Nistagmo vertical inferior: ¿es obligada la resonancia magnética? / Inferior vertical nystagmus: is magnetic resonance imaging mandatory?

Introducción. La aparición de un nistagmo vertical inferior clásicamente obliga a descartar una patología vascular o de la unión craneocervical mediante resonancia magnética (RM). Estudios recientes demuestran una baja rentabilidad de esta prueba, ya que sugieren que este signo oculomotor puede tener una causa vestibular periférica, sobre todo cuando el paciente presenta un vértigo posicional paroxístico benigno (VPPB) del canal semicircular superior. Objetivo. Comprobar la rentabilidad de la RM en una población de pacientes con nistagmo de posición vertical inferior. Pacientes y métodos. Estudio retrospectivo de 42 pacientes consecutivos a los que se les realizó una historia clínica, exploración física, y pruebas vestibulares calóricas y rotatorias. A todos ellos se les practicó una RM craneal y cervical. Resultados. El 52% de los pacientes con nistagmo de posición vertical inferior presentaba una clínica y exploración física compatibles con VPPB del canal semicircular superior. La RM fue normal en un 67%, un 26% mostraba datos de espondilopatía y un 5% de microangiopatía cerebral no relacionados con la clínica del paciente. La prevalencia de malformación de Arnold-Chiari de tipo I fue de un 9% en la población estudiada, sin que nadie tuviera un antecedente reciente de VPPB. Los resultados obtenidos en las pruebas complementarias vestibulares no aportaron información adicional para llegar a un diagnóstico etiológico. Conclusión. En los pacientes con un VPPB, la RM craneal y las pruebas vestibulares tienen una baja rentabilidad diagnóstica, y se debe evaluar la necesidad real de esta prueba con el contexto clínico (AU)

Introduction. The presentation of a down-beating nystagmus force to discard vascular pathology of brain and cervical joint with magnetic resonance imagine (MRI). Recent studies support the low profitability of this study and is subjected that this oculomotor sign has a peripheral origin especially when the patient has a benign paroxysmal positional vertigo (BPPV) with affection of the superior semicircular canal. Aim. To evidence the profitability of MRI in a population of patients with positional down-beating nystagmus. Patients and methods. We present a retrospective study with 42 consecutive patients. A complete clinical history and physical examination was performed. All of them perform vestibular tests (caloric and rotatory), cranial and cervical MRI. Results. Fifty-two percent of patients present clinical manifestations and physical exploration compatible with BPPV. MRI was normal in 67%. We found spondylopathy in 26% and vascular cerebral pathology in 5%. Prevalence of type I ArnoldChiari malformation was 9% in our population. None of them was founded when the main symptom was suggestive of BPPV. Results obtained of vestibular tests didn’t contribute additional information to give an ethiologic diagnosis. Conclusion. The profitability of vestibular tests and MRI in our population with down beating nystagmus was very low. We must evaluate the real necessity of this test with the clinical context (AU)

Bocio intratorácico asociado a vértigo / Intrathoracic goitre associated with vertigo

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Visual-vestibular interactions during vestibular compensation: role of the pretectal not in horizontal VOR recovery after hemilabyrinthectomy in rhesus monkey.

Damage to the vestibular labyrinth leads to profound nystagmus and vertigo. Over time, the vestibular-ocular system recovers in a process called vestibular compensation leading to reduced nystagmus and vertigo provided visual signals are available. Our study was directed at identifying sources of visual information that could play a role in vestibular compensation. Specifically, we investigated the role of the pretectal nucleus of the optic tract (NOT) in vestibular compensation after hemilabyrinthectomy (HL) in rhesus monkeys. We chose the NOT because this structure provides critical visual motion information for adaptive modification of the vestibular ocular reflex (VOR). We produced bilateral NOT lesions by injecting the excitotoxin ibotenic acid. We compared vestibular compensation after HL in NOT-lesioned and control animals with intact NOTs. We measured eye movements with an electromagnetic method employing scleral search coils. Measurements included slow-phase eye velocity during spontaneous nystagmus, per- and postrotatory nystagmus and the horizontal VOR (hVOR) gain (eye-velocity/head velocity) associated with per- and postrotatory and sinusoidal (0.2-2.0 Hz; 30-90 degrees/s) whole body oscillation around the earth-vertical axis. VOR gain was low (<0.5) for rotation toward the HL side. Our control animal evinced significant vestibular compensation with VOR gains approaching unity by 100 days post HL. In contrast, monkeys with bilateral lesions of the NOT never obtained this significant recovery with hVOR gains well below unity at 100 days and beyond. Therefore our studies demonstrate that the NOT is an essential source of visual signals for the process of vestibular compensation after HL.

Can electromagnetic fields emitted by mobile phones stimulate the vestibular organ?

OBJECTIVES: Pulsating electromagnetic (EM) radiation emitted by mobile phones is often incriminated for causing tissue alterations by caloric effects. In particular, the eye and the ear were regarded as possible "hot spots," with heating up to 1 degree C, in which EM radiation might have negative effects. If so, these temperature increments should be large enough to cause vestibular excitation. In this study, we attempted to verify this theory by clinical testing and in vitro experiments. METHODS AND MEASURES: In our laboratory, a simulated GSM signal (889.6 MHz/2.2 W) was applied to 1 ear at a time, while video nystagmography was performed. The experimental setup was similar to that used for caloric (hot and cold water) testing of the peripheral vestibular organ. Data were evaluated by a computer system. There were 13 volunteers (26 ears) included in our study. In an additional experiment, temperatures of human temporal bones were measured by thermography, while a continuous or pulsating EM field was applied. RESULTS: In no volunteer could EM radiation-induced nystagmus be recorded. This corresponds well to our findings that in the human temporal bone very weak caloric effects could only be found in the tissue layers next to the radiation source (antenna of the mobile phone), whereas deeper regions (horizontal semicircular canal) seemed unaffected (at least less than 0.1 degree C). CLINICAL SIGNIFICANCE: These results do not support the theory that mobile phone-induced EM radiation may cause caloric negative effects in the human ear.

[Thermal irritation of the organ of equilibrium by means of heat radiation (NIR)]. / Thermische Reizung des Gleichgewichtsorganes mittels Wärmestrahlung (NIR).

BACKGROUND AND OBJECTIVE: Convection and conduction are the main factors involved in caloric response. Heat radiation has also been discussed as an important factor. The present work tests whether heat radiation is an essential part of the caloric response and whether caloric irritation of the semicircular canals is possible using two sources with a different near infrared (NIR) spectrum. In addition, we tested whether it is possible to induce a detectable nystagmus reaction using either NIR-radiation sources. RESULTS: NIR is able to penetrate bone tissue. The temperature elevation in dry and wet bones was almost immediately registered. With high optical power, specific temperature maxima could be seen by focal and selective broad spectrum and monochromatic NIR irritation of the three semicircular canals. Nystagmus could be generated after using both NIR emission sources in five probands. CONCLUSIONS: NIR generates temperature differences and nystagmus. By using a broad scale as well as a monochromatic NIR-emission source, it is possible to generate a nystagmus. The procedure of NIR-irritation occurs without physical contact, is painless and quiet.

Comparación entre los reflejos vestibuloocular y vestibuloespinal tras la estimulación calórica / Comparing the vestibuloocular and vestibulospinal reflexes after caloric stimulation

Introducción-Objetivo: Utilizando electronistagmografía (ENG) y craneocorpografía (CCG), comparamos el nistagmo ocular (RVO) y las desviaciones corporales (RVE) provocadas por un mismo estímulo calórico. Material y métodos: A 50 voluntarios sanos se les realizaron cinco pruebas en posición de Romberg con ojos tapados y cuello en hiperextensión: una basal (sin estimulación) con registro CCG y cuatro tras estimulación calórica con aire binaural y bitermal y registro simultáneo ENG/CCG. Resultados: La oscilación lateral (OL) y la oscilación anteroposterior tras estimulación fueron mayores que las de las CCG basales (p<0,00001). El movimiento corporal lateral fue siempre inverso al del nistagmo y el anteroposterior fue hacia delante con frío y hacia atrás con calor. Existió una correlación lineal débil entre OL y la frecuencia del nistagmo (r= 0,40; p=0,01) y entre OL y el número de nistagmos (r= 0,37; p=0,02).Discusión y conclusiones: La CCG es un método válido para registrar los RVEs producidos por la estimulación calórica. Nuestros resultados sugieren la acción sinérgica de ambos reflejos, así como la diferente modulación extralaberíntica de la aferencia vestibular calórica (AU)

Eye movement changes in albinism--a case report with electronystagmographic findings.

Albinism is associated with neural anomalies including foveal hypoplasia and aberrant optic pathway projection that result in a variety of oculomotor instability. We present a 38-years-old man with oculocutaneous albinism who had horizontal jerk-type nystagmus, which showed a reverse in direction by any extraneous light stimulation which was documented by electronystagmogram. The mechanism of the nystagmus in this case is uncertain. These findings in albinism have not been reported previously, to our knowledge, and suggest a defect in the visual pathway system.

Eye movement changes in albinism : a case report with electronystagmographic findings

Albinism is associated with neural anomalies including foveal hypoplasia and aberrant optic pathway projection that result in a variety of oculomotor instability. We present a 38-years-old man with oculocutaneous albinism who had horizontal jerk-type nystagmus, which showed a reverse in direction by any extraneous light stimulation which was documented by electronystagmogram. The mechanism of the nystagmus in this case is uncertain. These findings in albinism have not been reported previously, to our knowledge, and suggest a defect in the visual pathway system.

Subdural application of hemoglobin to the cerebellum blocks vestibuloocular reflex adaptation.

Vestibuloocular reflex (VOR) was induced by horizontal sinusoidal whole-body rotation in darkness in rabbits and a monkey. One eye was observed through an infrared TV camera. The gain of VOR was adaptively changed when the animal was continuously rotated for 3 h with the observed eye exposed to the screen moving in phase or out of phase with the head. Injection of 0.1 ml saline solution containing 10 microM hemoglobin into the subdural space over the cerebellar flocculus ipsilateral to the observed eye abolished the VOR adaptation. Since hemoglobin absorbs nitric oxide, which mediates synaptic plasticity in the cerebellar cortex, these results support the view that synaptic plasticity of the flocculus plays a key role in the VOR adaptation.