RESUMEN
The roles of histaminergic and cholinergic neuron systems in the regulation of body temperature have been studied almost exclusively in animals. Recently, we have found that motion sickness, i.e. a condition where hippocampal cholinergic mismatch signals induce a release of histamine in the vomiting centre, accelerates the decline in body temperature in men during exposure to cold. In the present study we measured the thermoregulatory effects of two substances commonly used against motion sickness, i.e. the histamine (H1) receptor blocker dimenhydrinate (DMH) and the muscarine receptor blocker scopolamine (SCOP). In three trials, control (CN), DMH and SCOP, 10 male subjects were immersed in 15 degrees C water for a maximum of 90 min. The trials were separated by a minimum of three days and their order was alternated between subjects. In all trials the subject received, in a double blind fashion, a transdermal patch (SCOP or placebo) 12-14 h before immersion and a tablet (DMH or placebo) 1h before immersion. Mean skin temperature, rectal temperature (T(rec)), the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (T(ff)), and oxygen uptake (VO(2)) were recorded. The fall in T(rec) was smaller in the DMH than in the CN and SCOP conditions. The recordings of T(ff) and VO(2) suggest that SCOP attenuates peripheral vasoconstriction while DMH increases shivering thermogenesis. Notably, thermal discomfort was reduced in the SCOP condition. Findings are thoroughly discussed in the context of animal studies on the neuropharmacology and neurophysiology of thermoregulation and motion sickness.
Asunto(s)
Regulación de la Temperatura Corporal/efectos de los fármacos , Frío , Dimenhidrinato/farmacología , Antagonistas de los Receptores Histamínicos H1/farmacología , Antagonistas Muscarínicos/farmacología , Escopolamina/farmacología , Adulto , Temperatura Corporal/efectos de los fármacos , Método Doble Ciego , Humanos , Masculino , Consumo de Oxígeno/efectos de los fármacos , Percepción/efectos de los fármacos , Tiritona/efectos de los fármacos , Factores de Tiempo , Sistema Vasomotor/efectos de los fármacos , Adulto JovenRESUMEN
A morphometric analysis of 43 human maculae utriculi is presented. Individual data on the shape, total area and relative area of the pars interna are given. In addition, the sensitivity of the entire macula to shear stimuli in different directions was estimated. The mean area of 39 maculae from adults and children was 4.30 +/- 0.30 (SD) mm(2). The pars interna was slightly but significantly smaller than the pars externa. The interindividual variability was larger for the shape of the macula than for the total area and the percentage of the pars interna. The estimated responsiveness of the macula was largest for shear directed anteromedially and smallest for shear directed posteriorly. The data are discussed taking into consideration clinical findings on patients with unilateral loss of otolith function.
Asunto(s)
Sáculo y Utrículo/anatomía & histología , Sáculo y Utrículo/fisiología , Localización de Sonidos/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Preescolar , Técnicas de Cultivo , Células Ciliadas Auditivas/fisiología , Humanos , Persona de Mediana Edad , Sáculo y Utrículo/embriologíaRESUMEN
Recently Minor and co-workers described patients with sound- and pressure-induced vertigo due to dehiscence of the superior semicircular canal. Identifying patients with this 'new' vestibular entity is important, not only because the symptoms are sometimes very incapacitating, but also because they can be treated. We present symptoms and findings in eight such patients, all of whom reported pressure-induced vertigo that increased during periods of upper respiratory infections. Pulse-synchronous tinnitus and gaze instability during head movements were also common complaints. All patients lateralized Weber's test to the symptomatic ear. In some of the patients the audiogram also revealed a small conductive hearing loss. However, the stapedius reflexes were always normal. A vertical/torsional eye movement related to the superior semicircular canal was seen in most of the patients in response to pressure changes and/or sound stimulation. One patient also had superior canal-related positioning nystagmus. Testing vestibular evoked myogenic potentials revealed in all patients a vestibular hypersensitivity to sounds. In the coronal high-resolution 1-mm section CT scans the dehiscence was visible on 1 to 4 sections. Moreover, the skull base was rather thin in this area and cortical bone separating the middle ear and the antrum from the middle cranial fossa was absent in many of the patients. Two of the patients have undergone plugging of the superior semicircular canal using a transmastoid approach and both patients were relieved of the pressure-induced symptoms.
Asunto(s)
Enfermedades del Laberinto/diagnóstico , Enfermedades del Laberinto/cirugía , Canales Semicirculares , Adulto , Anciano , Audiometría , Movimientos Oculares , Femenino , Humanos , Masculino , Persona de Mediana Edad , Acúfeno/etiología , Tomografía Computarizada por Rayos X , Vértigo/complicacionesRESUMEN
Recently Minor and co-workers described patients with sound- and pressure-induced vertigo due to dehiscence of bone overlying the superior semicircular canal. Identifying patients with this "new" vestibular entity is important, not only because the symptoms can be very incapacitating, but also because they are surgically treatable. We present symptoms and findings for three such patients. On exposure to sounds, especially in the frequency range 0.5-1 kHz, they showed vertical/torsional eye movements analogous to a stimulation of the superior semicircular canal. They also showed abnormally large sound-induced vestibular-evoked myogenic potentials (VEMP), i.e. the short latency sternomastoid muscle response considered to be of saccular origin. The VEMP also had a low threshold, especially in the frequency range 0.5-1 kHz. However, in response to saccular stimulation by skull taps, i.e. when the middle ear route was bypassed, the VEMP were not enlarged. This suggests that the relation between the sound-induced and the skull tap-induced responses can differentiate a large but normal VEMP from an abnormally large response due to dehiscence of bone overlying the labyrinth, because only the latter would produce large sound-induced VEMP compared to those induced by skull taps.
Asunto(s)
Potenciales Evocados/fisiología , Enfermedades del Laberinto/diagnóstico , Canales Semicirculares/fisiopatología , Vestíbulo del Laberinto/fisiopatología , Adulto , Anciano , Electromiografía/métodos , Electromiografía/estadística & datos numéricos , Movimientos Oculares/fisiología , Humanos , Enfermedades del Laberinto/complicaciones , Enfermedades del Laberinto/fisiopatología , Masculino , Enfermedad de Meniere/diagnóstico , Enfermedad de Meniere/etiología , Enfermedad de Meniere/fisiopatología , Persona de Mediana Edad , Estimulación Física/métodosRESUMEN
Measurements of the subjective visual horizontal (SVH) were performed in 11 healthy test persons during an increase of the resultant gravitoinertial force vector in a large swing-out gondola centrifuge. Three levels of hypergravity (1.5 g, 2.0 g, 2.5 g) were used, each with a duration of 4 minutes and with 1-2 minute pauses at 1.0 g in between. The direction of the resultant gravitoinertial force vector was always parallel with the head and body length axis. Hence, there was no roll stimulus to the otolith organs. The swing-out of the gondola during acceleration, however, is sensed by the vertical semicircular canals as a change in roll head position, thus creating an otolith-semicircular canal conflict. After acceleration of the centrifuge there was a tilt of the SVH relative to the resultant gravitoinertial horizontal. This tilt gradually decayed during the 4-minute period of recordings. For a subgroup of seven test subjects who had completely normal ENG-recordings in 1 g environment, the initial offset of SVH and the time constants for exponential decay were determined for each g level; initial offsets: 9.9 degrees (1.5 g), 7.7 degrees (2.0 g), 6.1 degrees (2.5 g); time constants: 89s (1.5 g), 74s (2.0 g), 37s (2.5 g). The offset of SVH is interpreted as being the result of mainly the stimulus to the vertical semicircular canals during acceleration of the centrifuge. The slow decay, however, does not correspond to the dynamics of the semicircular canal system, and is suggested to reflect some kind of central position storage mechanism. A smaller offset and more rapid decay for the higher g loads may be explained by an increasing dominance of graviceptive input, presumably from the saccules. In conclusion, these results might suggest the role of the vertical semicircular canals as well as the sacculus in the formation of SVH. They may also have relevance with regard to the spatial disorientation problem in aviators.
Asunto(s)
Sáculo y Utrículo/fisiología , Canales Semicirculares/fisiología , Percepción Visual/fisiología , Adulto , Centrifugación , Electronistagmografía , Gravitación , Humanos , Persona de Mediana Edad , Membrana Otolítica/fisiología , Valores de ReferenciaRESUMEN
The subjective visual horizontal (SVH) was measured by means of a small, rotatable, luminous line in darkness in the upright head and body position and at 10, 20 and 30 degrees of tilt to the right and left before, and repeatedly during a follow-up period of 1 year after intratympanic gentamicin instillations in 12 patients with recurrent vertigo attacks. This treatment caused a loss of the bithermal caloric responses on the diseased side. Shortly after treatment there was a significant tilt of SVH towards the treated side (group mean = 10.6 degrees). Repeated testing made it possible to characterize mathematically the changes with time for SVH. For the group of patients as a whole this otolithic component of vestibular compensation was best described by a power function, SVH = 8.65t(-0.16) degrees, where t is time in days after maximum tilt of SVH. After 1 year, SVH was still significantly tilted towards the treated side (group mean = 3.16 degrees). Gentamicin treatment also caused a significant reduction in the perception of head and body tilt towards the deafferented side, while the perception of tilt towards the healthy side did not show any significant changes. During follow-up there was a gradual improvement in the perception of tilt towards the treated side. However, a significant asymmetry in roll-tilt perception was still present 1 year after deafferentation. There was no correlation between SVH in the upright position and roll-tilt perception, suggesting that these parameters are to some extent dependent on different afferent input from the vestibular organ. They were also found to be complementary for the detection of vestibular disturbance.
Asunto(s)
Antibacterianos/farmacología , Gentamicinas/farmacología , Vértigo/terapia , Vestíbulo del Laberinto/fisiopatología , Percepción Visual/fisiología , Vías Aferentes/fisiología , Pruebas Calóricas , Electrooculografía , Femenino , Estudios de Seguimiento , Humanos , Masculino , Enfermedad de Meniere/terapia , Persona de Mediana Edad , Factores de Tiempo , Pruebas de Función Vestibular , Vestíbulo del Laberinto/efectos de los fármacosRESUMEN
The subjective visual horizontal (SVH) was measured by means of a small rotatable luminous line in darkness in the upright body position and at 10, 20 and 30 degrees of body tilt to the right and left prior to, and during a follow-up period after, stapedotomy in 12 patients with otosclerosis. In the acute stage after surgery, SVH in the upright body position was significantly tilted away from the operated side. In addition, the perception of roll tilt towards the operated side (Kop) was significantly increased after stapedotomy, while the perception of roll tilt towards the healthy side (Khe) showed a slight but not significant reduction. After exclusion of two outliers, a statistically significant correlation was found between changes in Kop and in Khe. The slope of the regression line was 1.8:1, probably corresponding to a preference of the utricle for ipsilateral as opposed to contralateral head tilt. In four patients there was a weak ( < 1 degrees/s) spontaneous nystagmus, not systematically related to the side of surgery, while in most cases there were no nystagmus or subjective vertigo symptoms. These specific changes in the subjective horizontal show that the otolithic effects on perception can be dissociated from canal effects. Further, the results are opposite to those for patients with unilateral loss of vestibular function. The tilt of SVH after stapedotomy indicates an increase in resting activity of utricular afferents. In addition, based on recent theories on otolith function, we suggest that an increased activity in saccular afferents is of major importance for the changes in roll-tilt perception because of its interaction with the utricle on the central nervous level.
Asunto(s)
Vías Aferentes/fisiología , Orientación/fisiología , Membrana Otolítica/inervación , Otosclerosis/cirugía , Postura/fisiología , Cirugía del Estribo , Adulto , Anciano , Electronistagmografía , Femenino , Humanos , Modelos Lineales , Masculino , Persona de Mediana EdadRESUMEN
Intratympanic instillation of gentamicin may not exclusively be a treatment for Ménière's disease. We present case reports of successful vertigo control in peripheral vestibular disorders other than Ménère's disease. Cases 1 and 2 illustrate treatment of vertigo attacks caused by vestibular dysfunction in deaf ears. Case 3 illustrates treatment of brief sensations of linear acceleration in a patient who had suffered idiopathic sudden hearing loss a few years earlier. Case 4 illustrates treatment of disabling benign paroxysmal positioning vertigo. Case 5 illustrates treatment of severe and frequent attacks of vertigo in an elderly patient with a medium-sized acoustic neuroma who did not want surgical extirpation of the tumor.
Asunto(s)
Gentamicinas/uso terapéutico , Vértigo/tratamiento farmacológico , Enfermedades Vestibulares/tratamiento farmacológico , Adolescente , Adulto , Femenino , Humanos , Instilación de Medicamentos , Masculino , Persona de Mediana Edad , Vértigo/etiología , Enfermedades Vestibulares/complicacionesRESUMEN
The functional status of the velocity storage mechanism was studied in patients at long-term follow-up (2 to 4 years) after unilateral vestibular neurectomy. The time constant of the vestibulo-ocular reflex (VORtc), the effect of head tilt on postrotatory nystagmus, optokinetic after-nystagmus (OKAN), and nystagmus after rapid head shaking were studied in 10 patients. In agreement with previous findings, VORtc was found to be short and most patients manifested OKAN, suggesting that unilateral peripheral vestibular loss is associated with a complete loss of storage within the the VOR but only a partial loss of velocity storage for visual input. However, at postrotatory head tilt the VOR time constant was further shortened, supposedly due to discharge of functioning velocity storage. Moreover, most patients manifested nystagmus after head shaking. These findings on tilt suppression and head-shaking nystagmus suggest that velocity storage within the VOR may function even in patients with complete unilateral vestibular lesions.
Asunto(s)
Movimiento/fisiología , Nistagmo Optoquinético/fisiología , Nistagmo Fisiológico/fisiología , Reflejo Vestibuloocular/fisiología , Nervio Vestibular/cirugía , Adulto , Anciano , Pruebas Calóricas , Electronistagmografía , Movimientos Oculares/fisiología , Femenino , Estudios de Seguimiento , Cabeza , Humanos , Masculino , Persona de Mediana Edad , Rotación , Nervio Vestibular/fisiopatologíaRESUMEN
In order to establish a method for estimation of the perceptual horizontal as a test of otolith function in diagnosis of atypical vertigo, in a first study we have standardized a test procedure and characterized a body of normal material consisting of 72 healthy subjects, 24 of them examined with tests followed by retests. The perceptual visual horizontal in darkness was estimated in the upright body position and at body tilts of 10, 20, and 30 degrees to the right and to the left by means of a narrow luminous bar. The deviation of the perceptual horizontal relative to the gravitational horizontal is expressed as a function of body tilt. In the upright body position, 95% had a perceptual horizontal within the range of +/- 2.5 degrees. In the tilted positions, there was a tendency to set the light bar tilted oppositely with respect to the body tilt. The results suggest that roll tilt to the right and to the left is sensed by two independent functional units. Furthermore, the results imply that some other factor might be of importance and that the perceptual horizontal in the upright position and tilt perception are complementary in reflecting vestibular function. Differences between individuals were great in comparison with intraindividual variability and the test-retest variability. The results are discussed against the background of the extensive literature.
Asunto(s)
Orientación/fisiología , Postura/fisiología , Núcleos Vestibulares/fisiología , Percepción Visual/fisiología , Femenino , Humanos , MasculinoRESUMEN
The subjective visual horizontal is mainly dependent on the otolithic system. A group of 11 patients with sudden unilateral vestibular impairment were asked to set a dimly illuminated bar according to their subjective horizontal when they were seated upright and tilted 10, 20, and 30 degrees to the right and left in a completely darkened room (Bias test). The patients were examined within 1 week, after 3 and 6 weeks, and 9 patients consented to the 11-week follow-up. The results were compared with ENG examinations. In the acute stage of the disease all patients, when they were in upright position, set the light bar tilted towards the affected side. At roll tilt to the affected side, 9 of the 11 patients set the light bar in the same direction as their body tilt (undercorrection). At a tilt to the unaffected side 6 of the 11 patients made an undercorrection. For the group of patients the magnitude of undercorrection was larger at tilt to the affected side than to the unaffected side. The patients' ability to correctly align the light bar with the true horizontal gradually improved but was found normal in both upright and tilted positions in only three of the nine patients at the last follow-up. In four of the six patients who still demonstrated pathologic results, these were met only in tilted positions. No significant correlation was found between the intensity of spontaneous nystagmus or the degree of caloric side difference and the deviation in setting of the light bar in upright or tilted positions. The large asymmetric perceptual responses at tilt found at onset might be explained by the two-directional organisation of the utricle.