Chapter contents
Overview
Origin & central course
Intracranial course
Final innervation
Coordination of muscles
Lower motor neuron lesion
Upper motor neuron lesion
MLF syndrome
| Cranial Nerve VI - Abducens Nerve | Page 6 of 8 |
Clinical correlation - lower motor neuron (LMN) lesion
Damage to the abducens nucleus or its axons results in weakness or paralysis of the ipsilateral lateral rectus muscle.
This is indicated by:
Medially directed eye on the affected side due to the unopposed action of the medial rectus muscle.
Inability to abduct the affected eye beyond the midline of gaze (up to approximately the midline, the superior and inferior oblique muscles can abduct the eye).
Strabismus - the inability to direct both eyes to the same object. When asked to look at an object located laterally to the side of the lesion, the patient's affected eye will be unable to be abducted beyond the midline of gaze. The opposite normal eye will be adducted to effectively fixate on the object.
Horizontal diplopia (double vision) due to the strabismus. Patients may compensate by turning their head so that the affected eye is focused on an object and then moving the normal eye so as to fixate on the object.
CN VI paralysis is the most common isolated palsy due to the long peripheral course of the nerve.
Figure 6-6. Lower motor neuron lesion.
