Trigeminal Evoked Responses to Improve Rhizotomy

Trigeminal neuralgia (TGN) is a debilitating pain syndrome where electrical, shock- like jolts of pain affect the face. Trigeminal somatosensory evoked potentials (TSEPs) provide a promising modality for measuring the trigeminal sensory and nociceptive pathway by using peripheral stimulation of the trigeminal nerve (on the skin) and measuring low latency evoked potentials on the scalp (contralateral sensory cortex). While TSEPs have been measured in the past, it is not clear if implementing TSEPs into a routine neurosurgical rhizotomy procedure will be feasible. This is a prospective cohort study examining the feasibility of routinely performing TSEPs during rhizotomies for TGN.

TGN patients recruited for this study will already be undergoing percutaneous rhizotomy surgery. TSEPs will be measured at baseline prior to surgery. During the rhizotomy procedure, an electrode or balloon is placed through a metal sheath to then damage the nerve. A stylet is introduced to clear tissue from the sheath in preparation for the electrode or balloon. Prior to the final insertion of the RF electrode where the gasserian ganglion will be damaged, we will place a standard stereotactic EEG electrode (SEEG). Following damaging the nerve (clinical procedure), we will record again to measure differences in the TSEPs following cell body damage. The Neuralynx system will be used to record the potentials at 40 KHz.

TSEPS will also be recorded from healthy controls in a lab setting; all procedures for the healthy controls will be non-invasive.

Inclusion Criteria: Adults of 18 years or older Scheduled to undergo percutaneous rhizotomy for facial pain Exclusion Criteria: For TGN: Facial pain of unclear origin (i.e. not clearly TGN pain) or Rhizotomy procedure canceled For Healthy control: Diagnosis or history of facial pain such as TMD or TGN, History of migraine, History of any functional pain disorder: fibromyalgia, IBS, CRPS or Recent chronic pain (within last month)