Test 209 (Neuroophthalmology)

1. The following areas are involved in the initiation of a saccadic eye
    movement:

a. inferior colliculus

b. posterior parietal cortex

c. frontal eye fields

d. dorsal prefrontal cortex

e. temporal cortex

Answer
a. F   b.T   c.T   d.T   e.F
Areas involved in the initiation of saccadic movement to the opposite side include the frontal eye fields and dorsal prefrontal cortex of the frontal cortex, the posterior parietal cortex and the superior colliculus.

2. In a patient with a right internuclear ophthalmoplegia (INO):

a. the lesion is in the right medial longitudinal fasciculus 
    (MLF)

b. the convergence is abnormal

c. there is a left adduction deficit

d. a left abduction nystagmus is normal

e. there is saccadic movement abnormality of the left eye

Answer
a.T   b.F   c.F   d.T   e.F
A right internuclear ophthalmoplegia indicates a lesion in the right MLF and there is right adduction deficit with a left abduction nystagmus. Convergence is normal as it is controlled by the midbrain not the brainstem. Abnormal saccadic movement occurs in the right eye in right INO.

3. The following are true about the medial longitudinal fasciculus (MLF):

a. it allows the eyes to perform conjugate movement

b. it connects the sixth nerve nucleus with the ipsilateral 
    third nerve nucleus

c. it ascends from the medulla to the pons

d. a lesion in the MLF causes an ipsilateral adduction 
    deficit

e. a partial lesion in the MLF causes an ipsilateral lag in 
    the adducting saccade 

Answer
a.T   b.F   c.F   d.T   e.T
MLF arises from the sixth nerve nucleus and ascends the pons to be connected with the medial rectus nuclei of the contralateral third nerve nucleus in the midbrain. It allows the eyes to perform conjugate movement. A lesion in the MLF causes an ipsilateral adduction deficit and an incomplete lesion in the MLF causes ipsilateral adducting saccade. 

4. The following are involved in vergence eye movements:

a. conjugate movement

b. pupillary constriction

c. accommodation

d. sympathetic pathway

e. rapid eye movement

Answer
a.F   b.T   c.T   d.F   e.F
Vergence eye movements are dysjunctive movement in which the eyes move in opposite directions and inwards to ensure the eyes see the same object and hence produce single vision. These eye movements are slow and consist of: convergence, pupillary constriction and accommodation.

5. With regard to the vestibular system:

a. it is concerned with optokinetic nystagmus

b. it comprises the semicircular canals, utricle and saccule

c. the seimcircular canals respond to linear acceleration of 
    head movement

d. the utricle responds to rotational acceleration of head 
    movement

e. the saccule responds to linear acceleration of head 
    movement. 

Answer
a.F   b.T   c.F   d.F e.F
The vestibular system is concerned with the vestibular eye movements and comprises the semicircular canals, utricle and saccule. The semicircular canals respond to rotational acceleration of head movement whereas t
he utricle and saccule respond to the linear acceleration of head movement.

 

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