questions 2

Eye Movement

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Topic updated on 11/26/16 9:17pm

Control systems
  • Pathway 
    • frontal eye field in cortex controls voluntary eye movement
      • destruction leads to contralateral eye deviation towards the side of the lesion
    • frontal eye field (R)→ PPRF (L)→ abducens nuclei (L) → abducens muscle (L) + oculomotor nucleus (R) via medial longitudinal fasciculus (MLF)
      • results in combined movement of both eyes to the left with synchronized (L) abducens + (R) medial rectus
    • abnormal in internuclear opthalmoplegia (INO) / MLF syndrome
      • cause
        • lesion in the medial longitudinal fasiculus (MLF)
          • results in medial rectus palsy on attempted lateral gaze
      • presentation during lateral gaze
        • nystagmus in abducting eye + lack of movement in adducting eye
        • convergence is normal
      • MC in many patients with multiple sclerosis
  • Cranial nerves involved
    • CN III
      • muscles of innervation
        • medial rectus → adducts eye
        • superior rectus → elevates, intorts, adducts eye
        • inferior rectus → depresses, extorts, adducts eye
        • inferior oblique → elevates, extorts, abducts eye
          • innervates all muscles except for lateral rectus and superior oblique
      • damage 
        • eye looks down and out
        • ptosis
        • pupillary dilation
    • CN IV
      • muscle of innervation
        • superior oblique → depresses, intorts, abducts eye
      • damage
        • diplopia with downward gaze
          • can reduce diplopia by tilting head toward lesion
    • CN VI
      • muscles of innervation
        • lateral rectus → abducts eye
      • damage
        • medially directed eye
          • due to unopposed action of medial rectus
    • overview
      • "superior" muscles intort while "inferior" muscles extort
      • "oblique" muscles abduct
Testing
  • Each direction tests a specific pair of muscles



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