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STEREOTACTIC RADIOSURGERY FOR TRIGEMINAL NEURALGIA

- Introduction
- SRS Procedure and Results
- Follow-up
- SRS Team
- References

Introduction :

Trigeminal Neuralgia (TN), is a pain syndrome which effects about 10,000 people per year in the United States. It is a severe pain condition, which effects the 5th Cranial Nerve. Patients classically describe the pain, as intermittent sharp, stabbing, shooting, electric shocks. They will often rate the pain at 10/10, with 10 being the worst they can imagine. Some patients report suicidal ideation. The pain is thought to be caused by a blood vessel coming into contact with the 5th Cranial Nerve root as it enters the brainstem. Management options include, medical management, glycerol rhizotomy, radiofrequency rhizotomy, balloon compression, open surgery with microvascular decompression, and Stereotactic Radiosurgery (SRS). SRS can be delivered via Gamma Knife or X-Knife technology. Taha and Tew reported the following surgical results in an extensive literature review in 1996 [1] :

TRIGEMINAL NEURALGIA OUTCOME BY TREATMENT

Initial
Treatment #Pts Pain Relief Pain Recurrence Numbness
Glycerol Rhizotomy 1,217 91% 54% 60%
Radiofrequency Rhizotomy 6,205 98% 23% 98%
Balloon Compression 759 93% 21% 72%
Open Surgery (MVD) 1,417 98% 15% 2%
Partial Rhizotomy 250 92% 18% 100%

Invasive surgical procedures carry risks of infection, bleeding, blood clots, and mortality. Recent years have witnessed the increasing use of SRS in the management of TN. Most investigators have reported that about 70% of patients report complete or significant long-term pain relief after SRS. The only significant complication has been facial numbness, which appears to compare favorably to surgical results. Patients undergoing SRS have frequently been treated with all of the other techniques, so that these SRS results have been achieved in a difficult patient population. The following data are representative of the literature [2-6] :

TRIGEMINAL NEURALGIA OUTCOME WITH SRS

Initial
Author #Pts Pain Relief Pain Recurrence Numbness
Petit 112 77% 16% nr
Pollock 117 57% 2% 25%
Kondziolka 220 86% 30% 10%
Rogers 54 96% nr 10%
Young 110 95% 3% 3%

SRS Procedure :
SRS technique calls for placement of a frame or halo by a Neurosurgeon. The frame serves to hold the patient's head still during SRS. The frame also gives the Radiation Physicist a reference point to perform 3-Dimensional Computer Radiation Treatment Planning. The patient then undergoes MRI, CT Scanning, and a CT Cisternogram for identification of the treatment target. The images are then sent by fiberoptic link for 3-Dimensional Computer Radiation Treatment Planning. The target is the 5th CN V Entry Root Zone into the brainstem. The target and radiation doses are then identified and agreed on by the Neurosurgeon and Radiation Oncologist. Our protocol with the X-Knife has been to deliver 87 Gy to the CN V entry root zone into the brainstem, while limiting the 20% IDL to the anterior surface of the brainstem. We have treated 22 patients over the past year, with 77% (17/22) of patients reporting good to excellent pain relief. Regarding complications, 4% (1/22) have reported facial numbness. These results appear to be comparable to Gamma Knife.
Following completion of SRS treatment planning, the patient undergoes treatment on the Linear Accelerator (X-Knife). SRS treatment typically lasts for about 1 hour. The treatment is painless. Following completion of SRS treatment, the frame is removed and the patient sent to a Hospital Room for overnight observation. There is a slight risk of acute edema and seizures following SRS. So far, we have not seen these problems in any patient.

Follow-up :
Following SRS, pain may resolve immediately. However, this is unusual. The effects of radiation on the nerve usually do not occur for 8-12 weeks. Therefore, we recommend that patients do not begin to taper off of their TN medications until then. If SRS is unsuccessful on the 1st attempt, a 2nd SRS session can be given. About 70% of patients who undergo a 2nd SRS report good to excellent pain relief.

SRS Team :
Our SRS Team includes Neurosurgeons, Radiologists, Radiation Oncologists, Physicists, Nurses, and Radiation Therapy Technologists. Our team has experience in more than 1,000 SRS cases with Gamma Knife, and more than 100 cases with X-Knife.

References :
1. J Neurosurg, 1996 ; 38[5] : 865-871
2. Int J Radiat Oncol Biol Phys, 2003 ; 56[4] : 1147-1153
3. J Neurosurg, 2002 ; 97[2] : 347-353
4. Clin J Pain, 2002 ; 18 [1] : 42-47
5. Int J Radiat Oncol Biol Phys, 2000 ; 47[4] : 1013-1019
6. Stereotact Funct Neurosurg, 1998 ; 70 [1] : 192-199