Eye Movements pp 127-144 | Cite as

Abducens to Medial Rectus Pathway in the MLF: A Possible Cellular Basis for the Syndrome of Internuclear Ophthalmoplegia

  • Stephen M. Highstein


The neurological syndrome of internuclear ophthalmoplegia consists of defects in horizontal and vertical eye movements: a prominent feature is the loss of conjugate horizontal gaze (Bender & Weinstein, 1944; Cogan, 1948; Cogan et al., 1960; Christoff et al., 1960; Carpenter & McMasters, 1963; Carpenter & Strominger, 1965; Cohen, 1971). Horizontal gaze deficits are caused by an apparent palsy of the medial rectus extraocular muscle which is manifested as a weakness of medially directed gaze in the affected eye. With interruption of/or damage to the medial longitudinal fasciculus (MLF) on one side, the ipsilateral eye is abducted at rest and does not cross into the nasal or medial field of gaze except during convergence movements. Medially directed saccades in the affected eye are slowed (Evinger et al., in press) and neither vestibular, visual nor voluntarily induced eye movement can cause the eye to deviate into the medial hemifield (Evinger et al., in press; Cohen, 1971). It is noted that the adductive paresis is also present during electrical stimulation of the pontine reticular formation, a powerful stimulus which usually produces ipsilaterally directed conjugate horizontal eye movement (Cohen, 1974). The profound nature of this adductive paresis implies the necessity of an intact MLF for the production of all conjugate horizontal eye movements (Cohen, 1971; Cohen, 1974).


Abducens Nerve Medial Rectus Medial Longitudinal Fasciculus Oculomotor Nucleus Pontine Reticular Formation 
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Copyright information

© Plenum Press, New York 1977

Authors and Affiliations

  • Stephen M. Highstein
    • 1
  1. 1.Department of Neuroscience Division of Cellular NeurobiologyAlbert Einstein College of MedicineBronxUSA

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