Glycerol, a component of fats, is toxic to nerve fibres when in direct contact with them, so injections can be used to gradually damage the nerve, preventing the transmission of pain.
It normally takes around an hour, during which you are awake but heavily sedated. The cheek is numbed with local anaesthetic and a hollow needle is then guided into position at the trigeminal ganglion. After checking the position of the needle with an X-ray, dye is injected into the pea-sized cavity around the ganglion to establish the amount of glycerol needed for the procedure, generally with the patient sitting upright.
Glycerol is then injected into the cavity, a process that is painful for several minutes. The glycerol gradually damages the nerve fibres enough to interfere with the pain signals.
You will be required to sit upright for a couple of hours after the procedure, to stop the glycerol draining out before it has had time to work. Most people can go home soon afterwards. Pain relief should follow in the days after the procedure, if not immediately.
It may take several days or even a week for pain relief to occur.
It is less effective for atypical TN cases and could even make neuropathic pain worse.