[Simple method of differential diagnosis of peripheral and central vertigo--development of diagnostic method and...

In patients who complain of vertigo or who have equilibrium disorders, it is often difficult to determine the etiology of the disorder, that is to determine whether it is dependent on a peripheral or central vestibular disorder. To attempt to determine the etiology in these cases, we divised a new method, the caloric eye tracking pattern test (CETP-Test). Seventeen normal subjects and 161 patients were tested. The latter group included 33 with peripheral disorders such as Meniere's disease, benign paroxysmal positional nystagmus, and others, and 128 with central disorders such as vertebral basilar artery insufficiency, cervical vertigo, and others, were tested. The cases of central disorders were limited to those patients whose eye tracking pattern before the caloric stimulation was normal. In normal subjects and in patients with peripheral disorders, it is well known that caloric nystagmus has little influence on the eye tracking pattern. In contrast, in patients with central vestibular disorders, caloric nystagmus evokes abnormalities on the eye tracking pattern, either superimposed or saccades, despite the fact that the eye tracking pattern before the caloric stimulation is normal. First we administer the eye tracking stimulation test using a target which moves horizontally at 0.3 cycle per second. Next, we perform the caloric test on the right ear, using 20 c.c. of ice water for 10 seconds. During the evoked caloric nystagmus we administer the eye tracking test once again. The eye tracking pattern is recorded for 20 seconds beginning 50 seconds after the start of the ice water injection. The procedure repeated on the left ear. The results on each case are presented as three patterns of ENG-recording. We may stat that in normal subjects and in patients with peripheral vestibular disorders, visual suppression of caloric nystagmus remains functional. Caloric induced nystagmus does not affect the CETP. In patients with central vestibular disorders, visual suppression of caloric nystagmus does not function properly because of defects in the visual suppression mechanism. Therefore, caloric nystagmus greatly influences the CETP. Consequently, the CETP may not be smooth when CETP test is administered to patients with central vestibular disorders. We may say also that the visual suppression to the vestibular nystagmus is evoked more strongly by pursuing a moving visual stimulus than by gazing a stational target. These results allow for a differential diagnosis between peripheral and central disorders.