Anatomy-5

A10-year boy is examined because his parents
noticed that “his eyes never seem to look in
the right direction.” On examination, the left
eye of the child is unable to move laterally
(abduction) and when asked to look toward
the nose (adduction), the eyeball retracts into
the socket and the eye opening narrows.
Sometimes, the eye also moves superiorly. The
child is diagnosed with Duane syndrome, a
congenital ocular motility disorder characterized
by limited abduction of the affected eye.
This is due to absence of the abducens (fifth
cranial) nerve with aberrant innervation by the
oculomotor (third cranial) nerve. Which of the
following muscles is normally innervated by
the abducens nerve?
(A) inferior oblique
(B) lateral rectus
(C) medial rectus
(D) superior oblique
(E) superior rectus

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