Carotid artery-cochlear dehiscence: a review

Causes of Pulsatile Tinnitus and Treatment Options

Pulsatile tinnitus (PT) requires detailed workup to evaluate for an underlying structural cause. With advances in neuroimaging, structural venous abnormalities that can cause PT have becoming increasingly recognized. A number of anomalies, including dural arteriovenous fistulas, idiopathic intracranial hypertension, transverse sinus stenosis, sigmoid sinus wall abnormalities, jugular venous anomalies, and hypertrophied emissary veins, have been implicated in flow disruption and turbulence in the vicinity of auditory structures, resulting in PT. Endovascular treatment options, including stenting, coiling, and embolization with liquid agents, have demonstrated high efficacy and safety. These treatments can lead to symptomatic relief in carefully selected cases.

Carotid-Cochlear Apex Dehiscence: A Family Affair

We report two cases of carotid-cochlea dehiscence involving the cochlear apex, with, to our knowledge, the first description of this anomaly in two members of a family (mother-daughter). Pure tone audiometry revealed a bilateral mild sensorineural hearing loss predominantly on the left in the daughter, and a left mild mixed hearing loss with a predominance of sensorineural loss in the medium frequencies in the mother Carotid-cochlear dehiscence is a rare anomaly with a multiform expression, which should be investigated in cases of third mobile window symptoms, but also atypical sensorineural hearing loss, or before any cochlear implantation. Laryngoscope, 134:2912-2914, 2024.

Third window lesions of the inner ear: A pictorial review

PURPOSE

Radiographic review of pathologies that associate with third window syndrome.

METHODS

Case series and literature review.

RESULTS

Eight unique third window conditions are described and illustrated, including superior, lateral, and posterior semicircular canal dehiscence; carotid-cochlear, facial-cochlear, and internal auditory canal-cochlear dehiscence, labyrinthine erosion from endolymphatic sac tumor, and enlarged vestibular aqueduct.

CONCLUSION

The present study highlights the characteristic imaging features and symptoms to differentiate third window pathologies for expedient diagnosis and management planning.

Proposal for a Unitary Anatomo-Clinical and Radiological Classification of Third Mobile Window Abnormalities

Introduction: An increased number of otic capsule dehiscence (OCD) variants relying on the third window pathomechanism have been reported lately. Therefore, a characterization of the anatomical structures involved and an accurate radiological description of the third window (TW) interface location have become essential for improving the diagnosis and appropriate therapeutic modalities. The purpose of this article is to propose a classification based on clinical, anatomical, and radiological data of third mobile window abnormalities (TMWA) and to discuss the alleged pathomechanism in lesser-known clinical variants.

Materials and Methods: The imaging records of 259 patients who underwent, over the last 6 years, a high-resolution CT (HRCT) of the petrosal bone for conductive hearing loss were analyzed retrospectively. Patients with degenerative, traumatic, or chronic infectious petrosal bone pathology were excluded. As cases with a clinical presentation similar to those of a TW syndrome have recently been described in the literature but without these being confirmed radiologically, we thought it necessary to be integrated in a separated branch of this classification as “CT - TMWA.” The same goes for certain intralabyrinthine pathologies also recently reported in the literature, which mimic to some extent the symptoms of a TW pathology. Therefore, we suggest to call them intralabyrinthine TW-like abnormalities.

Results: Temporal bone HRCT and, in some cases, 3T MRI of 97 patients presenting symptomatic or pauci-symptomatic, single or multiple, unilateral or bilateral OCD were used to develop this classification. According to the topography and anatomical structures involved at the site of the interface of the TW, a third-type classification of OCD is proposed.

Conclusions: A classification reuniting all types of TMWA as the one proposed in this article would allow for a better systematization and understanding of this complex pathology and possibly paves the way for innovative therapeutic approaches. To encompass all clinical and radiological variants of TMWA reported in the literature so far, TMWAs have been conventionally divided into two major subgroups: Extralabyrinthine (or “true” OCD with three subtypes) and Intralabyrinthine (in which an additional mobile window-like mechanism is highly suspected) or TMWA-like subtype. Along these subgroups, clinical forms of OCD with multiple localization (multiple OCD) and those that, despite the fact that they have obvious characteristics of OCD have a negative CT scan (or CT – TMWA), were also included.

Audiovestibular Quantification in Rare Third Window Disorders in Children

Third window disorders are structural abnormalities in the bony otic capsule that establish a connection between the middle/inner ear or the inner ear/cranial cavity. Investigated extensively in adults, they have hardly been studied in children. This study is a retrospective study of children (aged 5-17 years) diagnosed with rare third window disorders (third window disorders reported rarely or not reported in children) in a tertiary pediatric vestibular unit in the United Kingdom. It aimed to investigate audiovestibular function in these children. Final diagnosis was achieved by high resolution CT scan of the temporal bones. Of 920 children attending for audiovestibular assessment over a 42 month period, rare third windows were observed in 8 (<1%). These included posterior semicircular canal dehiscence (n = 3, 0.3%), posterior semicircular canal thinning (n = 2, 0.2%), X linked gusher (n = 2, 0.2%), and a combination of dilated internal auditory meatus/irregular cochlear partition/deficient facial nerve canal (n = 1, 0.1%). The majority of them (87.5%) demonstrated a mixed/conductive hearing loss with an air-bone gap in the presence of normal tympanometry (100%). Transient otoacoustic emissions were absent with a simultaneous cochlear pathology in 50% of the cohort. Features of disequilibrium were observed in 75% and about a third showed deranged vestibular function tests. Video head impulse test abnormalities were detected in 50% localizing to the side of the lesion. Cervical vestibular evoked myogenic potential test abnormalities were observed in all children in the cohort undergoing the test where low thresholds and high amplitudes classically found in third window disorders localized to the side of the defects in 28.5%. In the series, 71.4% also demonstrated absent responses/amplitude asymmetry, some of which did not localize to the ipsilesional side. Two children presented with typical third window symptoms. This study observes 2 new rare pediatric third window phenotypes and the presence of a cochlear hearing loss in these disorders. It emphasizes that these disorders should be considered as an etiology of hearing loss/disequilibrium in children. It also suggests that pediatric third window disorders may not present with classical third window features and are variable in their presentations/audiovestibular functions.

Perilymphatic Fistula: A Review of Classification, Etiology, Diagnosis, and Treatment

A perilymphatic fistula (PLF) is an abnormal communication between the perilymph-filled inner ear and the middle ear cavity, mastoid, or intracranial cavity. A PLF most commonly forms when the integrity of the oval or round window is compromised, and it may be trauma-induced or may occur with no known cause (idiopathic). Controversy regarding the diagnosis of idiopathic PLF has persisted for decades, and the presenting symptoms may be vague. However, potential exists for this condition to be one of the few etiologies of dizziness, tinnitus, and hearing loss that can be treated surgically. The aim of this review is to provide an update on classification, diagnosis, and treatment of PLF. Particular attention will be paid to idiopathic PLF and conditions that may have a similar presentation, with subsequent information on how best to distinguish them. Novel diagnostic criteria for PLF and management strategy for PLF and PLF-like symptoms is presented.

Carotid-cochlear dehiscence: a dangerous mimicker of inner ear pathologies

A 67-year-old woman was referred to the otolaryngology service after presenting to the emergency department for dizziness and loss of balance. She reported several similar episodes over the past years. Physical examination was unremarkable. A temporal bone CT scan revealed dehiscence between the bony carotid canal and the cochlea resulting in the diagnosis of carotid-cochlear dehiscence (CCD). CCD is an extremely rare condition involving the thinning of the bony canal separating the internal carotid artery from the cochlea. CCD is best diagnosed with temporal bone CT scan. Treatment options include observation as well as chemical or surgical labyrenthectomy. Despite similar clinical and diagnostic characteristics of reported CCD cases, general trends and consensus on treatment options cannot be ascertained due to the extreme rarity of this condition. Regardless of these limitations, CCD is a critical diagnosis as it mimics other inner ear conditions and poses a potential, significant surgical risk for the otolaryngologist.

Hypotympanic Sound Baffle for Amelioration of Pulsatile Tinnitus due to Carotid and Jugular Bulb Dehiscence

OBJECTIVE

To share our experience with treating pulsatile tinnitus by insulating a dehiscent carotid artery with a hypotympanic sound baffle, and compare outcomes with a similar resurfacing approach for jugular bulb wall anomalies.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary academic medical center.

PATIENTS

Adult patients with troublesome pulsatile tinnitus with radiologic evidence of carotid artery dehiscence or jugular bulb wall anomaly within the temporal bone.

INTERVENTION

Hypotympanic exposure of vessel followed by resurfacing using hydroxyapatite cement (carotid dehiscence) or autologous tissue (jugular bulb wall anomalies).

MAIN OUTCOMES MEASURES

Alleviation or reduction of pulsatile tinnitus.

RESULTS

Two patients presented with unilateral, debilitating pulsatile tinnitus and history and imaging consistent with carotid dehiscence and underwent hypotympanic resurfacing with hydroxyapatite cement. Both had considerable initial improvement of tinnitus, and 40% resolution of tinnitus with improved quality of life at an average follow-up of 13.5 months. Two patients with jugular bulb dehiscence/diverticulum treated by resurfacing had complete elimination of symptoms at an average follow up of 17.3 months. There were no major adverse outcomes (permanent hearing loss, vascular injury, or intracranial hypertension).

CONCLUSION

Creation of a hypotympanic sound baffle offers promise as a means of reducing pulsatile tinnitus emanating from a dehiscent carotid artery transmitted to the tympanum, with substantial improvement in reported functional ability. Treatment of venous etiologies of pulsatile tinnitus with similar techniques demonstrates higher success rates, which may be attributable to incomplete resurfacing of carotid artery dehiscence along its extent towards the petrous apex due to safety concerns.

Superior Canal Dehiscence Syndrome: Lessons from the First 20 Years

Superior semicircular canal dehiscence syndrome was first reported by Lloyd Minor and colleagues in 1998. Patients with a dehiscence in the bone overlying the superior semicircular canal experience symptoms of pressure or sound-induced vertigo, bone conduction hyperacusis, and pulsatile tinnitus. The initial series of patients were diagnosed based on common symptoms, a physical examination finding of eye movements in the plane of the superior semicircular canal when ear canal pressure or loud tones were applied to the ear, and high-resolution computed tomography imaging demonstrating a dehiscence in the bone over the superior semicircular canal. Research productivity directed at understanding better methods for diagnosing and treating this condition has substantially increased over the last two decades. We now have a sound understanding of the pathophysiology of third mobile window syndromes, higher resolution imaging protocols, and several sensitive and specific diagnostic tests. Furthermore, we have a treatment (surgical occlusion of the superior semicircular canal) that has demonstrated efficacy. This review will highlight some of the fundamental insights gained in SCDS, propose diagnostic criteria, and discuss future research directions.

Pulsatile tinnitus associated with dehiscent internal carotid artery: An irremediable condition?

Dehiscent internal carotid artery (ICA) in the middle ear is a rare condition, with conservative treatment primarily recommended. We report the case of a 63-year-old patient referred to the Ear, Nose, and Throat (ENT) ward for unbearable pulsatile tinnitus. Otoscopy revealed a normal right tympanic membrane, with pulsatile tinnitus but without hearing impairment. Based on imaging studies, including computed tomography (CT) and magnetic resonance imaging (MRI) of the temporal bone, as well as Doppler ultrasound of the internal carotid artery and sigmoid sinus, the diagnosis of ICA canal dehiscence into the tympanic cavity was established, thus excluding the diagnosis of aberrant ICA. Following the patient's own request, we undertook surgical correction, with the technique used described in the report. Immediately postoperatively, the pulsatile tinnitus had disappeared, with no surgical complications noted. At the 9-month follow-up, otoscopy revealed a healthy right tympanic membrane and the patient reported no remaining symptoms.

Spectrum of Third Window Abnormalities: Semicircular Canal Dehiscence and Beyond

Third window abnormalities are defects in the integrity of the bony structure of the inner ear, classically producing sound-/pressure-induced vertigo (Tullio and Hennebert signs) and/or a low-frequency air-bone gap by audiometry. Specific anatomic defects include semicircular canal dehiscence, perilabyrinthine fistula, enlarged vestibular aqueduct, dehiscence of the scala vestibuli side of the cochlea, X-linked stapes gusher, and bone dyscrasias. We discuss these various entities and provide key examples from our institutional teaching file with a discussion of symptomatology, temporal bone CT, audiometry, and vestibular-evoked myogenic potentials.

The surgical challenge of carotid artery and Fallopian canal dehiscence in chronic ear disease: a pitfall for endoscopic approach

OBJECTIVE

Endoscopic procedures are becoming common in middle ear surgery. Inflammation due to chronic ear disease can cause bony erosion of the carotid artery and Fallopian canals, making them more vulnerable during surgery. The objective of this study was to determine whether or not chronic ear disease increases dehiscence of the carotid artery and Fallopian canals.

DESIGN

Comparative human temporal bone study.

SETTING

Otopathology laboratory.

PARTICIPANTS

We selected 78 temporal bones from 55 deceased donors with chronic otitis media or cholesteatoma and then compared those two groups with a control group of 27 temporal bones from 19 deceased donors with no middle ear disease.

MAIN OUTCOME MEASURES

We analysed the middle ear, carotid artery canal and Fallopian canal, looking for signs of dehiscence of its bony coverage, using light microscopy.

RESULTS

We found an increased incidence in dehiscence of the carotid artery and Fallopian canals in temporal bones with chronic middle ear disease. The size of the carotid artery canal dehiscence was larger in the middle ear-diseased groups, and its bony coverage, when present, was also thinner compared to the control group. Dehiscence of the carotid artery canal was more frequently located closer to the promontory. The incidence of Fallopian canal dehiscence was significantly higher in temporal bones from donors older than 18 years with chronic middle ear disease.

CONCLUSION

The increased incidence of the carotid artery and Fallopian canal dehiscence in temporal bones with chronic middle ear disease elevates the risk of adverse events during middle ear surgery.

The impact of the cochlear-carotid interval on tinnitus perception

PURPOSE

We hypothesized that the cochlear-carotid interval (CCI), which is defined as the smallest distance along the petrous segment of the internal carotid artery and basal turn of cochlea, may be associated with direct stimulation of hair cells, thereby affecting tinnitus perception. The aim of this study was to investigate the relationships between the CCI, tinnitus perception, and accompanying hearing loss in patients with tinnitus.

METHODS

The CCI on both sides was measured independently by two observers from the temporal 3D b-FFE MR images of 25 patients with tinnitus and 20 age/gender matched control subjects. The relationships between CCI, tinnitus visual analog scale (VAS), and tinnitus handicap inventory (THI) were investigated.

RESULTS

CCI ranged 0.2-5.6 mm (1.9 ± 1.5) on the right and 0.1-5.4 mm (2.2 ± 1.6) on the left side in the patient group and 0.5-5.4 (1.9 ± 1.4) mm on the right and 0.3-6.7 (2.3 ± 1.7) on the left side in the control group. The differences between the two groups were not statistically significant (p > 0.05). CCI showed a strong negative correlation with THI and VAS scores on both sides. Correlation of audiologic findings with CCI revealed a significant negative correlation with pure tone average of the ipsilateral ear most affectedly at high frequencies.

CONCLUSION

The strong negative correlation of CCI with tinnitus-related distress and accompanying sensorineural hearing loss predominantly at high frequencies suggests that further studies on patients with tinnitus that focus on this small area may help to improve the knowledge of tinnitus pathophysiology.

Impingement of the carotid canal on the basal turn of the cochlea as pertaining to cochlear implantation

HYPOTHESIS

To evaluate the relation of the basal turn of the cochlea with the carotid canal as pertaining to cochlear implantation.

BACKGROUND

Cochlear implantation is an established mode of treatment for patients with bilateral profound sensorineural hearing loss. An intricate knowledge of both the typical and atypical topography of the cochlea with the carotid canal is essential for safely conducting cochlear implantation.

DESIGN

Fifty-eight cadaveric temporal bones were microdissected to expose the medial wall of the middle ear. To open the basal turn of the cochlea, the promontory was drilled. The carotid canal was unroofed to reveal the internal carotid artery. The minimum distance between the basal turn of the cochlea and the vertical part of the carotid canal was measured.

RESULTS

The minimum distance between the basal turn of the cochlea and the carotid canal ranged from 0 to 3.9 mm (mean ± SD, 1.3 ± 0.8 mm). The carotid canal was abutting the basal turn of the cochlea in three cases, and impingement of the carotid canal on the anterior cochlear wall was found in five (8.6%) cases.

CONCLUSION

Preoperative knowledge of findings like impingement (8.6%) and abutment (5.2%) of the carotid canal on the basal turn of the cochlea is of immense importance in cochlear implantation, which may otherwise lead to disastrous consequences during surgery.

Cochlear-facial dehiscence--a newly described entity

Dehiscence of the cochlear otic capsule has recently been described as a pathologic entity. We describe two cases of cochlear-facial dehiscence, which are the first reported: a 69-year-old male who complained of hearing loss, autophony, and pulsatile tinnitus and a 41-year-old female who complained of left-sided hearing loss, pulsatile tinnitus, and vertigo. In both, computed tomography (CT) showed bony dehiscence between the facial nerve and cochlea. Cochlear-facial dehiscence is another example of otic capsule dehiscence that produces symptoms of third-window lesions. When patients present with symptoms of third-window lesions and CT does not show superior canal dehiscence, cochlear-facial dehiscence should be considered.

Pulsatile tinnitus: imaging and differential diagnosis

BACKGROUND

Pulsatile tinnitus, unlike idiopathic tinnitus, usually has a specific, identifiable cause. Nonetheless, uncertainty often arises in clinical practice about the findings to be sought and the strategy for work-up.

METHODS

Selective literature review and evaluation of our own series of patients.

RESULTS

Pulsatile tinnitus can have many causes. No prospective studies on this subject are available to date. Pulsatile tinnitus requires both a functional organ of hearing and a genuine, physical source of sound, which can, under certain conditions, even be objectified by an examiner. Pulsatile tinnitus can be classified by its site of generation as arterial, arteriovenous, or venous. Typical arterial causes are arteriosclerosis, dissection, and fibromuscular dysplasia. Common causes at the arteriovenous junction include arteriovenous fistulae and highly vascularized skull base tumors. Common venous causes are intracranial hypertension and, as predisposing factors, anomalies and normal variants of the basal veins and sinuses. In our own series of patients, pulsatile tinnitus was most often due to highly vascularized tumors of the temporal bone (16%), followed by venous normal variants and anomalies (14%) and vascular stenoses (9%). Dural arteriovenous fistulae, inflammatory hyperemia, and intracranial hypertension were tied for fourth place (8% each).

CONCLUSION

The clinical findings and imaging studies must always be evaluated together. Thorough history-taking and clinical examination are the basis for the efficient use of imaging studies to reveal the cause of pulsatile tinnitus.