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Background High-resolution MR imaging enables the visualization of individual nerves in the internal auditory canal (IAC). Cochlear nerve deficiency (CND) is recognized as one of the major causes of sensory neural hearing loss (SNHL), especially in cases of unilateral hearing loss in childhood. Some patients with CND are thought to have accompanying vestibular nerve deficiency (VND). However, there have been few reports focusing on VND and vestibular function in these children. Aims The aim of this study was to evaluate the frequency of VND and vestibular dysfunction in children with unilateral SNHL caused by CND. Material and methods Thirty-eight children with unilateral SNHL, who were diagnosed with CND by 3 T-MRI, were evaluated for VND and underwent caloric testing and cervical vestibular evoked potential (cVEMP). Results Fourteen of 38 patients (37%) had VND, and eleven (29%) of the patients [ten of the patients (71%) with VND] had at least one vestibular dysfunction. The patients with VND had significantly worse hearing and an IAC of smaller diameter than did patients without VND. Conclusions and significance We should pay attention to VND as well as vestibular dysfunction in hearing loss patients with CND.

Although there was a statistically significant relationship between the results of the vHIT and the caloric test, the limited strength of this relationship suggests that, for unilateral vestibular schwannoma (UVS), caloric testing and vHIT may provide complementary information on vestibular function.There is limited information that can be used to determine which of the video head impulse test (vHIT) and caloric test might be better used in the diagnosis and management of UVS. In this study, a group of participants with un-operated UVS was studied using both methods.The subjects' vestibular function was assessed using the vHIT and caloric testing. Tumour size was quantified using MRI and their balance disturbance assessed using the Jacobsen Dizziness Handicap Inventory (DHI).Twenty of 30 subjects had an abnormal canal paresis according to the Jongkees' criterion ( 0.25); however, only 10/30 had an ipsilesional vHIT gain of0.79. Canal paresis could be predicted from the ipsilesional and contralesional vHIT gains. Tumour size could also be predicted from the ipsilesional vHIT gain and canal paresis. However, DHI scores could not be predicted from the degree of canal paresis, vHIT gain, or the MRI measures.

The data suggests that gadolinium-enhanced inner ear MR imaging is useful for diagnosis of delayed endolymphatic hydrops (DEH) because it is independent of inner ear function, and the size of the affected endolymphatic space is clearly enlarged.This study was performed to semi-quantitatively evaluate the endolymphatic space in patients with all types of DEH using gadolinium-enhanced inner ear magnetic resonance (MR) imaging.Seven patients (age range = 21-77 years; five female, two male) with ipsilateral DEH (n = 5), contralateral DEH (n = 1), and bilateral DEH (n = 1). All patients underwent 3T MR imaging 4 h after intravenous injection of gadolinium. Software was used to determine the size of the endolymphatic space. Pure tone audiometry and caloric testing using an electronystagmogram were carried out.One side of the endolymphatic space was dominantly extended in patients with ipsilateral DEH, and both sides of the space were extended in patients with contralateral and bilateral DEH. In patients with ipsilateral DEH, the volume ratio of endolymph to vestibule was 2.5-4.3-times that in the unaffected ear. The volume ratio of endolymph to vestibule was nearly equal in patients with contralateral and bilateral DEH.

CONCLUSION: Subjectivity seems to play a definite role in the interpretation of the pendular test, but somewhat less for caloric testing, where pure visual analysis seems to be more reliable. Automated values provided by proof-tested software may be useful. OBJECTIVES: In some centers, the interpretation of videonystagmography is still based on direct visual analysis of recorded tracings. Our study addresses the importance of subjectivity in the interpretation of videonystagmographic readings. PATIENTS AND METHODS: Two experts (one junior and the other senior) were asked to interpret the same caloric and pendular tests on two different occasions, 3 months apart. Initial reading was performed without knowledge of the patient's history or the results of other neuro-otological tests. Three months later, interpretations were done with complete access to the patient's charts. The experts' answers were compared to the values provided by the computer software. RESULTS: For the pendular test, inter-expert agreement was poor. With knowledge of the patient's history, the expert's interpretations tended to coincide with the software's calculations. For the caloric test, interpretation was less variable.

Bithermal caloric testing was carried out in 57 normal subjects and 374 patients presenting with subjective complaints of vertigo over a 4-year period from December 1984 to December 1988. Responses were quantitatively assessed using a DEC PDP 11/73 laboratory minicomputer. Patients were classified as normal and abnormal according to caloric responses based on standard methods of calculating unilateral hypoexcitability and directional preponderance using the maximum slow component velocity. Results obtained from the slow component velocity for unilateral hypoexcitability and directional preponderance were compared to the same values obtained from the overall positional envelope calculated by an integration of the slow component velocity vs. time curve. Although duration of nystagmus varies extensively in normal subjects and has not proven clinically useful in identifying abnormalities, the integral of response amplitude over time gives a more complete description of the vestibular response. However, when compared to the maximum slow component velocity in abnormal patients, the positional envelope identified only 94 of the total 119 abnormalities (79%). Therefore, maximum slow component velocity is the more sensitive response parameter in identifying vestibular pathology.

All patients who complained of dizziness during 1981 and in whom the nystagmograms indicated either central damage or were found normal, were investigated further regarding changes in their R-factor (an expression for amplitude). This was deduced from the nystagmographic readings produced by caloric testing in these patients. It was thus found that patients with pain or stiffness in the neck had a significantly raised R-factor in all age groups.

The observation that the caloric nystagmus response is dependent on body position has been repeated in several studies during the course of this century. For many, this position-dependent modulation of the caloric response has been interpreted as evidence in favour of the thermoconvection theory as originally proposed by Bárány. However, the adequacy of this theory has been put into question by recent observations of caloric nystagmus during weightlessness in orbital flight. These zero-g findings clearly demonstrate that any hypothesis based on thermoconvection alone must prove insufficient as a description of the caloric nystagmus response. In the light of these recent findings, it has also become necessary to reconsider the influence of body position on caloric nystagmus intensity and the physiological mechanisms involved. Caloric testing was performed with a group of 30 healthy test subjects. Each person was tested in eight different body positions in the sagittal plane. Caloric nystagmus response was registered by means of horizontal and vertical EOG. The observed modification of the caloric response (SPV) by assumed body position is discussed with reference to associated reports in the literature.

A new caloric irrigation method is described. In the new method, the temperature of a continuous aural irrigation is switched between hot and cold values at precisely specified times. The durations of hot and cold pulses have been calculated to produce specific caloric stimulation intensities based on known heat transmission characteristics of the labyrinth area. A brief "washout" irrigation is used to eliminate promptly all caloric stimulation effects at the conclusion of each test. The present study concentrated upon the question of how long the "washout" pulse should be in order to obtain optimum results. Repetitive application of a uniform stimulus intensity to 6 normal subjects indicated that short inter-test intervals can be used without causing vestibular habituation. Prompt removal of the caloric stimulus can be accomplished by proper timing the "washout" phase of the new technique.

In 108 patients referred for caloric testing, head-shaking nystagmus (HSN) was noted in 37 electronystagmography (ENG) recordings. A canal paresis was found in 31 patients and a sensorineural or mixed hearing loss in one or both ears was found in 45 patients. Both HSN and canal paresis were insensitive predictors of either hearing loss or of each other. HSN was less sensitive as well as less specific than canal paresis for hearing loss. These data suggest that HSN is not as powerful a test as canal paresis in detecting lesions of the 8th nerve.

Vestibular caloric testing (10-49°C, 40 sec duration) was performed on 22 cats in an optimal position for horizontal semicircular canal stimulation (fronto-occipital axis at 45° angle) and in a position where otoliths provoke maximal stimulation of the macular hair cells (fronto-occipital axis at 135° angle). The order of angles was randomized and the stimulation separated by a 10 min rest interval. Nystagmus was electrically recorded by four-channel recorder and duration of post-caloric nystagmus and eye velocity in the slow and fast phase were analyzed. Caloric testing performed at the 135° angle (maximal stimulus for the otolith organ but not an optimal position for the horizontal semicircular canal) provoked significantly longer duration of post-caloric nystagmus than at the 45° angle. Thus, the otolith system may act as a controlling, regulatory mechanism over the duration of post-caloric nystagmus, or the stimulation of the otolith organ may itself produce nystagmus under certain physiological condi...