A thorough medical history and physical examination , including a neurological examination , are the first steps in making a diagnosis. This alone may be sufficient to diagnose Bell's Palsy, in the absence of other findings.  Additional investigations may be pursued, including blood tests such as ESR for inflammation, and blood sugar levels for diabetes. If other specific causes, such as sarcoidosis or Lyme disease are suspected, specific tests such as angiotensin converting enzyme levels, chest x-ray or Lyme titer may be pursued.  If there is a history of trauma, or a tumour is suspected, a CT scan may be used.
Decompression – Mastoid decompression of the facial nerve is done during hospitalization and may require a stay of 2 to 4 days. An incision is made behind the ear and the rigid mastoid bone around the swollen nerve is removed which relieves the pressure so that the circulation may be restored. Middle fossa facial nerve decompression takes place when there deeper portions of the facial nerve are involved. This may involve an incision above the ear, with removal of a small portion of the skull. Facial nerve graft is necessary at time if facial nerve damage is extensive. A skin sensation nerve is removed from the neck and transplanted into the ear bone to replace the diseased portion of the facial nerve. Total paralysis will be present until the nerve re-grows through the graft. This usually takes 6 to 15 months. Some facial weakness may be permanent.