A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
А 42-уеаr-old woman рrеѕеntѕ wіth fасіаl аѕуmmеtrу. The patient says yesterday she noticed that her face appeared to be dеvіаted to the rіght. Ѕhе dеnіеѕ аnу trаumа or rесеnt trаvеl. Неr раѕt mеdісаl hіѕtorу іѕ nonсontrіbutorу. Her vitals are blood pressure 110/78 mm Hg, temperature 36.5°C (97.8°F), pulse 78/min, and respiratory rate 11/min. Оn рhуѕісаl ехаmіnаtіon, thеrе іѕ drooріng of thе left ѕіdе of thе fасе. Тhе left nаѕolаbіаl fold іѕ аbѕеnt, аnd ѕhе іѕ unаblе to сloѕе hеr left еуе or wrinkle thе left ѕіdе of hеr forеhеаd. Whеn the patient аѕkеd to ѕmіlе, thе resulting аѕуmmеtrу is shown in the given photograph. The remainder of the nеurologіс ехаm іѕ normаl. A noncontrast CT scan of the head is unremarkable. Which of the following is the most likely cause of her presentation?
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A
Lyme diseaseIncorrect. Lyme disease can cause facial palsy (especially bilateral), but the patient has no travel/tick exposure and no other features (erythema migrans, arthralgias). Bell palsy is far more common.
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B
IdiopathicCorrect. Acute peripheral CN VII palsy with forehead involvement, normal exam otherwise, and unremarkable CT defines idiopathic Bell palsy.
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C
Cerebrovascular accidentIncorrect. A stroke would produce upper motor neuron facial weakness, which spares the forehead due to bilateral cortical innervation; this patient cannot wrinkle her forehead, indicating peripheral nerve injury.
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D
MalignancyIncorrect. Parotid or skull-base malignancy infiltrating CN VII typically causes slowly progressive, not abrupt overnight, weakness and usually has a palpable mass or other findings.
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E
Ramsay Hunt syndromeIncorrect. Ramsay Hunt syndrome (VZV reactivation in the geniculate ganglion) causes peripheral facial palsy but is accompanied by a painful vesicular rash in the ear canal and on the pinna — neither of which is described in this patient.
↑ Tap an answer to reveal the reasoning
Answer: B. Acute-onset unilateral facial weakness involving both the upper face (inability to wrinkle forehead, close the eye) and lower face (loss of nasolabial fold, asymmetric smile) in a healthy young adult with a normal head CT is the classic presentation of Bell palsy — an idiopathic peripheral (lower motor neuron) facial nerve palsy. Involvement of the forehead is the key feature distinguishing peripheral CN VII palsy from a central (upper motor neuron) lesion, which spares the forehead due to bilateral cortical innervation of the upper face.
Bell palsy is diagnosed clinically once secondary causes are excluded. By definition it is idiopathic, though herpes simplex virus reactivation in the geniculate ganglion is implicated in many cases. Standard treatment is high-dose oral corticosteroids (prednisone) started within 72 hours; antivirals (valacyclovir) are sometimes added in severe cases. Most patients recover completely within weeks to months.
Lyme disease can cause bilateral or unilateral facial palsy but typically occurs in endemic regions with tick exposure or erythema migrans history. A cerebrovascular accident would spare the forehead and show other neurologic signs. Malignancy (parotid tumor, schwannoma) typically causes slowly progressive, not abrupt, palsy.
**Why each option:**
**A.** Lyme disease can cause facial palsy (especially bilateral), but the patient has no travel/tick exposure and no other features (erythema migrans, arthralgias). Bell palsy is far more common.
**B.** Correct. Acute peripheral CN VII palsy with forehead involvement, normal exam otherwise, and unremarkable CT defines idiopathic Bell palsy.
**C.** A stroke would produce upper motor neuron facial weakness, which spares the forehead due to bilateral cortical innervation; this patient cannot wrinkle her forehead, indicating peripheral nerve injury.
**D.** Parotid or skull-base malignancy infiltrating CN VII typically causes slowly progressive, not abrupt overnight, weakness and usually has a palpable mass or other findings.