A patient presents with unilateral facial paralysis and inability to wrinkle the forehead; what is the next step?

• A. No further testing indicated
• B. Urgen CT scan
• C. Lumbar puncture
• D. Lyme disease serology testing

Answer: (D)

Unilateral facial paralysis with inability to wrinkle the forehead points to a peripheral facial nerve (lower motor neuron) palsy on the affected side, not a central (upper motor neuron) lesion. In this scenario, it’s important to consider infectious causes that can present this way, especially in areas where Lyme disease is common, because facial nerve palsy is a frequent manifestation of Lyme neuroborreliosis. Therefore the next step is to test for Lyme disease to determine if Borrelia burgdorferi is the cause, which would steer treatment toward appropriate antibiotics. Urgent imaging with a CT scan isn’t typically needed here unless you suspect a stroke or another intracranial process, and a lumbar puncture isn’t indicated unless there are signs of meningitis or other concerning neurologic features. If Lyme serology is positive, treat with the appropriate antibiotic; if negative, manage as a typical Bell palsy with anti-inflammatory therapy as indicated.