Oscillatory neural responses evoked by natural vestibular stimuli in humans.

While there have been numerous studies of the vestibular system in mammals, less is known about the brain mechanisms of vestibular processing in humans. In particular, of the studies that have been carried out in humans over the last 30 years, none has investigated how vestibular stimulation (VS) affects cortical oscillations. Here we recorded high-density electroencephalography (EEG) in healthy human subjects and a group of bilateral vestibular loss patients (BVPs) undergoing transient and constant-velocity passive whole body yaw rotations, focusing our analyses on the modulation of cortical oscillations in response to natural VS. The present approach overcame significant technical challenges associated with combining natural VS with human electrophysiology and reveals that both transient and constant-velocity VS are associated with a prominent suppression of alpha power (8-13 Hz). Alpha band suppression was localized over bilateral temporo-parietal scalp regions, and these alpha modulations were significantly smaller in BVPs. We propose that suppression of oscillations in the alpha band over temporo-parietal scalp regions reflects cortical vestibular processing, potentially comparable with alpha and mu oscillations in the visual and sensorimotor systems, respectively, opening the door to the investigation of human cortical processing under various experimental conditions during natural VS.

Perception of Discomfort Caused by a Unilateral Hearing Loss in People Suffering from a Total Bilateral Vestibular Loss.

The quality of life of patients suffering from a bilateral vestibular loss is severely altered. Patients mainly complain of oscillopsia, imbalance, and spatial disorientation. Up to now, there is no efficient treatment. Some teams around the world are working on the development of a vestibular implant for the restoration of the vestibular function based on the concept similar to that of a cochlear implant, stimulating the neural vestibular pathways through electrical pulses. There are different potential stimulation sites of the vestibular system, all raising the major concern about a potential hearing loss in the implanted ear. As this implant does not exist yet, patients cannot be informed of the risk of hearing loss due to the surgical intervention versus the benefits brought by the vestibular prosthesis. In order to better inform future vestibular implant candidates, we need to evaluate the handicap of patients with an actual unilateral hearing loss, and to compare it to the way that patients suffering from a bilateral vestibular loss perceive a potential unilateral hearing loss. For this, we used the HHIA questionnaire (Hearing Handicap Inventory for Adults) on 3 groups of participants, i.e. patients with a unilateral hearing loss, patients suffering from a bilateral vestibular loss but having normal hearing, and healthy subjects. The scores reported by patients with a unilateral hearing loss were much lower than those of the other 2 groups, indicating that people whose hearing is normal overstate the disability related to a unilateral hearing loss. Patients to whom a vestibular implant is proposed in order to correct their balance disorders may use this information to decide whether or not to choose an operation.

Enchondroma of the nasal septum due to Ollier disease: a case report and review of the literature.

BACKGROUND: Morbus Ollier is characterized by the presence of multiple enchondromas (ie, benign intraosseous cartilaginous lesions). Although their manifestation in the limb bones is well described, only a few cases with ear, nose, and throat (ENT) involvement, primarily arising from the skull, have been reported. The malignant transformation toward slowly growing low-grade chondrosarcomas is the most severe form of progression. METHODS: We report a unique case of a 54-year-old patient with Ollier disease with an extensive nasal enchondroma apparently eroding the middle nasal concha and expanding to the lateral nasal wall that raised suspicion of malignant transformation. RESULTS: Radiological and histological features of enchondromas can be controversial and seem to have limited sensitivity to exclude low-grade malignancy. The clinical symptoms play a decisive role in differentiation between enchondromas and low-grade chondrosarcomas. CONCLUSION: Surgery remains the only effective solution in removing an enchondroma and preventing the tendency toward malignant transformation.

Ethical, anatomical and physiological issues in developing vestibular implants for human use.

Effort towards the development of a vestibular implant for human use are being made. This paper will summarize the first important steps conducted in Geneva towards this ambitious goal. Basically, we have faced three major issues. First, an ethical issue. While it was clear that such development would require the collaboration of human volunteers, it was also clear that stimulation of the vestibular system may produce periods of significant incomfort. We know today how to minimize (and potentially eliminate) this type of incomfort. The second issue was anatomical. The anatomical topology of the vestibular system is complex, and of potentially dangerous access (i.e. facial nerve damage). We choose not to place the electrodes inside the ampullae but close the vestibular nerve branches, to avoid any opening of the inner ear and limit the risk of hearing loss. Work on cadaver heads, confirmed by acute stimulations trials on patients undergoing ear surgery under local anesthesia, demonstrated that it is possible to stimulate selectively both the posterior and lateral ampullary nerves, and elicit the expected vertical and horizontal nystagmic responses. The third issue was physiological. One of the goal of a vestibular implant will be to produce smooth eye movements to stabilize gaze direction when the head is moving. Indeed, after restoring a baseline or "rest" activity in the vestibular pathways with steady-state electrical stimulation, we demonstrated that modulation of this stimulation is producing smooth eye movements. In conclusion, humans can adapt to electrical stimulation of the vestibular system without too much discomfort. Surgical access to the posterior and lateral ampullary nerves have been developed and, electrical stimulation of the vestibular system can be used to artificially elicit smooth eye movements of different speeds and directions, once the system is in adapted state. Therefore, the major prerequisites to develop a prototype vestibular implant for human use are fulfilled.