The Neurotological Significance of Alterations of Pursuit Eye Movements and the Pendular Eye Tracking Test

Abstract

Smooth pursuit eye movements can be studied if the patient follows a target that moves horizontally in a pendular way. The eye movements can be recorded with electro-oculographic technique, and the tracings obtained studied for abnormalities. This constitutes the Pendular Eye Tracking Test (PETT). Three different deformations of PETT tracings have been observed: 1) a basically normal shaped curve with superimposed fast movements; 2) a deformed curve and 3) an absence of the normal sinusoidal tracing. In diseases of the inner ear, the PETT usually shows a normal curve, but sometimes can be slightly modified by the appearance of small, fast movements. In diseases of the central nervous system, the PETT is very often altered, and these alterations are very distinct. Although the three main deformations of the curve can be observed in lesions of any localization in the nervous system, there appears to be certain systematization. The normal curve with superimposed fast movements tends to be associated with cerebellar disease. The deformed curve often appears in connection with a more widespread localization of encephalic lesions, perhaps due to repercussion in the brain stem; and the disappearance of the curve apparently is due to an important lesion in the oculomotor pathways in the tegmentum of the pons and midbrain. The PETT has localizing diagnosic value, especially in the differentiation between diseases of the internal ear and of the central (neurological) connections of the vestibular system.