Snapshot A 33-year-old man presents to the emergency department for slurred speech. His symptoms began a few hours prior to presentation and it has progressively worsened. He reports to having difficulty with closing his right eye and being sensitive to sound in the right ear. Physical examination is notable for loss of the nasolabial fold on the right and an inability to close the eye. There are vesicles found by the external acoustic meatus. Sensation is intact throughout the face. He is started on prednisone. Introduction Clinical definition a neurologic deficit secondary to weakness of the facial nerve Epidemiology Incidence 11-40 per 100,000 population Demographic 15-45 years of age Etiology Idiopathic Herpes simplex virus common in most cases Varicella-zoster virus Lyme disease Sarcoidosis Malignancy Diabetes mellitus Pathogenesis Facial nerve palsy may result from inflammatory or infectious insults to the facial nerve Anatomy The facial nerve is a mixed nerve that arises from the pontomedullary junction and contains motor fiber input to the facial muscles parasympathetic fibers to the lacrimal glands submandibular glands sublingual salivary glands afferent fibers from the taste receptors of the anterior two-thirds of the tongue external auditory canal and pinna Presentation Symptoms and physical exam unilateral facial weakness eyebrow sagging inability to close the eye an absence of the nasolabial fold corner of the mouth droops decreased tearing hyperacusis loss of taste sensation of the anterior two-thirds of the tongue Peripheral (lower motor neuron) vs central (upper motor neuron) lesion a lower motor neuron lesion involves the forehead an upper motor neuron lesion spares the forehead Studies Diagnostic criteria clinical diagnosis Differential Stroke differentiating factors infarction noted on MRI brain without contrast Multiple sclerosis differentiating factor MRI brain demonstrating demyelinating lesions Myasthenia gravis differentiating factor presence of acetylcholine receptor (AChR) or muscle-specific kinase (MuSK) antibodies in the serum Treatment Supportive eye ointment indication to lubricate the eye due to the patient's inability to close the eye Medical glucocorticoids indication oral glucocorticoids are the mainstay of pharmacologic treatment in patients with acute idiopathic Bell palsy Complications Ocular manifestations corneal drying and abrasion Prognosis Most patients recover