The dynamic head-tilt test and the concept of a supranuclear trochlear palsy

The "dynamic head-tilt test" introduced in this article examines the influence of the vestibular semicircular canals on the eye muscles during the head tilt. Normally, a rotatory nystagmus results. If under certain pathological circumstances, the vestibulo-ocular reflex is transmitted only to the rectus muscles and not to the obliques, the cyclorotatory nystagmus is converted into a vertical nystagmus. We have found this condition in five cases; in two it was very pronounced. During head tilt to the right, the slow phases of the nystagmus were directed upward in the right eye and downward in the left eye. During head tilt to the left, the nystagmus directions were reversed. Since other signs of oblique muscle palsy such as incomitance and cyclotropia were lacking or inappropriately slight, the author suggests the presence of a supranuclear lesion eliminating the vestibular input to the trochlear nucleus and to the subnucleus of the inferior oblique muscle while leaving the input for voluntary and visual gaze signals intact.