Showing papers in "Advances in oto-rhino-laryngology in 2006"
TL;DR: Olfactory senescence starts at about the age of 36 years in both sexes and accelerates with advancing years, involving pleasant odours preferentially and olfactory dysfunction is near-universal, early and often severe in IPD and AD developing before any movement or cognitive disorder.
Abstract: There has been gradual increase of interest in olfactory dysfunction since it was realised that anosmia was a common feature of idiopathic Parkinson's disease (IPD) and Alzheimer-type dementia. It is an intriguing observation that a premonitory sign of a disorder hitherto regarded as one of movement or cognition may be that of disturbed sense of smell. In this review of aging, IPD, parkinsonian syndromes, tremor, Alzheimer's disease (AD), motor neuron disease (MND), Huntington's chorea (HC) and inherited ataxia, the following observations are made: (1) olfactory senescence starts at about the age of 36 years in both sexes and accelerates with advancing years, involving pleasant odours preferentially; (2) olfactory dysfunction is near-universal, early and often severe in IPD and AD developing before any movement or cognitive disorder; (3) normal smell identification in IPD is rare and should prompt review of diagnosis unless the patient is female with tremor-dominant disease; (4) anosmia in suspected progressive supranuclear palsy and corticobasal degeneration is atypical and should likewise provoke diagnostic review; (5) subjects with hyposmia and one ApoE4 allele have an approximate 5-fold increased risk of later AD; (6) impaired sense of smell may be seen in some patients at 50% risk of parkinsonism, and possibly in patients with unexplained hyposmia; (7) smell testing in HC and MND where abnormality may be found is not likely to be of clinical value, and (8) biopsy of olfactory nasal neurons reveals non-specific changes in IPD and AD and at present will not aid diagnosis.
275 citations
TL;DR: The chapter will begin with a brief overview of what the human nose can do, contesting notions that human olfaction is a second-rate system, and will cover the neural correlates of human Olfactory function, including aspects of basic chemosensory processing and higher-order olfactory operations.
Abstract: This chapter focuses on central olfactory processing in the human brain. As the psychophysiology of human olfactory function is important for appreciating its underlying neurophysiology, the chapter will begin with a brief overview of what the human nose can do, contesting notions that human olfaction is a second-rate system. It will be followed by an anatomical survey of the principal recipients of olfactory bulb input, with some comments on the unique organizing properties that distinguish olfaction from other sensory modalities. The final section will cover the neural correlates of human olfactory function, including aspects of basic chemosensory processing (odor detection, sniffing, intensity, valence) and higher-order olfactory operations (learning, memory, crossmodal integration), with particular emphasis on functional imaging data, though human lesion studies and intracranial recordings will also be discussed.
224 citations
TL;DR: An overview of the various vocoder-centric processing strategies proposed for cochlear implants since the late 1990s is provided including the strategies used in different commercially available implant processors.
Abstract: The principles of the most recent cochlear implant processors are similar to that of the channel vocoder, originally used for transmitting speech over telephone lines with much less bandwidth than that required for transmitting the unprocessed speech signal. An overview of the various vocoder-centric processing strategies proposed for cochlear implants since the late 1990s is provided including the strategies used in different commercially available implant processors. Special emphasis is placed on reviewing the strategies designed to enhance pitch information for potentially better music perception. The various noise suppression strategies proposed over the years based on multi-microphone and single-microphone inputs are also described.
215 citations
TL;DR: Using the latency of cortical auditory evoked potentials (CAEPs) as a measure, it is found that central auditory pathways are maximally plastic for a period of about 3.5 years.
Abstract: A common finding in developmental neurobiology is that stimulation must be delivered to a sensory system within a narrow window of time (a sensitive period) during development in order for that sensory system to develop normally. Experiments with congenitally deaf children have allowed us to establish the existence and time limits of a sensitive period for the development of central auditory pathways in humans. Using the latency of cortical auditory evoked potentials (CAEPs) as a measure we have found that central auditory pathways are maximally plastic for a period of about 3.5 years. If the stimulation is delivered within that period CAEP latencies reach age-normal values within 3-6 months after stimulation. However, if stimulation is withheld for more than 7 years, CAEP latencies decrease significantly over a period of approximately 1 month following the onset of stimulation. They then remain constant or change very slowly over months or years. The lack of development of the central auditory system in congenitally deaf children implanted after 7 years is correlated with relatively poor development of speech and language skills [Geers, this vol, pp 50-65]. Animal models suggest that the primary auditory cortex may be functionally decoupled from higher order auditory cortex due to restricted development of inter- and intracortical connections in late-implanted children [Kral and Tillein, this vol, pp 89-108]. Another aspect of plasticity that works against late-implanted children is the reorganization of higher order cortex by other sensory modalities (e.g. vision). The hypothesis of decoupling of primary auditory cortex from higher order auditory cortex in children deprived of sound for a long time may explain the speech perception and oral language learning difficulties of children who receive an implant after the end of the sensitive period.
168 citations
TL;DR: Improvement in speech coding strategies, implantation at younger ages and in children with greater preimplant residual hearing, and rehabilitation focused on speech and auditory skill development are leading to a larger proportion of children approaching spoken language levels of hearing age-mates.
Abstract: Development of spoken language is an objective of virtually all English-based educational programs for children who are deaf or hard of hearing. The primary goal of pediatric cochlear implantation is to provide critical speech information to the child's auditory system and brain to maximize the chances of developing spoken language. Cochlear implants have the potential to accomplish for profoundly deaf children what the electronic hearing aid made possible for hard of hearing children more than 50 years ago. Though the cochlear implant does not allow for hearing of the same quality as that experienced by persons without a hearing loss, it nonetheless has revolutionized the experience of spoken language acquisition for deaf children. However, the variability in performance remains quite high, with limited explanation as to the reasons for good and poor outcomes. Evaluating the success of cochlear implantation requires careful consideration of intervening variables, the characteristics of which are changing with advances in technology and clinical practice. Improvement in speech coding strategies, implantation at younger ages and in children with greater preimplant residual hearing, and rehabilitation focused on speech and auditory skill development are leading to a larger proportion of children approaching spoken language levels of hearing age-mates.
154 citations
TL;DR: Recent studies indicate that pheromone-like compounds are most likely registered at the level of olfactory receptor cells, rendering the chemical information system more independent of specific organ structures.
Abstract: The vomeronasal organ (VNO) is a complex of different structures that forward specific
chemical signals commonly called pheromones to the central nervous system. In some macrosmatic
animals, e.g. ro
143 citations
TL;DR: Findings are relevant to the design of future implant devices and to various important issues regarding the surgical technique used for implantation, including the possible use of the round window as a portal of entry for electrode insertion.
Abstract: The development of hybrid electroacoustic devices has made conservation of residual hearing an important goal in cochlear implant surgery. Our laboratory has recently conducted anatomical studies directed toward better understanding mechanisms underlying loss of residual hearing associated with electrode insertion. This paper provides an overview of observations based on microdissection, scanning electron microscopy and temporal bone histology relating to inner ear injury that may occur during implant surgery. Trauma to cochlear structures including lateral wall tissues, the basilar membrane, the osseous spiral lamina and the modiolus is considered in relation to the implications of specific types of injury for hearing preservation. These findings are relevant to the design of future implant devices and to various important issues regarding the surgical technique used for implantation, including the possible use of the round window as a portal of entry for electrode insertion.
142 citations
TL;DR: No effective therapy exists even though specific olfactory training might be promising, and central mechanisms cannot completely be ruled out in post-URTI disorders.
Abstract: Postviral olfactory disorders usually occur after an upper respiratory tract infection (URTI) associated with a common cold or influenza. With a prevalence between 11 and 40% they are among the common causes of olfactory disorders. Women are more often affected than men and post-URTI disorders usually occur between the fourth and eighth decade of life. The exact location of the damage in post-URTI is not yet known even though from biopsies a direct damage of the olfactory receptor cells is very likely. Nevertheless, central mechanisms cannot completely be ruled out. The diagnosis is made according to the history, clinical examination and olfactory testing. Affected patients usually recall the acute URTI and a close temporal connection should be present to establish the diagnosis. Spontaneous recovery might occur within 2 years. So far, no effective therapy exists even though specific olfactory training might be promising.
109 citations
TL;DR: It has, however, not been possible to reveal a relationship between the degree of survival of spiral ganglion cells and performance of cochlear implants, and it is important to understand the histopathological changes that follow co chlear implantation.
Abstract: The most common forms of severe hearing loss and deafness are related to morphological
changes in the cochlea Many individuals with such forms of hearing disorders have
received cochlear implants
94 citations
TL;DR: This chapter considers the current state of knowledge in anatomy, taste bud physiology, molecular biology of bitter, sweet, sour, savory and salty tastes, afferent signaling and quality coding, human perception, and pathophysiology and senescence of taste.
Abstract: The anatomy, physiology and psychology of taste provide a glimpse into a uniquely heterogeneous sensory world; a world that is robust in its importance to flavor, redundant in its transductive heterogeneity and complexity, requisite in that feeding and hence life usually depend upon taste input, regenerative in that taste cells constantly turn over and regrow after tissue damage, and resistant to disease, loss of neural innervation and epithelial destruction. This chapter considers our current state of knowledge in anatomy, taste bud physiology, molecular biology of bitter, sweet, sour, savory and salty tastes, afferent signaling and quality coding, human perception, and pathophysiology and senescence of taste. We highlight some of the advances made in molecular biology of taste and point out areas where further research is needed ranging from taste bud development and regeneration, to within-taste bud processing, to central/perceptual coding networks for taste. Our hope is that this chapter will provide a background for greater understanding of taste physiology, perception, disease, and future sensory research.
93 citations
TL;DR: It is demonstrated that the ABI can stimulate the central auditory system in a way that gives the ability of open set speech understanding, and can thus be indicated in nontumor adult patients who are not candidates for a cochlear implant.
Abstract: Auditory brainstem implants (ABIs) are currently indicated for patients older than 12
years with neurofibromatosis type 2 (NF2) who had bilateral schwannoma removed. Over
the last 10 years, we have
TL;DR: The anatomical pathways for the two primary animal models (rodent and nonhuman primate) are provided followed by the presumed human gustatory pathway and a review of flavor processing.
Abstract: The purpose of this chapter is to provide a general overview of the central representation
of gustatory information in the human brain. The anatomical pathways for the two primary
animal models (rod
TL;DR: Based on the analysis of the data on developmental sensitive periods in auditory plasticity of hearing, hearing-impaired and deaf, cochlear-implanted, animals and comparable data from humans, a co chlear implantation within the first 2 years of age is recommended.
Abstract: The benefit of cochlear implantation crucially depends on the ability of the brain to learn to classify neural activity evoked by the cochlear implant. Brain plasticity is a complex property with massive developmental changes after birth. The present paper reviews the experimental work on auditory plasticity and focuses on the plasticity required for adaptation to cochlear implant stimulation. It reviews the data on developmental sensitive periods in auditory plasticity of hearing, hearing-impaired and deaf, cochlear-implanted, animals. Based on the analysis of the above findings in animals and comparable data from humans, a cochlear implantation within the first 2 years of age is recommended.
TL;DR: Using converging methods from psychophysics, anatomy, and genetics, it is demonstrated that valid uses of modern chemosensory testing in clinical diagnosis and intervention are demonstrated.
Abstract: Psychophysical measures attempt to capture and compare subjective experiences objectively. In the chemical senses, these techniques have been instrumental in describing relationships between oral sensation and health risk, but they are often used incorrectly to make group comparisons. This chapter reviews contemporary methods of oral sensory assessment, with particular emphasis on suprathreshold scaling. We believe that these scales presently offer the most realistic picture of oral sensory function, but only when they are used correctly. Using converging methods from psychophysics, anatomy, and genetics, we demonstrate valid uses of modern chemosensory testing in clinical diagnosis and intervention.
TL;DR: The history of the development of cochlear implants and auditory brainstem implants and the different strategies of signal processing that are in use in these devices are discussed.
Abstract: Cochlear implants have evolved during the past 30 years from the single-electrode device introduced by Dr. William House, to the multi-electrode devices with complex digital signal processing that are in use now. This paper describes the history of the development of cochlear implants and auditory brainstem implants (ABIs). The designs of modern cochlear and auditory brainstem implants are described, and the different strategies of signal processing that are in use in these devices are discussed. The primary purpose of cochlear implants was to provide sound awareness in deaf individuals. Modern cochlear implants provide much more, including good speech comprehension, and even allow conversing on the telephone. ABIs that stimulate the cochlear nucleus were originally used only in patients with neurofibromatosis type 2 who had lost hearing due to removal of bilateral vestibular schwannoma. In such patients, ABIs provided sound awareness and some discrimination of speech. Recently, similar degrees of speech discrimination as achieved with cochlear implants have been obtained when ABIs were used in patients who had lost function of their auditory nerve on both sides for other reasons such as trauma and atresia of the internal auditory meatus.
TL;DR: Patients with posttraumatic olfactory loss may be unable to detect important warning signs such as gas leaks, volatile chemical fumes and fires and therefore place themselves and coworkers at an increased risk for serious injury or death.
Abstract: Head injury is the leading cause of posttraumatic anosmia. Complete or partial loss of olfactory function may occur when the nasal passages are blocked, olfactory nerves are injured or there are contusions or hemorrhages in olfactory centers of the brain. Evaluation of patients with posttraumatic olfactory loss should include a physical examination by the otolaryngologist. Nasal endoscopy and radiological studies should be performed as well as olfactory function tests to determine the degree and type of olfactory impairment. Although treatment options may be limited, physicians should provide information and counseling regarding the risks and hazards associated with loss of olfactory function. For some individuals such as cooks, firefighters, and research scientists, an assessment of vocational activities should be performed prior to reentry into the workplace. Individuals with impaired olfactory function may be unable to detect important warning signs such as gas leaks, volatile chemical fumes and fires and therefore place themselves and coworkers at an increased risk for serious injury or death.
TL;DR: In order to assess changes related to the patients' quality of life or effects of qualitative olfactory dysfunction, questionnaires are being used, e.g. tests for odor identification, and odor thresholds.
Abstract: Numerous techniques are available for the investigation of chemosensory functions in
humans. They include psychophysical measures of chemosensory function, e.g. odor identification,
odor discriminat
TL;DR: As a result of the relative sizes of the various compartments in the nasal cavity, the bulk of the airflow is along the floor of the nose, and the percent of airflow directed to the olfactory region is about 10%.
Abstract: As a result of the relative sizes of the various compartments in the nasal cavity, the bulk of the airflow is along the floor of the nasal cavity. The percent of airflow directed to the olfactory region (the superior region of the nasal cavity) is about 10%. Structural changes in the nasal cavity can alter airflow pathways and the characteristics of the airflow (e.g. laminar, mixed or turbulent) within nasal compartments. The relationship between the olfactory response and the stimulus is complex and may vary depending on the physiochemical properties of the odor and the rate at which odorants are delivered to the olfactory receptors. Changes in nasal airflow may impact the various olfactory functions (e.g. identification, differentiation) differently. When there is a nasal obstruction, a decline in olfactory ability may not simply be an access problem, since nasal disease can affect olfactory processing at many levels.
TL;DR: The basis of electrical stimulation of neurons within the central auditory pathway via an auditory brainstem implant is reviewed with an emphasis on pathophysiology and safety.
Abstract: Sensorineural hearing loss is the most common form of deafness in humans. In patients with a severe-profound sensorineural hearing loss therapeutic intervention can only be achieved by direct electrical stimulation of the auditory nerve via a cochlear implant, or - in cases where a cochlear implant is not a surgical option - neurons within the central auditory pathway via an auditory brainstem implant. This paper reviews the basis of electrical stimulation of these structures with an emphasis on pathophysiology and safety.
TL;DR: In caring for patients with taste disorders, the clinical assessment should include complete examination of the cranial nerves and, in particular, gustatory testing, which is essential to look for additional, even mild, neurological signs and symptoms.
Abstract: In caring for patients with taste disorders, the clinical assessment should include complete
examination of the cranial nerves and, in particular, gustatory testing. Neurophysiological
methods such
TL;DR: The present chapter focuses on those ENT surgical procedures where at least some prospective and systematic studies on gustatory dysfunction exist, and taste disorders after middle ear surgery, tonsillectomy and dental interventions are largely discussed.
Abstract: Clinical taste testing in humans is far from being routinely performed in ear, nose and throat (ENT) clinics. Consequently, most reports on posttraumatic and postoperative taste disorders are case reports and mainly consist of qualitative (e.g. dysgeusia, metallic taste) taste changes after either head injury or ENT surgery. Since quantitative taste deficiencies (ageusia, hypogeusia) often go unnoticed by the patients, the real incidence of ageusia and hypogeusia after head trauma and various surgical procedures remains largely unknown. This lack of reliable clinical data is partly due to the lack of easy, reproducible and rapid clinical taste testing devices. The present chapter tries to resume the current knowledge on postoperative and posttraumatic taste disorders. Despite the sparse literature, the chapter focuses on those ENT surgical procedures where at least some prospective and systematic studies on gustatory dysfunction exist. Accordingly, taste disorders after middle ear surgery, tonsillectomy and dental interventions are largely discussed.
TL;DR: Chronic rhinosinusitis encompasses a group of disorders characterized by inflammation of the mucosa of the nose and paranasal sinuses of at least 12 weeks' duration, and most studies show that improved olfactory sensation in this setting is usually transient and incomplete.
Abstract: Chronic rhinosinusitis encompasses a group of disorders characterized by inflammation
of the mucosa of the nose and paranasal sinuses of at least 12 weeks’ duration. In addition
to nasal obstruction
TL;DR: The surgical anatomy of the nucleus and surgical placement of the ABI in patients with neurofibromatosis type 2 are described, and surgical considerations in this group of challenging patients are detailed.
Abstract: Patients with neurofibromatosis type 2 often develop bilateral life-threatening vestibular schwannoma necessitating tumor removal, which results in deafness. We developed the auditory brainstem implant (ABI) in order to be able to electrically stimulate the cochlear nucleus complex in patients with bilateral cochlear nerve injury from bilateral schwannoma. After tumor removal, the electrode array of the ABI is inserted into the lateral recess of the fourth ventricle and placed over the surface of the ventral and dorsal cochlear nuclei. The ABI is designed to stimulate auditory neural structures within the cochlear nucleus in order to convey salient cues about the frequency, amplitude, and temporal characteristics of sounds. To date, more than 200 patients have received an ABI device at our institution. Recently, penetrating ABIs were introduced, and preliminary results of penetrating ABIs are discussed in this paper. The surgical anatomy of the nucleus and surgical placement of the ABI in patients with neurofibromatosis type 2 are described, and surgical considerations in this group of challenging patients are detailed.
TL;DR: This chapter describes a procedure for the use of electrophysiology to aid placement in the operating room, which makes it possible to position the majority of electrodes over the surface of the cochlear nucleus thus minimising stimulation of other cranial nerves, which might result in undesirable side effects.
Abstract: The number of electrodes that elicit usable auditory sensations with an auditory brainstem implant varies significantly between subjects. For those with only very few, movement of the array by only a few millimetres could make a significant improvement to their outcome, but yet the point at which this is normally discovered is during activation, weeks after the surgery. The number of the electrodes that are able to stimulate the auditory system can be more reliably assured by the use of electrophysiologic guidance in the placement of the implanted electrode array. This chapter describes a procedure for the use of electrophysiology to aid placement in the operating room. The procedure involves stimulating the individual electrodes and recording electrical auditory brainstem responses (EABR) as an aid in positioning the electrode array. This procedure makes it possible to position the majority of electrodes over the surface of the cochlear nucleus thus minimising stimulation of other cranial nerves, which might result in undesirable side effects. Correctly positioned electrodes elicit an EABR response with between 1 and 4 peaks with average latencies approximately (in ms) 0.7 (0.4-0.9), 1.5 (1.2-1.9), 2.7 (2.1-3.4) and 3.7 (3.4-4.0). These waves likely correspond to waves III-VI of the traditional ABR (and wave II if an excitable stump of the auditory nerve is present). No further peaks within a 10-ms window should be seen nor should activation of other cranial nerves occur. The response to stimulation of bipolar combinations of electrodes covering lateral, medial and distal positions provide information about the insertion depth. In individuals with a large lateral recess, measuring other combinations may assist in sideways and rotational orientation of the electrode array.
TL;DR: Cochlear implants and ABIs are successful in providing speech discrimination because of redundancy in the processing in the ear, redundancy of the speech signal and because the auditory nervous system has a high degree of plasticity.
Abstract: Cochlear implants bypass functions of the cochlea that have been regarded to be fundamental for discrimination of the frequency (or spectrum). Frequency discrimination is essential for discrimination of sounds, including speech sounds, and the normal auditory system is assumed to make use of both (power) spectral and temporal information for frequency discrimination. Spectral information is represented by the place on the basilar membrane that generates the largest amplitude of vibration on the basilar membrane. Evidence has been presented that the temporal representation of frequency is more robust than the place representation and thus regarded more important for speech discrimination. The fact that some cochlear implants provide good speech discrimination using only information about the energy in a few spectral bands seems to contradict these studies. In that way, frequency discrimination may be similar to trichromatic color vision, which is based on the energy in only three different spectral bands of light, accomplished by different color-sensitive pigments in the cones of the retina. Cochlear nucleus implants (ABIs) also bypass the auditory nerve, which does not perform any processing. Therefore, it may be expected that ABIs are equally efficient as cochlear implants. However, experience from the use of ABIs in patients with bilateral vestibular schwannoma has not been encouraging, but recent studies of the use of ABIs in patients with other causes of injuries to the auditory nerve have shown similar speech discrimination as achieved with modern cochlear implants. Cochlear implants and ABIs are successful in providing speech discrimination because of redundancy in the processing in the ear, redundancy of the speech signal and because the auditory nervous system has a high degree of plasticity. Expression of neural plasticity makes the auditory nervous system adapt to the change in demands of processing of the information provided by cochlear implants.
TL;DR: An understanding of these potential toxins and their impact on gustation will help physicians better recognize, and potentially limit the impact of such taste alterations on their patients.
Abstract: A large number of substances and disease processes may impact the sense of taste Toxic substances may cause taste dysfunction from their effects on the gustatory system from the salivary gland, to the taste bud, to the central neural pathways A number of external toxins, including industrial compounds, tobacco, and alcohol, may adversely affect taste, most commonly through local effects in the oral cavity Blood-borne toxins, such as medications and those present in autoimmune and other systemic disorders (eg renal or liver failure), have access to all parts of the gustatory system, and thus may exhibit varied effects on taste function An understanding of these potential toxins and their impact on gustation will help physicians better recognize, and potentially limit the impact of such taste alterations on their patients
TL;DR: Disease, infection, injury or aging can interfere with neuronal cell replacement as well as transduction and coding processes, resulting in impairment and distortions of olfactory performance.
Abstract: Odor transduction and quality coding involves a cascade of events that occur at the level
of the olfactory epithelium and olfactory bulbs Odorants bind to one or a few specific olfactory
receptors