The abducens nucleus in the lower pons is the horizontal gaze centre of the brainstem. It contains motor neurons for the lateral rectus muscle of the same eye and interneurons that cross and ascend in the medial longitudinal fasciculus to the opposite medial rectus. Together they turn both eyes to the same side.
| Location | Lower pontine tegmentum under the facial colliculus in the floor of the fourth ventricle, encircled by the genu of the facial nerve fibres |
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| Connections |
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| Blood Supply | Paramedian and short circumferential branches of the basilar artery; Anterior inferior cerebellar artery |
Generates conjugate horizontal eye movement toward the same side, coordinating the lateral rectus of one eye with the medial rectus of the other.
An abducens nucleus lesion causes a horizontal gaze palsy toward that side, not just a lateral rectus weakness, and often a facial palsy from the nearby facial genu (facial colliculus syndrome). Combined with an MLF lesion it produces the one-and-a-half syndrome. In contrast, a sixth nerve lesion only weakens abduction of one eye.
Inability of both eyes to look toward the side of a lesion of the abducens nucleus.
A dorsal pontine lesion, often demyelination or stroke, causing ipsilateral gaze palsy and lower motor neuron facial weakness.
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