A 9-year-old boy is seen in the pediatrician’s office with a several days’ history of weakness of his mouth. He reports that he had a viral upper respiratory tract infection (URI) about 2 weeks prior. He denies headache, fever, vomiting, constipation, or other weakness. He has been a healthy child without serious previous illnesses. On physical examination the vital signs are normal. The left side of his mouth droops, he is unable to completely close his left eye, and his smile is asymmetric (Photograph). The mucous membranes are pink, moist, and without lesions. Extraocular eye movement and fundoscopic examinations are normal. Gait, sensation, and deep tendon reflexes are normal. Which of the following is the most likely diagnosis?
(Reproduced with permission from Knoop KJ, Stack LB, Storrow AB: Atlas of Emergency Medicine, 2nd ed. New York, NY: McGraw-Hill Education; 2002.)
a. Guillain-Barré syndrome
c. Cerebral vascular accident
The answer is e. (Hay et al, pp 819-820. Kliegman et al, pp 844, 3014-3015. Rudolph et al, p 2233.) Bell palsy is an acute, unilateral facial nerve palsy that begins about 2 weeks after a viral infection. Although the exact pathophysiology is unknown, reactivation of herpes simplex or varicella-zoster virus seems to be the most common cause; demyelination through an autoimmune process or allergic inflammation may also play a part in some cases. On the affected side, the upper and lower face are typically paretic, the mouth droops, and the patient cannot close the eye. Treatment consists of maintaining moisture to the affected eye (especially at night) to prevent keratitis. Complete, spontaneous resolution occurs in about 85% of cases, 10% of cases have mild residual disease, and about 5% of cases do not resolve. Occasionally infants will have facial nerve palsy at birth; this is usually related to compression from forceps and spontaneously resolves over several weeks. As this is a compression neuropathy, it should not be called congenital Bell palsy.
When evaluating a facial weakness, special care must be taken to evaluate the movement of the forehead. A peripheral facial neuropathy like Bell palsy will cause upper and lower facial weakness on the affected side. However, a central facial palsy will spare the forehead due to bilateral innervation.
Guillain-Barré syndrome is classically described as a demyelinating neuropathy that causes ascending weakness and diminished reflexes. Symptoms of paresthesia (occasionally pain) classically start in the hands or feet and then move centrally before affecting facial, respiratory, or other central structures.
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