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Nystagmus:@0:10
→ Involuntary oscillatory to and fro movement of the eyes.
→ Pendular → Phase of equal velocity
→ Jerk → Phase of unequal velocity
→ Direction → Direction of fast component, pathological movement is the slow one.
→ Trajectory → Horizontal, vertical, Rotatory
→ Conjugate → Both eyes same movement
→ Null zone → Gaze in which intensity is minimal.
Nystagmus Classification:@2:06
1. Physiological
• Optokinetic
• Vestibular
• End - Point
2. Infantile
• Congenital
• Manifest - Latent
3. Acquired
• Gaze evoked
• Vestibular
• Inter nuclear ophthamoplegia
• See- Saw
• Down - beat
Physiological :@3:04
• → Optokinetic → Looking at moving object
• → Vestibular → When cold/ warm saline stimulates endolymph
• → End point → Goes to extreme point and comes back
• → Specific localizing Nystagmus.
Congenital :@3:38
• → Present at birth or appear later shortly
• → Usually horizontal, pendular or Jerk
• → Abolished in sleep
• → Uniplanar → Plane remains unchanged in all gazes.
Latent :@4:05
• → Seen only when one eye is covered
• → Vision decreases due to nystagmus
• →When each eye tested separately improved when both uncovered.
Down Beat Nystagmus:@4:42
• → Fast phase down, while eye in primary position of rest.
• Pathology:
• → Arnold chiari malformation (most important)
• → Platybasia
Upbeat Nystagmus:@5:17
• → Fast phase up, eyes in primary position of rest
• Pathology:
• → Cerebellar degeneration (most important)***
• → Multiple Sclerosis
• → Brainstorm stroke
Vestibular Nystagmus:@5:29
• → Due to vestibular end organ dysfunction.
• → Mixed directional, usually horizontal - torsional.
• → Suppressed by visual fixation.
• →Associated with Vertigo, Tinnitus, deafness.
• → Eitology: Labyrinth, Neuritis, Meniere's disease
• → COWS: Cold opposite, warm saline
• →Cold water when passed into ear stimulates the endolymph & produce nystagmus in same direction.
Optokinetic Nystagmus(OKN):
• → Image stabilization when viewing a constantly moving visual field.
• → Asymmetric OKN is abnormal OKN, when target is moving in one direction compared to opposite.
• COGAN’S DICTUM :
• →It states that Homonymous hemianopia + Asymmetric OKN (Partial lobe lesion, probably mass lesion)
• →Homogenous Hemianopia + Symmetric OKN - Occipital lobe lesion, Vascular lesion.