Cranial Nerves III, IV, VI: Eye Movements

Published on 09/04/2015 by admin

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Last modified 09/04/2015

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Cranial Nerves III, IV, VI

Eye Movements

BACKGROUND

Eye movements can be divided into four types:

The sites of control of these eye movements differ (Fig. 9.1).

In the brainstem, the inputs from the frontal and occipital lobes, the cerebellum and the vestibular nuclei are integrated so that both eyes move together. Important structures are the centre for lateral gaze in the pons and the medial longitudinal fasciculus (MLF), which runs between the nuclei of the III and IV cranial nerves (in the midbrain) and the VI (in the pons).

The III, IV and VI cranial nerves then control the following muscles (Fig. 9.2):

Abnormalities can arise at any level (Fig. 9.1):

No double vision (generally):

Double vision:

Internuclear and supranuclear lesions rarely cause double vision.

WHAT TO DO

Look at the position of the head.

Look at the eyes.

Look at the position of the eyes in primary gaze.

Perform the cover test (Fig. 9.3).

The cover test

What to do

This is a test for latent squint.

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