Signs of CN

1. CN is not suppressed by fixation.

2. The pattern of beating is irregular: During the slow phases, the velocity of movement changes. Most cases show acceleration of the movement during the slow phases. Purely pendular movements are rare.

3. CN beats mostly in a purely horizontal motion that is retained in both upgaze and downgaze, but vertical, rotary, and mixed beating patterns are occasionally found.

4. In most cases, the intensity of the nystagmus and the shape of the slow phases change with gaze direction. The position of gaze where movement is minimal is variously called the neutral point, the quiet point, or the null point. The patient prefers this gaze direction. If the null point is in the midline, the head will be held straight. If it is eccentric, a compensatory head posture will be present.

5. In most cases, CN diminishes with accommodative convergence.

6. OKN stimuli frequently evoke saccades in the direction of stimulus movement, instead of slow nystagmus phases.

7. Under everyday viewing conditions, patients with CN do not experience oscillopsia. However, during fixation of a point of light in an otherwise darkened room, oscillopsia can appear.

8. Nutation (involuntary head nodding or shaking) is frequently seen in patients with CN, particularly when they are under psychic stress.

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