The study intervention is to perform standard somatosensory evoked responses limited to the face during rhizotomy procedures of the gasserian ganglion (trigeminal ganglion) for the treatment of trigeminal neuralgia. The evoked responses will be measured at two locations before and after the clinical rhizotomy including: the standard contralateral scalp (EEG) and at the gasserian ganglion through an FDA-approved recording electrode.

Inclusion Criteria (TGN):

• Adults of 18 years or older
• Scheduled to undergo percutaneous rhizotomy for facial pain

Exclusion Criteria (TGN):

• Facial pain of unclear origin (i.e. not clearly TGN pain)
• Rhizotomy procedure canceled

Inclusion Criteria (Healthy controls)

• Adults of 18 years or older

Exclusion Criteria (Healthy Controls)

• Diagnosis or history of facial pain such as TMD or TGN
• History of migraine
• History of any functional pain disorder: fibromyalgia, IBS, CRPS
• Recent chronic pain (within last month)
• Unwilling to participate for two hours in lab
• Current acute pain

Adults of 18 years or older who are scheduled to undergo percutaneous rhizotomy for facial pain