0826 - Eye Movement Disorders

Question 1

What is strabismus? What are the types?

Answer 1

Misalignment or deviation of the visual axes.
Tropia - Relative deviation of visual axis with both eyes viewing.
Phori - Relative deviation of visual axes with one eye covered (latent misalignment)
Eso-Exo-Hyper - divergent, convergent, vertical misalignment

Question 2

What muscles are supplied by CNIII? by which division?

Answer 2

Superior Rectus - Sup
Levator palpebrae superioris - Sup
Inferior Rectus - Inf
Inferior Oblique - Inf
Medial rectus - Inf
Pupil/ciliary body - Inf

Question 3

What muscle is supplied by CNIV?

Answer 3

Superior Oblique

Question 4

What muscle is supplied by CNVI?

Answer 4

Lateral rectus

Question 5

From primary position, which muscles abduct and adduct eye?

Answer 5

Lateral rectus abducts

Medial rectus adducts

Question 6

From abducted position, which muscles elevate and depress eye?

Answer 6

Superior rectus elevates eye

inferior rectus depresses eye

Question 7

From adducted position, which muscles elevate and depress the eye?

Answer 7

Inferior oblique elevates eye

Superior oblique depresses eye.

Question 8

Where are the nuclei for CNs III, IV, and VI located in the brainstem?

Answer 8

III and IV in dorsal midbrain. VI in dorsal pons.

Question 9

What is the effect of a CNIII palsy?

Answer 9

Complete ptosis, with affected eye looking down and out (IV and VI unopposed now). Pupil may be dilated. Can’t look up, down, or medially, but can abduct eye (Unless CNVI palsy too).

Question 10

What is the effect of a CNIV palsy?

Answer 10

Innervates superior oblique, which intorts eye and depresses eye.
Head tilt away from side of lesion. Failure of depression in eye when looking medially. Difficult to detect.

Question 11

What is the effect of a CNVI palsy?

Answer 11

Slight adduction in primary position. Failure of abduction when trying to move eyes medially, however.

Question 12

What is Gaze palsy? How does it arise?

Answer 12

Lesion on CNVI nucleus prevents eye looking to one side (i.e. in same direction. It occurs via 2 nerves (VI, III), as the lesion in nucleus of VI prevents communication with III via the medial longitudinal fasciculus.

Question 13

What is Internuclear ophthalmoplegia? How does it arise?

Answer 13

Affected eye cannot look medially (i.e. it will fail to adduct on abduction of the other). Similar mechanism to gaze palsy, but lesion is in medial longitudinal fasciculus (MLF) rather than VI nucleus, so VI can abduct, but III cannot communicate with it.

Question 14

What is One and a half syndrome? How does it arise?

Answer 14

Combination of a gaze palsy and internuclear ophthalmoplegia. A lesion on BOTH CNVI nucleus and MLF means One eye can abduct (due to the unaffected CNVI nucleus), but otherwise the eyes cannot move side to side.

Question 15

What are the three common types of pathological nystagmus?

Answer 15

Vestibular - Linear slow phase (i.e. steady build then jerk)
Cerebellar/brainstem - Inability to hold gaze, with fast phase in direction of gaze and exponentially decreasing slow phase
Congenital - Generally horizontal. Exponentially increasing slow-phase

Question 16

What is nystagmus?

Answer 16

A condition in which the eyes make repetitive, uncontrolled movements that have both a ‘fast’ and ‘slow’ phase. The ‘fast’ phase is the one that describes the condition (i.e. fast lateral, slow medial movements = lateral nystagmus).