- Most commonly (65-75%) idiopathic (aka Bell's palsy) - which is probably from HSV infection
- Other possibilities: lyme, sarcoid, amyloid, compression from parotid tumor
- For Bells, age peak is 15-45
- Acute dysfunction of muscles controlling facial expression→ inability to smile, raise forehead, close eye on affected side
- With Bell's palsy, onset can be over 72 hours, sometimes decreased lacrimation, hyperacusis
- Weakness or inability to wrinkle forehead, close eye, smile
- With Ramsey-Hunt from VZV, get CN8 involvement too, which causes decreased hearing (sensori-neural), vesicles on ear drum
- If related to mass (e.g. parotid or other tumor), then may be palpable