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.

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.

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.

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.

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.

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.

Origin, course and distribution of the nerves to the posterosuperior wall of the external acoustic meatus.

Patients with Ramsay Hunt syndrome have various clinical symptoms including vesicular rash of the external acoustic meatus and auricle. In addition to facial nerve paresis, neurological disturbances of various cranial nerves such as the acoustic nerve, glossopharyngeal nerve and vagus nerve are reported in patients of Ramsay Hunt syndrome. To understand the reasons for the clinical symptoms, we observed the nerve branches of the auricle and external acoustic meatus. We used 18 halves of 11 Japanese cadavers. All cadavers were fixed in 8% formalin and preserved in 30% ethanol. Dissection was performed under a stereomicroscope and the communication among the nerve branches was analyzed. Posterosuperior wall of the acoustic meatus was innervated by nerve branches that emerged from the tympanomastoid fissure in 17 specimens (17/18). These branches always crossed the facial canal and had more than one communicating branch with the facial nerve inside the canal (17/17) or in the petrous bone (1/17). These branches originated from the superior ganglion of the vagus. In the origin from the vagus nerve, some of these branches communicated with the glossopharyngeal nerve (3/17). In addition to these branches, the facial nerve, after originating from the stylomastoid foramen, bifurcated into two nerve branches in some specimens (7/17). Nerve branches around the external acoustic meatus and the auricle have various communications before reaching the central nervous system. The variety of communications could explain the varied symptoms of Ramsay Hunt syndrome.

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.

CNS BOLD fMRI effects of sham-controlled transcutaneous electrical nerve stimulation in the left outer auditory canal - a pilot study.

BACKGROUND: It has recently been shown that electrical stimulation of sensory afferents within the outer auditory canal may facilitate a transcutaneous form of central nervous system stimulation. Functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) effects in limbic and temporal structures have been detected in two independent studies. In the present study, we investigated BOLD fMRI effects in response to transcutaneous electrical stimulation of two different zones in the left outer auditory canal. It is hypothesized that different central nervous system (CNS) activation patterns might help to localize and specifically stimulate auricular cutaneous vagal afferents. METHODOLOGY: 16 healthy subjects aged between 20 and 37 years were divided into two groups. 8 subjects were stimulated in the anterior wall, the other 8 persons received transcutaneous vagus nervous stimulation (tVNS) at the posterior side of their left outer auditory canal. For sham control, both groups were also stimulated in an alternating manner on their corresponding ear lobe, which is generally known to be free of cutaneous vagal innervation. Functional MR data from the cortex and brain stem level were collected and a group analysis was performed. RESULTS: In most cortical areas, BOLD changes were in the opposite direction when comparing anterior vs. posterior stimulation of the left auditory canal. The only exception was in the insular cortex, where both stimulation types evoked positive BOLD changes. Prominent decreases of the BOLD signals were detected in the parahippocampal gyrus, posterior cingulate cortex and right thalamus (pulvinar) following anterior stimulation. In subcortical areas at brain stem level, a stronger BOLD decrease as compared with sham stimulation was found in the locus coeruleus and the solitary tract only during stimulation of the anterior part of the auditory canal. CONCLUSIONS: The results of the study are in line with previous fMRI studies showing robust BOLD signal decreases in limbic structures and the brain stem during electrical stimulation of the left anterior auditory canal. BOLD signal decreases in the area of the nuclei of the vagus nerve may indicate an effective stimulation of vagal afferences. In contrast, stimulation at the posterior wall seems to lead to unspecific changes of the BOLD signal within the solitary tract, which is a key relay station of vagal neurotransmission. The results of the study show promise for a specific novel method of cranial nerve stimulation and provide a basis for further developments and applications of non-invasive transcutaneous vagus stimulation in psychiatric patients.

Posterior auricular nerve found anterior to the cartilage of the external auditory meatus--a previously unreported variant.

We describe a previously unreported anatomical variant of the posterior auricular nerve found during parotidectomy, and discuss its clinical implications.

The nervus intermedius: a review of its anatomy, function, pathology, and role in neurosurgery.

BACKGROUND: Geniculate neuralgia, although uncommon, can be a debilitating pathology. Unfortunately, a thorough review of this pain syndrome and the clinical anatomy, function, and pathology of its most commonly associated nerve, the nervus intermedius, is lacking in the literature. Therefore, the present study aimed to further elucidate the diagnosis of this pain syndrome and its surgical treatment based on a review of the literature. METHODS: Using standard search engines, the literature was evaluated for germane reports regarding the nervus intermedius and associated pathology. A summary of this body of literature is presented. RESULTS: Since 1968, only approximately 50 peer-reviewed reports have been published regarding the nervus intermedius. Most of these are single-case reports and in reference to geniculate neuralgia. No report was a review of the literature. CONCLUSIONS: Neuralgia involving the nervus intermedius is uncommon, but when present, can be life altering. Microvascular decompression may be effective as a treatment. Along its cisternal course, the nerve may be difficult to distinguish from the facial nerve. Based on case reports and small series, long-term pain control can be seen after nerve sectioning or microvascular decompression, but no prospective studies exist. Such studies are now necessary to shed light on the efficacy of surgical treatment of nervus intermedius neuralgia.

Anatomy and anaesthesia of the equine external ear canal.

Anaesthesia of the external ear canal (external acoustic meatus) is usually performed by blocking both the great and internal auricular nerves by regional infiltration. However, exact landmarks for blocking the internal auricular nerve to accomplish effective anaesthesia have not been described yet. In this study, detailed anatomical dissection of the equine external ear canal and its nerve supply was carried out on fifteen cadaver heads. Tissue samples of the dissected nerves were taken from two cadaver heads processed and were evaluated microscopically. Prior to the dissection, the region of interest was evaluated ultrasonographically, and injection of a local anaesthetic was simulated with an injection of methylene blue on ten cadaver heads. The tympanic membranes of three cadaver heads were obtained by microdissection and processed for microscopic evaluation. The entrance point of the internal auricular nerve, which is a branch of the facial nerve, into the ear canal is formed by the styloid process of the auricular cartilage. Using ultrasound, the styloid process presented as a thin hyperechoic line 2.17-2.97 cm deep, based on the skin surface. Landmarks for performing a complete and reliable anaesthesia of the external ear canal were established, and the simulated anaesthesia with methylene blue injection was evaluated as successful in all ten cases. Additionally, the histological composition of the equine tympanic membrane is described and illustrated.

Auricular syncope.

OBJECTIVE: To describe a previously unreported syndrome of recurrent syncopal attacks provoked by light stimulation of the external auditory canal. CASE REPORT: A 13-year-old girl had been receiving treatment for presumed absence seizures, with inadequate treatment response. Imaging was normal. Careful history taking indicated that the recurrent syncopal attacks were precipitated by external auditory canal stimulation. Targeted autonomic function tests confirmed a hyperactive vagal response, with documented significant bradycardia and lightheadedness, provoked by mild stimulation of the posterior wall of the left external auditory canal. Abstinence from ear scratching led to complete alleviation of symptoms without any pharmacological treatment. CONCLUSIONS: Reflex syncope consequent to stimulation of the auricular branch of the vagus nerve is proposed as the pathophysiological mechanism for this previously undocumented syndrome.

Non-invasive measurement of vagus activity in the brainstem - a methodological progress towards earlier diagnosis of dementias?

In Alzheimer's disease (AD), mild functional disturbances should precede gross structural damage and even more clinical symptoms, possibly by decades. Moreover, alterations in the brainstem are supposed to occur earlier as cortical affections. Based on these considerations, we developed a new method aiming at the measurement of vagal brainstem functioning by means of evoked potentials after electrical stimulation of the cutaneous representation of the vagus nerve in the external auditory channel. In the current study, a first sample of patients with Alzheimer's disease (n = 7) and mild cognitive impairment (n = 3) were investigated (6m, 4f, range from 57 to 78 y, mean age 68.6 years). Vagus somatosensory evoked potentials (VSEP) were characterized by significantly longer latencies as compared to healthy age- and gender-matched controls (p < 0.05). Future large scale studies - also including preclinical stages of AD - have to assess the value of this non-invasive, fast and cheap method in the early diagnosis of neurodegenerative disorders.