Test 165  (Ocular anatomy )

1. The following are true about the oculomotor nuclear complex:

a. the levator muscles are supplied by a central caudal 
    nucleus

b. the nucleus for each superior rectus supplies the 
    contralateral muscle

c. the nucleus for each medial rectus supplies the 
    ipsilateral muscle

d. the nucleus for each inferior rectus supplies the 
    contralateral muscle

e. the Edinger-Westphal nucleus is located in the 
    ventromedial region
 

Answera.T   b.T  c.T   d.F  e.F
The nucleus for each rectus muscle supplies the ipsilateral muscle except for the superior rectus which receives innervation from the contralateral nucleus. Levator muscles are unusual in that they receive innervation from a central motor nucleus. Edinger-Wesphal nucleus is located in the dorsomedial region.
 
 

2. With regard to trochlear nerve:

a. it contains the least number of nerve fibres of all 
    cranial nerves

b. the nucleus is situated dorsal to the aqueduct 
    of Sylvius

c. the nucleus is bounded ventrolaterally by 
    the medial longitudinal fasciculus

d. it is the only motor nerve that exits dorsally from 
    the nervous system

e. it is sensitive to retrobulbar anaesthesia
 

Answera.T  b.F  c.T  d.T  e.F
The trochlear nerve is situated central to the aqueduct 
of Sylvius. The nerve is located outside the muscle cone and is therefore not usually affected by retrobulbar anaesthesia.
 
 

3. The facial nerve:

a.  contains only motor nerves

b. is important for tear production

c. divides into five branches after emerging from the 
    parotid gland

d. is important for normal blinking reflexes

e. innervates the orbicularis oculi via its zygomatic 
    and temporal branches
 

Answer
a.F   b.T  c.F   d.T  e.T
The facial nerve contains both motor and sensory nerve. The facial nerve divides into five branches within the substance of parotid gland.

 

4. The nucleus of abducent nerve:

a. lies at the floor of the fourth ventricle

b. gives off fibres that loop around the nucleus of 
    seventh nerve before leaving the central nervous system

c. gives off fibres that pass through the paramedian 
    pontine reticular formation

d. lies lateral to the medial longitudinal fasciculus

e. contains only motor component  
 

Answer
a.T   b.F  c.T  d.T  e.T
The nucleus of abducent nerve lies in caudal pons
in the floor of the fourth ventricle. The fibres from facial nucleus loop around the abducent nucleus. 
 
 

5. A left fourth nerve palsy causes:

a. head tilt to the left

b. left ocular hypodeviation in the primary position

c. left ocular hyperdeviation on right gaze

d. increased diplopia with head tilt to the right

e. torsional diplopia 
 

Answer
a.F  b.F  c.T  d.F  e.T
The affected eye shows hyperdeviation and there is a resultant inferior oblique overaction causing ipsilateral hyperdeviation when the eye is adducted. The head tilt is to the contralateral side and the diplopia is increased with head tilt to the affected side.
.

 

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