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PubMed1998

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.

Adult↗
PubMed1979

The vestibulo-ocular (caloric) reflex in the diagnosis of cerebral death.

Correlation between vestibulo-ocular (caloric) reflex and the electroencephalogram was examined in 25 apparently brain-dead and 17 severely brain-injured patients. Among the apparently cerebrally dead, 3 patients still had some EEG activity and in 2, there was some response to caloric testing. In the control group of patients some EEG activity was present in all, and the caloric response was absent in 1. It is concluded that absence of caloric response has similar power to the electroencephalogram in confirming cerebral death. The diagnosis, however, must be made on the total information available, including history and examination of the patient. The policy of the Intensive Care Unit of Prince Henry Hospital in this regard is outlined.

Brain Death↗
PubMed1987

Vestibular habituation training and posturography in benign paroxysmal positioning vertigo.

A number of cases with typical positioning vertigo (BPPV) show a unilateral vestibular hypofunction (UVH) by caloric testing. However, treatment by habituation exercises (VHT) improves vertigo independently of the presence of UVH. Moreover, VHT has no influence upon the results of caloric and rotation tests. These findings prove the independence of the pathogenetic mechanisms of the peripheral vestibular disturbances UVH and BPPV.

Caloric Tests↗
PubMed1987

The effects of alerting tasks on caloric induced vestibular nystagmus.

The present study compared the effects of four different mental altering tasks on the speed of the nystagmic slow component during caloric testing in 40 young adults. Subjects were randomly divided into four groups (10/group) and stimulated twice in each ear in a counterbalanced manner according to test ear, irrigating temperature, and alerting task. Analysis of the data revealed significant differences between treatment effects on the magnitude of the slow phase velocity of nystagmus. Results suggest that passive listening does not sufficiently alert subjects to ensure the adequate release of nystagmus suppression during vestibular testing.

Acoustic Stimulation↗
PubMed1992

Caloric irregularity in experimentally induced perilymphatic fistula.

The term "caloric irregularity" was coined to refer to a gross irregularity in the amplitude and/or frequency of a caloric-induced nystagmus, having a variable slow-phase velocity and prolonged duration. Twelve of 46 guinea pigs with experimentally induced perilymphatic fistula had irregular responses to the ice-water caloric test 1 week after creation of a fistula. The long-term vestibular consequences in animals with caloric irregularities were either resolution and return to normal function (i.e. caloric return) or continuing deterioration to canal paresis. Morphological examination of ears with caloric irregularity revealed that there had been partial collapse of the membranous labyrinth and the creation of a floating labyrinth.

Animals↗
PubMed1981

Vestibular testing in basilar artery migraine.

Vestibular function studies were performed in 20 children with symptoms suggesting basilar artery migraine. Sixteen children had abnormalities on bithermal caloric testing. Labyrinthine preponderance was found in 1 child with labyrinthine concussion and in 6 children with symptoms suggesting ischemia of the territory supplied by the basilar artery and the occipital branches of the posterior cerebral arteries. Directional preponderance was found in 4 children with symptoms suggesting ischemia of the posterior temporal branches of the posterior cerebral arteries. Five children had both labyrinthine and directional preponderance. normal electronystagmographic findings were present in 4 children and correlated clinically with a milder illness. Head trauma was the triggering factor for the migraine in 5 children. Five children developed complex partial seizures and had evidence of directional preponderance (2 children) and combined labyrinthine and directional preponderance (2 children). The presence of abnormalities on electronystagmography in children with basilar artery migraine correlates with the severity of the disease. Directional preponderance or labyrinthine and directional preponderance are more frequently correlated with ischemia in the posterior temporal branches of the posterior cerebral arteries and may suggest a higher risk of developing vertiginous seizures when ischemia is prolonged.

Adolescent↗
PubMed1992

The effect of stimulus duration using the Brookler-Grams closed-loop caloric irrigator.

Nystagmic responses to traditional 40-sec, 30 degrees C water calorics were recorded and compared to those obtained with the Brookler-Grams closed-loop irrigator using 30 degrees C, 40-, 50-, and 60-sec irrigations. Significant differences were noted between the responses to the water irrigator and the 40- and 50-sec closed-loop irrigations. The 60-sec closed-loop irrigation produced responses that were equivalent to the responses obtained with the water irrigation in slow component velocity, amplitude, frequency, latency, and duration. The 30 degrees C 60-sec closed-loop irrigation is an acceptable stimulus in electronystagmographic caloric testing.

Adolescent↗
PubMed2000

Results of serial vestibular testing in unilateral Ménière's disease.

OBJECTIVE: To determine the prevalence and character of vestibular abnormalities and the changes in vestibular function that occur in unilateral Ménière's disease. STUDY DESIGN: Retrospective case review. SETTING: Ambulatory patients at a tertiary care facility. PATIENTS: Entry criteria included a diagnosis of unilateral Ménière's disease and test results from at least two vestibular test sessions at the Johns Hopkins Otologic Vestibular Laboratory. One hundred twenty-two cases were evaluated. MAIN OUTCOME MEASURES: Electronystagmographic evaluation, including caloric testing; audiometric tests; and medical records. RESULTS: Caloric weakness was demonstrated in 58% of patients on the involved side and in 19% on the normal side. Complete paralysis was found in 7%. Directional preponderance was seen in 33% of patients and completely normal scores in 27%. During the course of the disease, responses become weaker in 26% of patients and stronger in 11%. Of 39 patients tested more than twice, 26% showed both increases and decreases in caloric responses. After an acute attack, only one of eight patients showed a depressed response on the diseased side, and three showed an increased response. Spontaneous nystagmus, seen within 24 hours of an attack in 54 cases, was directed away from the diseased ear in only about one half of the cases. Benign paroxysmal positional vertigo was found in 44% of these patients. CONCLUSIONS: Possible pathophysiologic explanations for the various test results in Ménière's disease are discussed. Interpretation of caloric test results should take into account the absolute value of the slow phase eye speed scores, in addition to the right-left difference score. Also, established standards for the normal range of fluctuation in both absolute and comparative scores should be used when more than one test session has been undertaken.

Acute Disease↗
PubMed1996

Do Frenzel glasses have a place in the modern electronystagmography laboratory?

Electronystagmography (ENG) is generally performed with the patient's eyes closed to prevent visual fixation. In this way, direct observation of eye movements is impossible. By means of Frenzel glasses (FG), the direct observation of eye movements is possible, but the effectiveness of visual fixation suppression and the diagnostic contribution of FG must still be studied. One hundred seven patients with vertigo participated in this study. Each patient underwent a complete ENG test under two fixation modalities: (a) closed eyes and (b) open eyes with FG. The spontaneous nystagmus and the Hallpike test did not show any significant difference between the two fixation modalities. The slow-phase velocity of nystagmus with the caloric test was significantly greater with closed eyes, but the pattern of nystagmus with FG fixation was more tooth-shaped and regular than that with closed eyes. It is concluded that using FG when performing an ENG may improve its diagnostic value.

Adolescent↗
PubMed1983

Practical value of a simplified air caloric stimulation with freon.

Caloric testing is the only method to examine the vestibular function of each labyrinth separately. When a perforated drum is present, caloric stimulation has to be achieved by air injection. In this study we examine the applicability and reliability of a simplified stimulator with Fréon. This comparative study proves it to be a reliable method for daily ENT practice.

Adult↗
PubMedDate not supplied

Vestibular responses to bithermal caloric and harmonic acceleration.

Vestibulo-oculomotor responses from 33 patients with either peripheral labyrinthine or central pathology were compared using the standardized Fitzgerald-Hallpike bithermal caloric and harmonic accelerations. In numerous cases (40%), patients with normal caloric responses reflected abnormalities in either their phase relationships or labyrinthine preponderance to sinusoidal acceleration. Results clearly indicate that harmonic acceleration provides additional information to the clinician in the evaluation of vestibulo-oculomotor pathology that is not reflected in the responses to standard caloric tests.

Adult↗
PubMed2000

Charles Skinner Hallpike and the beginnings of neurotology.

Although the symptom of vertigo had been well-recognized for several thousand years, it was not until the pioneering work of Prosper Ménière in the mid-19th century that it was appreciated that vertigo could originate from damage to the inner ear. Before that time, patients with vertigo (regardless of the cause) were said to have "cerebral congestion," a condition resulting from excessive blood filling the brain. Bloodletting and leeches to relieve the congestion were the treatment of choice. The discovery of endolymphatic hydrops in temporal bone specimens from patients with Ménière's disease by Hallpike and Cairns in 1938 marked the beginning of modern neurotology. For the first time, vertigo was correlated with specific pathophysiology. Propelled by his temporal bone work, Charles Hallpike received an appointment at the National Hospital at Queen Square, where he developed an internationally renowned neurotology clinic. His bithermal caloric test and positional tests are still routinely used in evaluation of the vertiginous patient.

Caloric Tests↗
PubMedDate not supplied

Evaluation of hyperactive caloric responses in patients with inner ear diseases.

Twenty-three patients with various types of inner ear diseases, who showed hyperactive caloric responses (21 patients showed unilateral hyperactive caloric responses, and 2 patients showed bilateral hyperactive caloric responses) were monitored during 2-10 years and underwent caloric tests repeatedly (2-7 times). None of them showed continuous hyperactivity of the labyrinth throughout their clinical courses. It seems that hyperactive caloric responses in patients who suffer from inner ear disease may be a transient phenomenon, caused by fluctuations of the vestibular condition, central compensation, age and/or mental state of the patients.

Adult↗
PubMed1993

[Periodic alternating nystagmus in familial congenital cerebellar ataxia].

We noted periodic alternating nystagmus (PAN) in two patients (mother and daughter) who were diagnosed as familial congenital cerebellar ataxia. The mother was 51-year-old and her PAN had about 4 minutes cycle. During eye closure there was a deviation of arms and trunk parallel to the direction of the slow phase of nystagmus. Vestibular stimulation during rotatory and caloric tests disclosed enhanced vestibulo-ocular reflexes, changes of direction and prolonged cycle of PAN. The patient had no visual suppression during caloric stimulation. The daughter was 14-year-old and although she had no spontaneous PAN she had latent PAN by showing changes of direction of nystagmus during the caloric stimulation. She had also no visual suppression during caloric stimulation. From these results the mechanism of PAN could be attributed to the periodic hyperfunction of vestibular nuclei caused by reduced suppression from cerebellar uvula and nodulus.

Adolescent↗
PubMed1978

Reliabilities of air and water caloric responses.

Air is a safer and more convenient caloric-irrigating medium than water, but many otologists are reluctant to use it because they suspect that it yields less reliable nystagmus responses. To compare reliabilities of air and water caloric responses, we subjected eight normal persons to 12 irrigations each of 50 degrees C air, 44 degrees C water, 24 degrees C air, and 30 degrees C water. Standard caloric-testing conditions were used, and nystagmus responses were recorded by the method of electronystagmography. We found that the reliabilities of air and water caloric responses were not significantly different. A single observation permitted estimation of response strength within approximalely +/- 5 degrees/sec (95% confidence level), regardless of whether air or water was used as the irrigating medium.

Adult↗
PubMedDate not supplied

Spontaneous nystagmus in normal subjects.

We investigated the incidence of spontaneous nystagmus in 30 normal volunteers using electronystagmography (ENG). In all subjects, ENG was performed with the eyes open in the primary position, with the eyes closed, and with the eyes open in total darkness. Spontaneous nystagmus was detected in 5 (16.7%) of 30 subjects. In 15 subjects who underwent 2 ENG examinations, 4 subjects (26.7%) exhibited spontaneous nystagmus. Caloric testing was performed in 26 of 30 subjects. Spontaneous nystagmus was detected in 3 subjects who had a right-left difference in caloric response of over 40%, and in 2 of 23 subjects who had a difference of less than 40%. Our results showed that spontaneous nystagmus was detected in more subjects when the ENG examinations were repeated. Thus, a single ENG examination cannot exclude the possibility of spontaneous nystagmus.

Adult↗
PubMed2000

Isolated directional preponderance of caloric nystagmus: II. A neural network model.

HYPOTHESIS: The purpose of this study was to simulate an isolated directional preponderance (DP) on bithermal caloric testing by constructing a realistic neural network model. The simulation was designed to capture not only the characteristics of the nystagmus response to caloric stimulation but also the response to rotational stimulation in patients with an isolated caloric DP. BACKGROUND: The nature of an isolated DP--that is, a DP in the absence of a significant spontaneous nystagmus or canal paresis--is outlined in the preceding article. In this article, the authors investigate the possible neural basis for an isolated caloric DP using the mathematic modeling technique of neural network simulation. Neural network models are typically abstract in nature; however, in this case the network was based on the known structure and function of the central vestibular system. METHODS: The neural network model was based on the known neuroanatomy and neurophysiology of the horizontal vestibuloocular reflex pathway. A leftward-rightward asymmetric modification of the dynamic responses of simulated medial vestibular nucleus type IA neurons on one side, or of type 2 neurons on the other side, to peripheral input would generate an isolated caloric DP. RESULTS: The values of DP and associated canal paresis produced by the network were within the same range as in the patient group. The network also predicted that the rotational DP would be lower than the caloric DP: between 2.5% and 56.9% of the caloric DP value. The actual rotational DP value was between 3% and 57% (average 41%) of the corresponding caloric DP value. CONCLUSIONS: An isolated caloric DP can be simulated by a neural network model by modifying the activity of model units that represent medial vestibular nucleus neurons. An asymmetric dynamic response by a gain-enhancement function of either type 1A neurons on one side or of type 2 neurons on the other was sufficient to produce an isolated caloric DP. Excitatory gain enhancement of type 2 neurons produced a smaller rotational DP than a similar modification of type 1 neurons. This result indicates a potential neural locus for the generation of an isolated DP in patients with vestibular disorders.

Caloric Tests↗
PubMed2005

Sacculo-collic pathway dysfunction accompanying auditory neuropathy.

CONCLUSIONS: In a patient with bilateral auditory neuropathy (AN), the vestibular-evoked myogenic potential (VEMP) was probably absent because of a neuropathy involving the inferior vestibular nerve and/or its end organ, the saccule. Our result can therefore be interpreted as a concomitant unilateral sacculo-collic neuropathy. We suggest the use of more precise terms to characterize AN patients with involvement of different parts of the inner ear and its innervations. We encourage detailed vestibular assessment in patients with AN in order to assess the co-existence of any symptomatic or asymptomatic vestibular disorder. Information such as that provided in this report will be valuable for clinicians caring for this group of patients. OBJECTIVE: AN is a disorder characterized by the absence or severe impairment of auditory brainstem responses in the presence of normal cochlear outer hair cell function as revealed by otoacoustic emissions (OAEs) and/or electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology. In most literature reports the auditory profile of patients with AN is discussed. However, the extent of vestibular involvement, especially that involving the saccule, is not known. We performed vestibular tests to assess the status of the saccule in a patient with AN. MATERIAL AND METHODS: One patient with AN was studied. The patient was a right-handed 21-year-old female with chief complaints of hearing loss and speech perception difficulty. RESULTS: The auditory test results were consistent with the diagnosis of AN, i.e. absent auditory brainstem responses, moderate hearing loss, an inappropriately profound speech discrimination score and the presence of OAEs and measurable cochlear microphonics on ECoG. On neurological examination, gait and balance tests were normal. Ice-water caloric testing induced a sensation of dizziness in both ears. Short tone-burst VEMPs showed no response on left-ear stimulation and a biphasic response with normal latency and amplitude on right-ear stimulation.

Adult↗