Nerve
Medial longitudinal fasciculus
A link between eye and head movement pathways
High-yield
An MLF lesion can produce internuclear ophthalmoplegia: the eye on the affected side adducts poorly during horizontal gaze, while the other eye may show abducting nystagmus. Convergence may remain possible, but its preservation is not required.
Overview
Each medial longitudinal fasciculus (MLF) runs close to the brainstem midline. One important connection carries signals from an abducens nucleus to the opposite oculomotor nucleus, allowing one eye to abduct while the other adducts. Vestibular connections help the eyes remain directed at a target when the head moves.
Reference facts
- Origin
- Inputs include vestibular nuclei, abducens internuclear neurons and other brainstem gaze-control regions.
- Course
- Paired bundles travel near the aqueduct and fourth-ventricle floor; descending connections extend toward the cervical spinal cord.
- Motor
- Connections among the III, IV and VI systems coordinate eye movements; links to cervical motor pathways contribute to eye–head coordination.
- Sensory
- Vestibular signals carried here contribute to the vestibulo-ocular reflex, which compensates for head movement.
Clinical correlation
Demyelination and brainstem ischemia are common causes. Bilateral involvement in a younger adult raises suspicion for demyelination; unilateral involvement in an older adult often has a vascular cause. These patterns guide investigation rather than establish a diagnosis.
Frequently asked questions
Where does the medial longitudinal fasciculus arise?
Inputs include vestibular nuclei, abducens internuclear neurons and other brainstem gaze-control regions.
What muscles does the medial longitudinal fasciculus supply?
Connections among the III, IV and VI systems coordinate eye movements; links to cervical motor pathways contribute to eye–head coordination.
What is the sensory distribution of the medial longitudinal fasciculus?
The medial longitudinal fasciculus carries sensation from the vestibular signals carried here contribute to the vestibulo-ocular reflex, which compensates for head movement.
What is the course of the medial longitudinal fasciculus?
Paired bundles travel near the aqueduct and fourth-ventricle floor; descending connections extend toward the cervical spinal cord.