Table 4 Differentiating end-point from gaze-evoked nystagmus
End-point nystagmus | Gaze-evoked nystagmus (GEN) |
|---|---|
Unstained (dampens after a few beats) | Sustained. Continues after 20 s of eccentric fixation attempt |
Delayed after the eccentric eye movement | Immediate on eccentric fixation |
Usually only seen in extreme eccentric gaze | Often seen in only mildly eccentric gaze |
Often low amplitude | Often high amplitude |
Symmetrical | Often asymmetrical |
No rebound nystagmus seen (nystagmus beating in the opposite direction once the eye has returned to its central position after 60 s eccentric gaze) | Rebound often seen |
No other supranuclear eye movement abnormalities found. | Very rarely seen without co-existing smooth pursuit abnormalities |
Typically horizontal nystagmus on side gazes only | May be horizontal and/or vertical |
