ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Orbital spaceflight exposes astronauts to an environment in which gravity is reduced to negligible magnitudes of 10-3to 10-6G. Upon insertion into earth orbit, the abrupt loss of the constant linear acceleration provided by gravity removes the otolith stimulus for vestibular sensation of vertical orientation constantly present on Earth. Since the central nervous system (CNS) assesses spatial orientation by simultaneously interpreting sensory inputs from the vestibular, visual, and proprioceptive systems, loss of the otolith-mediated vertical reference input results in an incorrect estimation of spatial orientation, which, in turn, causes a degradation in movement control. Overtime, however, the CNS adapts to the loss of gravitational signals. Upon return to Earth, the vertical reference provided by gravitational stimulation of the otolith organ reappears. As a result, a period of CNS readaptation must occur upon return to terrestrial environment. Among the physiological changes observed during the postflight CNS readaptation period is a disruption of postural equilibrium control. Using a dynamic posturography system (modified NeuroCom EquiTest), 16 astronauts were tested at 60, 30, and 10 days preflight and retested at 1 to 5 hours, and 8 days postflight. All astronauts tested demonstrated decreased postural stability immediately upon return to Earth. The most dramatic increases in postural sway occurred during those sensory conditions in which both the visual and proprioceptive feedback information used for postural control were altered by the dynamic posturography system, requiring reliance primarily upon vestibular function for control of upright stance. Less marked but statistically significant increases in sway were observed under those conditions in which visual and foot support surface inputs alone were altered. Recovery to preflight postural stability levels, which were well within normal clinical limits, occurred in all subjects by 8 days postflight. The results demonstrate that 5- to 10-day losses of gravitational inputs from the vestibular otoliths to the CNS during orbital flight severely disrupt the otolith mediated sensorimotor interactions required for normal terrestrial postural control. Readaptation to normal postural control was complete in all astronaut subjects within 8 days postflight

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Ninety-two middle-aged and elderly patients with disabling tinnitus participated in a double-blind randomized clinical trial comparing nortriptyline (a tricyclic antidepressant) to placebo. The study was stratified for presence (n=38) or absence (n=54) of current major depression (by DSM-III criteria). Both active drug and placebo were given for 6 weeks following a dose adjustment phase; the median nightly dose of nortriptyline was 100 mg. The two primary outcome variables were global satisfaction questions: “Has the medication helped you in any way?” and “Has your tinnitus improved?” Sixty-seven percent of nortriptyline patients stated the drug had helped them, versus 40 percent of placebo patients (chi-square=7.14, p=0.008). However, tinnitus severity was not significantly affected by nortriptyline (active: 43%; placebo: 30%; chi-square=1.567, p=N/S). Benefit was more likely to be reported by depressed patients, by patients with insomnia, by women, and by patients without cervical musculoskeletal disease. Nortriptyline is useful in some patients with disabling tinnitus, but has not been shown to directly affect tinnitus sensation. Placebo effects were strongly significant and must be considered important in tinnitus therapy. It is difficult to specify the most appropriate outcome measures for tinnitus therapeutic trials

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Betahistine (BH) has been used widely to treat cochlear disorders, such as tinnitus and Meniere's disease. The mechanism of action of BH in the cochlea is assumed to be based on its histamine-like effect on H, receptors in the cochlear vasculature, leading to an increased cochlear blood flow (CBF). Recently it has been shown that BH can strongly affect H3 heteroreceptors (a novel histamine receptor subclass) in the periphery, via an autonomic ligand. This mechanism may also contribute to the BH effects on CBF. This study was to validate BH effects in the cochlear vasculature and to investigate the possible mechanisms of action of this drug in the inner ear vasculature. We assessed the effects of BH on CBF with the laser Doppler flowmeter in 23 rats and concluded that BH affects vascular conductivity in the cochlea in a dose-dependent fashion; betahistine diffuses through the round window, but does not have access to vascular receptors or Iigands once in the labyrinthine fluids; and the H, receptors mediate the systemic and peripheral vascular effects of BH, whereas the cochlear effect involves cholinergic receptors.

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The retrosigmoid approach is utilized in a variety of cerebellopontine angle and internal auditory canal procedures. Drill curettageofthe posterior internal auditory canal enhances lateral exposure, however, this step may also increase the patient's risk for postoperative cerebrospinal fluid (CSF) otorrhea. Obliteration of perilabyrinthine air cells is technically difficult and muscle graft displacement frequently occurs. A technique for posterior petrous dural flap stabilization of a temporalis muscle plug has proved successful in decreasing the risk of postoperative CSF fistula following retrosigmoid surgery. Temporal bone air-cell anatomy, as it relates to retrosigmoid, posterior internal auditory canal surgery is reviewed. Our technique for internal auditory canal closure, with bone wax, bone pate, muscle grafts, and petrous ridge dural flaps is outlined

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The clinical utility of otoacoustic emissions (OAEs) has been well established in adults. The purpose of this investigation was to determine the efficacy of OAE testing in children. Distortion-product OAE (DPOAE) audiograms, response/growth functions, and transiently evoked OAEs elicited with clicks were measured from the ears of both healthy volunteers, aged 4 to 13 years, and children with confirmed middle ear disorders. These measures established the means and variabilities for DPOAE and noise-floor amplitudes of normal and diseased young ears. Compared with adult emissions, the healthy young ears exhibited greater mean DPOAE and noise-floor amplitudes. In contrast, ears with type B and type C tympanogram patterns showed absent or markedly reduced OAE amplitudes, when compared with emissions measured in their control counterparts. Finally, ears with ventilating tubes exhibited OAE amplitudes lower than amplitudes from healthy ears, but higher than those of the untreated diseased ears. Although these findings imply that using OAEs to test the outer hair-cell reserve of infected ears is problematic, emitted responses provide useful information concerning the normalcy of middle ear function

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The ultrastructural distribution of calcitonin gene-related peptide immunoreactivity (CCRPi) was examined in sections of decalcified temporal bones in order to study the complex peptidergic innervation patterns of this efferent neuromodulator in the peripheral vestibular system of the rat. A new method of preembedding immunoelectron microscopy was developed to accomplish this study. Unmyelinated CGRPi axons, measuring 1 to 3 jam in diameter, passed among the primary afferent fibers in Scarpa's ganglion, and these fibers continued through the subepithelial regions of the vestibular end-organs. Within the neurosensory epithelia of the maculae and cristae, the CGRPi axons ramified to produce numerous CGRPi terminals. Immunoelectron microscopic localization of CGRPi terminals in the maculae and cristae revealed an extensive innervation pattern on the afferent vestibular pathway. Calcitonin gene-related peptide immunoreactive terminals made synaptic contacts with the unmyelinated portions of the primary afferent vestibular fibers innervating both type I and type II hair cells. Abundant synaptic contact between CGRPi terminals and the chalices surrounding type I hair cells was observed. Rare direct contact between CGRPi terminals and type I or type II hair cells was observed. In addition, vesiculated efferent terminals without CGRPi were seen contacting type II hair cells. These data suggest that the efferent vestibular system has a much more complex innervation pattern on the afferent vestibular pathway than previously believed

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

It has been reported, in animal models and recently in human beings, that intravenous fluorescein is taken up in peri lymph and may be useful as a tracer for the detection of perilymphatic fistulas. We attempted to reproduce the results of these animal experiments. Twenty-one middle ears of eight cats and four dogs were exposed. Fluorescein was given intravenously. Fluorescence was initially noted in transudates pooling in the oval and round window niches. Fistulas created with a straight pick produced a bright fluorescence in the leaking fluids, possibly from a ruptured small membrane vessel. Fistulas created with the carbon dioxide laser and with complete hemostasis demonstrated no fluorescence. We concluded that intravenously administered fluorescein causes dramatic fluorescence of vessels and transudates that may be interpreted falsely as fluorescence of perilymph. Fluorescence was not evident in perilymph when complete hemostasis was obtained

ISSN:0192-9763    

出版商:OVID    

年代:1993

数据来源: OVID