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KMID : 1036520160060020027
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Clinical Neuro-Ophthalmology
2016 Volume.6 No. 2 p.27 ~ p.30
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Gaze Evoked and Periodic Alternating Nystagmus
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Park Jae-Han
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Abstract
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Gaze-evoked nystagmus (GEN) is a drift of the eye which is only present for certain directions of gaze away from straight ahead. It is the most common form of nystagmus encountered in clinical practice. End point nystagmus is a variant of GEN. It is basically GEN in persons who are otherwise normal. It is more frequently seen with prolonged gaze holding and also with large eccentricities. It is often somewhat torsional. The judgement as to whether nystagmus is called GEN or end point, is presently one made by the experience of the examiner. We think it best to avoid the term end point nystagmus entirely. Other nystagmus related to GEN are centripetal and rebound nystagmus. If patients with GEN are encouraged to sustain their attempt to look eccentrically, their nystagmus may reverse direction (“centripetal nystagmus”) and the eyes are then returned to the central position, a short live reverse directed nystagmus, which is called rebound nystagmus. Periodic alternating nystagmus (PAN) refers to horizontal or horizontal rotary nystagmus that reverses its direction with a periodicity of 1 to 6 minutes and is characterized by a quiescent interval of 4 to 20 seconds between reversals. However, periodicity and quiescence are not regular in all cases and can be as short as a few seconds. PAN is most commonly found either in its congenital form or after cerebellar or pontomedullary lesions. Rarely, PAN has been described in peripheral disorders.
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KEYWORD
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Gaze evoked nystagmus, End point nystagmus, Periodic alternating nystagmus
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