X-linked progressive mixed hearing loss: computed tomography findings

X-Linked Gusher Disease DFNX2 in Children, a Rare Inner Ear Dysplasia with Mixed Hearing and Vestibular Loss

Conductive hearing losses are typically present in disorders of the external/middle ear. However, there is a rare group of inner ear conditions called third windows that can also generate a conductive hearing loss. This is due to an abnormal connection between the middle and the inner ear or between the inner ear and the cranial cavity. X-linked gusher disorder is an extremely rare congenital inner ear dysplastic syndrome with an abnormal connection due to a characteristic incomplete cochlear partition type III and an incomplete internal auditory meatus fundus. The disorder is inherited in an X-linked fashion due to the mutation of the POU3F4 gene. We present two siblings diagnosed with the condition and their long-term follow-ups. They both presented audiovestibular symptoms and showed progressive mixed losses and bilateral vestibular weakness. They were treated with cochlear implant, digital amplification and with vestibular rehabilitation. Significant others around them were involved in their journey with the medical team, and in both, a very favourable outcome was achieved. This is the first time that we have reported evolving audiovestibular function with vestibular quantification in X-linked gusher disorder and emphasize on the multidisciplinary holistic approach to manage these children effectively.

A New Treatment Option in Incomplete Partition Type III: The Varese Bone-Air Stimulation (B.A.S.)

The incomplete partition type III is a severe cochlear malformation present in X-linked deafness. It is a rare, non-syndromic cause of severe to profound mixed hearing loss, often progressive. The complete absence of bony modiolus and the wide communication between the cochlea and the internal auditory canal make cochlear implantation challenging, with still no consensus on the management of these patients. To the best of our knowledge, no results have ever been published in the literature on the treatment of these patients with hybrid stimulation (bone and air). We present three cases in which this hybrid stimulation gave better audiological results then air stimulation alone. A literature review on audiological results of the current treatment options in children affected by IPIII malformation was conducted independently by two researchers. Ethical considerations on the treatment of these patients were conducted by the Bioethics department of the University of Insubria. In two of the patients, the bone-air stimulation, associated with prosthetic-cognitive rehabilitation, meant that surgery was avoided, obtaining similar communication performances of those present in the literature. We believe that, when the bone threshold appears partially preserved, a stimulation through the bone or hybrid modality, such as the Varese B.A.S. stimulation, should be attempted.

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.

Answer to quiz case: Temporal bone imaging

Computed tomographic scanning of the petrous bone and magnetic resonance imaging sequences of the inner ear and cerebellopontine angle of a deaf patient were performed to find an explanation for his deafness, and to establish whether he would be a good candidate for cochlear implantation. The imaging features were considered pathognomonic for incomplete partition type III (IP type III). Further management and discussion of this deafness subtype are detailed.

HRCT and MRI findings in X-linked non-syndromic deafness patients with a POU3F4 mutation

OBJECTIVE

The aim of this study was to analyze HRCT and MRI findings in patients with X-linked non-syndromic deafness and a POU3f4 mutation.

METHODS

HRCT and MRI data of four patients (males, 2-19 years old) with a POU3f4 mutation were collected and a retrospective review was performed. Cochlea, internal auditory canal (IAC), vestibule, semicircular canals, vestibular aqueduct, nerve canals in the IAC fundus, stapes and cochlear nerve were evaluated on 2D images (multi-planner reformation, MPR) and cochlear foramen on 3D images (CT virtual endoscopy, CTVE). Ten cases with normal hearing subjected to CT and MR exams served as controls.

RESULTS

Inner ear malformations were bilateral and symmetrical. Cochlear malformation was shown to consist of as a relatively normal outer coat shape, absence of a cochlear modilous, and a direct intercommunication between the IAC and cochlear inner cavity. The lateral portion of the IAC was dilated. A spiral cochlear inner cavity was observed with CTVE images versus a helical cochlear nerve foramen as seen in controls. The labyrinthine facial nerve canal and superior vestibular nerve canal were enlarged. The Bill's bar was hypertrophic and partially pneumatized. A thickened stapes footplate was present and a fissura ante fenestram was absent in seven ears examined. A column shaped stapes was observed in one ear.

CONCLUSIONS

The absence of a cochlear modilous with a dilated lateral IAC and thickened stapes footplate were the remarkable features observed with imaging these in X-linked non-syndromic deafness patients with a POU3F4 mutation. Preoperative recognition of the image features in these patients is important because it precludes stapedectomy and indicates the risks in the surgery of cochlear implantation including CSF gusher and electrode insertion into IAC.

Computed tomography findings of a patient with severe dysplasia of the inner ear and recurrent meningitis: a case report of gusher ear in a five-year old boy

Communication between subarachnoid and perlymphatic spaces can be due to a deficiency of lamina cribrosa (stapes gusher). Recognition of the condition may alter the course of treatment that can avoid perilymph gushing. A five-year-old boy presented with a history of congenital hearing loss and recurrent meningitis. The computed tomography (CT) of the temporal bone showed severe bilateral dysplasia in the inner ears in favor of gusher disease.

X-linked hearing loss: two gene mutation examples provide generalizable implications for clinical care

PURPOSE

To describe the inheritance patterns and auditory phenotype features of 3 Canadian families with mutations in 2 X-linked "deafness" genes (DFNX).

METHOD

Audiological, medical, and family histories were collected and family members interviewed to compare hearing thresholds and case histories between cases with mutations in SMPX versus POU3F4.

RESULTS

The family pedigrees reveal characteristic X-linked inheritance patterns. Phenotypic features associated with the SMPX (DFNX4) mutation include early onset in males with rapid progression from mild and flat to sloping sensorineural loss, with highly variable onset and hearing loss severity in females. In contrast, phenotypic features associated with the POU3F4 (DFNX2) mutation are characterized by an early onset, mixed hearing loss with fluctuation in males, and a normal hearing phenotype reported for females.

CONCLUSIONS

The study shows how this unique inheritance pattern and both gender and mutation-specific phenotype variations can alert audiologists to the presence of X-linked genetic etiologies in their clinical practice. By incorporating this knowledge into clinical decision making, audiologists can facilitate the early identification of X-linked hearing loss and contribute to the effective team management of affected families.

Congenital X-linked Stapes Gusher Syndrome

X-Linked sensorineuronal hearing loss (SNHL) is a rare but recognized cause of bilateral SNHL associated with CSF gusher. We report a case presenting a varied imaging spectrum and clinical scenario of a one year old boy with unilateral profound hearing loss and recurrent meningitis due to spontaneous oval window gusher. Imaging showed a unilateral abnormality, with the fistula leaking from the oval window into the middle ear cleft.

Congenital X-linked Stapes Gusher Syndrome in an Infant

Congenital X-linked deafness with stapes gusher is a rare, but well-known clinical entity with characteristic radiological features. Recognition of these findings is important as it changes the treatment course and precludes stapedectomy, which if done can lead to stapes gusher in these patients. We present the case of a nine-month-old male infant with hearing loss. CT scan showed typical radiological features of X-linked stapes gusher syndrome. In addition, the superior semicircular canals appeared dehiscent which could be due to immature ossification or less likely due to defective development as part of the disease. To the best of our knowledge this is the youngest patient prospectively identified by imaging in the English medical literature.

Pathology of the vestibulocochlear nerve

Imaging of the vestibulocochlear nerve has evolved dramatically over the past few decades. The imaging specialist now is involved in the diagnosis of far more diagnostic entities than ever before. With this increased involvement comes the responsibility to increase collective knowledge regarding the pathophysiology of these diagnostic entities. This article is organized in a conventional way and covers congenital deformity of the internal auditory canal, neoplastic and pseudoneoplastic lesions, with special detailed emphasis on schwannoma of the eight cranial nerves (acoustic neuroma), nonneoplastic IAC/CPA pathology, including vascular loops, and numerous additional differential diagnostic entities, with particular emphasis on non-neoplastic meningeal disease. Lesions of the auditory pathway and an overview of cochlear implant surgery are also included in this discussion.

Conductive hearing loss caused by third-window lesions of the inner ear

BACKGROUND

Various authors have described conductive hearing loss (CHL), defined as an air-bone gap on audiometry, in patients without obvious middle ear pathologic findings. Recent investigations have suggested that many of these cases are due to disorders of the inner ear, resulting in pathologic third windows.

OBJECTIVE

To provide an overview of lesions of the inner ear resulting in a CHL due to a third-window mechanism. The mechanism of the CHL is explained along with a classification scheme for these disorders. We also discuss methods for diagnosis of these disorders.

DATA SOURCES

The data were compiled from a review of the literature and recent published research on middle and inner ear mechanics from our laboratory.

CONCLUSION

A number of disparate disorders affecting the labyrinth can produce CHL by acting as a pathologic third window in the inner ear. The common denominator is that these conditions result in a mobile window on the scala vestibuli side of the cochlear partition. The CHL results by the dual mechanism of worsening of air conduction thresholds and improvement of bone conduction thresholds. Such lesions may be anatomically discrete or diffuse. Anatomically discrete lesions may be classified by location: semicircular canals (superior, lateral, or posterior canal dehiscence), bony vestibule (large vestibular aqueduct syndrome, other inner ear malformations), or the cochlea (carotid-cochlear dehiscence, X-linked deafness with stapes gusher, etc.). An example of an anatomically diffuse lesion is Paget disease, which may behave as a distributed or diffuse third window. Third-window lesions should be considered in the differential diagnosis of CHL in patients with an intact tympanic membrane and an aerated, otherwise healthy, middle ear. Clues to suspect such a lesion include a low-frequency air-bone gap with supranormal thresholds for bone conduction, and presence of acoustic reflexes, vestibular evoked myogenic responses, or otoacoustic emission responses despite the CHL. Imaging studies can help confirm the diagnosis.

An overview of congenital/developmental sensorineural hearing loss with emphasis on the vestibular aqueduct syndrome

The evaluation of children with congenital/developmental hearing loss has undergone substantial transformation in recent years. This communication focuses on the most common cause of this type of hearing loss for which there are imaging findings: the vestibular aqueduct syndrome. The normal anatomy of the vestibular aqueduct is discussed in detail. The cochlear aqueduct with which it is commonly confused is also discussed. An overview of other congenital defects and abnormal middle/inner ear communications is also included. A brief discussion of cochlear implants is also included for completeness.

Dimensions of the cochlear nerve canal: a radioanatomic investigation

The purpose of this study was to determine the normal variations of cochlear nerve canal dimensions, which is useful information to have when assessing congenital malformations, i.e. during the preoperative evaluation of cochlear implant candidates. The length and diameter of the cochlear nerve canal were measured in 117 casts from randomly selected temporal bone specimens obtained from the Uppsala Temporal Bone Laboratory. In 16 of the casts the dimensions were correlated with those obtained from CT scans of the same temporal bone. Measurements were also made from CT examinations of the temporal bone of 50 patients referred for evaluation of cholesteatoma or chronic otitis media. The mean length and diameter in the axiopetrosal plane measured in casts were 1.17 and 2.58 mm, respectively. The mean diameter in the axial plane was 2.59 mm. The mean length and diameter determined from CT scans of the specimens were 1.19 and 1.98 mm, respectively. The mean length and diameter determined from CT examinations of patients were 1.08 and 1.91 mm, respectively. In conclusion, the cochlear nerve canal is short, with a circular cross-section. If the diameter of the canal is < 1.4 mm then the possibility of cochlear nerve abnormality should be considered; if it is > 3.0 mm then other anomalies may coexist.

X-linked deafness with stapes gusher in females

A 22-year-old woman presented with severe mixed hearing loss and a flow of cerebrospinal fluid in the middle ear during stapes surgery (stapes gusher). HRCT of the temporal bones showed characteristic abnormalities of the inner ear (bulbous dilatation of the lateral portion of the internal acoustic meatus with incomplete separation from the cochlea, and widening of the first part of the facial nerve canal) described in X-linked progressive mixed deafness with stapes gusher. The evaluation of the patient's family revealed a sister with the same clinical history and identical HRCT findings, and 11 normal male relatives. This is the first report with typical findings of this entity that affects only female members of a family, suggesting another type of inheritance.

The temporal bone. Contemporary diagnostic dilemmas

The entire topic of temporal bone imaging cannot be addressed in a single article. This article discusses the clinical areas in which there have been particularly important advances: inflammatory disease, sensorineural hearing deficit, pulsatile tinnitus, facial nerve dysfunction, and the postoperative temporal bone. The common thread linking those sections is an attempt to emphasize their pitfalls.

A particular case of deafness-oligodontia syndrome

Two previous case reports described two sibs affected with both sensorineural hearing loss and oligodontia. Here, we report a similar syndrome in a male patient with an, as yet, undescribed vestibular aqueduct enlargement on tomodensitometry. The analysis of the parent's audiograms is consistent with the suggested autosomal recessive mode of inheritance of this disorder.

Molecular analysis of the POU3F4 gene in patients with clinical and radiographic evidence of X-linked mixed deafness with perilymphatic gusher

The molecular defect in some patients with X-linked mixed deafness with perilymphatic gusher at stapes surgery (DFN3) was recently attributed to mutations in the POU3F4 gene. In this manuscript we describe the molecular analysis of the POU3F4 gene in 5 patients with clinical and radiographic evidence of DFN3. Novel mutations were found in 2 of the 5 patients analyzed, while 3 had an entirely normal protein coding sequence. The fact that 3 of the 5 patients with clinical histories and radiographic abnormalities characteristic of X-linked mixed deafness with perilymphatic gusher displayed normal POU3F4 gene sequences supports the possibility that not all patients with the characteristic phenotype have involvement of the POU3F4 gene.