Several percutaneous techniques have been developed to treat pain by injuring the trigeminal ganglion. Percutaneous is the term for procedures in which the nerve, accessed through the cheek, and is compressed (balloon compression,) heated (radio frequency thermal rhizotomy,) or chemically treated (glycerol rhizotomy) to prevent the trigeminal nerve from sending pain signals to the brain. Radiosurgery, often known as Gamma Knife, uses targeted radiation to achieve the same goal. All four procedures share the tactic of partially and selectively damaging the nerve on purpose in order to trade off a chance of reliving pain with a risk of numbness. As such, all four procedures are also known as palliative destructive procedures. Each procedure has its relative advantages and disadvantages.
- Of the percutaneous procedures, radio frequency thermal rhizotomy is associated with the lowest rate of pain recurrence. Studies have documented that pain-free outcomes are strongly associated with the degree of postoperative facial numbness after radio frequency procedures. However, thermal rhizotomy of the trigeminal nerve is associated with the highest incidence of Anesthesia Dolorosa, a very rare condition in which there is constant severe pain in an area of total numbness.
- Glycerol rhizotomy is less likely to produce changes in facial sensation, and the incidence of postoperative differentiation pain is very low; however, the recurrence rate of pain has been estimated to range from 30 to 50 percent.
- Similar to thermal rhizotomy, the goal of balloon compression is facial numbness. Postoperative weakness of the masseter muscle occurs in approximately 25 percent of patients after ganglion compression.
The other issue with palliative destructive procedures is their recurrence rate. Since they are designed to treat the symptom (palliative) and not the cause (potentially curative) of the condition, they tend to have a constant annual recurrence rate. Meta-analyses of these four procedures generally show a median time to recurrence of 3-5 years, however a smaller subset of patients may enjoy relief for up to 10-15 years.
In this procedure, the needle delivers sterile glycerol which damages the trigeminal nerve to block pain signals to the brain. The patient’s pain may recur when the nerve grows back, but the procedure can be repeated.Glycerol rhizotomy risks include bleeding, infection, nausea, vomiting, and Anesthesia Dolorosa.
Radio Frequency Thermal Lesioning
In this procedure, an electrode is threaded through the needle. A mild electrical current is delivered to the trigeminal ganglion through the tip of the electrode. The patient is under anesthesia but conscious so he or she can indicate to the surgeon which part of the nerve is sending the pain signals. Once the location is identified, the patient is sedated. Then the electrode is heated until it damages the nerve fibers, creating a lesion to block pain signals to the brain. If the pain is not eliminated, the surgeon may create additional lesions.This procedure has a higher likelihood of causing Anesthesia Dolorosa than glycerol rhizotomy.
In this procedure, a tiny balloon is threaded through the needle and inflated against the trigeminal ganglion to damage the nerve to block pain signals to the brain. After several minutes, the balloon and needle are removed.
Also known as Gamma Knife and Cyber Knife, in this procedure, the surgeon delivers a single highly concentrated dose of ionizing radiation to a small, precise target at the trigeminal nerve root.
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