Lyme disease is the most common infectious cause of bilateral face weakness. Usually, however, face weakness is associated with other findings such as ptosis and ocular muscle weakness. I, there are neurologic findings in addition to the face weakness. For instance, in amyotrophic lateral sclerosis, one ordinarily sees evidence of atrophy and fasciculations in the tongue or the extremities. In ischemic lesions of the brain stem, patients usually demonstrate multiple symptoms and findings such as weakness, ataxia, and ophthalmoplegia.
Most neoplasms also cause a variety of other neurologic symptoms and findings as well.
A thorough history and physical examination are the most important steps in the diagnostic workup of bilateral face weakness. Life threatening diseases such as Guillain-Barre' syndrome and botulism should be ruled out. If these are not suspected, the patient can be worked up as an outpatient.4 Helpful historical information includes time of onset, prior history of face weakness, recent upper respiratory tract infection, history of tick bites or rashes, otologic symptoms, malignancy, recent dental problems, diabetes, other illnesses, and other neurologic symptoms. Physical examination should include special emphasis on the head and neck and a thorough neurological examination.3 Initial laboratory studies should include a complete blood count, erythrocyte sedimentation rate, and blood glucose. In addition, syphilis serology, Lyme titer, screening for mononucleosis, and HIV testing should be considered.