REBOUND NYSTAGMUS

Timothy C. Hain, MD

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Rebound nystagmus is a primary position nystagmus which is provoked by prolonged eccentric gaze holding. It appears after the eyes are returned to primary position.

There are two methods of eliciting rebound. The traditional method is to have the patient follow ones finger to one side, hold gaze there for 10 seconds (with constant encouragement by the examiner to keep looking), and then rapid return to central gaze. At that point, the examiner looks for a nystagmus that beats away from the previous direction of gaze holding, lasting for at least 5 beats.

A more modern and sensitive method of eliciting rebound is to use video-freznel goggles. (as shown above). Otherwise the technique is similar. The video-frenzels make it much easier to see small amounts of nystagmus.

An abnormal amount of rebound in the light, as shown below, consists of at least 3 beats of clear nystagmus, with the slow-phases directed towards the previous position of gaze. It must reverse direction according to the direction of previous gaze. When using the video-frenzel goggles, at least 5 beats should be observed.

	Rebound Nystagmus -- a right-beating nystagmus occurs after 10 seconds of gaze holding to the left.
	A left-beating nystagmus appears after 10 seconds of gaze holding to the right.

Supplemental material on the site DVD: Video of rebound nystagmus

 

Rebound after gaze holding for periods more prolonged than 30 sec, or for eccentricities larger than about 45 deg is of uncertain significance as normal subjects may exhibit rebound under such circumstances (Gordon et al, 1986). Vertical rebound is rare but it can also occur.

Rebound is nearly always pathological, and is related to brainstem or cerebellar disease. Accordingly, if an unusually large gaze-evoked nystagmus is observed, one should automatically look for rebound nystagmus. On the other hand, gaze-evoked nystagmus without rebound is usually of little significance. Rebound is always associated with poor pursuit, but the poor pursuit does not inevitably mean that the person will have rebound.

Rebound using the video goggles is a sensitive and specific sign of cerebellar disturbance. Clinical situations in which rebound is commonly encountered include MS involving the pons, typically a lesion of the middle cerebellar peduncle, and ischemic pontine hypertensive lesions. Rebound nystagmus is also a feature of EA2 (Episodic ataxia, type 2). Rebound also can occur in congenital nystagmus, but it is not at all a universal feature of CN.

 

References:

Gordon SE, Hain TC, Zee, DS and Fetter M. (1986) Rebound nystagmus. Soc. Neurosci. Abstr., 12:1091.