LXXIII The Diagnostic Value of Caloric Tests in Otoneurology

Computerized analysis of the caloric response

Caloric responses from 50 consecutive patients, referred routinely for investigation of hearing and/or balance problems, were evaluated by computer and manual methods of analysis. Using measures of nystagmic slow-phase velocity, there was found to be a high degree of correlation between the two methods. Of the 50 patients, the manual method of analysis identified 20 as having abnormal caloric patterns. All of these patients (and an additional 3) were similarly identified by the computer method. The computerized technique was found to be effective, even in the evaluation of irregular signals, making it suitable for use in the clinical situation. Since no decision making on the part of the operator is required, the method described is considered to be a significant advance in computerized methods of analysis of nystagmic slow-phase velocity.

Electronystagmography outside the hospital using a pocket-sized electrocardiograph

It is the desire of the neurotologic clinician to record routinely the nystagmus of patients with vestibular disorders but it is troublesome to have it done frequently. We tried to have patients record their own nystagmus using a portable electrocardiograph. It is pocket-sized and can be operated easily at any time and any place by laymen and often provides beneficial information. When we performed the caloric test on nine patients, we recorded the nystagmus with an ordinary electronystagmograph and with this equipment simultaneously. It has been recognized that the records with a portable electrocardiograph bear close resemblance to the records obtained with an ordinary electronystagmograph. According to the experience in twenty cases of dizzy patients using this recording system, it was concluded that the equipment is useful not only for the diagnosis of dizzy patients, but also for evaluating the effect of drugs and for recommending changes in the mode of living for some patients.

Vestibular diagnosis in Menière's disease

Vestibular diagnosis of Menière's disease must be based on the results of an elaborate test battery. The latter should include a complete caloric test (stimulation with cold and warm water), carried out under nystagmographic control. Statistical analysis of caloric responses recorded in 100 normal test subjects by D.C. nystagmography show clearly that culmination frequency and culmination eye velocity are the most reliable parameters indicating an unilateral loss of function. With respect to the differential diagnosis - endorgan or neuronal lesion - only the galvanic test allows an unequivocal localisation of the site of the lesion. An analysis of 50 cases of Menière's disease reveals normal liminal and supraliminal galvanic responses without exception, thus indicating that the concomitant reduced caloric response is due to a lesion strictly confined to the vestibular endorgan. Hence the galvanic test may serve the same diagnostic purposes as supraliminal tests in pure tone audiometry.