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Nystagmus A Clinical Approach

Nystagmus A Clinical Approach . Abdullah El-Menaisy, MD, FRCS Neuro-ophthalmology & Investigation Service, Dhahran Eye Specialist Hospital, Dhahran, Saudi Arabi a. Nystagmus is a rhythmic biphasic oscillation of the eyes. There are three main control mechanisms for maintaining steady gaze:

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Nystagmus A Clinical Approach

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  1. NystagmusA Clinical Approach Abdullah El-Menaisy, MD, FRCS Neuro-ophthalmology & Investigation Service, Dhahran Eye Specialist Hospital, Dhahran, Saudi Arabia

  2. Nystagmus is a rhythmic biphasic oscillation of the eyes

  3. There are three main control mechanisms for maintaining steady gaze: • Fixation • Vestibulo-ocular reflex • Gaze-holding system (neural integrator)

  4. Mechanisms of Gaze Stability The visual fixation mechanism: • Detection of retinal image drift • Programming of corrective eye movements • Suppression of unwanted saccades The vestibulo-ocular reflex:   • Compensates for head movements Gaze-holding mechanism:   • Sustains eye at an eccentric position in the orbit against the elastic pull of the globe's suspensory ligaments and muscles

  5. Failure of any of these control systems will cause disruption of steady fixation • There are 2 types of abnormal fixation: • Nystagmus • Saccadic intrusions & oscillations • The difference between them lies in the initial movement that disrupts fixation • In nystagmus, it is a slow drift, while in saccadic intrusions and oscillations, it is a fast movement that moves the eyes off target

  6. Classification of Nystagmus • Age of onset: congenital, acquired • Nature of movement: pendular, jerk • Plane of movements: horizontal, vertical, torsional • Effect of fixation block: latent, manifest, latent-manifest

  7. Pendular, Jerk

  8. Horizontal, Vertical, Torsional

  9. Latent, Manifest

  10. Types • Congenital Nystagmus • Spasmus nutans • Monocular • Vestibular • Gaze-evoked • Dissociated • Periodic alternating • Downbeat • Upbeat • Convergence retraction • See-saw • Drug-induced • Optokinetic Nystagmus (OKN)

  11. Congenital Nystagmus • At birth or during 4 m after birth • No oscillopsia • Pendular, horizontal (may be rotary or rarely vertical) • May have jerk properties in end gaze • Remains horizontal in vertical gaze • Has null point • Dampens with convergence • Exacerbates with fixation • Shows reverse optokinetic response • Associated with high refractive error including astigmatism

  12. Congenital Nystagmus Etiology: • Sensory: due to disorders of afferent visual pathway - optic nerve hypoplasia - ocular albinism - Leber’s congenital amaurosis • Motor: due to efferent pathway disorder - sporadic, autosomal dominant, recessive, X-linked

  13. Congenital Nystagmus Evaluation: • Vision • Pupils • Fundus • Refraction • VEP,ERG Treatment: • Glasses, contact lenses • Prism to shift null point to primary gaze • Surgery (kestenbaum) • Botox injection

  14. Spasmus Nutans • Triad of: (1) nystagmus (2) torticollis (3) head nodding • Starts between 4 - 14 m • Almost always resolved by 5y • Pendular of low amplitude & high frequency • May be horizontal, vertical or rotary • May be associated by optic pathway glioma • Neuroimaging is important

  15. Monocular Nystagmus • Slow vertical pendular oscillations • Due to severe monocular visual loss (Heimann-Bielschowsky phenomenon) • Can appear several years after visual loss • May resolve if vision is restored • May be associated with chiasmal glioma • Needs neuroimaging

  16. Vestibular Nystagmus Peripheral vestibular nystagmus: • Horizontal rotary • Horizontal in different directions of gaze • Amplitude increases when eyes move in the direction of fast phase (Alexander’s law) • The fast phase is opposite to site of the lesion • Patients fall towards the site of the lesion • Associated with vertigo, hearing loss or vomiting • Causes includes: labyrinthitis, vestibular neuritis, Meniere’s disease, migraine, benign positional vertigo (BPV)

  17. Vestibular Nystagmus Central vestibular nystagmus: • Pure torsional nystagmus • Asymmetric • Vertical in primary position • Change direction in different gaze positions • Causes include: pontine & cerebellar lesions (stroke, tumor, MS,…..)

  18. Gaze-evoked Nystagmus • Asymmetric in right & left gaze • High amplitude (< 4 degrees) • Unilateral gaze-evoked nystagmus may indicate cerebellar or brain stem lesion • Gaze-evoked upbeat nystagmus commonly due to bilateral INO • When presents in horizontal & upgaze, it signifies toxic metabolic process • Brun’s nystagmus may be seen in cerebellopontine angle lesions

  19. Gaze-evoked Nystagmus • Causes: lesions in - medial vestibular nucleus - nucleus prepositus hypoglossi - cerebellum - peripheral vestibular pathway • Physiological gaze-evoked nystagmus: - symmetric in different directions of gaze - has low amplitude

  20. Dissociated Nystagmus • Nystagmus of abducted eye with impaired adduction of contralateral eye • Occurs in INO • due to adaptive phenomenon that attempt to increase the innervation to the week adducting eye

  21. Periodic Alternating Nystagmus (PAN) • Acquired or congenital • Change direction every 90 sec with a rest period of 5 -10 sec • May be due to degenerative process of cerebellum • May associate downbeat nystagmus or skew deviation • Persists during sleep & remains horizontal in vertical gaze • Baclofen ameliorates the acquired form while the congenital form can be corrected by large horizontal recti resection

  22. Downbeat Nystagmus • Craniocervical junction lesion • Other causes are hypomagnesemia, thiamine & vit B12 deficiency, phenytoin, alcohol & lithium toxicity • Congenital cases show spontaneous remission • Treatment by clonazepam, gabapentin, baclofen. Prism therapy can help

  23. Upbeat Nystagmus • Due to midbrain, cerebellum or medullary lesions • 2 types: (1) a course large amplitude nystagmus increases in upgaze (cerebellar vermis lesion) & (2) a small amplitude nystagmus in primary position (medullary lesion) • Causes are MS, infarction, cerebellar degeneration & tumors • Tobacco smoking can produce upbeat nystagmus in normal subjects when fixation is removed

  24. Convergence Retraction Nystagmus • It is not a true nystagmus (no slow phase) • Convergent saccades in attempting upgaze • In pretectal dysfunction • Due to cofiring of horizontally & vertically acting EOM

  25. See-Saw Nystagmus • Pendular • Spontaneous elevation & intorsion of one eye with depression & extorsion of the other eye and the cycle is reversed • Usually due to sellar mass lesion • Some patients display ½ see-saw cycle with corrective quick phase (hemi or jerk see-saw nystagmus). It is typically due to midbrain lesion • Baclofen or clonazepam may help in treatment

  26. Drug-induced Nystagmus • Common • In horizontal endgaze & upgaze and not in downgaze • Symmetric & doesn’t fatigue • Medications include: anticonvulsants, sedatives, barbiturates & phenothiazines • Carpamazepine, phenytoin & lithium may produce downbeat nystagmus • Acute alcohol intoxication can cause horizontal endgaze nystagmus (positional alcohol nystagmus)

  27. Optokinetic Nystagmus (OKN) • A physiological involuntary reflex • Elicited by moving a striped tape or drum in front of the patient • A slow phase in the direction of movement of tape or drum & a corrective fast phase in the opposite direction

  28. Optokinetic Nystagmus (OKN) • OKN is a diagnostic tool in: 1 - a reverse OKN is characteristic of congenital nystagmus 2 - preserved vertical OKN indicates intact vision in congenital nystamus 3 - asymmetric OKN indicates deep parietal lesion 4 - In malingerers, intact OKN means that vision is at least CF 5 - moving the tape downwards to elicit convergence retraction nystagmus in patients with Parinaud’s syndrome

  29. Nystagmoid Eye Movements • Not pure forms of nystagmus (no slow phase) • Saccades interrupt fixation • Represent disorder of saccades • Includes: - Square wave jerks - Ocular dysmetria - Opsoclonus - Ocular flutter - Ocular bobbing - Superior oblique myokymia

  30. Square Wave Jerks • Horizontal saccades with intersaccadic interval • Can be seen in normal individuals (> 9 jerks per min) • Causes include: cerebellar disease, Schizophrenia, Parkinson’s disease

  31. Opsoclonus • Involuntary conjugate multidirectional saccades (saccadomania) occur without intersaccadic interval • Associated with eye blinking, facial twitching, myoclonus & ataxia • 50% of children with opsoclonus has neuroblastoma • Responds to tumor removal, ACTH, prednisone, gamma globulin, plasmapheresis • Other causes include: parainfectious cerebellitis or encephalitis, paraneoplastic disease, drug induced (amitriptyline, lithium, cocaine)

  32. Ocular Flutter • Horizontal saccades without intersaccadic interval (no vertical component) • Can be associated with ocular dysmetria • Has the same localizing value & differential diagnosis of opsoclonus

  33. Ocular Bobbing • Quick conjugate down movements followed by slow drift back to midline • Some patients show movements in the opposite direction • Reflects pontine dysfunction • May be associated with horizontal gaze palsy • Causes includes: stroke, tumors, toxic-metabolic conditions or inflammatory process

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