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?
Correct Answer: Hyperacusis of the left ear
Description: 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 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 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 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 the trigeminal nerve (CN V). Ref: Rosenga A.J., Novakovic R.L., Frank J.I. (2005). Chapter 67. Coma, Persistent Vegetative State, and Brain Death. In J.B. Hall, G.A. Schmidt, L.D. Wood (Eds),Principles of Critical Care, 3e.
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