Abducens nerve

89. The tarts

The cranial nerves passing through the superior orbital fissure in order from top to bottom:

Answers...

The one and a half syndrome is characterized by a conjugate horizontal gaze palsy in one direction and an impairment of the abduction of the eyes in the other. (T/F?)
Horizontal gaze palsy is seen on looking away from the side of the lesion. (T/F?)
The ipsilateral eye has no horizontal movement. (T/F?)
The most common cause of the one-and-a-half syndrome in the young people is Miller-Fisher syndrome. (T/F?)
The most common cause of the one-and-a-half syndrome in older people is multiple sclerosis. (T/F?)
When the lesion that causes a damage to PPRF or abducens nucleus and medial longitudinal fasciculus, also affects the facial nerve, we can talk about an eight-and-a-half syndrome. (T/F?)

Henry Vandyke Carter [Public domain], via Wikimedia Commons

Innervates only one single muscle of the eye, the lateral rectus muscle?
Axons from the abducens nerve loop around the facial motor nucleus, creating the facial colliculus that is visible on the floor of the fourth ventricle?
Besides the motor neurons, which directly innervate ipsilateral lateral rectus muscle via the abducens nerve, abducens nucleus contains also interneurons, which project to the contralateral oculomotor nucleus and cause conjugate movement (adduction) of the contralateral eye?
Besides the motor neurons, which directly innervate ipsilateral medial rectus muscle via the oculomotor nerve, oculomotor nerve nucleus contains also interneurons, which project to the contralateral abducens nucleus and cause conjugate movement (abduction) of the contralateral eye?
A lesion to the nucleus of the abducens nerve causes inability to move the eyes together in the direction of the side with the lesion?
In peripheral abducens palsy, the contralateral eye is slightly adducted because of the unopposed tonic action of the medial rectus muscle?

Results in double vision, due to lesion of the medial longitudinal fasciculus (MLF), which connects the nuclei of oculomotor and abducens nerves. (T/F?)
Is always unilateral. (T/F?)
Diplopia is elicited with the gaze to the opposite side of the affected eye. (T/F?)
Affected eye shows impairment ( slower rate or failure ) of adduction. (T/F?)
Contralateral (not affected) eye shows vertical nystagmus with abduction. (T/F?)
If the left eye is affected, the patient will have diplopia when looking to the left. (T/F?)
With rostral MLF lesions, near the oculomotor nucleus, convergence of the eyes may be impaired. (T/F?)

Henry Vandyke Carter [Public domain], via Wikimedia Commons

Internuclear ophthalmoplegia is also called medial longitudinal fasciculus syndrome or MLF syndrome.
MLF syndrome can occur unilaterally or bilaterally. Bilateral internuclear ophthalmoplegia is highly suspected for multiple sclerosis, specially with young people.

Contralateral eye characteristically shows horizontal nystagmus with abduction.
If the left eye is affected, the patient will show horizontal diplopia with gaze to the opposite, right side.

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