Deafness in cochlear and auditory nerve disorders

Sensorineural hearing loss is the most common type of hearing impairment worldwide. It arises as a consequence of damage to the cochlea or auditory nerve, and several structures are often affected simultaneously. There are many causes, including genetic mutations affecting the structures of the inner ear, and environmental insults such as noise, ototoxic substances, and hypoxia. The prevalence increases dramatically with age. Clinical diagnosis is most commonly accomplished by measuring detection thresholds and comparing these to normative values to determine the degree of hearing loss. In addition to causing insensitivity to weak sounds, sensorineural hearing loss has a number of adverse perceptual consequences, including loudness recruitment, poor perception of pitch and auditory space, and difficulty understanding speech, particularly in the presence of background noise. The condition is usually incurable; treatment focuses on restoring the audibility of sounds made inaudible by hearing loss using either hearing aids or cochlear implants.

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.

Underlying mechanisms of tinnitus: review and clinical implications

BACKGROUND

The study of tinnitus mechanisms has increased tenfold in the last decade. The common denominator for all of these studies is the goal of elucidating the underlying neural mechanisms of tinnitus with the ultimate purpose of finding a cure. While these basic science findings may not be immediately applicable to the clinician who works directly with patients to assist them in managing their reactions to tinnitus, a clear understanding of these findings is needed to develop the most effective procedures for alleviating tinnitus.

PURPOSE

The goal of this review is to provide audiologists and other health-care professionals with a basic understanding of the neurophysiological changes in the auditory system likely to be responsible for tinnitus.

RESULTS

It is increasingly clear that tinnitus is a pathology involving neuroplastic changes in central auditory structures that take place when the brain is deprived of its normal input by pathology in the cochlea. Cochlear pathology is not always expressed in the audiogram but may be detected by more sensitive measures. Neural changes can occur at the level of synapses between inner hair cells and the auditory nerve and within multiple levels of the central auditory pathway. Long-term maintenance of tinnitus is likely a function of a complex network of structures involving central auditory and nonauditory systems.

CONCLUSIONS

Patients often have expectations that a treatment exists to cure their tinnitus. They should be made aware that research is increasing to discover such a cure and that their reactions to tinnitus can be mitigated through the use of evidence-based behavioral interventions.

Cochlear implant in a patient with mondini's deformity of the cochlea: pilot patient in Pakistan

Autosomal-recessive genes account for about 80% of the patients of non-syndromic deafness, and a major portion of those lead to cochlear pathology. Given the strong cultural practice of consanguineous marriages and the lack of awareness regarding screening modalities, a high prevalence of hereditary pre-lingual deafness is seen in Pakistan. Considering the situation, cochlear implant surgery was introduced by Aga Khan University Hospital (AKUH), Karachi, Pakistan, in 2003. Recently we decided to expand the profile and services available and conducted the first ever cochlear implant on an anatomically-challenged cochlea. The case report relates to the experience of our pilot patient who was suffering from Mondini's deformity.

Late pneumolabyrinth after undiagnosed post-traumatic perilymphatic fistula. Case report illustrating the importance of systematic emergency management

INTRODUCTION

Temporal bone fracture is a common complication of high-energy cranial trauma. Labyrinth involvement is rare, but there is a risk of perilymphatic rupture that is often underestimated on initial clinical examination due to the predominance of neurological and/or somatic symptoms.

CASE REPORT

A patient presented with overlooked perilymphatic fistula, decompensated by hyperpressure effort due to poorly adapted management.

DISCUSSION

Following a review of the literature on post-traumatic pneumolabyrinth, overall management (from diagnosis to treatment, via prevention advice) was analyzed. A constructive critique of the patient's treatment was thus made.

CONCLUSION

We argue for a systematic management protocol in cranial trauma with temporal bone fracture, comprising ENT examination, millimetric-scale cross-sectional imaging of the fracture site, and standardized counseling to prevent late complications.

[The estimation of the efficacy of manual therapy included in the combined treatment of cochlear-vestibular disorders based on the results of computed stabilography]

The objective of the present study was to estimate the efficacy of the combined treatment of spondylogenic cochlear-vestibular disorders with the use of both medicamental and non-medicamental modalities. Computed static stabilometry was applied for diagnostics of postural disbalance and evaluation of the treatment outcomes. It was shown that the application of manual therapy for the management of 56 patients presenting with spondylogenic cochlear-vestibular disorders resulted in the decrease of tinnitus and the improvement of vestibular and cochlear functions.

Computed Tomography measurements of the normal and the pathologic cochlea in children

BACKGROUND

Radiological investigation is frequently undertaken to assess the aetiology of sensorineural hearing loss (SNHL).

OBJECTIVE

To establish the CT measurements of the normal cochlea in children and to determine radiological criteria correlated with SNHL.

MATERIALS AND METHODS

A retrospective study of temporal bone CT performed in 159 children, age range from 3 days to 16 years between February 1999 and July 2004. A control group (n = 88) comprised children without SNHL; the SNHL group comprised 71 children. The width of the second turn of the cochlea (CW), the cochlear height (CH), and the width of the bony canal for the cochlear nerve (WCN) were measured on a reference plane containing the modiolus, the posterior semicircular canal, the footplate, and the stapes arch.

RESULTS

Width of the canal measurements <or=1.7 mm or >or=2.5 mm supported the diagnosis of SNHL with a specificity of 97% and 91%, respectively. Cochlear width was found to be significantly smaller in the SNHL group (5.61 +/- 0.51 mm) than in the control group (5.75 +/- 0.31 mm, P < 0.02), a size <5.4 mm being highly suggestive of SNHL with a specificity of 90%. No significant variations of all measurements were found with age.

CONCLUSION

Appropriate measurements of WCN and CW are highly correlated with SNHL.

Causation of permanent unilateral and mild bilateral hearing loss in children

Children with permanent unilateral or mild bilateral hearing loss have been a focus of concern by audiologists, educators, and physicians for at least 2 decades. These children are known to be at risk for psychoeducational difficulties. However, despite this concern, little has been learned about the causative factors of these hearing losses and how those factors might be contributing to child development. This review of known causes of permanent unilateral and mild bilateral hearing loss in children is meant to draw attention to the importance of the search for etiologic factors. That is, the identification of the hearing loss should not signal the end of the diagnostic process but, rather, the beginning of a search for causation. With the combined efforts of audiologists, otolaryngologists, pediatricians, geneticists, and other medical professionals, we may enhance our understanding of the primary causes of unilateral and mild bilateral hearing loss and, perhaps, create links between causative factors and psychosocial and psychoeducational outcomes.

Recurrent meningitis and cerebrospinal fluid leak-two sides of the same vestibulocochlear defect: report of three cases

Cochlear dysplasia is a rare congenital anomaly. However, early detection of this anomaly can prevent serious consequences. We describe three cases of cochlear dysplasia that presented with recurrent meningitis and cerebro-spinal fluid (CSF) leak in children in which early diagnosis prevented further complications.

Hematopoietic stem cells prevent hair cell death after transient cochlear ischemia through paracrine effects

Transplantation of hematopoietic stem cells (HSCs) is regarded to be a potential approach for promoting repair of damaged organs. Here, we investigated the influence of hematopoietic stem cells on progressive hair cell degeneration after transient cochlear ischemia in gerbils. Transient cochlear ischemia was produced by extracranial occlusion of the bilateral vertebral arteries just before their entry into the transverse foramen of the cervical vertebra. Intrascalar injection of HSCs prevented ischemia-induced hair cell degeneration and ameliorated hearing impairment. We also showed that the protein level of glial cell line-derived neurotrophic factor (GDNF) in the organ of Corti was upregulated after cochlear ischemia and that treatment with HSCs augmented this ischemia-induced upregulation of GDNF. A tracking study revealed that HSCs injected into the cochlea were retained in the perilymphatic space of the cochlea, although they neither transdifferentiated into cochlear cell types nor fused with the injured hair cells after ischemia, suggesting that HSCs had therapeutic potential possibly through paracrine effects. Thus, we propose HSCs as a potential new therapeutic strategy for hearing loss.

[Distortion product otoacoustic emissions in newborns treated by ototoxic drugs]

OBJECTIVE

The aim of this prospective longitudinal study is to research the amplitude of distortion product otoacoustic emissions caused by the ototoxic drugs used, between the end of the administration and from 15 to 40 days after its use.

METHODS

It was a prospective longitudinal study composed by term and preterm newborns from the Santo André city hospital, in the period from July 2003 to September 2004. The first evaluation occurred on the hospital discharge day. Three groups were evaluated: control group with 33 term and healthy newborns; term study group with 19 term newborns with more than 37 weeks exposed to amikacin and/or vancomycin; and preterm study group with 15 preterm newborns from 32 to 37 weeks exposed to the same ototoxic. The newborns did not present risk factors for hearing loss according to the JCIH, 2000 concomitant to the neonatal infection. All newborns were evaluated at a corrected gestational age greater than 37 weeks. The otoacoustic emissions amplitudes obtained at the hospital discharge were compared to the ones obtained from 15 to 40 days after the discharge.

RESULTS

The otoacoustic emissions amplitudes of the preterm study group were smaller than the amplitudes of the control group and the term study group in both moments of the test. The amplitude of the newborns' otoacoustic emissions increased in the second moment of the test. The otoacoustic emissions amplitudes of the control group in the second moment of the test were similar to the term study group in the first moment of the research.

CONCLUSION

There are the increase of the distortion product otoacoustic emissions amplitude from the discharge moment until 15 to 40 days after in the post-natal period. The exposure to amikacin and vancomycin on the recommended dose by Neofax, 2003/2004 did not alter the amplitude of the emissions in the newborns without risk indicators concomitant with neonatal infection.

Intrakochleäres Schwannom als Ursache für eine Surditas

Inner ear extension caused by schwannomas, which can cause hearing loss, tinnitus and vertigo, is an extremely rare finding. We report a male patient who presented with progressive hearing loss as well as tinnitus in the right ear. Despite rheologic infusion therapy with glucocorticosteroids at another hospital, the patient showed an explicit hearing loss and vertigo related to the right ear. In the pure tone audiogram, we found complete deafness of the right ear, the equilibriometry with caloric testing showed complete loss of the labyrinth. In the HR-MRI, a structure appeared in ranges of the basal and middle cochlea with enhancement of the contrast medium. From the MRI aspect, this appeared to be a small intracochlear schwannoma. As a differential diagnosis, a chronic granulation is also possible. In agreement with the patient, we decided to control the structure clinically every 6 months using MRI; no further growth of the structure appeared. A precise imaging via HR-MRI is required to detect intracochlear schwannomas. Observation is an appropriate option for patients who have serviceable hearing. Surgical exploration can be recommended in cases of progressive diseases and growth into the inner ear with recurrent vertigo attacks. The option of radiotherapy for the treatment of intrameatal acoustic neurinomas should be considered.

Benzodiazepines and GABAergics in treating severe disabling tinnitus of predominantly cochlear origin

Severe disabling tinnitus (SDT) refers to a symptom severe enough to disrupt affected patients' routine and keep them from performing their daily activities. SDT of a predominantly central origin has been treated successfully with benzodiazepines and GABAergic drugs. Our aim was to test the control of SDT of predominantly cochlear origin by benzodiazepines and GABAergic drugs. We followed the format of a prospective, randomized, single-blind clinical trial at an academic tertiary-care hospital. We studied 30 patients, all with SDT of clear cochlear origin. We treated 10 patients with placebo (group 1), 10 with benzodiazepine drugs (group 2), and 10 with benzodiazepine and GABAergic drugs (group 3). We recorded a decrease in the annoyance and intensity of SDT as measured by a visual analog scale ranging from 1 (negligible) to 10 (unbearable). We found statistically significant improvement in comparing groups 2 and 3 with group 1 but found no significant difference when groups 2 and 3 were compared. Addition of GABAergic to benzodiazepine drugs does not modify the treatment results in SDT of a predominantly cochlear origin.

Auditory brainstem implant (ABI): new frontiers in adults and children

Previous studies have considered only patients with neurofibromatosis type 2 (NF2) older than 12 years as candidates for an auditory brainstem implant (ABI). Our study expands the potential criteria to include both children and adult subjects with other cochlear or cochlear nerve malfunctions who either would not benefit at all from a cochlear implant (eg, cochlear nerve aplasia or avulsion) or whose benefit was or would be severely compromised (eg, cochlear ossification, cochlear fracture).

STUDY DESIGN

In our department, over the period from April 1997 to September 2002, 29 patients, 20 adults and 9 children, were fitted with ABIs. Their ages ranged from 14 months to 70 years. Thirteen subjects had tumors, 10 NF2 and 3 solitary vestibular schwannoma, and 16 patients had a variety of nontumor (NT) cochlear or cochlear nerve diseases. A retrosigmoid-transmeatal approach was used in T and a retrosigmoid approach in NT patients. The electrode array was inserted into the lateral recess of the fourth ventricle and correct electrode positioning was monitored with the aid of electrically evoked auditory brainstem responses (EABRs).

RESULTS

Correct implantation was achieved in all patients. No complications were observed due to implantation surgery or related to ABI activation or long-term use. Auditory sensations were induced in all patients with various numbers of electrodes (from 5 to 15). Different pitch sensations were identifiable with different electrode stimulation. Closed-set word recognition, open-set sentence recognition, and speech tracking scores achieved by the patients are reported in detail. The auditory performance of the patients showed significantly better outcomes than controls (Multicentric European clinical investigations on ABI with NF2).

CONCLUSION

We have shown that the indications for the ABI can be extended to include NT patients with severe cochlear and/or cochlear nerve abnormalities. The degree of auditory benefit varies as a function of the underlying pathological conditions, with NT subjects exhibiting significantly better outcomes than the T patients.

Auditory Neuropathy or Endocochlear Hearing Loss?

AIMS

The purpose of the study was to define boundaries between endocochlear hearing loss and auditory neuropathy in children with congenital profound hearing loss and positive otoacoustic emissions.

PATIENT

A child presented with bilateral profound hearing loss, which was confirmed by the absence of evoked auditory potentials at 110 dB and with conserved otoacoustic emissions. The lack of any relevant medical history, a normal neurologic pediatric examination, and the improvement obtained with powerful hearing aids suggested an endocochlear cause. Genetic testing identified mutations in OTOF, responsible for the DFNB9 recessive form of hearing loss.

RESULTS

In recent years, cases of children with hearing loss associated with positive otoacoustic emissions have been labeled as "auditory neuropathy." Classically, this form of hearing loss is refractory to the use of hearing aids and cochlear implants. Mutations in OTOF lead to inner hair cells dysfunction, whereas the outer hair cells are initially functionally preserved. As this form of endocochlear hearing loss can be detected at a molecular level, genetic testing can be proposed for cases of nonsyndromic auditory neuropathy, as those children could benefit from cochlear implantation.

CONCLUSION

It is advisable to reserve the term "auditory neuropathy" for patients who present hearing loss and conserved otoacoustic emissions in the context of a neurologic syndrome or for children with suggestive perinatal history. In other cases, genetic testing for mutations in OTOF should be carried out.