Eyelid movements in facial paralysis.

We studied the eyelid movements of six patients with unilateral, isolated, facial paralysis using the magnetic search coil. The most significant abnormality consisted of a reduction in the magnitude of the orbicularis oculi contraction with slowing of the peak velocity of the closing phase of the blink. The closing phase blink velocity, which normally increases linearly as a function of amplitude (main sequence), in our patients displayed a relationship characterized by a slow saturating power function that fell off the main sequence. The contralateral normal lid in some cases can show adaptive signs of hyperactivity during the closing phase of the blink. Lid saccades showed a small but consistent decrease in amplitude and velocity compared with the contralateral unaffected eyelid. Unlike the closing phase of the blink, peak velocities of lid saccades stayed on the main sequence. In this study, we discuss how the eyelid executes downward lid saccades based purely on a passive mechanism.