Nystagmus

Nystagmus

1. Nystagmus Presenter:Dr.Vikram S Nakhate Moderator: Dr.Atul Seth

2. Defination Nystagmus is a regular,repetitive to and fro movement of the eyes ( horizontal,vertical or torsional ) with 2 phases 1. slow drift from the target of interest f/b 2. corrective saccade back to the target

3. Terminologies Amplitude Frequency Intensity Null zone Pursuit / Saccade Conjugate / Dissociated Jerk / Pendular

4. Amplitude Amplitude is the excursion of the nystagmus and described as Fine : less than 5 Moderate: 5 -15 Large greater than 15

5. Frequency Frequency is the number of to and fro movements in one second Described an cycles/sec or Hertz (Hz) Slow : (1-2 Hz) Medium : (3-4 Hz) Fast: (5 Hz or more)

6. Intensity Intensity = amplitude * frequency Null zone: position where nystagmus is minimised Patient assumes a head posture, such that the eyes are in null zone

7. Pursuit /Saccade Pursuit eye movements allow the  eyes to closely follow a moving object. Pursuit differs from the  vestibulo -ocular reflex, which only occurs during movements of the head and serves to stabilize gaze on a stationary object Saccades are quick, simultaneous movements of both eyes in the same direction

8. Conjugate/Dissociated Conjugate : nystagmus which is symmetric in direction,amplitude and rate Dissociated: when it differs in any one of the parameters between two eyes

9. Jerk / Pendular Jerk nystagmus Pendular nystagmus Alternation of slow phase drift f/b rapid corrective saccade in opp direction Sinusoidal oscillation with slow phase in both directions and no corrective saccade Direction of jerk nystagmus = direction of the fast phase Pendular nystagmus may be horizontal or vertical Right or left beating nystagmus Upbeat or downbeat nystagmus Not characterised by right,left,up,down beating as there is no fast phase

10. Alexanders law It states that the amplitude of jerk nystagmus is largest in the gaze of direction of fast component 1 degree: nystagmus only in the direction of the fast component 2 degree: nystagmus in primary gaze position 3 degree: nystagmus in addition to above gazes,also present in the direction of the slow component

11. Mechanism of nystagmus Foveal centration of an object of regard is necessary to obtain the highest level of visual acuity Three mechanisms are involved in maintaining foveal centration of an object of interest : Fixation The vestibulo -ocular reflex T he neural integrator.

12. Fixation Fixation in the primary position involves the visual system's ability to detect drift of a foveating image and signal an appropriate corrective eye movement to refoveate the image of regard. The vestibular system is intimately and complexly involved with the oculomotor system

13. Vestibulo -ocular reflex The vestibulo -ocular reflex is a complex system of neural interconnections that maintains foveation of an object during changes in head position. The proprioceptors of the vestibular system are the semicircular canals of the inner ear . The semicircular canals respond to changes in angular acceleration due to head rotation

14. Neural integrator When the eye is turned in an extreme position in the orbit, the fascia and ligaments that suspend the eye exert an elastic force to return toward the primary position To overcome this force, a tonic contraction of the extraocular muscles is required . A gaze-holding network called the neural integrator generates the signal. The cerebellum, ascending vestibular pathways, and oculomotor nuclei are important components of the neural integrator.

15. Classification Congenital Acquired

16. Infantile nystagmus Usually not noted at birth but becomes apparent during first few months of life

17. Characteristics Horizontal nystagmus ( mixed pendular and jerk) b/l conjugate movements of the eyes Nystagmus not present during sleep Associated latent nystagmus Head turn to achieve null point Decreases with convergence Increases with fixation

18. Reverse response to OKN stimulus ( fast phase in direction of moving OKN drum) May be seen in isolation or associated with strabismus,afferent visual defects

19. Treatment Base out prisms to induce convergence ( dampens the nystagmus and may improve visual acuity) Use of prisms to shift the viewing position to null position Contact lenses may dampen nystagmus Gabapentine may dampen nystagmus

20. Surgical Includes moving the extraocular muscles to place the null zone in primary position( kestenbaum procedure) Recessing all 4 rectus muscles to decrease tension (large recession procedure)

21. Spasmus nutans Triad of symptoms: N ystagmus Head nodding Torticollis (head tilt or head turn)

22. Onset usually in the first year of life (3-15 months) Disappears by 3-4 yrs of age The nystagmus typically consists of small-amplitude, high frequency oscillations and usually is bilateral, but it can be monocular, asymmetric, and variable in different positions of gaze Usually benign Neuroimaging recommended ( gliomas may mimic spasmus nutans )

23. Infantile monocular pendular nystagmus Usually due to visual loss( often optic neuropathy or chiasmal glioma ) In cases of b/l visual loss,there is b/l nystagmus ,with nystagmus greater in eye with poorest vision

24. Acquired Physiological: End point nystagmus Vestibular (caloric or rotational) nystagmus Optokinetic nystagmus

25. End point nystagmus Jerk nystagmus On looking extreme lateral or upwards Angle of gaze > 45

26. Vestibular nystagmus Jerk nystagmus Altered inputs from vestibular nuclei to PPRF Demonstrated by caloric test : normal response Cold water : opposite side Warm water : same side Cold water in both ears: upwards Warm water in both ears : downwards

27. Optokinetic nystagmus Jerk nystagmus Induced by moving a full visual field stimulus Slow phase (pursuit) : eye follows the target Fast phase ( saccade): eye fixates on next target Uses: Detecting malingering Testing visual potential in children

28. Pathological causes Nystagmus associated with poor vision (sensory) Anterior segment: cataract,aniridia Retinal diseases: RB,ROP,Intrauterine infections

29. Nystagmus associated with neurological diseases (motor) 1.End gaze paretic nystagmus ( horizontal gaze center) 2.Convergence retraction nystagmus ( vertical gaze,parinaud’s )

30. 3.Vestibular nystagmus : Central ( brainstem nuclei) Peripheral ( labyrinths, VIII CN) 4.Downbeat nystagmus ( cervicomedullary junction) 5.Upbeat nystagmus ( cerebellum,medulla )

31. 6. S eesaw nystagmus ( parasellar lesions) 7. periodic alternating nystagmus

32. Gaze paretic nystagmus Most common type Absent in primary position and is not visually disabling Beats in the direction of gaze Causes: anticonvulsants brainstem lesions cerebellar lesions

33. Convergence-retraction nystagmus Not truly a nystagmus b/l adducting saccades causing convergence of both eyes Elicited by having the patient to look up,at which time the eyes converge & retract Causes: midbrain lesions

34. Vestibular nystagmus Feature Peripheral Central Disease of vestibular origin Disease of the brainstem Direction Intensity increases when the eyes are turned in direction of fast phase Direction of nystagmus may change with gaze Visual fixation Inhibits nystagmus No inhibition Severity of vertigo Severe Mild Induced by head movements Often Rare Associated eye movement deficits None Pursuit or saccadic defects Other findings Hearing loss CNS involvement

35. Upbeat nystagmus Type of jerk nystagmus with fast phase upward in primary position Often worsens in upgaze Causes: lesions of medulla, cerebellar vermis,midbrain Rx: base up prisms in reading glasses can be used to force the eyes downward

36. Downbeat nystagmus Type of jerk nystagmus with fast phase downward in primary position Often worsens in downgaze Oscillopsia is usually prominent Causes: lesions at cervicomedullary junction Rx: base down prisms in reading glasses can be used to force the eyes upward

37. Seesaw nystagmus Defined as pendular nystagmus with elevation and intorsion of one eye simultaneous with depression and extorsion of other eye Followed by reversal of cycle,so that the eyes move like a seesaw

38. Causes: parasellar lesions,pituitary tumors Produces very disabling oscillopsia that responds poorly to any Rx

39. Periodic alternating nystagmus (PAN) PAN is a conjugate , horizontal jerk nystagmus with the fast phase beating in one direction for a period of approximately 1-2 minutes. The nystagmus has an intervening neutral phase lasting 10-20 seconds The nystagmus begins to beat in the opposite direction for 1-2 minutes then, the process repeats itself

40. Periodic alternating head turn to minimise nystagmus & oscillopsia Causes: lesions of the cerebellum

41. Acquired Congenital Form Pure sinusoidal Variable waveform Direction Omnidirectional ( vertical,torsional ) Horizontal,uniplanar Rarely vertical or torsional OKN reversal Never Frequent Oscillopsia Frequent Mild (if present)

42. Nystagmus associated with strabismus Latent /manifest-latent nystagmus Manifest nystagmus Nystagmus blockage syndrome

43. Manifest nystagmus Manifest-latent nystagmus Pendular nystagmus Jerk nystagmus No change on abduction Increased on abduction No change on covering one eye Increase on covering one eye Null zone is present Fast phase always towards fixing eye Less commonly associated with infantile esotropia Always associated with esotropia Binocular visual acuity same as uniocular Binocular visual acuity better than uniocular

44. Nystagmus blockage syndrome Inverse relationship with esotropia Esotropia is a mechanism of blocking the nystagmus The fixing eye is preferred to be in adduction ,face turn is in the direction of fixing eye

45. Nystagmoid conditions Movements which are not regular and rhythmic: Oculopalatal myoclonus Opsoclonus Ocular bobbing

46. Oculopalatal myoclonus Type of vertical pendular nystagmus Coexisting with tremor of the facial muscles,larynx,palate Present during sleep Cause : usually develops months after an infarction or h’hage involving mollaret triangle Rx: Gabapentine

47. Ocular bobbing Characterised by conjugate eye movements, beginning with a fast downward movement f/b slow drift back to midline Causes: 1. comatose patients with massive pontine lesion 2.metabolic encephalopathy

48. Superior oblique myokymia Defined as oscillation of one eye due to intermittent firing of the superior oblique muscle Produces oscillopsia or intermittent diplopia elicited by having the patient look in the direction of the superior oblique muscle Characterised by monocular,rapid,intorsional movements

49. Usually benign No underlying etiology is found Neuroimaging : r/o post fossa tumors Refractory cases: surgical weakning of the superior oblique muscle can be performed

50. Treatment Nonsurgical : non neurological causes 1.Optical devices Glasses: overminus lenses stimulate accomodative convergence and thus dampens nystagmus Contact lenses: helpful in high refractive errors by giving good visual stimulus for fusional control

51. Prisms : can be used for 2 purposes 1. to induce fusional convergence by using 7 PD base out prism in front of each eye 2. pre op evaluation in a patient with face turn prisms are inserted with the apex in direction of gaze Useful as a diagnostic trial ,but as a therapeutic alternative are not helpful

52. Occlusion therapy: Trials with conventional occlusion have been found to be effective As amblyopia gets corrected and vision improves,nystagmus finally decreases

53. Pharmacologic Mx These drugs hypothetically inhibit excitatory neurotransmitters within CNS Baclofen : congenital nystagmus , seesaw nystagmus,periodic alternating nystagmus Carbamazepine : widely used for superior oblique myokymia

54. Pharmacologic denervation Botulinum toxin A act by blocking the neuromuscular transmission used in 2 distinct ways to dampen nystagmus 3 units of toxin is injected in each of the 4 horizontal rectus muscles Single large dose of drug into the retrobulbar space Effect last for only few months

55. Surgical Based on 3 principles: To shift the null position if any to the primary position To induce extra convergence innervation by weakening medial recti,to dampen nystagmus To reduce the amplitude of the nystagmus by weakening the muscle force of all recti

56. Kestenbaum surgery Devised first surgical approach using recession-resection of all four horizontal recti Advocated an equal amount of 5 mm for all recti Left face turn (null in dextroversion ): Right eye: LR recession & MR resection Left eye : MR recession & LR resection

57. Anderson surgery Advocated only recessions Left face turn (null in dextroversion ): Right eye : LR recession Left eye : MR recession

58. Parks surgery Recommended lesser amount of recessions and for medial rectus surgery compared to lateral rectus surgery. Advocated a 5,6,7,8 plan MR recession : 5 mm MR resection : 6 mm LR recession : 7 mm LR resection : 8 mm

59. Carlow TJ : medical treatment of nystagmus and ocular motor disorders.Int Ophthalmol Clin 1986;28:355 Rosenberg ML,Glaser JS:Superior oblique myokymia.Ann Neurol 1983;13:667 Helveston EM, Pogrebniak AE : Treatment of acquired nystagmus with botulinum toxin A. Am J Ophthalmol 1988;106:584