USMLE · Question #600
A 35-year-old female comes to the physician due to headaches of two months' duration. She has no history of pre-existing medical illnesses. Vital signs are within normal limits. A head CT reveals a ma
The correct answer is B. decreased corneal reflex in the left eye. The trigeminal nerve (CN V) is a mixed (sensory and motor) nerve. It provides sensory innervation to the face, cornea, mucous membranes of the nasal and oral cavities, frontal sinus, anterior two-thirds of the tongue, teeth, and hard palate. It also provides motor innervation for
Question
A 35-year-old female comes to the physician due to headaches of two months' duration. She has no history of pre-existing medical illnesses. Vital signs are within normal limits. A head CT reveals a mass above the left petrous bone and biopsy reveals a malignant schwannoma on the left trigeminal nerve. The patient undergoes surgery for resection of the mass. If there is damage to the involved nerve during the surgery, there will be
Options
- Adecreased accommodation in the left eye
- Bdecreased corneal reflex in the left eye
- Cdecreased gag reflex
- Ddecreased taste from the anterior two thirds of the tongue
- Einability to adduct the left eye
How the community answered
(20 responses)- A5% (1)
- B85% (17)
- C10% (2)
Explanation
The trigeminal nerve (CN V) is a mixed (sensory and motor) nerve. It provides sensory innervation to the face, cornea, mucous membranes of the nasal and oral cavities, frontal sinus, anterior two-thirds of the tongue, teeth, and hard palate. It also provides motor innervation for the muscles of mastication (temporalis, masseter, lateral and medial pterygoids). If this patient's left trigeminal nerve is injured during surgery, she could lose the corneal reflex on the left. The (sensory) limb for this reflex is transmitted by CN V (unilaterally) and the efferent (motor) limb (bilaterally) is transmitted by the facial nerve, CN VII. Additional symptoms that patient could also have include left facial anesthesia, ipsilateral flaccid paralysis of muscles of mastication, deviation of the jaw to the left, hypoacusis and trigeminal neuralgia.
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