Dehiscence of the superior semicircular canal: a review of the literature on its possible pathogenic explanations.

The dehiscence of superior semicircular canal is a well-known affection which is able to explain some cases of hearing loss, tinnitus and/or vertigo unexpectedly presenting in adults without previous otologic affections. Although a diagnostic algorithm has been assessed and a surgical therapy has been indicated, the review of the literature shows that a completely satisfactory explanation for the reason why symptoms of a supposed congenital condition only occur in adulthood is still lacking. A pathogenic hypothesis based on the slow metabolism of the bony labyrinth, which could in time result in a prevalence of bone re-absorption on new bone formation leading to a dehiscence, despite some controversial findings could represent a the most reliable explanation for the question.

Ocular vestibular evoked myogenic potentials in patients with acoustic neuroma.

To assess the usefulness of vestibular testing in patients with acoustic neuroma, considering two main aspects: to compare diagnostic sensitivity of the current vestibular tests, especially considering ocular vestibular evoked myogenic potentials (OVEMPs) and to identify pre-operative localization of the tumor (inferior vestibular nerve vs. superior vestibular nerve) only with the help of vestibular electrophysiological data. Twenty-six patients with unilateral acoustic neuroma (mainly intracanalicular type) were studied with a full audio-vestibular test battery (pure tone and speech audiometry, caloric bithermal test, vibration-induced nystagmus test (VIN), cervical and OVEMPs). 18 patients (69 %) showed abnormal caloric responses. 12 patients (46.2 %) showed a pattern of VIN test suggestive of vestibular asymmetry. 16 patients (61.5 %) showed abnormal OVEMPs (12 only to AC, 4 both to AC and BC). 10 patients (38.5 %) showed abnormal cervical vestibular evoked myogenic potentials (5 both to AC and BC, 5 only to AC). In one case, results of vestibular evoked potentials and caloric test were confirmed by intra-operative and post-operative findings. Results of electrophysiological tests in AN patients could be helpful for planning the proper surgical approach, considering that sensitivity of every exam is quite low in intracanalicular lesion; clinical data allow a better interpretation of vestibular evoked myogenic potentials.

Management of growing vestibular schwannomas.

Conservative management of small vestibular schwannomas is frequently proposed as most tumours do not grow. Anyway, tumour growth is reported in 30-40 % of the cases, so that surgery is consequently generally proposed. We primarily observed 161 patients affected by unilateral vestibular schwannomas. All patients were examined by means of gadolinium-enhanced magnetic resonance imaging scans. Tumour growth was recorded in 58 cases (35.8 %) and these subjects set up the group of study. Twenty-two (37.9 %) patients were surgically treated; tumour was always completely removed, all patients had normal facial function after surgery and only one patient suffered from a major complication (cerebellar haematoma). Fourteen patients (24.1 %) were submitted to radiotherapy, while one patient was lost at follow-up and another one died because of other medical reasons. Finally, 20 (34.5 %) subjects continued to be observed for different reasons. The mean follow-up period after identification of growth was 6.1 years. Nine tumours continued to grow, nine tumours stopped growing, one tumour grew and then regressed in size and one tumour decreased. Sixty percent of patients with useful hearing at diagnosis preserved it during the entire observation period. In conclusion, most of VS do not grow; in case of tumour growth, a surgical procedure may be suggested and the outcomes are not negatively influenced by the delay of the procedure. But in some cases, patients can still follow the "wait and scan" policy. In fact, only less than half of the growing tumours continued to grow. Moreover, most of the patients continued to retain a useful hearing.

Do signs of natural plugging of superior semicircular canal dehiscence exist?

Our experience with 102 patients having superior semicircular canal dehiscence confirm that the clinical manifestations of the disease are very diverse; we also identified 3 patients who showed Meniere-like symptoms. Clinical examination during an acute vertigo attack of a patient with Meniere disease for several years and whom we subsequently diagnosed as having large superior semicircular canal dehiscence on the affected side allowed us to hypothesize that a natural plugging of the superior semicircular canal by the overhanging dura mater could be responsible for the recurrence of symptoms. Clinical and instrumental data were very similar to those recorded in 7 of 9 patients immediately after surgical plugging. The aim of the study was to understand which semiological and instrumental elements could be clinically useful, first in distinguishing Meniere disease from superior semicircular canal dehiscence and, secondly, in understanding if signs of natural plugging are present.

The possible role of proton pump inhibitors of the homeostasis of the inner ear.

The possibility of a benefit in some cases of inner ear sufferance by using proton pump inhibitors has been considered after a casual observation. The hypothesis is advanced considering the adverse effect of reflux on the eustachian tube function, the possible influence of the latter on inner ear symptoms and, from a more general point of view, the trigger effect which a gastric dysfunction requiring proton pump inhibitors could exert on the sympathetic system. These considerations, deserving a further study, seem to be based on logical assessment and therefore in our opinion deserve to be kept in mind in trying to define inner ear disorders of uncertain origin.

Possible influence on heart rate on tinnitus.

Assuming the possibility of the inner ear damage due to a hemodynamic imbalance essentially due to an abnormal vasomotor regulatory response, the possibility that heart rate (HR) has a correlation with the onset and/or the enhancement of tinnitus is hypothesized. In fact, recent studies have drawn the influence of other factors than blood pressure, in normotensive subjects, in taking part to the regulation of peripheral resistance, outlining the importance of both cardiac output (CO) - which is a function of heart rate (HR) and stroke volume (SV) and SV itself as a dynamic component to baroreflex control of muscle sympathetic nerve activity (MSNA). From this point of view, it could be possible that a condition of bradycardia can enhance tinnitus regardless of its cause, and conversely that a more elevated HR can be related to a relief of this symptom.

Inner ear dysfunction of uncertain origin: a multidisciplinary approach could give something more.

In order to find out any possible cause of an alteration of the vasomotor reactivity which can be responsible for a more or less severe sufferance of the inner ear, announced by the onset or the enhancement of sensorineural hearing loss, tinnitus, and some kind of dizziness and vertigo, a multidisciplinary approach should be considered. The possibility of an influence of hemodynamic imbalance due to hypotensive changes followed by vasomotor changes affecting the microcirculation of the inner ear has already been widely discussed; moreover, an increase in prevalence of tinnitus (which in many cases can be considered as a symptom of sufferance of the inner ear) has been found in subjects submitted to an "aggressive" antihypertensive therapy as well as in patients with severe heart failure, thus demonstrating a relationship between hemodynamic changes and inner ear dysfunction. For the same reason, the research for this mechanism of imbalance could concern other conditions possibly activating an abnormal response of the autonomic nervous system, which could in turn lead to a circulatory impairment of the labyrinth: among these, affections concerning central nervous system, endocrine system, metabolism, renal apparatus and even gastroenteric diseases with a functional component and any other factor which could interfere with vasomotor regulation should be considered. Thus, the absence of reliable causes for a sufferance of the inner ear should not lead to catalogue it as a disorder of "idiopathic" nature, but should represent a reason for a multidisciplinary investigation on all the possible causes of hemodynamic imbalance and/or autonomic dysregulation.

Bone vibration-induced nystagmus is useful in diagnosing superior semicircular canal dehiscence.

OBJECTIVE: To explore vestibular integrity by bone vibration-induced nystagmus (VIN) during bedside examination. Disease or dysfunction of vestibular end organs would reduce or eliminate their contribution to total eye movement response to VIN. BACKGROUND: It is assumed that vibration of the mastoid (at a frequency of 100 Hz) stimulates all vestibular end organs (semicircular canals and otolith structures). Previous studies have described oculomotor responses to vestibular activation by vibratory stimulus. Stimulation of individual semicircular canals produces eye movement in the plane of the stimulated canal. Vibratory stimulation of otolith structures (utricular macula) produces changes in ocular torsional position. Superior semicircular canal dehiscence (SCD) is responsible for nontypical cochleovestibular symptoms. Diagnosis is difficult without resorting to imaging, high-resolution computed tomography (HRCT) being the only tool providing reliable assessment. To avoid unnecessary referral for expensive imaging, it would be useful to have a simple screening test to select cases for HRCT. METHODS: Video eye movements were recorded in complete darkness in patients diagnosed with SCD. The eye movement responses to long-lasting unilateral vibratory stimulation applied to the mastoid surface were evaluated. RESULTS: VIN evoked a response in all cases, mostly demonstrating excitation of the affected side. The pattern of vertical, torsional and horizontal eye velocity and eye position was evaluated with three-dimensional infrared video-oculography (50 Hz sampling). CONCLUSION: Analysis of VIN, recently proposed to study transmission of excitatory stimuli by bone conduction, may be appropriate for altered immittance caused by dehiscence. This promises to be an interesting new field of research.

Nystagmus induced by bone (mastoid) vibration in otosclerosis: a new perspective in the study of vestibular function in otosclerosis.

BACKGROUND: The aim was to explore vestibular responses to bone vibration-induced nystagmus (BVIN) during bed-side examination in patients with otosclerosis and conductive hearing loss. It is assumed that vibration of the mastoid (at 100 Hz) stimulates all vestibular end organs (semicircular canals and otolith structures). Previous studies described oculomotor responses to vestibular activation by vibratory stimulus. Stimulation of individual semicircular canals produces eye movement in the plane of the stimulated canal. Vibratory stimulation of otolith structures (utricular macula) produces changes in ocular torsional position. Otosclerosis is responsible for conductive hearing loss and symptoms such as dizziness and vertigo. Diagnosis is usually by a combination of family medical history, conductive hearing loss pattern, absence of air-VEMP, and CT scan of the temporal bone. MATERIAL/METHODS: Eye movements of patients diagnosed with otosclerosis and conductive hearing loss were recorded in complete darkness. These oculomotor responses to long-lasting unilateral vibratory stimulation applied to the mastoid surface were evaluated and the patterns of vertical, torsional, and horizontal eye velocity and eye position were measured by three-dimensional computerized infrared video oculography. RESULTS: Mastoid vibration evoked responses in all cases, mostly demonstrating excitation of the affected side. In all cases, three-dimensional infrared video oculography showed mostly horizontal nystagmus directed with the slow phase to the healthy side. CONCLUSIONS: Three-dimensional analysis of BVIN in patients with otosclerosis and conductive hearing loss may be appropriate in evaluating the vestibular function and altered immittance related with this clinical entity. This promises to be an interesting new field of research.

Could echocardiography yield a cardiovascular profile of the tinnitus prone subject?

The possible genesis of some damage of the inner ear from a hemodynamic imbalance of functional origin, possibly linked to hypotension followed by an abnormal vasomotor regulatory activity, has been pointed out by our group over the years. As tinnitus, which is often referable to an inner ear origin, can represent a signal of incoming sufferance of the organ of Corti and may not necessarily be linked to hearing impairment, it seemed of some utility to investigate on the prevalence of tinnitus under various well monitored hemodynamic conditions. This led to observe that the prevalence of this symptom, regardless of audiological features, was increased under "aggressive" antihypertensive therapy as well as in particularly severe degree of heart decompensation. These data represent a first step and encourage in searching for a profile of subject who could be more prone to the development of tinnitus with respect to the normal population, even in absence of pathological conditions. With this aim, echocardiography is thought to be able to yield useful informations in addition to standard and ambulatory blood pressure monitoring, in order to obtain a better definition of the correlations between cardiovascular function (and related changes) and inner ear insufficient perfusion.

Superior canal dehiscence with tegmen defect revealed by otoscopy: Video clip demonstration of pulsatile tympanic membrane.

Superior canal dehiscence is a pathologic condition of the otic capsule acting as aberrant window of the inner ear. It results in reduction of inner ear impedance and in abnormal exposure of the labyrinthine neuroepithelium to the action of the surrounding structures. The sum of these phenomena leads to the onset of typical cochleo-vestibular symptoms and signs. Among them, pulsatile tinnitus has been attributed to a direct transmission of intracranial vascular activities to labyrinthine fluids. We present the first video-otoscopic documentation of spontaneous pulse-synchronous movements of the tympanic membrane in two patients with superior canal dehiscence. Pulsating eardrum may represent an additional sign of third-mobile window lesion.

Is tinnitus useful in early detection of incoming heart decompensation?

In previous studies the possibility of a mechanism of hemodynamic imbalance consequent to a sharp decrease in blood pressure causing a more or less transient inner ear impairment was evaluated and to some extent demonstrated. In this scenario, tinnitus is very frequently present as a debilitating symptom associated to cochlear impairment. On the other hand, a possible cause of a sharp decrease in blood pressure is represented by major cardiovascular disorders, requiring an early assessment in order to avoid fatal consequences. In this paper, the hypothesis of resorting to tinnitus as a simple warning method for self detecting a possibly incoming cardiovascular imbalance in patients with heart failure (HF) is advanced.

Is there a role for atrial peptides in the labyrinthine "disease"?

The important role of atrial natriuretic peptides (ANP) in regulating blood pressure and changing vascular permeability has been widely studied and assessed during the last ten years. Considering the characteristics of this mechanism, which is responsible for a hypotensive and hypovolemic effect, and the possible role of hypotension associated with a default of autoregulatory sympathetic reactions in inner ear unexplained disorders, it seems reasonable to hypothesize a possible involvement of ANP system in the genesis of such disorders. As a matter of fact, the presence of specific receptors for ANP in the inner ear has been widely reported in studies concerning both rat and human inner ear, although their precise role in the labyrinthine homeostasis has not been satisfactory explained until now. Some aspects concerning vascular and fluid regulation of the inner ear under different conditions still remain not totally clear, and consequently a detailed explanation to the possible mechanism causing inner ear disorders of functional origin is lacking; from this point of view, an investigation on the serum level of ANP in subjects with labyrinthine affections of uncertain origin could be of some utility in contributing to assess the role of this system in the inner ear fluid regulation and in the inner ear perfusion and to investigate on the possible influence of an abnormal ANP release in some kind of inner ear damage.

Prevalence of tinnitus in patients withhypertension and the impact of different anti hypertensive drugs on the incidence of tinnitus: A prospective, single-blind, observational study.

BACKGROUND: Tinnitus is a common symptom in audiology and neurologypatients. Controversial data have been reported in the literature about the prevalence of tinnitus in hypertensive patients, whereas its relationship with the extent of blood pressure (BP) control has not been substantially explored. OBJECTIVE: The aim of this study was to determine the prevalence of tinnitus in hypertensive patients, and the impact of different antihypertensive drugs on the incidence of tinnitus in these patients. METHODS: This prospective, single-blind, observational study was conducted at the Hypertension Clinic, St. Orsola-Malpighi Hospital, Bologna, Italy. Patients aged 18 to 75 years with uncontrolled hypertension and receiving antihypertensive therapy were enrolled. Patients were asked to complete a standardized questionnaire to assess the presence, frequency, and duration of tinnitus and the apparent effect of their antihypertensive treatment on it. Patients considered by the investigator to have tinnitus, regardless of their audiologic condition, underwent a complete clinical cardiovascular examination, including supine systolic BP (SBP) and diastolic BP measurement and standard 12-lead electrocardiography. Twelve-hour ambulatory BP monitoring was also performed, and patients were asked to record, using patient diaries, times of the onset and resolution of tinnitus that occurred during those 12 hours. From these data, correlations between the onset of tinnitus and BP were calculated. RESULTS: A total of 476 patients participated in the study (283 men, 193 women). Of these, 84 (17.6%) patients reported occasional or prolonged spontaneous tinnitus, whereas 392 (82.4%) reported no tinnitus. The incidence of tinnitus was significantly higher in patients receiving diuretics (72/265 [27.2%]) compared with those receiving angiotensin lI receptor blockers (5/37 [13.5%]), α-blockers (12/55 [21.8%]), or 3-hydroxy-3-methylglutaryl coenzyme A reduc tase inhibitors (9/73 [12.3%]) (all, P < 0.05). Mean (SD) SBP was significantly higher in patients without tinnitus compared with those with it (143.2 [11.1 ] vs 140.6 [10.3] mm Hg; P < 0.005). In 10 (11.9%) patients with tinnitus, the onset was correlated with a sudden decrease in SBP (<140 mm Hg). CONCLUSIONS: In this study of tinnitus in patients receiving antihypertensivetherapy, tinnitus was found in 17.6% of patients. Tinnitus was associated with the use of diuretics and with low SBP. Further studies are needed.

Bilateral dehiscence of the bony cochlear basal turn.

OBJECTIVE: To identify bony labyrinth defects as causing symptoms that might otherwise be difficult to understand. DESIGN: Imaging investigation on cases of lowered vestibular evoked myogenic potentials (VEMP) threshold. SETTING: Academic tertiary case-referral medical center. PATIENTS: One patient with continuous bilateral tinnitus. INTERVENTIONS: High-resolution computed tomography of petrous bone was performed after audiometry, impedance, and VEMP recording. RESULTS: We found a previously unreported dehiscence of the bony plate between the basal turn of the cochlea and the carotid canal. CONCLUSIONS: A VEMP study could prompt diagnostic imaging tests that might otherwise be neglected. Moreover, it is important to consider the possibility of a bony dehiscence involving not just the semicircular canals.

Endoscopic treatment of benign tumors of the nose and paranasal sinuses.

OBJECTIVE: The endoscopic approach can be successfully employed for the treatment of benign tumors such as fibroosseus and vascular lesions, pleomorphic adenomas, gliomas, and schwannomas. STUDY DESIGN AND SETTING: Nineteen patients diagnosed with benign tumors of the nasal cavity and paranasal sinuses and treated using an endoscopic approach were retrospectively reviewed. The endoscopic approach was used exclusively in 15 cases and was associated with an external approach in 4 cases (due to an intracranial extension of the tumor in 3 patients and its location at the level of the anterior wall of the frontal sinus in the last case). RESULTS: The resection of the lesions was radical in 18 patients and subtotal in 1 case. The mean follow-up was 27 months and only 1 recurrence (5%) was observed in the juvenile angiofibroma group 20 months postoperatively. CONCLUSION: and significance In selected cases, endoscopic surgery can be considered an effective treatment for the resection of benign tumors involving the sinonasal tract.

Relationship between multidetector CT imaging of the vestibular aqueduct and inner ear pathologies.

This study investigated the relationships between morphological changes in the vestibular aqueduct (VA) in different inner ear pathologies. Eighty-eight patients (34 males and 54 females, ranging from seven to 88 years of age; average age 49.2 years) with cochleovestibular disorders underwent temporal bone CT (with a 64-channel helical CT system according to temporal bone protocol parameters; 0.6 mm slice thickness, 0.6 mm collimation, bone reconstruction algorithm). All patients with cochleovestibular disorders who underwent temporal bone CT had been previously divided into six different suspected clinical classes: A) suspected pathology of the third window; B) suspected retrocochlear hearing loss; C) defined Ménière's disease; D) labyrinth lithiasis; E) recurrent vertigo. On CT images we analyzed the length, width and morphology of the VA, contact between the VA and the jugular bulb (JB), the thickness of the osseous capsule covering the semicircular canals, the pneumatization rate of the temporal bone and the diameter of the internal auditory canal. At the end of the diagnostic work-up all patients were grouped into six pathological classes, represented as follow: 1) benign paroxysmal positional vertigo (BPPV), 2) recurrent vertigo (RV), 3) enlarged vestibular aqueduct syndrome (EVAS), 4) sudden or progressive unilateral sensorineural hearing loss (SNHL), 5) superior semicircular canal dehiscence syndrome (SSCD), 6) recurrent vestibulocochlear symptoms in Ménière's disease. We evaluated 176 temporal bones in 88 patients. The VA was clearly visualized in 166/176 temporal bones; in ten ears the VA was not visualized. In 14 ears (11 patients, in three of whom bilaterally) we found an enlarged VA while in 31 ears the VA was significantly narrower. In 16 ears a dehiscence of the JB with the vestibular or cochlear aqueduct was noted. In all six patients with suspected EVAS we found a AV wider than 1.5 mm on CT scans; moreover CT identified four patients with large VA and ill-defined clinical symptoms. Most patients with BPPV (11 patients, Class 1) we did not find any VA abnormalities on CT scans, confirming the clinical diagnosis in ten patients; in the remaining patients we found an enlarged VA, not clinically suspected. In the RV class (eight patients, Class 2) we found three patients with negative CT scans, two patients with narrow aqueduct and subsequently reclassified as Ménière's disease patients, and three patients with ectasic JB dehiscence with the VA. In patients suffering from SNHL we found no statistically significant correlation with the morphological abnormalities. The clinical suspicion of SSCD was confirmed by CT in 11/13 patients (84.6 %); in addition another seven patients showed a thinning or dehiscence of the superior semicircular canals as the prevailing alteration on CT scans, and were reclassified in this group. Ménière's disease symptoms were correlated with a VA alteration in more than half of the cases; the most striking finding in this class was that the VA was significantly narrower (21 patients). Our study demonstrates that alterations of the VA morphology are not only related to EVAS but are also found in other inner ear pathologies such as Ménière's disease. Furthermore, MDCT may confirm the presence of correlations between the morphology of inner ear structures such as VA, semicircular canals or JB dehiscence, and alterations of vestibulocochlear function.

Superior semicircular canal dehiscence and enlarged vestibular aqueduct.

Superior semicircular canal dehiscence is a well described labyrinthine defect, detect in pediatric population too. We report a case of superior semicircular canal dehiscence, which radiological diagnosis was confirmed by multiplanar reformatted CT images, associated to omolateral enlarged vestibular aqueduct in a 16-year-old female who presented with congenital hearing loss without vestibular symptoms. Both inner ear malformations act as a third mobile window into the labyrinth and cochleo-vestibular symptoms can result from loud sounds or pressure changes. An early diagnosis should be strived for preserve inner ear functions.