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The clinical significance of ‘directional preponderance’ concluded by electronystagmography

IN recent years we are faced with a growing discontent with the contribution made by electronystagmography to final diagnosis of diseases. Lack of unified approach to interpretation of results may be the main reason for this discontent. One of the most controversial issues is the interpretation of 'directional preponderance' concluded by electronystagmography. The significance of 'directional preponderance' of the nystagmus evoked by vestibular stimulation was investigated for over fifty years. Fitzgerald and Hallpike (1942) treated the subject of 'directional preponderance' resulting from cerebral lesions. They presented 10 cases with parietal lobe lesions that responded to bithermal caloric stimulation with 'directional preponderance' in the direction of the lesion. The authors also mentioned the experimental studies of Barany and DeKleyn, where removal of one cerebral hemisphere in rabbits resulted in 'directional preponderance', and to the clinical reports of DeKleyn and Vesteegh where 'directional preponderance' was found in cases with brain lesions. In a subsequent article, Cawthorne, Fitzgerald and Hallpike (1942) presented nine cases of Meniere's disease after unilateral labyrinthectomy. In addition to labyrinthine preponderance, the patients presented had 'directional preponderance' in the direction of the post-operative nystagmus. Practically, one might conclude that these studies demonstrate that 'directional preponderance' might be of a central origin as well as of a peripheral origin. Other reports confirmed this conclusion, apparently diminishing the diagnostic value of the 'directional preponderance' obtained by rotation or bithermal calorization. With the introduction of electronystagmography in clinical practice, the positional test as well as the bithermal caloric irrigation are performed under different test conditions. With the elimination of inhibitory factors such as light and fixation and facilitation of nystagmus by aroused concentration, these tests were altered to the extent that electronystagmography can be considered an independent vestibular test. A spontaneous