Medial longitudinal fasciculus syndrome (INO) is associated with infarction at which location?

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Multiple Choice

Medial longitudinal fasciculus syndrome (INO) is associated with infarction at which location?

Internuclear ophthalmoplegia comes from a lesion of the medial longitudinal fasciculus, a midline brainstem tract that links the oculomotor nucleus with the contralent abducens nucleus to coordinate horizontal gaze. Damaging the MLF disrupts adduction of the affected eye during lateral gaze, while the other eye may abduct with nystagmus. Because the MLF runs along the dorsal midline of the brainstem, including the rostral pons and midbrain, an infarct in that midline brainstem region best explains INO. Lateral medulla infarction involves other pathways and nuclei not responsible for the MLF, cortex lesions don’t produce this specific gaze deficit, and basilar tip infarction tends to cause broader brainstem/cerebral involvement rather than a focused MLF disruption.

Internuclear ophthalmoplegia comes from a lesion of the medial longitudinal fasciculus, a midline brainstem tract that links the oculomotor nucleus with the contralent abducens nucleus to coordinate horizontal gaze. Damaging the MLF disrupts adduction of the affected eye during lateral gaze, while the other eye may abduct with nystagmus. Because the MLF runs along the dorsal midline of the brainstem, including the rostral pons and midbrain, an infarct in that midline brainstem region best explains INO. Lateral medulla infarction involves other pathways and nuclei not responsible for the MLF, cortex lesions don’t produce this specific gaze deficit, and basilar tip infarction tends to cause broader brainstem/cerebral involvement rather than a focused MLF disruption.

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