Written by Travis M. Moore
Last edited 11-Oct-2019
It is easy to administer tests of ocular motility; it is quite another thing to interpret and describe pathological results. In this section, we walk through each test discussed in the Ocular Motility Testing module and consider what abnormal results tend to look like, and how to report those abnormal results to other clinicians.
Because there are so many different types of nystagmus and other eye movements that could occur during gaze stability testing, it is important to use standard language so other clinicians can instantly tell what you saw without reading paragraphs of descriptive text. When reporting the presence of gaze-evoked nystagmus, the following characteristics should be mentioned:
The degree of nystagmus tells us in what positions the nystagmus was present. First degree means the nystagmus was only present when the patient looked in the direction of the fast phase. Second degree means nystagmus was observed when the patient looked in the direction of the fast phase, and in primary gaze. Third degree tells us that nystagmus was present when the patient looked in the direction of the fast phase, primary gaze, and in the direction of the slow phase.
The direction of the nystagmus is reported as the direction of the fast phase.
When nystagmus follows Alexander's law, it increases in amplitude and speed when the patient looks in the direction of the fast phase, and the nystagmus decreases or disappears when the patient looks in the direction of the slow phase. This is an intuitive finding for peripheral gaze-evoked nystagmus because when the patient looks in the opposite direction of the fast phase, the patient is fighting against the signal that the body is rotating. Alexander's law does not apply to central gaze-evoked nystagmus because there is no false signal from the peripheral vestibular system to overcome. Central nystagmus exists because there is a lesion in the higher-level anatomy.
Let's put everything together using an example. Say your gaze stability test revealed spontaneous nystagmus, with the fast phase toward the right, with and without fixation. When the patient looked to the right, the nystagmus increased in amplitude and frequency. When the patient looked to the left, the nystagmus disappeared. A standardized way to report these results would be: "Second-degree, right-beating gaze-evoked nystagmus with fixation and following Alexander's law, was noted."
REFERENCESBaloh, R. W., & Honrubia, V. (2001). Clinical Neurophysiology of the Vestibular System (Third ed. Vol. 18): Oxford University Press, Inc.