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A neurological examination of a 47-year-old woman reveals a normal corneal reflex in her right eye, but no
consensual corneal reflex in her left eye. Which of the following additional findings might be expected?
A. Absence of pupillary light reflex of the left eye
B. Hyperacusis of the left ear
C. Inability to abduct the right eye
D. Loss of pain and temperature of the left face
E. Loss of taste from the anterior two-thirds of the right tongue
F. Ptosis of the left eye
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The correct answer is B. The first trick to this question is to determine where the lesion is. The corneal reflex is
tested by touching a cotton wisp to the eye. A normal response would be blinking of the ipsilateral eye as well
as the contralateral eye (consensual reflex). The afferent limb of the corneal reflex is contained within the
ophthalmic division of the ipsilateral ophthalmic nerve (V1), the efferent limb is by both (right and left) facial
nerves (VII). This woman had a normal corneal reflex in her right eye, indicating a normal right V1 and right VII.
However, she lacked a consensual reflex, indicating an abnormal left VIIth nerve. The next trick to this question
is to determine what other signs a lesion in the left VIIth nerve could produce. A lesion in the left VIIth would also
produce hyperacusis (increased sensitivity to sound) in the left ear because of paralysis of the stapedius
muscle, which ordinarily dampens sound transmission through the middle ear.
The absence of a pupillary light reflex of the left eye (choice A) could be caused either by a lesion of the left
optic nerve (CN II; afferent limb) or by a lesion of the left oculomotor nerve (CN III; efferent limb).
The inability to abduct the right eye (choice C) could be caused by a lesion of the right abducens nerve (CN
VI), which innervates the lateral rectus muscle.
Loss of pain and temperature of the left face (choice D) could be caused by a lesion of the spinal nucleus of V.
This nucleus is located in the medulla, and receives pain and temperature information from the face via the
trigeminal nerve (CN V).
Loss of taste from the anterior two-thirds of the right tongue (choice E) could result from a lesion of the right CN
VII.
Ptosis of the left eye (choice F) could result from a lesion of the left oculomotor nerve (CN III) because of
denervation of the levator palpebrae muscle. A lesion of the left VII would result in the inability to close the left
eye.
