Evaluation of CyberKnife Radiosurgery for Recurrent Trigeminal Neuralgia.

Aldo Berti,Gail Suarez,George Ibars,Alex Sabo,James G Schwade,Robert E Jacobson,Xiaodong Wu,Michelle Granville

doi:10.7759/cureus.2598

Abstract

Stereotactic radiosurgery (SRS) has evolved as an accepted treatment for medication resistant trigeminal neuralgia. Initial results are very good but follow-up over three to five years shows a gradual return of pain in up to 50% of treated patients, often requiring further treatment. The results with repeat SRS using the isocentric Gamma Knife (GK) (Elekta, Stockholm, Sweden), especially in patients having initially good results, are very similar to the outcomes after the initial treatment although there is an increased risk of residual facial numbness secondary to the additional radiation dose to the trigeminal nerve. However, after 2000, non-isocentric SRS systems began to be used for treating trigeminal neuralgia including the CyberKnife (CK) (Accuray, Sunnyvale, California) as well as various linear accelerator (LINAC) based systems. This report specifically examines a series of recurrent trigeminal cases treated by the same group of physicians with the CK system. Similar doses and locations on the trigeminal nerve and/or the root entry zone were used for both initial and repeat SRS treatment regardless of system used. Although there are numerous series reporting the use of GK for recurrent treatment for recurrent trigeminal neuralgia, there are no series reviewing the results and long-term effectiveness using CK for repeat SRS for recurrent trigeminal pain. We reviewed 23 cases that had initial treatment for trigeminal neuralgia either surgically or with SRS with either the GK or CK and then a later second procedure only with CK. The follow-up after the second CK SRS ranged from three to 13 years found that the results are very similar to the multiple reports in the literature describing second or third SRS treatments with the GK. Results of repeat radiosurgery treatment of recurrent trigeminal neuralgia appear to be independent of the system used and are primarily based on proper target and dose to the trigeminal nerve.

Highlights

After initial success between 75 to 93%, the failure rate gradually increases with continued follow-up over three, five, and 10 years after the initial treatment, so that up to 50% of the patients with initial good results based on the Barrow Neurologic Institute (BNI) scale are faced with the need for possible retreatment [1,3,4,5]
It is possible with careful evaluation of the dosing to the adjacent brainstem, temporal lobe, cornea, and other critical structures that additional treatment beyond the second stereotactic radiosurgery (SRS) can be tolerated with recurrent trigeminal neuralgia [41,42,48]
The results demonstrate similar effectiveness with excellent and good results in the immediate two to three years after the second SRS being about 60%

Summary

Introduction

CC-BY 3.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. In follow-up after initial SRS, the majority of patients continue with good relief up to the second or third year and the results gradually deteriorate with pain recurrence [31]. The average second dose with the CyberKnife was 63.76 Gy, 10% lower than the initial dose, ranging between 60 to 75 Gy. Review of the actual radiosurgery plans revealed that 18 of the 23 cases treated between four and six millimeters of the trigeminal nerve and only five of the 23 had any extension of the radiation field into the root entry zone of the adjacent pons (Figure 1). Three patients had later radiofrequency trigeminal rhizotomy rather than a third SRS treatment at three, four, and six years after the repeat procedure, one had a balloon compression and two patients were able to maintain pain control with peripheral trigeminal branch blocks. Over 12 years only 29% eventually had other procedures, which is consistent with what has been reported after repeat GK studies [1,5,33,34,35,36,37,38,39,40]

Discussion

Findings

Conclusions

Disclosures