Gaze Evoked Nystagmus
Nystagmus that occurs
only when the eye at an eccentric position in
the orbit is called
gaze-evoked nystagmus. It is the most
common form of nystagmus encountered in clinical
practice.
Although the terms gaze-evoked nystagmus, end-point nystagmus, and
gaze-paretic nystagmus are often used
synonymously, gaze-evoked nystagmus is a general
term that includes both physiologic and
pathologic nystagmus. When the nystagmus is
physiologic, the term end-point nystagmus is
appropriate . When the nystagmus is associated
with a paresis of gaze, the term gaze-paretic nystagmus is appropriate.
Gaze-evoked nystagmus may be caused by a variety
of medications, including alcohol,
anticonvulsants, and sedatives. It may also be
caused by structural lesions of
the vestibulocerebellum
network, the medulla, the midbrain
and the cerebellum.
Differences between Physiologic End-Point
Nystagmus
and Pathologic Gaze-Evoked Nystagmus
End-point nystagmus typically occurs on looking far laterally and is
poorly sustained. The nystagmus is primarily
horizontal
or rarely have a torsional component.
It is usually symmetric, but it may be
asymmetric . In such individuals, this
physiologic form of gaze-evoked nystagmus
can usually be differentiated from that
caused by disease, since the former has
lower intensity (i.e., slower drift) and,
most importantly, is not accompanied by
other ocular motor abnormalities.
Pathologic gaze-evoked nystagmus, in
contrast, is accompanied by other defects of
eye movements, such as impaired smooth
pursuit
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