A 17-year-old high school
football player presented to a neurology clinic because his mother thought that
he may have acquired neck problems during a game. A month before, he had
sustained a concussion from a blow to his head from another player. Shortly
after, she noted that he intermittently tilted his head to the side. When asked
what was the matter, he simply said that sometimes he had double vision, and
that the images were situated on top of each other vertically, making it
difficult to go down stairs. When examined, there was no neck pain or
limitation of motion. He tended to keep his head tilted to the right side. When
asked to follow the doctors finger with his head in a straight position, his
left eye would not move downward when his eyes were turned to the right, and
tended to remain slightly deviated toward the left. At this point, he stated
that he had double vision, and felt better if his head was tilted to the right.
The remainder of his eye movements, as well as the remainder of his exam, was
Which of the following muscles is weakened?
A. Superior rectus B. Inferior rectus C. Lateral rectus D. Superior oblique E. Inferior oblique
Superior oblique -damage to the trochlear nerve causes weakness of the superior oblique muscle, resulting in the inability of the orbit to deviate downward when the eye is intorted. to compensate for the classically vertical double vision, the patient tends to tilt his head to the contralateral side, causing the contralateral eye to intort. the trochlear nerve supplies the superior oblique muscle. the trochlear nerve is the only nerve to decussate peripherally, and also to emerge from the dorsal aspect of the brainstem. in this case, the damaged nerve emerged from the right (contralateral) dorsal midbrain. the action of the superior oblique muscle is to rotate the orbit medially and downward. because the trochlear nerve is not only the smallest cranial nerve but also has the longest course of any cranial nerve, it is especially vulnerable to trauma. one of the most common causes of trochlear nerve palsy is trauma.