Biomedical subjects
Publications and source records attributed to S M Sakala.
Our standard rotational test battery includes tests of optokinetic nystagmus (OKN), the vestibulo-ocular reflex (VOR), and visual-vestibular interaction. Lesions of the peripheral vestibular system characteristically impair only the VOR, whereas lesions of the central system impair OKN and visual-vestibular interaction. The pattern of abnormal responses can help localize lesions within the central vestibular pathways.
The visually controlled eye tracking systems (saccadic, smooth pursuit, and optokinetic) were compared in 25 young and middle-aged normal subjects (mean age, 42 years), 14 elderly patients with vertebrobasilar insufficiency (VBI) (mean age, 67 years) and 14 elderly normal subjects (mean age, 65 years). The young normal subjects were consistently superior to both elderly groups on all measurements, but there was no significant difference between the performance of patients with VBI and the elderly normal subjects. This study emphasizes the critical importance of taking age into consideration when evaluating saccades, smooth pursuit and optokinetic nystagmus.
A characteristic nystagmus profile of benign paroxysmal positional nystagmus was determined from analyses of horizontal and vertical electro-oculographic recordings in 32 patients. The vertical component was upbeat in both eyes (fast phase toward the ground in the head-hanging position), whereas the horizontal component was dissociated with the ipsilateral eye beating away from the down ear and the contralateral eye beating toward the down ear. The amplitude of the vertical component was larger in the ipsilateral eye. This dissociated nystagmus profile is consistent with a burst of excitatory activity originating in the posterior canal of the ear that is undermost at the end of the positioning maneuver.