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Supranuclear disorders of ocular motility

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Supranuclear disorders of ocular motility

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Supranuclear disorders of ocular motility

  1. 1. SUPRANUCLEAR AND INTERNUCLEAR DISORDERS OF OCULAR MOTILITY DR ARPITA
  2. 2. • Extraocular muscles are supplied by 3,4,6 th cranial nerves which have their nuclei in the brainstem • Centres controlling the nuclei – Supranuclear • Pathways connecting the nuclei – Internuclear • Nerves supplying the EOM - Infranuclear
  3. 3. • The eyes move in SIX WAYS FAST EYE MOVEMENTS (300°-600°/SEC) 1)SACCADES 2)NYSTAGMUS SLOW EYE MOVEMENTS (5°-50°/SEC) 1) SMOOTH PURSUIT 2) OPTOKINETIC 3) VESTIBULAR 4) VERGENCE
  4. 4. SACCADES • Derived from french word “Saquer” which means to pull or tug • REDIRECT eyes from one target to another • Voluntary or reflex ( in response to visual , auditory or pain stimulus )
  5. 5. • Always conjugate • Ballistic – once initiated they cannot be stopped or modified • Speed of saccade is directly proportional to size of movement Velocity of a larger saccade is faster than the velocity of a slow saccade , this is known as Main sequence • Visual suppression occurs - even though the visual world is sweeping across retina , there is no sense of a blurred image
  6. 6. Pathways for saccades
  7. 7. CROSSED PATHWAY
  8. 8. Synthesis of a saccade- “pulse step”
  9. 9. Clinical examination Thefixation objects should be presented at an angular separation of about 20 to 30°.
  10. 10. Clinical examination • SPEED - slowing of saccades can be seen in AIDS dementia complex , Lipid storage disorders , PSP , drug intoxications • SMOOTHNESS – affected in cerebellar diseases • ACCURACY – Hypometric or Hypermetric , affected in cerebellar diseases
  11. 11. SMOOTH PURSUIT • Slow eye movements that permits the eyes to conjugately follow/track a target during movements of the target or observer or both • Have the capcity for compensation unlike saccades - when speed of target is varied after initiation of the movement , speed of pursuit can be varied.
  12. 12. • Initiated by a slow moving target across the fovea • Visual fixation holds the image of a stationary object on the fovea
  13. 13. Pathway for pursuit movements DOUBLE DECUSSATION
  14. 14. • Parieto – occipito – temporal region is the confluence of Brodman areas 19, 37 and 39 • A pure occipital lobe lesion will not affect smooth pursuit movements • Deep parietal lobe lesions disrupt smooth pursuit to ipsilateral side
  15. 15. VESTIBULAR REFLEX • Coordinates eye movements with head movements, holds image steady during brief head rotations • Stimulation of Ampulla of horizontal semicircular canal conjuate movement towards contralateral side • Information from anterior and posterior semicircular canals - combination of vertical and torsional eye movements
  16. 16. “COWS”
  17. 17. OPTOKINETIC REFLEX • Stimulus – sustained head rotation • With sustained head rotation at a constant velocity , vestibular response fades and optokinetic response takes over • OKN prevents a continuous blur from relative motion of the moving visual field .
  18. 18. Turning the drum to the right elicits an ipsilateral pursuit movement to the right and a contralateral saccade to the left.
  19. 19. VERGENCE • Allows bifoveation of an object moving in Z axis • Stimuli – • Retinal blur – accomodative vergence • Disparity of location of images- fusional vergence • Pathway : Occipital cortex – midbrain reticular formation – 3rd nerve nucleus
  20. 20. INTERNUCLEAR PATHWAYS
  21. 21. • Vertical saccades require simultaneous activation of both FEF • Unilateral activation of the riMLF generates torsional eye movements • Right riMLF – clockwise movements • Left riMLF – anticlockwise movements
  22. 22. Supranuclear disorders... • Affect both eyes • Do not produce diplopia • Dolls eye phenomenon and Bells phenomenon remain intact
  23. 23. DISORDERS OF HORIZONTAL GAZE A) SACCADIC DISORDERS • INABILITY TO PRODUCE SACCADES 1) Frontal lobe lesions - Injury • Cannot generate contralateral saccades • Preferential gaze to affected side • Pursuit , OKN ,VOR are normal • Recovers after several weeks due to activation of projections from ipsilateral FEF to PPRF
  24. 24. • 2) Congenital ocular motor apraxia (COMA) • Cannot initiate voluntary horizontal saccades • Vertical saccades are normal • “ Head thrusting occurs ” • Becomes less prominent with age
  25. 25. • 3) Acquired ocular motor apraxia • Aka Balints syndrome • Seen in extensive B/L cerebral disease (parieto – occipital) • Simultagnosia – inability to perceive more than one object at a time • Optic ataxia – inaccurate arm pointing • Dementia • Visual field defects
  26. 26. • SLOWING OF SACCADES 1) Progressive supranuclear palsy • Aka Steel – Richardson – Olszewski syndrome • Progressive conjugate paresis of gaze in all directions especially downward • Associated neurological symptoms include dementia , dysarthria , nuchal and axial rigidity • Recurrent falls early in course • Death within several years of diagnosis
  27. 27. • 2) Olivopontocerebellar degeneration • Presents early in adulthood • Ataxia , slurred speech and dementia • Eye movements in all directions are progressively affected • Eventually leads to total ophthalmoplegia
  28. 28. • Dysmetric saccades • Hypometric saccades are not necessarily pathological;they can be the product of inattention or poor cooperation. • Hypermetric saccades on the contrary are always pathological and strongly suggest the presence of a lesion in the cerebellar vermis.
  29. 29. • UNWANTED SACCADES • Square wave jerks – named for their appearance of eye movement recordings • Sporadic saccades that return to fixation within 100-200 msec • Greater than 1 degree = pathologic • Associated with cerebellar disease • Called as “ sed rate of CNS “ as more than 10/min is a non specific indicator of CNS disease
  30. 30. • Ocular flutter • Intermittent brief volley of horizontal oscillations aroud fixation • No intersaccadic interval unlike square wave jerks
  31. 31. • Opsoclonus • Chaotic saccades occuring randomly in any direction • Aka saccadomania • Causes – cerebellar disease , post viral encephalopathy , paraneoplastic sign , drug toxicity
  32. 32. • Internuclear ophthalmoplegia • Lesion of the MLF
  33. 33. • INO is named for the side of the MLF lesion • Posterior INO – convergence is preserved • Anterior INO – absence of convergence • WEBINO – bilateral INO • Myaesthenia can present similarly – pseudo INO
  34. 34. • One and a half syndrome – PPRF lesion plus ipsilateral MLF lesion • Only movement left is contralateral abduction • “Paralytic pontine exotropia”- transient phenomenon seen during first few days of one and a half syndrome – due to unopposed action of contralateral PPRF
  35. 35. DISORDERS OF VERTICAL GAZE • Downgaze palsy – • Occlusion of posterior thalamo-subthalmic artery which enters from anterior part of midbrain (Percheron's artery), • Upgaze palsy – lesion in rostral midbrain (posterior comissure)
  36. 36. • Dorsal midbrain syndrome • Aka Parinauds syndrome / Sylvian aqueduct syndrome • Paresis of vertical gaze –mainly upward • Light near dissociation of pupils • Convergence retraction nystagmus • Lid retraction – Colliers sign • Spasm / paresis of convergence • Spasm / paresis of accomodation
  37. 37. • Skew deviation • Acquired vertical and torsional deviation • May be comintant or incomitant • Due to imbalance of otolithic inputs from utricule and saccule to ocular motor neurons • With lower brainstem lesions the ipsilateral eye tends to be hypotropic , with pontine and midbrain lesions the eye tends to be hypertropic
  38. 38. • Ocular tilt reaction • Due to lesion affection central or peripheral otolithic pathways • Destructive lesion of INC leads to : • Contralateral head tilt • Depression and extorsion of contralateral eye • Elevation and intortion of ipsilateral eye
  39. 39. • 4th nerve palsy extortion of hypertropic eye • OTR intortion of hypertropic eye
  40. 40. • Tonic downward deviation of gaze, or forced downgaze, is associated with medial thalamic hemorrhage, acute obstructive hydrocephalus, severe metabolic or hypoxic encephalopathy, or massive subarachnoid hemorrhage. • When associated with lid retraction, the corneas can be buried below the lower lid (sundowning). • In this setting, elevated intracranial pressure is a major concern.

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