Chronic vestibular and auditory effects of marijuana

The objective of this study was to ascertain vestibular dysfunction and impaired hearing resulting from the chronic use of marijuana. Electro-nystagmography was utilized to record gaze nystagmus, tracking a pendulum, spontaneous nystagmus, positional nystagmus, and rotation on the torsion swing. Pure tone thresholds were also obtained. The results of these tests, for normals and heavy marijuana users, were then compared. The comparison of these results showed significant changes in vestibular functions for chronic marijuana users in: a. decrease in maximum amplitude on torsion swing; b. increase in incidence of nystagmus in two or more supine positions; and c. decrease in speed of slow component on caloric tests.     

Aging effects on monoamines in rat medial vestibular and cochlear nuclei

Noradrenaline (NA), dopamine (DA), serotonin (5-HT) and their metabolites — 3-methoxy,4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) — were determined using HPLC in medial vestibular nucleus (MVN), anteroventral cochlear nucleus (AVCN), dorsal+posteroventral cochlear nucleus (DCN+PVCN), locus coeruleus (LC) and raphe dorsalis of Dark Agouti-Hanovre (DA-HAN) rats aged 4, 21 and 24 months. In older rats, the main noradrenergic changes were a decrease of NA content with an increase of the MHPG/NA ratio in MVN and a selective NA increase in AVCN. 5-HT and 5-HIAA levels were increased in all the brainstem nuclei except raphe dorsalis. DA and DOPAC remained unchanged. These data show that noradrenergic neurons in sensory nuclei are differently affected by aging whereas serotonergic activation occurs in most of them possibly as a compensatory response to dysfunction of sensory input and processing. The increase of NA stores in the AVCN of aged rats is in line with the elevated auditory brainstem threshold reported in old rats and could improve the signal-to-noise ratio. Noradrenergic neurons in the MVN seem to be more sensitive to age effect than cochlear nuclei; however, even if neuronal loss occurs, NA synthesis and/or metabolism increase to ensure normal or increased noradrenergic activity.     

Aging effects on vestibulo-ocular responses in C57BL/6 mice: comparison with alteration in auditory function

Age-related changes in auditory function are well documented in animal models; however, this is not the case as regards vestibular function. In this study, we evaluated age-related changes in vestibulo-ocular responses in C57BL/6 mice that are considered as a model of presbycusis. The functional data were substantiated by the findings of histological analysis of vestibular and auditory peripherals. The gain in vestibulo-ocular reflex, which reflects functionality of the vestibular system, increased in an age-dependent manner until 12 weeks and exhibited limited functional loss due to aging after 24 weeks. By contrast, no alteration in the thresholds of the auditory brainstem response (ABR) was observed from 3 to 12 weeks of age; however, ABR thresholds were significantly elevated from age 24 weeks and onwards. Histological analysis demonstrated that the degeneration of auditory peripherals was closely related with functional loss due to aging. Vestibular peripherals also exhibited age-related degeneration morphologically, although age-related dysfunction was not apparent. Age-related changes in the vestibular function of C57BL/6 mice followed a different time course when compared to changes in auditory function. These findings indicate that mechanisms for age-related changes in vestibular function differ from those of auditory function.     

Central auditory and vestibular pathology

MR is the radiologic examination of choice when a patient's symptoms indicate the presence of some retrolabyrinthine pathology. CT dynamic studies now permit both heart and brain assessment for poor blood circulation problems of the hindbrain.     

Human auditory steady state responses: effects of intensity and frequency

Human auditory steady state responses were recorded in 41 normal subjects and 22 patients with hearing loss. The effect of intensity on the responses at different tonal frequencies was assessed using the sweep technique. The amplitude of the responses increases and the phase delay decreases with increasing intensity. Both the amplitude and the phase delay are smaller for high frequency tone bursts. Notched noise decreases the amplitude of the response by a factor of two but does not affect the phase of the responses. Thresholds were estimated in waking subjects using two techniques: intensity sweeps analyzed by linear regressions, and fixed intensities analyzed by Hotelling's T2 test. Frequency-specific thresholds obtained with notched noise were less variable and more accurate with the fixed intensity technique. In patients with sensorineural hearing loss the amplitude increased more with increasing intensity above threshold than in patients with conductive hearing loss.     

Development of auditory processing in 6-12-year-old children: a longitudinal study

The development of auditory processing in children was investigated in a longitudinal study. A group of 20 children with normal cognitive and language development underwent several auditory tests at the ages of 6, 7, 8, 10 and 12 years. At the age of 10 years, three subjects were lost to follow-up, as was one more subject at the age of 12 years. The auditory performance of the children was compared to the performance of a group of 20 adults. The auditory test battery consisted of a speech-in-noise test, a filtered speech test, a binaural fusion test and two auditory sequencing tests. At the ages of 6, 7 and 8 years, data on the performance on an auditory word discrimination test, an auditory synthesis test, an auditory closure test and a number recall test were also obtained. All auditory tests except the speech-in-noise test showed a clear effect of age on the performance of children. Our data suggest that maturational effects play an important role in auditory processing (at least) up to an age of 12-13 years. Correlations between the tests are in general not indicative of large amounts of overlap between the different tests. Factor analysis shows that three factors account for 68-70% of explained variance, with the three factors contributing equally. A composite score obtained by averaging all (sub)test scores can be used next to the individual test scores to describe the development of auditory processing abilities in children.     

The geriatric auditory and vestibular systems

Age-related declines in auditory and vestibular function are becoming more prevalent and better understood. The personal and societal impact of these disorders is impressive, and present techniques of amplification or balance training can be of great benefit. However, many issues await investigation, and continued integration of ever-increasing technologies promises many new answers, and questions, in the future.     

Habilitation of auditory and vestibular dysfunction

Although unilateral hearing loss is often the initial sign of vestibular schwannoma (VS), the pathogenesis of the associated structures within the cerebellopontine angle can result in vestibular, facial, or vascular symptoms. Removal of a VS causes deficits in hearing, balance, and gaze stability. The resulting hearing loss eliminates the benefits of binaural listening that provide localization, loudness summation, and listening-in-noise ability. Reduced balance and gaze stability increase fall risk. This review discusses modern treatment options for auditory and vestibular rehabilitation including contralateral routing of signals (CROS), bilateral CROS, bone-anchored implants, tinnitus management, gaze and gait stability exercises.     

Aging and the peripheral vestibular system

Whereas much has been learned about age-related auditory changes in the inner ear, relatively little is known about the aging effects on the vestibular part of the inner ear-the peripheral vestibular system. Here we review relevant literature with regard to the prevalence of vestibular dysfunction, vestibular functional and structural changes in the elderly. The prevalence of vestibular dysfunction increases with age. Functionally, as age increases, VEMP amplitudes decrease, VEMP thresholds increase, VOR gain of HIT decreases. Due to the complexity of the vestibular system, variations in subject age and measurement techniques, findings in VEMP latency and caloric tests are conflicting. To address this, a direct measure of the peripheral vestibular system should be applied. Structurally, age-related loss in vestibular ganglion and otoconia have been noted; hair cell changes are not well defined; while subcellular changes remain to be explored. Defining how the onset of vestibular dysfunction correlates with structural degeneration will offer insights into the mechanisms underlying vestibular aging.     

Aging effects on the activation of the auditory cortex during binaural speech listening in white noise: an fMRI study

The functional significance of age-related pathology of the auditory cortex is not well established. The purpose of this study was to elucidate the activation pattern of the auditory cortex in aged subjects in response to speech signals. Functional magnetic resonance imaging was performed on 12 elderly subjects with normal hearing acuity during selective listening with both ears to speech sounds in quiet and in white noise. Twelve young, normal-hearing subjects served as controls. Our results showed that activation of the auditory cortex during selective listening to speech decreased in elderly subjects compared to young subjects, especially in noise. Reduced activation occurred in the anterior and posterior regions of the bilateral superior temporal gyrus (STG), but mainly in the posterior part of the left STG. In addition, background noise had a greater masking effect on speech perception in the elderly subjects than in the young ones. These findings suggest that early functional changes associated with central presbycusis occur mainly in the posterior part of the left STG.     

听神经病对前庭功能的影响

目的探讨听神经病患者的前庭功能,以了解听神经病患者的平衡能力。方法对32例听神经病患者及正常对照组患者行前庭功能检查,包括眼震电图检查和静态姿势描记图检查,并将2组的结果进行比较。结果听神经病患者的平衡能力减低,眼震电图检查异常者6例(18.75%),姿势描记图检查结果明显异常,睁、闭眼状态下,重心晃动的轨迹长度与晃动速度与正常对照组相比较,差异有显著性意义(P<0.05)。结论在今后的临床工作中,对听神经病患者不妨加行前庭功能检查,以进一步了解其第Ⅷ颅神经的功能状态,尤其是静态姿势描记图,该测试快速、简单,结果客观可靠。     

Conservative management of vestibular schwannomas - second review of a prospective longitudinal study

Vestibular schwannomas have been traditionally managed with microsurgical removal and in recent years, stereotactic radiotherapy. However, there is a group of patients in whom a conservative management approach might represent a desirable alternative. The aim of this study was to determine the natural history and outcome following the conservative management of 72 patients with unilateral vestibular schwannomas. This is a prospective cohort review of a previously published group of patients [Clin. Otolaryngol. (2000) 25, 28-39] with unilateral vestibular schwannoma that were initially analysed at our institution in 1998 [Walsh R.M., Bath A.P., Bance M.L. et al., Clin. Otolaryngol. (2000) 25, 28]. The mean duration of follow-up was 80 months (range 52-242 months). All the patients in the study underwent serial magnetic resonance imaging (MRI) for assessment of tumour growth. Patients were deemed to have failed conservative management if there was evidence of rapid radiological tumour growth and/or increasing signs and symptoms, which necessitated active intervention. The mean tumour growth rate for the entire group at the second review was 1 mm/year (range -0.84-9.65 mm/year). The mean growth rate for cerebellopontine angle tumours (1.3 mm/year) was significantly greater than that of internal auditory canal (IAC) tumours (0 mm/year) (P = 0.005). The majority of tumours (87.14%) grew <2 mm/year. There was significant tumour growth seen in 38.9%, no or insignificant growth in 41.7%, and negative growth in 19.4%. Twenty-three patients (32%) failed conservative management at the second review. There was no difference in the outcome of these failed patients in comparison with patients who underwent primary treatment without a period of conservative management. The mean growth rate of tumours in patients that failed conservative management (3.1 mm/year) was significantly greater than that in patients who did not fail (0.2 mm/year) (P < 0.001). No factors predictive of tumour growth or failure of conservative management were identified. Hearing deterioration with pure tone averages (0.5, 1, 2, 3 kHz) and speech discrimination scores occurred irrespective of tumour growth. This prospective study further emphasizes the role of conservative management in selected cases of vestibular schwannomas. Tumours in this study confined to the IAC typically demonstrated minimal or no growth on serial MRI scanning. Regular follow-up with interval scanning is mandatory in all patients.     

The effects of diazepam on the auditory brain stem responses

Sedation is widely used to improve the quality of auditory brain stem response (ABR) recording. This study demonstrated a small but significant increase in I-V interval following diazepam administration. There was no apparent effect on the ABR amplitudes.