early auditory evoked potentials (EAEP) were investigated in 23 volunteers (mean age: 26.5 +/- 3.6 years) under resting conditions and during continuous and frequency modulated (2 Hz) laser stimulation in the external auditory meatus. METHODS: Using a new ear adapter, the outer region of the auditory canal was stimulated with laser light (685 nm, 4 x 30-40 mW, duration: 10 minutes). RESULTS: The EAEPs were significantly changed during continuous (p=0.019), as well as frequency modulated (p=0.014) laser stimulation compared with control measurements. DISCUSSION: Physiologic alterations of inner ear mechanism such as extra-cerebral changes in conductance or stimulation-dependent depolarization processes in extra-cerebral regions of the auditory system could be possible explanations for the significant difference in measurement parameters.

Internal auditory canal stenosis in congenital sensorineural hearing loss.

OBJECTIVE: Sensorineural hearing loss (SNHL) due to internal auditory canal (IAC) stenosis with hypoplasia of the cochleovestibular nerve is a rare disorder. The diagnosis of the IAC stenosis requires both high resolution computed tomography scan (HRCT) and magnetic resonance imaging (MRI). METHODS: A retrospective review over 6 years in an academic tertiary referral center was performed. RESULTS: Six patients with congenital SNHL were diagnosed with congenital IAC stenosis. Four had unilateral and two had bilateral IAC stenosis after imaging. MRI showed hypoplastic vestibulocochlear nerve in all cases. CONCLUSIONS: This paper highlights the importance of imaging in diagnosing IAC stenosis and detecting the presence of cochleovestibular nerve in cases of congenital SNHL.

Isolated Deep Ear Canal Pain: Possible Role of Auricular Branch of Vagus Nerve-Case Illustrations with Cadaveric Correlation.

Glossopharyngeal, nervus intermedius, and vagus neuralgias can all present with ear pain. However, to our knowledge, there have been no reports of otalgia as the only symptom of vagus neuralgia. The seventh, ninth, and tenth cranial nerves have many interneural connections, and the exact anatomy and pathophysiology of these neuralgias are often not clear. Moreover, symptoms due to involvement of any of these nerves can be difficult to attribute solely to 1 of them. The overlapping sensory innervation of the external auditory canal can lead to misdiagnosis in patients suffering from otalgia. This report presents a case of pure otalgia due to vascular compression of the vagus nerve (VN) and considers the microanatomic differences between glossopharyngeal and nervus intermedius neuralgia via cadaveric dissections. We report 2 cases of external auditory canal pain that continued following microvascular treatment of trigeminal neuralgia. Intraoperatively and at secondary operation, the posterior inferior cerebellar artery was found to be adherent and to penetrate between the fibers of the VN. Following microvascular treatment of the VN, the pain resolved. CONCLUSION: This is the first report of vagus neuralgia presenting solely with ear pain. Surgeons should be aware that primary external auditory canal pain can be due to vagus neuralgia via its auricular branch and that such patients can be misdiagnosed with glossopharyngeal or nervus intermedius neuralgias.

A new evaluation of heat distribution on facial skin surface by infrared thermography.

OBJECTIVE: The aim of this study was to identify the facial areas defined by thermal gradient, in individuals compatible with the pattern of normality, and to quantify and describe them anatomically. METHODS: The sample consisted of 161 volunteers, of both genders, aged between 26 and 84 years (63 ± 15 years). RESULTS: The results demonstrated that the thermal gradient areas suggested for the study were present in at least 95% of the thermograms evaluated and that there is significant difference in temperature between the genders, racial group and variables "odontalgia", "dental prothesis" and "history of migraine" (p < 0.05). Moreover, there was no statistically significant difference in the absolute temperatures between ages, and right and left sides of the face, in individuals compatible with the pattern of normality (ΔT = 0.11°C). CONCLUSIONS: The authors concluded that according to the suggested areas of thermal gradients, these were present in at least 95% of all the thermograms evaluated, and the areas of high intensity found in the face were medial palpebral commissure, labial commissure, temporal, supratrochlear and external acoustic meatus, whereas the points of low intensity were inferior labial, lateral palpebral commissure and nasolabial.

Tympanomastoid suture and digastric muscle in cadaver and live parotidectomy.

OBJECTIVES/HYPOTHESIS: To prove that the tympanomastoid suture (TMS) is a significantly closer and less variable anatomic landmark to the facial nerve than the posterior-superior margin of the posterior belly of the digastric muscle (PBD) in parotid surgery. MATERIALS AND METHODS: A prospective study of 14 cadaver specimens and 22 live patients comparing the closest measured distances between the TMS and PBD to the facial nerve. RESULTS: The mean closest distances from the TMS and PBD to the facial nerve were 1.8 (range 0-4) mm and 12.4 (range 7-17) mm, respectively (P < .05) for cadavers. The mean closest distances in live patients from the TMS and PBD to the facial nerve were 2.0 (range 0-4) mm and 10.7 (range 5-14) mm, respectively (P < .05). CONCLUSIONS: Facial nerve identification and preservation is the key to successful parotid surgery. The TMS is a significantly closer and less variable anatomic landmark compared with the PBD both in cadaver dissection and in live patients.

Growth of distortion product otoacoustic emissions with primary-tone level in humans.

This study addressed the hypotheses that the growth of the level of distortion product otoacoustic emissions (LDP) with primary-tone level reflects the behavior of a third-order nonlinear polynomial system, and that two sources exist for these distortion products. The results indicated that the 2f1-f2 otoacoustic emission in humans can be measured over a much larger stimulus range than reported previously, even for stimuli (L1 = L2) as low as 10 dB SPL (re 20 microPa). The input/output functions are best described as a straight line with a rate of growth of about 1 dB/dB of stimulus level. For stimulus levels at which metabolically active, nonlinear cochlear processes are in operation, the system does not behave as a simple third-order nonlinear polynomial. Small plateaus and sharp discontinuities or 'notches' can occur in the functions at stimulus levels of approximately 55 dB SPL. These characteristics are consistent with the notion of two separate sources of the LDP, one at low stimulus levels, and one at high levels. An alternative explanation is that the measured otoacoustic emission does not represent only the activity at a single location along the basilar membrane but includes the effects of interactions among similar signals arising from multiple locations, or from the original source via multiple paths.

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.

Facial nerve near the external auditory meatus in man: computer reconstruction study--preliminary report.

The anatomy of the facial nerve relative to its intratemporal and extratemporal courses varies over time with developmental changes. Otologic and parotid surgery in infants and children demands detailed knowledge of the precise anatomy of the facial nerve with respect to the tympanic ring and external auditory canal. The authors analyzed this area using our three-dimensional (3-D) computer-aided reconstruction and measurement method studying the spatial relations of the facial nerve to the tympanic ring and stylomastoid foramen. Temporal bones from five normal individuals aged 36 gestational weeks, 3 months, 8 months, 4 years, and 17 years were retrieved from the temporal bone collection stored at the Elizabeth McCullough Knowles Otopathology Laboratory in Pittsburgh. Three-dimensional reconstruction of the facial nerve comparing the developmental anatomy across the various age groups provides the surgeon with the technical information necessary to address problems in this area.

Arnold's nerve reflex among pollinosis patients: sign of predictable asthma?

Examination of the external auditory canals in a group of 53 asymptomatic (before the season) grass pollen-sensitive patients was performed by means of fiberoptic otoscope. The mechanical irritation of the walls of the auditory canals resulted in a cough reflex in 11 patients. An analysis of the lack or presence of any bronchial symptoms, during or out of season, in the whole group was performed. It was concluded that otorespiratory (or otocough) reflex may be a predictive measure for bronchial symptoms among pollinosis patients. In this aspect, the sensitivity of the test was 50 percent, but its specificity was 92 percent.

Surgical anatomy of the rat middle ear.

This study was designed to aid experimental otologic studies of the rat middle ear. The topographic anatomy of the albino rat middle ear is described. A set of microphotographs with matching illustrations presents the structural details at several surgical exposures. Anatomic differences between the rat, guinea pig, and cat are noted.

The temporal branch of the facial nerve: how reliably can we predict its path?

A thorough examination of the temporal branch of the facial nerve was performed to characterize precisely the number of rami crossing the zygomatic arch and their location with respect to bone and soft-tissue landmarks. Fresh cadaver dissection was performed in 12 facial halves, dissecting the facial nerve superiorly from the stylomastoid foramen to identify all branches crossing the zygomatic arch. There were a median of three (range two to four) rami of the temporal branch crossing the lower aspect of the zygomatic arch, with distinct anterior and posterior divisions identified in each dissection. In 8 of the 12 dissections, one or more separate middle divisions of the nerve also were seen at the inferior aspect of the zygomatic arch. Superior to the zygomatic arch, frequent interconnections were noted between all divisions of the temporal branch, but no connections were noted to other branches of the facial nerve. Previous descriptions of the course of the temporal branch based on soft-tissue landmarks most closely correlated with nerve rami that were found in the present study to be located within the anterior division of the nerve. On crossing the inferior aspect of the zygomatic arch, the anterior and middle divisions of the temporal branch were located a median of 12 and 4 mm anterior to the articular eminence, respectively; the posterior division ranged in location from 10 mm posterior to 7 mm anterior to the articular eminence. The range over which rami of the temporal branch crossed the inferior aspect of the zygomatic arch was equally divided anterior and posterior to the articular eminence and covered up to 50 percent of the total length of the zygomatic arch. The present study confirms that the temporal branch is not a single nerve branch but consists of multiple rami that cross the zygomatic arch anywhere for over half the length of its inferior border. Techniques for localizing the nerve based on reference points from two soft-tissue landmarks are therefore unreliable.