Efecto de la rigurosidad de las condiciones sobre los resultados de la prueba calórica en sujetos sanos / Effect of the stringency of conditions on caloric test results in healthy subjects

La prueba calórica es una prueba ampliamente utilizada para evaluar la función vestibular, pero las condiciones en las cuales se realiza pueden variar. Se comparó el nistagmo calórico obtenido en 57 sujetos sanos: 24 sujetos estudiados en condiciones ideales y 33 sujetos estudiados en condiciones no ideales. Se observó una disminución estadísticamente significativa de la velocidad de fase lenta en las cuatro irrigaciones realizadas a los sujetos del grupo de condiciones no ideales. Esto debe ser considerado sobre todo al sospechar afectaciones bilaterales. Ser rigurosos en las condiciones permite disminuir el riesgo de diagnóstico erróneo de déficit bilateral (AU)

The caloric test is widely used to assess vestibular function, but the conditions in which it is performed can vary. Caloric nystagmus obtained in 57 healthy subjects were compared: 24 subjects studied in ideal conditions and 33 subjects in non-ideal conditions. A statistically significant decrease in the slow phase velocity of the 4 irrigations performed on the subjects in non-ideal conditions was observed. This must be considered, especially in subjects with suspected bilateral involvement. Stringent conditions reduce the risk of misdiagnosis with bilateral deficit (AU)

Behavioural improvement in a minimally conscious state after caloric vestibular stimulation: evidence from two single case studies.

OBJECTIVE: To investigate whether caloric vestibular stimulation, a non-invasive form of neuro-modulation, alters the level of awareness in people residing in a minimally conscious state. DESIGN: Single-case ( n = 2), prospective, controlled (ABAB) efficacy study. SETTING: Tertiary, neuro-rehabilitation inpatient ward within a university hospital. PARTICIPANTS: Two individuals in a minimally conscious state. INTERVENTION: Left ear caloric vestibular stimulation was performed in two four/five-week blocks interleaved with two four/five-week blocks of sham stimulation. Session duration and frequency gradually increased within each block from once per day for 10 minutes (Week 1) to once per day for 20 minutes (Week 2) to 20 minutes twice per day in the remaining weeks. MEASURES: Wessex Head Injury Matrix, JFK Coma Recovery Scale - Revised. RESULTS: Both participants' Wessex Head Injury Matrix scores indicated a transition from involuntary (i.e. mechanical vocalization) to voluntary (i.e. gesture making, selective responses to family members) behaviour that was time-locked to the onset of active stimulation. In one participant, this improvement persisted for at least four weeks after active stimulation, while in the other it diminished two weeks after stimulation. Allied, although less dramatic, changes were seen on the arousal and auditory subscales of the JFK Coma Recovery Scale - Revised. CONCLUSION: The data provide the first evidence that vestibular stimulation may help improve outcome in a low awareness state, although further studies are needed to replicate effect and determine longer-term benefit.

Relación entre el video head impulse test (vHIT) y la prueba calórica en el estudio evolutivo de pacientes con neuritis vestibular / Relationship between video head impulse test (vHIT) and caloric test in patients with vestibular neuritis

Introducción y objetivos: La prueba calórica es hasta ahora la prueba de referencia para el diagnóstico y el examen de una hipofunción vestibular unilateral. El video head impulse test (vHIT) valora el reflejo vestíbulo-oculomotor, mediante el registro videoasistido de la maniobra impulsiva. Se pretende comparar la variación de los resultados del vHIT y la prueba calórica en pacientes con neuritis vestibular respecto a su estado inicial en diferentes puntos de su evolución, y comprobar su grado de correlación entre sí y con el test Dizziness Handicap Inventory (DHI). Métodos: Exploración en la misma sesión mediante vHIT y prueba calórica de 20 pacientes con neuritis vestibular. Valoración de la correlación de dichas pruebas entre sí y con el test DHI en 2 momentos diferentes de la evolución para cada paciente. Resultados: La asimetría de la ganancia del vHIT y la paresia canalicular de la prueba calórica no evidenciaron una correlación lineal entre ellas. Tampoco se apreció una correlación entre el DHI y la recuperación de los parámetros de estas 2 pruebas. Las sacadas Covert mantienen una velocidad similar mientras están presentes en el vHIT, mientras que las Overt disminuyen su velocidad con el tiempo. Conclusiones: El vHIT y la prueba calórica muestran diferentes respuestas del reflejo vestíbulo-oculomotor, dado que exploran diferentes frecuencias del mismo. No se ha encontrado una correlación entre el vHIT, la prueba calórica y el DHI a lo largo de la evolución de la neuritis vestibular, siendo pruebas complementarias entre sí (AU)

Introduction and objectives: The caloric test is the gold standard for the loss of vestibular function diagnosis. The Video Head Impulse Test (vHIT) assesses the same reflex by using a video- assisted examination of the impulsive maneuver. We intend to compare the variation of results of the vHIT and the caloric test in patients with vestibular neuritis with respect to their initial condition at two different moments of their evolution and to check the level of correlation between them and with that of the DHI test. Methods: We explored 20 patients with neuritis by using both vHIT and the caloric test on the same day. We assessed the correlation between these two tests and with the DHI test for each patient at two different moments of their evolution. Results: We calculated gain asymmetry and compared it with the canal paresis, but we found neither a linear correlation between them, nor a correlation between the DHI test or improvement of these two other tests. We conclude that the covert saccades maintain a similar speed whilst present in the VHIT, but the overts diminish their speed over time. Conclusions: The VHIT and the caloric test show different responses of the vestibulo-ocular reflex, because they stimulate different frequencies of this reflex. No correlation was found between the VHIT, the caloric test and the DHI test. The tests appear to complement one another (AU)

Caloric stimulation with near infrared radiation does not induce paradoxical nystagmus.

Near infrared radiation can be used for warm stimulation in caloric irrigation of the equilibrium organ. Aim of this study was to determine whether near infrared radiation offers effective stimulation of the vestibular organ, whether it is well tolerated by the patients and especially whether it is a viable alternative to warm air stimulation in patients with defects of the tympanic membrane and radical mastoid cavities. Patients with perforations of the tympanic membrane (n = 15) and with radical mastoid cavities (n = 13) were tested both with near infrared radiation and warm dry air. A caloric-induced nystagmus could be seen equally effectively and rapidly in all patients. Contrary to stimulation with warm dry air, no paradoxical nystagmus was observed following caloric irrigation with a warm stimulus (near infrared radiation). Results of a questionnaire showed excellent patient acceptance of near infrared stimulation with no arousal effects or unpleasant feeling. In conclusion, near infrared radiation proved to be an alternative method of caloric irrigation to warm dry air in patients with tympanic membrane defects and radical mastoid cavities. Near infrared radiation is pleasant, quick, contact free, sterile and quiet. With this method an effective caloric warm stimulus is available. If near infrared radiation is used for caloric stimulus no evaporative heat loss occurs.

The dependency of air caloric stimulus effectiveness on delivery tip characteristics.

This brief study investigates the extent and origin of the apparent dependency of air delivery speculum size on the effectiveness of air used as a stimulus in the bi-thermal caloric test, using water as a reference stimulus. Eleven normal volunteers served as subjects. Six caloric stimulus delivery conditions included air with two speculum sizes, speculum only and with a rubber tube extension, and water. The resulting nystagmus was used as an index of stimulus efficiency. The effectiveness of the air stimulus was found to be dependent on the diameter of the speculum used for air delivery. The narrower speculum generated nystagmus that was typically twice that generated by the wider speculum. Users of air caloric equipment whose design includes a speculum that influences the effectiveness of the stimulus should be aware of this dependency and ensure their clinical interpretation of results is made with reference to appropriate normative data.

Caloric test versus rotational sinusoidal harmonic acceleration and step-velocity tests in patients with and without suspected peripheral vestibulopathy.

OBJECTIVE: To identify the predictive capabilities of caloric and rotational testing to distinguish peripheral from nonperipheral vestibular causes of vertigo. STUDY DESIGN: Retrospective case review. SETTING: Academic tertiary care vestibular function test center. PATIENTS: Two hundred dizzy patients (132 with and 68 without suspected peripheral vestibular dizziness) evaluated with bithermal binaural caloric and sinusoidal and step-velocity rotary chair (RC) tests. INTERVENTION: Caloric and RC tests. MAIN OUTCOME MEASURES: 1) Receiver operating characteristic (ROC) analysis of individual caloric and rotary parameters for area under the curve (AUC) as indication of predictive value, and 2) logistic regression analysis of parameter combinations for identification of optimal test battery for predicting peripheral vestibular dysfunction RESULTS: Analysis of the individual receiver operating characteristic (ROC) curves for each caloric and RC test parameter for prediction of peripheral vestibulopathy revealed that the best overall predictive parameter was percentage of caloric weakness (CW; AUC-ROC, 0.73; 95% confidence interval, 0.66-0.80). Using 29.5% as the optimal cutoff point for CW, a specificity of 84% and sensitivity of 55% were obtained. Because of the reduced AUC for the RC parameters, no optimal cutoff points were chosen. Using a logistic regression model in predicting patients with peripheral vestibulopathy demonstrated that either comprehensive caloric and RC testing or the combination of caloric and 0.025 Hz, 0.5 Hz, and time-constant rotational testing yielded the highest predictive value (AUC-ROC, 0.79) CONCLUSION: Calculation of CW was the most promising single marker for identifying peripheral from nonperipheral vestibulopathic patients. Individual RC parameters showed limited predictive value to differentiate peripheral from nonperipheral vestibular dysfunction. However, the combination of subtests yielded an AUC-ROC only slightly less than caloric testing. The combination of caloric and RC testing revealed the strongest predictive capabilities for identifying peripheral vestibular injury. Furthermore, the combination of an abbreviated form of RC testing with caloric testing yielded nearly identical results as full caloric and rotational testing.

[Near infrared stimulation of the equilibrium organ--first clinical experiences]. / Nahinfrarotreizung des Gleichgewichtsorgans--erste klinische Erfahrungen.

BACKGROUND: A new method for the stimulation of the organ of equilibrium by means of a broad-scale and monochromatic near infrared emission was developed. This method should be examined within the framework of a pilot study, evaluated and its clinical possible applications examined. PATIENTS AND METHODS: Healthy probands (n = 15), patients with a radical cave of the ear (n = 5), patients with a defect of the tympanic membrane (n = 5) and spontaneous nystagmus (n = 5) were examined. In healthy probands an irritation with broad-scale as well as monochromatic near infrared (NIR) was performed and compared with a water irrigation (44 degrees, 50 ml in 30 seconds). The subjective, local feelings during the application and the appearance of giddiness according to irritation were recorded and the nystagmus was registered by means of videonystagmography. In patients with radical cave of the ear and tympanic membrane defects, a broad-scale NIR-irritation before a comparative irritation with warm air (44 degrees) was performed exclusively. RESULTS: In all healthy probands, a nystagmus reaction could be seen with broad-scale and monochromatic NIR. Compared to the hot water irritation slow phase velocity (SPV) was decreased however registrable by means of Frenzel glasses and electronystagmography during the culmination stage. In patients with radical cave (n = 4) and tympanic membrane defects (n = 3) showing paradoxical nystagmus reaction during hot air irritation, a nystagmus to the site of stimulation resulted by means of light calorisation. In patients with a spontaneous nystagmus an attenuation (n = 1) or inversion (n = 2) could be achieved by NIR-radiation. CONCLUSIONS: The method of the NIR-radiation is suitable in clinical practice for the caloric test proofing warm reaction. Vaporization cold does not occur. The application of heat charm is better proportionable and steerable than during air irritation. The procedure is sterile, noiseless and non-contact. Difficulties in interpretation of results of vestibular tests because of evaporation coldness do not occur.

[A comparison of water and air stimulated bithermal-caloric test and the usefulness of both methods in otologic surgery]. / Porównanie przydatnosci wodnej i powietrznej próby dwukalorycznej w praktyce otochirurgicznej.

The most commonly used method of testing the responses of the labyrinths is Water Stimulated Bithermal-Caloric Test of Fitzgerald-Hallpike. Before planning an otiatric surgery it is necessary to support by documentary evidence the responses of the vestibular organ in the ear planned to be operated on, however, irrigation with water may cause damage to structures of the ear and may intensify symptoms of the diseases and eventually make the treatment more difficult. In some centers where Water Stimulated Bithermal-Caloric Test were used alone, or a combination of air and water stimulated caloric test were performed, it seemed to be difficult to compare the results of both tests. In this study I tried to establish parameters of stimuli obtained in the Air Stimulated Bithermal-Calorics test that evoked nystagmus, similar to those obtained in the Fitzgerald-Hallpike water stimulated test. It was determined that the duration of nystagmus in both water and air stimulated bithermal-caloric tests were identical when the temperature of "cold" air wave was 26 degrees C, whereas "warm" air wave had the temperature of 48 degrees C and the time of stimulation for both tests was 80 seconds.

Robert Bárány and the controversy surrounding his discovery of the caloric reaction.

It was not until the latter half of the 19th century that the vestibular part of the inner ear was recognized to have a function separate from hearing. Robert Bárány was one of the first clinicians to assess vestibular function systematically in patients. He developed standard caloric, rotational, and pointing tests and was the first to describe benign paroxysmal positional nystagmus. Bárány began his career working in the otology clinic of Adam Politzer at the University of Vienna. He received the Nobel Prize in Medicine in 1916 for his work on the mechanism of the caloric reaction. However, in the aftermath of the First World War and the controversy surrounding his selection for the Nobel Prize, Bárány left Vienna for Uppsala, Sweden, where he spent the last 20 years of his life in relative isolation.

Caloric stimulation of ampullar receptors: a new method to produce mechanically-evoked responses in frog semicircular canals.

A microthermistor positioned close to the exposed posterior semicircular canal in isolated labyrinth preparations of the frog was used to stimulate the sensory organ. Our results indicated that, depending on the position of the heater, the induced endolymphatic convection currents may result in either excitatory or inhibitory cupular deflections and thus in a modulation of ampullar receptor resting activity. Other possible thermal-dependent mechanisms, such as a direct action of the stimulus on vestibular sensors or endolymphatic volume changes, had, in the present experimental conditions, a minor role. Caloric stimulation could therefore represent a novel method to stimulate the semicircular canals 'in situ'.

[Thermographic detection of heat radiation in caloric vestibular function tests]. / Thermographischer Nachweis der Wärmestrahlung bei der kalorischen Vestibularisprüfung.

BACKGROUND: Since Bárány; caloric irrigations in the external ear canal have been used for unilateral stimulation of the peripheral vestibular system. However, the mechanism of heat transfer from the auditory canal to the vestibular organ is not completely known. From the physical point of view, three mechanisms may be discussed: heat conduction via the bone, convection via the middle ear gas, or radiation. Feldmann et al. (1991) singled out radiation as a very important factor in this regard. Using high-resolution thermography, we were able to "see" radiation almost directly in temporal bone experiments. METHODS: Using the system of infrared thermovision specially adapted for close-up studies, the effect of calorization can be observed and documented in colored planar thermograms. Fresh temporal bone specimens had to be prepared so as to permit simultaneous observation of the tympanic membrane and the medial tympanic wall. RESULTS: Changes in temperature were readily visible during experimental caloric tests: turning blue indicated cooling and red indicated warming. In the caloric test with 44 degrees C or 30 degrees C water, changes in color of the eardrum appeared immediately. At the very same time, however, an area of the medial tympanic wall also changed color. This velocity of transfer cannot be attained by conduction or convection: heat radiation is the only possible explanation. This could only be demonstrated at the very onset of the reaction; subsequent thermograms became more and more diffuse. In this stage the heat transfer may also be effected by conduction and/or convection. CONCLUSIONS: Thermography demonstrates that radiation is a very important factor in heat transfer; at least in the initial phase of calorization.

Contribution of the vertical semicircular canals to the caloric nystagmus.

Modulation of the caloric nystagmus in response to repositioning the plane of one vertical semicircular canal from gravitational horizontal to vertical during continuous caloric stimulation was used to measure the vertical canal's contribution to the nystagmus. The rationale was to examine the thermovective response from one vertical canal at a time, after a temperature gradient had been established across its two limbs. The nystagmus was measured and analysed in three dimensions using orthogonal head-referenced coordinates. The magnitude of each semicircular canal's contribution to the overall caloric response, the canal vector, was determined in non-orthogonal, contravariant semicircular canal plane coordinates. By using the canal plane reorientation technique and contravariant canal plane coordinates, we were able to measure the proportional thermovective response magnitude generated by each vertical canal during caloric stimulation. We found that the anterior canal contributed about one-third and the posterior canal about one-tenth as much as the lateral canal did to the overall caloric response magnitude when it was reoriented from horizontal to vertical. Comparison of the eye rotation axis before and after each vertical canal plane reorientation, with the geometry of the stimulated semicircular canals, also showed directional modulation of the caloric nystagmus by the vertical canal response. When one vertical canal plane was horizontal during caloric stimulation, the eye rotation axis aligned with the resultant of the other vertical canal and the lateral canal response axes. After vertical canal plane reorientation, the eye rotation axis realigned towards the resultant of the maximally stimulated vertical canal and the lateral canal, by 55.2+/-33.9 degrees (mean+/-SD) after anterior canal plane reorientation and by 32.3+/-21.2 degrees after posterior canal reorientation.

Vestibular function in the fetal sheep.

Little is known about the functional development of the vestibular system before birth. The purpose of this study was to determine whether vestibular response to caloric stimulation could be elicited in the fetal sheep in utero. Late gestational fetal sheep (n = 6) were instrumented through a midline hysterotomy. Copper caloric probes were inserted into the right bulla and beneath the left facial skin. Electrodes were placed in the skull for monitoring of electro-ocular activity. At least 3 days after surgery the probes were irrigated with water (100 ml/minute) at body temperature, 46 degrees C, and 6 degrees C. Cold water infusion of the bulla consistently produced well-recognized, slow-phase deviations followed by saccades directed contralaterally, findings consistent with vestibular nystagmus. The direction of the response reversed with warm water irrigation. The response was absent with irrigation at fetal body temperature. Only random eye movements were observed in response to caloric stimulation of the facial skin, regardless of water temperature. These results demonstrate that the sheep vestibular system is functioning prenatally. The importance of vestibular function for normal fetal brain maturation may be revealed in future studies using this animal model.

Three-dimensional eye movement analysis during caloric stimulation used to test vertical semicircular canal function.

HYPOTHESIS AND BACKGROUND: Quantitative caloric testing is considered to be one of the most sensitive parameters in the diagnosis of peripheral vestibular disorders. In the past, because of limitations in the methods, the evaluation of the caloric response was restricted to mainly lateral semicircular canal functions. In this study, the authors tried to extend caloric testing to the function of all semicircular canals by using three-dimensional (3-D) analysis techniques. METHODS: The authors studied in seven normal subjects 3-D eye movement responses to air caloric of the right ear with the subjects positioned in standard caloric position (lateral semicircular canal vertical) or such that one of the three semicircular canals of the right side was horizontal. Movement of the left eye was measured in 3-D with a dual-magnetic search coil. During stimulation, 10 seconds of maximum response were selected and desaccaded to yield the slow-phase velocity profile. From this profile, the average magnitude and direction of the eye rotation axis (velocity vector) were calculated in head coordinates. RESULTS: In all subjects, in standard caloric position, warm caloric produced eye velocity vectors that clustered closely along the direction expected from an excitation of the right lateral semicircular canal. When the subjects were positioned with one of the vertical semicircular canals horizontal, the orientation of the velocity vectors shifted toward a direction expected from the combined excitation of the lateral and the other vertical semicircular canal and vice versa. CONCLUSIONS: The 3-D eye movement recordings during caloric stimulation in different head positions allow the evaluation of the function of all semicircular canals.

[Stimulating conditions of cold air caloric test].

This study is to clarify the effects of stimulating conditions on caloric response evoked by cold air stimulation. The five parameters of caloric nystagmus (latency, maximum slow phase velocity [Max. spv], Max. spv arrival time, frequency and duration) were examined. The different stimulating air temperature(0 degree C, 5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C), flow rate (3.0, 4.0, 5.0, 6.0 l/m) and period(30, 45, 60, 90 sec) were used to evoke caloric nystagmus in normal subjects. 1. Effect to temperature When the intensity of air irrigation temperature increased, Max. spv, frequency and duration also tended to increase. Out of the five parameters, the duration of caloric nystagmus was the most relevant to the intensity of irrigation temperature. 2. Effect of stimulating period When the period of caloric stimuli increased, the Max. spv and its duration also increased. But, when the stimulating period was 90 seconds, the slow phase velocity reached to the maximum responses 60 seconds after starting the stimulation. Therefore, it is not necessary to stimulate for more than 60 seconds. 3. Caloric response evoked by 60 sec, 5.0 l/m at 5 degrees C air irrigation showed the same response as the caloric nystagmus provoked by 20 ml of water at 20 degrees C for 20 sec.

Caloric irrigators: air, open-loop water and closed-loop water.

Selective stimulation of the semicircular canal system of one ear by establishing a temperature gradient is still widely used in the clinic in the caloric test. The results obtained are noted for their imprecision and variability. This is, in part, due to a lack of uniformly applied standardized test protocols, as well as difficulties in applying a precise stimulus. The relative merit of the three types of irrigation are reviewed. Whilst some authors argue that both the closed-loop and air irrigators produce even more variability of response than open water systems, the present author believes that intratest replication studies indicate that the closed-loop irrigation stimulus is the least variable and best tolerated by the patient. In perhaps one-fifth of patients, response to the first irrigation is much stronger than subsequent stimulus applications. It is suggested that there may therefore be a case for routinely performing five irrigations in the bithermal caloric test, including a replication of the first irrigation. It is assumed that psychological factors, especially anxiety, may explain the phenomenon of enhanced initial response, and some of the variability of caloric test responses in general. Use of the closed-loop irrigator is advocated for ease of use, reduced routine maintenance and to minimize patient distress, thereby reducing anxiety and result variability.

Neurootologic findings in patients with so called Menière-like disease.

A group of 150 patients was clinically observed using a complete battery of neurootological methods. The patients were believed to suffer from Menière's disease (MD). After taking anamnestic data [NODEC III] and performing calorimetry, cranio-corpo-graphy and audiology tests we could confirm a former established diagnosis of MD in a few cases only.

Observation of positional nystagmus with infrared CCD camera.

Using infrared CCD camera and electronystagmography we analyzed positional nystagmus in 33 patients with peripheral positional vertigo. Patients were classified into three types; (a) lateral type: nystagmus occurs in lateral position, (b) sagittal type: nystagmus occurs in head-hanging position (so-called benign paroxysmal positional vertigo, BPPV), and (c) mixed type. Nystagmus in the lateral type was horizontal and that in the sagittal type was rotatory. In all types, the vertigo and nystagmus began with a few seconds' latency after head tilt and briefly increased to a maximum, and then gradually decreased. The duration of horizontal nystagmus in the lateral and mixed type was significantly longer than that of rotatory nystagmus in the sagittal type mixed type. The mean value of the former was 90.6 s and that of the latter 18.1 s. We suggest that the velocity storage mechanism of the horizontal vestibulo-ocular reflex (VOR) is considerably different from that in the vertical VOR.