What is the role of gamma knife surgery (GKS) in the treatment of trigeminal neuralgia (TN)?

Updated: Sep 30, 2019
  • Author: Kim J Burchiel, MD, FACS; Chief Editor: Brian H Kopell, MD  more...
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Answer

In 1953, Leksell irradiated the trigeminal nerve in 2 patients with good initial success, but the data were not published until 1971. [14] Progress with GKS began to accelerate when, in the 1990s, surgeons learned to target the nerve precisely with stereotactic magnetic resonance imaging (MRI), to determine the proper radiation dose for quickly relieving pain without incurring facial sensory loss, and to ascertain the length of nerve to be radiated. [15] Since 2000, GKS has become more widely available.

Stereotactic GKS is among the newest techniques for treating TN. It is less technically demanding and less operator-dependent than the percutaneous procedures, and it is the least invasive of all the surgical procedures. It appears to be about as effective as the percutaneous procedures, even in patients in whom prior surgery or medication trials failed, but it often takes weeks to months to bring relief and costs considerably more.

GKS consists of multiple rays (>200) of high-energy photons concentrated with high accuracy to deliver a 70-90 Gy dose to the target (ie, the trigeminal nerve root). [16, 17] This treatment destroys specific components of the nerve.

GKS can be used after a patient does not respond to any of the abovementioned procedures, including GKS itself. The device contains a stable source of radiation (60-Co) that frees this technique from requiring an external source of radioactivity (eg, cyclotron).

Of those treated with GKS, 60% of patients are immediately free of pain, and more than 75% of patients have greater than 50% relief after 1.5 years. Recurrence rates are around 25% between 1 and 3 years, and 50% at 3–4 years.  

In a study of 106 subjects, Kondziolka et al found that most patients already had no relief with either microvascular decompression or glycerol rhizotomy. [17] At a median follow-up point of 18 months, 60% of patients were pain free, 17% were moderately improved, and 23% were minimally or not improved. They concluded that this technique is minimally invasive, is associated with a low risk (10%) of facial paresthesias or sensory loss, and offers a high rate (86%) of significant, initial pain relief.

Henson compared GKS with PRGR in 188 patients and concluded that GKS improved pain more consistently and induced less residual facial paresthesia. Pollack reviewed a group of 121 individuals who underwent one or the other procedure and found the rates of complete pain relief similar, about 60% at 6 months and 54% at 24 months.

In a study of 151 patients, Sheehan et al reported that 47% were pain-free after 1 year and 34% after 3 years [18] ; 9% suffered incurred new facial numbness after the procedure. In a similar study of 49 patients followed for a mean of 49 months, one third of whom had also failed either MVD or PRGR, GKS provided complete relief, even off medications, in 14 patients (32%) and partial but durable relief in 27 patients (61%) (McNatt). Others report rather disparate complete pain relief, from 42% (Jawahar) to 59 % (Drzymala) to 60% (Pollack) to 80% (Urgosik).

In these prospective but open and uncontrolled trials, complete pain relief predictably waned substantially by year 3-5, as with the percutaneous procedures. Pain relief also arrives much more slowly, often coming only 3-12 weeks after the procedure, too long a wait perhaps for some individuals. New facial numbness or paresthesias develop slowly over the first 12-15 months after GSK, reaching bothersome levels in 9-20% of patients.


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