Trigeminal Neuralgia is a condition that affects one or more of the three branches of the trigeminal nerve that comes into the face just below the ear, and then branches into three: 1) the forehead 2) just under the eye, and 3) the chin.
I have lived with TN for about twenty-five years. My first episode woke me from a deep sleep, and I thought I had just been stung by a scorpion or something. It is excruciating, and very difficult to diagnose and treat.
It's origin for any given patient is often (usually?) unexplained. It just shows up one day, and then doesn't go away. Sometimes it appears to be congenital, but at other times (like mine) a cause can be presumed, if not exactly proven.
In my case, I was in a car accident (not wearing my seatbelt), and smashed the front windshield with my face. I suffered a blow-out fracture--cracking a hole in the bone that separates the eye cavity from the sinus, and had to have surgery to repair it. About thirty years later I suffered a ruptured disc in my c-spine, as well as my first episode of Trigeminal Neuralgia, both of which can probably be traced to the initial trauma from the car accident and/or the surgery.
I have read that when it is the lower (chin) branch of the nerve that is affected, a lot of people assume that some kind of dental procedure can fix it. Patients have been known to have teeth pulled and/or nerves severed.
Gabapentin is a drug used to treat epilepsy, and his been found to be pretty effective in treating TN. My doc started me on it once we ruled out other possible causes for the pain, and it has been an absolute life saver. I rarely have episodes anymore, and when I do they are usually brief. Unfortunately they are still crazy painful (it feels like an electric shock to the face), but they stop quickly. Gabapentin also helps with the pain from my ruptured disc. Another drug, Lyrica, is also used for nerve pain of various types, but Ive always stuck with gabapentin. When I first started it the only side effect was that I was VERY lethargic for a few weeks, but after that my energy returned and now I dont even notice it. It is cleared by the liver, so you do have to watch your booze intake and keep an eye on your liver function (I get yearly blood tests), but Ive never had a problem.
I dont know if this is your relatives problem, but you might read up on it. ( https://www.mayoclinic.org/diseases-conditions/trigeminal-neuralgia/symptoms-causes/syc-20353344 )
Good luck!