FUNCTIONAL RADIOSURGERY NONISOCENTRIC RADIOSURGICAL RHIZOTOMY FOR TRIGEMINAL NEURALGIA John R. Adler, Jr., M.D. Department of Neurosurgery, OBJECTIVE: Although stereotactic radiosurgery is an established procedure for treat- Stanford University Medical Center, ing trigeminal neuralgia (TN), the likelihood of a prompt and durable complete response Stanford, California is not assured. Moreover, the incidence of facial numbness remains a challenge. To Regina Bower, M.D. address these limitations, a new, more anatomic radiosurgical procedure was devel- oped that uses the CyberKnife (Accuray, Inc., Sunnyvale, CA) to lesion an elongated Department of Neurological Surgery, Mayo Clinic College of Medicine, segment of the retrogasserian cisternal portion of the trigeminal sensory root. Because Rochester, Minnesota the initial experience with this approach resulted in an unacceptably high incidence of facial numbness, a gradual dose and volume de- escalation was performed over sev- Gaurav Gupta, M.S.E. eral years. In this single- institution prospective study, we evaluated clinical outcomes Department of Neurosurgery, in a group of TN patients who underwent lesioning with seemingly optimized non- Stanford University Medical Center, Stanford, California isocentric radiosurgical parameters. METHODS: Forty- six patients with intractable idiopathic TN were treated between Michael Lim, M.D. January 2005 and June 2007. Eligible patients were either poor surgical candidates or had Department of Neurosurgery, failed previous microvascular decompression or destructive procedures. During a single Johns Hopkins School of Medicine, radiosurgical session, a 6-mm segment of the affected nerve was treated with a mean Baltimore, Maryland marginal prescription dose of 58.3 Gy and a mean maximal dose of 73.5 Gy. Monthly neurosurgical follow- up was performed until the patient became pain- free. Longer- term Allen Efron, M.D. follow- up was performed both in the clinic and over the telephone. Outcomes were Department of Neurosurgery, Ͼ Stanford University Medical Center, graded as excellent (pain- free and off medication), good ( 90% improvement while still Stanford, California on medication), fair (50–90% improvement), or poor (no change or worse). Facial numb- ness was assessed using the Barrow Neurological Institute Facial Numbness Scale score. Iris C. Gibbs, M.D. RESULTS: Symptoms disappeared completely in 39 patients (85%) after a mean latency Department of Radiation Oncology, of 5.2 weeks. In most of these patients, pain relief began within the first week. TN Stanford University Medical Center, Stanford, California recurred in a single patient after a pain- free interval of 7 months; all symptoms abated after a second radiosurgical procedure. Four additional patients underwent a repeat Steven D. Chang, M.D. rhizotomy after failing to respond adequately to the first operation. After a mean follow- Department of Neurosurgery, up period of 14.7 months, patient- reported outcomes were excellent in 33 patients Stanford University Medical Center, (72%), good in 11 patients (24%), and poor/no improvement in 2 patients (4%). Significant Stanford, California ipsilateral facial numbness (Grade III on the Barrow Neurological Institute Scale) was reported in 7 patients (15%). Scott G. Soltys, M.D. Department of Radiation Oncology, CONCLUSION: Optimized nonisocentric CyberKnife parameters for TN treatment Stanford University Medical Center, resulted in high rates of pain relief and a more acceptable incidence of facial numbness Stanford, California than reported previously. Longer follow- up periods will be required to establish whether or not the durability of symptom relief after lesioning an elongated segment of the Reprint requests: John R. Adler, Jr., M.D., trigeminal root is superior to isocentric radiosurgical rhizotomy. Department of Neurosurgery, KEY WORDS: CyberKnife, Nonisocentric, Radiosurgery, Rhizotomy, Trigeminal neuralgia Stanford University Medical Center, 300 Pasteur Drive, Neurosurgery 64:A84–A90, 2009 DOI: 10.1227/01.NEU.0000341631.49154.62 www.neurosurgery- online.com Stanford, CA 94305. Email: [email protected] he treatment of trigeminal neuralgia (TN) Received, June 13, 2008. ABBREVIATIONS: BNI, Barrow Neurological by radiosurgical rhizotomy was con- Accepted, October 27, 2008. Institute; CT, computed tomographic; Dmax, ceived by Lars Leksell (9). Over the past maximal dose; MRI, magnetic resonance imag- T Copyright © 2009 by the ing; TN, trigeminal neuralgia several decades, radiosurgical parameters for Congress of Neurological Surgeons treating this condition have been optimized, A84 | VOLUME 64 | NUMBER 2 | FEBRUARY 2009 SUPPLEMENT www.neurosurgery-online.com CYBERKNIFE RHIZOTOMY FOR TRIGEMINAL NEURALGIA especially for the gamma knife. By investigating a range of max- Stanford University Medical Center have been managed with a imal doses (Dmax), from 60 to 90 Gy (2, 8, 16), and a variety of relatively consistent radiosurgical lesion. In this study, we ana- lesion locations along the retrogasserian trigeminal root (from lyze the outcomes in this cohort of patients and compare them the root entry zone to just proximal to the semilunar ganglion) with outcomes in published radiosurgery series. (3, 5, 8, 12, 15, 16, 21), neurosurgeons are now able to maximize the likelihood of pain relief while minimizing the risk of facial PATIENTS AND METHODS dysesthesias or numbness. Recent outcome studies report that complete long- term pain relief can be achieved in 66 to 84% of Patients patients undergoing radiosurgical rhizotomy alone, whereas Patient data were reviewed under an Institutional Review Board- varying degrees of facial numbness are observed in 10 to 54% of approved protocol. All cases had idiopathic TN of several years’ dura- cases (13, 14, 16, 18). As a general rule, better pain relief appears tion; either pain symptoms were refractory to standard anticonvul- to correlate with higher rates of sensory loss (16, 19, 20). sants or the patient experienced severe drug- induced side effects. Cases Given the straightforward objective of radiosurgical rhizo- involving either multiple sclerosis or tumors were excluded from this tomy in patients with TN, it is unclear why outcomes vary so analysis, as was any patient with atypical facial pain. A total of 46 con- much among patients. The long latency to pain relief and its secutive TN patients who met these criteria underwent lesioning at poor durability in some patients are lingering shortcomings of Stanford University Medical Center by CyberKnife rhizotomy between the procedure. In contrast, immediate, long- lasting symptom January 2005 and June 2007 (Table 1). In this group were 17 men and 29 relief is routinely achieved in similar patients who undergo less women with a median age of 78 years (range, 40–94 years). The aver- expensive percutaneous radiofrequency rhizotomy (22). Perhaps age time from the earliest onset of TN symptoms to stereotactic radio- surgery was 8.6 years (range, 8 months–20 years). Eleven patients (24%) with these limitations in mind, some neurosurgeons have sought had failed previous surgical procedures (averaging 1.8 procedures per to improve the outcome after radiosurgery by increasing the patient) directed toward their trigeminal symptoms; previous proce- length of the irradiated nerve (1, 6, 11). However, this concept dures included microvascular decompression (14 patients) and rhizo- was discredited in a small randomized study by Flickinger et al. tomy by means of an open (3 patients), glycerol (5 patients), or gamma (6). In a multi- institutional study that used the gamma knife, 2 knife (3 patients) technique. Eleven patients (24%) reported either a adjacent 4-mm shots served to lengthen the segment of lesioned moderate or significant degree of facial numbness before CyberKnife trigeminal nerve. Because of a trend (albeit not statistically sig- rhizotomy, which, unfortunately, was not prospectively scored on the nificant) toward increased “complications” in the experimental Barrow Neurological Institute (BNI) Scale. group, the study was stopped short of complete patient accrual. The investigators concluded: “Increasing the treatment volume Radiosurgical Procedure to include a longer nerve length for trigeminal neuralgia radio- Radiosurgical trigeminal rhizotomy was performed with the surgery does not significantly improve pain relief but may CyberKnife radiosurgical system, using the technique reported previ- increase complications” (6, p 449). Although Flickinger et al. did not provide much qualitative detail, facial numbness and dyses- thesias were central to the early termination of this study. The TABLE 1. Patient characteristicsa outcomes of the study are surprising because they violate the Characteristic No. direct relation between target dose, target volume, and clinical Total patients 46 response that underlies much of radiosurgery. One would have anticipated that any increase in facial numbness would have Male/female 17/29 been accompanied by an improved rate and durability of pain Age (y) relief. It seems possible that chance may have contributed to the Median 78 paradoxical findings observed in the small Flickinger et al. series. Range 40–94 With the goal of enhancing the clinical response to radio- Time from TN onset to radiosurgery (y) surgery, in 2002, the first author (JRA) began to lesion a longer Mean 8.6 segment of the trigeminal sensory root using a relatively homogeneous radiation dose. Because of the capacity of the Range 8–20 CyberKnife (Accuray,