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Nystagmus

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Nystagmus

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Nystagmus

  1. 1. Nystagmus Presenter:Dr.Vikram S Nakhate Moderator: Dr.Atul Seth
  2. 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. 3. Terminologies • Amplitude • Frequency • Intensity • Null zone • Pursuit / Saccade • Conjugate / Dissociated • Jerk / Pendular
  4. 4. Amplitude  Amplitude is the excursion of the nystagmus and described as  Fine : less than 50  Moderate: 50-150  Large greater than 150
  5. 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. 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. 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. 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. 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. 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. 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  The neural integrator.
  12. 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. 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. 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. 15. Classification  Congenital  Acquired
  16. 16. Infantile nystagmus  Usually not noted at birth but becomes apparent during first few months of life
  17. 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. 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. 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. 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. 21. Spasmus nutans  Triad of symptoms:  Nystagmus  Head nodding  Torticollis (head tilt or head turn)
  22. 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. 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. 24. Acquired  Physiological:  End point nystagmus  Vestibular (caloric or rotational) nystagmus  Optokinetic nystagmus
  25. 25. End point nystagmus  Jerk nystagmus  On looking extreme lateral or upwards  Angle of gaze > 450
  26. 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. 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. 28. Pathological causes  Nystagmus associated with poor vision (sensory)  Anterior segment: cataract,aniridia  Retinal diseases: RB,ROP,Intrauterine infections
  29. 29.  Nystagmus associated with neurological diseases (motor)  1.End gaze paretic nystagmus ( horizontal gaze center)  2.Convergence retraction nystagmus( vertical gaze,parinaud’s)
  30. 30.  3.Vestibular nystagmus:  Central ( brainstem nuclei)  Peripheral ( labyrinths, VIII CN)  4.Downbeat nystagmus( cervicomedullary junction)  5.Upbeat nystagmus( cerebellum,medulla)
  31. 31.  6. Seesaw nystagmus (parasellar lesions)  7. periodic alternating nystagmus
  32. 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. 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. 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. 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. 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. 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. 38.  Causes: parasellar lesions,pituitary tumors  Produces very disabling oscillopsia that responds poorly to any Rx
  39. 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. 40.  Periodic alternating head turn to minimise nystagmus & oscillopsia  Causes: lesions of the cerebellum
  41. 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. 42. Nystagmus associated with strabismus  Latent /manifest-latent nystagmus  Manifest nystagmus  Nystagmus blockage syndrome
  43. 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. 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. 45. Nystagmoid conditions  Movements which are not regular and rhythmic:  Oculopalatal myoclonus  Opsoclonus  Ocular bobbing
  46. 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. 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. 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. 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. 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. 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. 52.  Occlusion therapy:  Trials with conventional occlusion have been found to be effective  As amblyopia gets corrected and vision improves,nystagmus finally decreases
  53. 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. 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. 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. 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. 57. Anderson surgery  Advocated only recessions  Left face turn (null in dextroversion):  Right eye : LR recession  Left eye : MR recession
  58. 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. 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

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