Internuclear Ophthalmoplegia

Aka: Internuclear Ophthalmoplegia, Lhermitte's Syndrome, Medial Longitudinal Fasciculus Syndrome, Conjugate Gaze Palsy

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II. Pathophysiology

  1. Medial Longitudinal Fasciculus (MLF) - normal function
    1. MLF is a myelinated pathway through the tegmentum of the Midbrain and dorsal pons
    2. On lateral gaze, Cranial Nerve 6 abducts the ipsilateral eye
    3. To maintain Conjugate Gaze, a signal is passed via MLF to the contralateral eye's CN 3 to adduct (medially) in parallel
  2. With a MLF lesion, the adducting eye via CN 3 fails to adduct
    1. In response, the abducting eye (via CN 6) demonstrates Nystagmus and Conjugate Gaze Palsy
  3. Bilateral MLF lesion results in a Wall-eyed appearance
    1. Bilateral adduction deficits result in Exotropia
  4. Extraocular Movement is normal in other directions
    1. Primary gaze remains parallel
    2. Eye convergence on near Vision remains intact

III. Causes

  1. Older adults (esp. unilateral involvement)
    1. Vascular disease affecting the vertebrobasilar circulation
  2. Young adults (esp. bilateral involvement)
    1. Multiple Sclerosis
  3. Children
    1. Pontine glioma (MRI)
    2. Vasculitis may also cause Internuclear Ophthalmoplegia in this age group
  4. Alcoholism
    1. Wernicke's Encephalopathy

IV. References

  1. Berson (1990) Ophthalmology Study Guide, AAO, p. 116-7

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