1. Nystagmus A 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

13. 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

14. 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

15. Spasmus Nutans
Triad of: (1) nystagmus (2) torticollis (3) head nodding
Starts between 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

17. 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

19. 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)

20. 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,…..)

23. 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

24. 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

26. 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

28. Periodic Alternating Nystagmus (PAN)
Acquired or congenital
Change direction every 90 sec with a rest period of 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

30. 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

32. 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

34. 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

36. 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

38. 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)

40. 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

42. 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

43. 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

44. 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

46. 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)

48. 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

49. 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

51. Superior Oblique Myokymia
High frequency monocular oscillations produced by spontaneous firing of one SO muscle
Idiopathic, but could be due to midbrain lesion
Treatment by carbamazepine, bacolfen, propranolol
Muscle surgery (SO tenotomy +/- IO resection or
Harado-Ito procedure)

53. Nystagmus with Localizing Value
Downbeat: cervicomedullary junction
Upbeat: pons, midbrain
See-saw: parrasellar, midbrain
Convergence retraction: dorsal midbrain
Spasmus nutans: chiasmal glioma

54. Evaluation History Visual acuity Inspection Cover test Ocular motility
Saccade & pursuit
VOR
Pupils
Fundus
Electronystagmography

55. Evaluation History: Onset : Associated symptoms: Medications
- Birth to 4 m: congenital
- < 4 m: acquired
Associated symptoms:
- Oscillopsia: acquired nystagmus
- Nausea & vomiting: peripheral vestibular disease
- Diplopia, dysarthria, facial numbness, dysphagia: brain stem lesions
Medications
Similar condition in the family

56. Evaluation Inspection: Type of nystagmus:
Pendular: slow phases are of equal velocity (no corrective saccades)
Jerk: slow & fast phases (the direction is defined by the fast phase). In torsional nystagmus (direction is defined towards patient’s right or left shoulder)

57. Type

58. Plane

59. Fixation Block

60. Amplitude & Frequency

61. Evaluation History Visual acuity Inspection Cover test Ocular motility
Saccade & pursuit
VOR
Pupils
Fundus
Electronystagmography

62. Videonystagmography Vestibular nystagmus: slow phase is linear
Congenital nystagmus: slow phase
shows increasing velocity
Gaze paretic nystagmus: slow phase is declining

63. Thank you

64. Latent Nystagmus Congenital Induced by covering one eye Jerk
Fast phase in the direction of the uncovered eye
May be associated by congenital esotropia or DVD

65. Rebound Nystagmus Jerk
When eyes turned from eccentric gaze to primary position, the eyes beat in the opposite direction for about 30 sec
Occurs inn cerebellar disease

66. Pendular Nystagmus Eyes move back & forth with equal velocity
Slow phases without jerk or fast component
Horizontal, vertical, oblique, elliptical or circular
May be dissociated when one eye has impaired vision
Acquired pendular nystagmus in adults is most probably due to MS or brain stem infarction

67. Ocular Dysmetria
During fixation the eyes overshoot (hypermetria) or undershoot (hypometria) then saccade back to fixation point
A sign of cerebellar dysfunction (similar to limb dysmetria)