Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation.

OBJECTIVE: The vestibular system provides essential information about balance and spatial orientation via the brain to other sensory and motor systems. Bilateral vestibular loss significantly reduces quality of life, but vestibular implants (VIs) have demonstrated potential to restore lost function. However, optimal electrical stimulation strategies have not yet been identified in patients. In this study, we compared the two most common strategies, pulse amplitude modulation (PAM) and pulse rate modulation (PRM), in patients. APPROACH: Four subjects with a modified cochlear implant including electrodes targeting the peripheral vestibular nerve branches were tested. Charge-equivalent PAM and PRM were applied after adaptation to baseline stimulation. Vestibulo-ocular reflex eye movement responses were recorded to evaluate stimulation efficacy during acute clinical testing sessions. MAIN RESULTS: PAM evoked larger amplitude eye movement responses than PRM. Eye movement response axes for lateral canal stimulation were marginally better aligned with PRM than with PAM. A neural network model was developed for the tested stimulation strategies to provide insights on possible neural mechanisms. This model suggested that PAM would consistently cause a larger ensemble firing rate of neurons and thus larger responses than PRM. SIGNIFICANCE: Due to the larger magnitude of eye movement responses, our findings strongly suggest PAM as the preferred strategy for initial VI modulation.

[Vestibular function: the 6th sense... ignored]. / La fonction vestibutaire: le sixième sens... ignoré.

Dizzy patients are often misunderstood by doctors. Those with a complete vestibular deficit and whose function is restored by a vestibular implant use all kinds of words to describe what they feel when the neuroprosthesis is turned on. Their feeling varied from a strong emotion to a feeling of heat. The notion of dizziness or motion was rare. How to describe the sensations provided by an ignored and unconscious sense? With the eyes, one sees; with the ears one hears; no term exists that describes what we do with the vestibular system! Should we say we vestibulise? The notion traditionally taught that patients suffering from a vestibular disorder should describe an imbalance or a rotatory vertigo, be able specify the direction of rotation, etc. is inadequate, unrealistic.

[The benefit of systematic hearing screening of school-age children]. / Bénéfice d'un dépistage systématique de la surdité chez l'enfant en âge scolaire.

The hearing is routinely tested in all newborns in most European countries. Thereafter, no hearing test is performed in a systematic way, despite the many conditions that can cause hearing loss in the first years of life. If language acquisition is possible with only one ear, even a unilateral hearing loss can be the cause of learning difficulties at school. In Geneva, a screening program for hearing deficit was introduced in 1955 in all primary schools of the canton. This paper shows the efficiency of the program, which can detect unnoticed deafness, sometimes in children whose neonatal screening had proved normal. Such a program should be applied to all private schools and to schools for disabled children.

[Aspirin ototoxicity: a rare situation today]. / Ototoxicité à l'Aspirine: une situation rare de nos jours.

Aspirin is commonly used most often at low daily doses. We report a case of acute aspirin intoxication resulting in a transitory hearing loss, tinnitus, and vertigo. Such intoxications occur at doses of several grams. The disorders caused by aspirin are fortunately reversible. The mechanisms of ototoxicity appear to involve, in part, electro-mobility of the outer hair cells of the inner ear by inhibiting the movement of prestin.

[Odd stories of patients suffering from Menière's disease]. / Les étranges histoires des patients... et de leurs docteurs (!) dans le tourbillon du Menière!

The cause of Meniere's disease is unknown. The postmortem examination of the temporal bone reveals an "endolymphatic hydrops" of the inner ear. Classically, patients describe episodes of vertigo, fluctuations of hearing and tinnitus. But some report "strange stories" that deserve doctor's attention. This article explains why their history (as those suffering from any other vestibular disorder) is often particular, to recall the few knowledge of the disease, how the endolymphatic hydrops was considered as the cause of the disorder, while it is rather an epiphenomenon, and to show how one can believe, wrongly, that a therapy is efficient after a study that seems however at first correctly performed.

[Causal relationship: and if "yes", and if "not"... on basis of which criterias?]. / Relation de cause à effet: et si "oui", et si "non", ... sur la base de quels critères?

A woman was referred to us 4 days after the sudden onset of continuous rotatory vertigo. The diagnosis of a left vestibular neuronitis was made. During the investigations, a meningioma of the contralateral posterior fossa was discovered. Is there any relationship between the two disorders? The etiology of peripheral vestibular disorders remains poorly understood in most cases. Anomalies of cells surrounding the sensory organs have been demonstrated in post-mortem examination of the inner ear of patients with a vestibular deficit that could be caused by a "biological stress". Therefore there may be a link between left vestibular deficit and the mass of the right posterior fossa, considered as a fortuitous discovery, at first.

Atypical presentations of malignant otitis externa.

INTRODUCTION: Malignant otitis externa is a life-threatening infection of the skull base. Its presentation is not always typical. CASE REPORTS: We report three cases of malignant otitis externa which illustrate the diversity of its clinical manifestations and the difficulties in its diagnosis. DISCUSSION: The perception of malignant otitis externa as an infection caused by Pseudomonas aeruginosa in diabetic patients is not always correct. The adoption of diagnostic criteria could be helpful in identifying atypical cases.

[Development of a vestibular implant for the rehabilitation of bilateral deafness]. / Développement d'un implant vestibulaire pour la réhabilitation des déficits vestibulaires bilatéraux.

The development of a vestibular implant for the rehabilitation of bilateral vestibular loss is funded on a concept comparable to that of the cochlear implant used in the rehabilitation of bilateral deafness. This paper carries an overview of the main aspects of such a development and describes the first experiments done in human subjects in Geneva.

[Cervical vertigo: myth or reality?]. / Vertiges d'origine cervicale: mythe ou réalité?

Patients displaying vertigo associated with cervical symptoms: what is the origin? Diagnosis of cervical vertigo is sometimes retained. It remains very controversial. Indeed there is neither a convincing pathological mechanism nor a diagnostic test. Despite lack of strong benefit evidence, manual therapy can be offered to selected patients.

[A series of tumors of the posterior fossa]. / Processus expansifs de la fosse postérieure.

This article presents a series of tumors of the posterior fossa. Imbalance or dizziness motivate patients to consult while they often neglect a hearing loss. However, any unilateral hearing impairment of any kind, even transitory, requires testings to rule out a retrocochlear lesion. In this series, 23% of vestibular schwannomas manifested by a sudden deafness, with a recovery of hearing in half of them.

[Neonatal hearing screening program and school education for deaf children in Switzerland]. / Dépistage systématique néonatal de la surdité et mode de scolarisation des enfants malentendants en Suisse.

A national hearing screening in newborns was introduced in Switzerland in the early 2000s. Since then, the number of maternities which applies has considerably increased. Test results are collected in a national database, giving a good overview of the quality of screening and incidence of deafness in Switzerland. The diagnosis and rehabilitation of deafness is earlier than before. This, combined to modem technologies allows mainstream integration of almost every deaf child.

[Dental implants and radiotherapy]. / Implants dentaires et radiothérapie.

Dental implants on irradiated and often grafted bone, in patients previously treated for head and neck cancer is a controversial issue. For some specialists, particularly in North-America they constitute a formal contra indication. However, a review of 21 studies reported mainly by European specialists argues that these implants can be done with an acceptable rate of complications, confirming our clinical observation. Patients have reported significant improvements in their quality of life after dental implantation.

Immuno-detection of Staphylococcus aureus biofilm on a cochlear implant.

CASE PRESENTATION: A 46-year-old man suffering from progressive deafness since childhood received a Clarion 90 K cochlear implant with the HiRes preformed electrode in his left ear in October 2006. A persistent Staphylococcus aureus infection failed to be treated with corticoids, amoxicillin/ clavulanate, ciprofloxaxin, and rifampin. The processor was removed on July 2007. INTERVENTIONS: The removed cochlear implant processor was treated with different reagents, with the aim of detecting a S. aureus and S. aureus biofilm: (1) fluorescein-coupled Fc of anti-human serum, (2) polyclonal anti-polysaccharide intercellular adhesion antibodies coupled to Alexa Fluor 568 goat anti-rabbit immunoglobulin (Ig)G, (3) crystal violet, (4) methylene blue, (5) acridine orange, (6) Gram stain, and (7) live/dead fluorescent stain. RESULTS: S. aureus and the major constituent of the S. aureus biofilm, the polysaccharide intercellular adhesion, were detected on the surface of the implant. S. aureus was isolated after a simple contact between the implant and a solid growth medium. The ability of the isolated S. aureus strain to produce biofilm in vitro was confirmed. INTERPRETATION: S. aureus biofilm was documented on the implant. Initial bacterial colonization could be related to the pocket of the removable magnet. Colonies of S. aureus without biofilm were found attached to the electrode wire. CONCLUSION: We report one case of a S. aureus biofilm infection documented on a cochlear implant, as assessed by immuno-microscopy. The biofilm was likely responsible for the persistent infection which manifested for many months after the implant surgery and could explain the unusual bacterial phenotypic resistance against administered antimicrobial agents.

[Otitis externa, a self-inflicted disease?]. / Otites externes: une maladie auto-infligée?

Otitis externa, an inflammation of the external auditory canal is the most frequent cause of ENT consultation all over the world. It can be caused by viral, bacterial or fungal infections. In most of the cases it is provoked by anatomical causes and, even more frequently inadvertently, by the patient himself. Typically, otitis externa is an isolated episode of short duration, easily treated with topical medication. It evolves rarely to the atypical forms of chronic otitis externa and malignant otitis externa. It is important to search for an allergy, eczema or immunodepression in cases of chronic otitis externa and for diabetes in cases of malignant otitis externa.