Friday, 14 October 2011

Cerebellar eye signs

Level 1 to 3

The following is a list of cerebellar eye signs; I suggest you remember them using a systematic approach to the examination of the eye movements:

Position of eyes in the neutral position with vision fixated in the distance:

1. Square-wave jerks: the eyes drift of their target in randomly and a quick saccade pulls the eyes back to the neutral position. When the jerks are only seen when looking at the optic disc with an ophthalmoscope they are referred to as micro-square wave jerks.

2. Distance esotropia; this is the term used to describe double vision that is present on looking into the distance but disappears with convergence and near vision.

3. Skew deviation; ocular deviation where the eyes move upwards (hypertropia), but in opposite directions.
Skew Deviation

Horizontal eye movements:

3. Gaze-evoked jerk nystagmus; this typically changes direction across the mid line. Please note that nystagmus due to peripheral vestibular lesions is usually worse to side of the lesion and does not change phase across the midline. The slow phase of nystagmus the abnormal phase with the fast phase the corrective phase.

4. Jerky pursuit eye movements; this is also referred to as saccadic intrusion. Pursuit eye movements are made up of many small saccades.

5. Slow saccades; there is a delay in starting the saccades and they are slow. Please note that a delay in initiating saccadic eye movements can also occur due to lesions of the frontal lobes that affect the frontal eye fields (voluntary saccades). In cerebellar disease both voluntary and involuntary saccades (in response to head movements) are slow.

6. Saccadic dysmetria; hypometric saccades refers to undershoot or not reaching the target and hypermetric saccades to overshoot or going past the target. This is the visual equivalent of what happens in the limbs.

7. Inability to suppress the vestibular-ocular rreflex (VOR); please see previous post on the VOR.

Additional web materialRobert B. Daroff Collection

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