VARIABILITY AND DIAGNOSTIC VALUE OF THE POSITIONAL NYSTAGMUS

Abstract

The positional nystagmus test is one of the most essential vestibular tests. Types of the positional nystagmus frequently suggest lesions of vertigo or dizziness. In the peripheral lesions, paroxysmal positional vertigo is the most common. They are direction-changing torsional nystagmus, or geotropic nystagmus. These types of nystagmus are occasionally mixed together, thus giving an impression of central lesions. Effects of tympanoplasty on the vestibular system was studied by observing nystagmus one day after the surgery. Half of the patients showed positional nystagmus beating toward the operated side. Tympanoplasty affects the vestibular system, especially the otolithic organ by vibratory effect of the surgical drill.
Several cases of periodically changing positional and positioning nystagmus are presented. All showed unremarkable findings on the neurological tests and brain MRI. The majority showed a direction-changing geotropic nystagmus and a down-beating nystagmus. The direction and type of the nystagmus frequently changed. The direction changing geotropic type often altered into the apogeotropic type, or was mixed with a down-beating nystagmus. A vascular disorder within the brain stem or cerebellum was suspected. The above findings support the importance of a nystagmus test, even when the MRI findings are unremarkable.