Gaze-Evoked Nystagmus and its Diferential Diagnosis

Gaze-evoked nystagmus (GEN) is a jerk nystagmus, not present in primary position, elicited by attempted maintenance of eccentric eye position, GEN may have a linear or a decreasing-velocity exponential slow phase; the latter has sometimes been referred to as gaze-paretic nystagmus but, unless it is due to a muscle or nerve paresis, the GEN terminology is preferred. Distinction should be made between nystagmus that is truly gaze evoked and that which is gaze modulated, Many types of nystagmus vary with gaze angle but are present in primary position and are not, therefore, GEN.