Radiosurgical target distance from the root entry zone in the treatment of trigeminal neuralgia.
OBJECTIVE
Stereotactic radiosurgery (SRS) provides a noninvasive treatment modality for patients with medically refractory trigeminal neuralgia. The root entry zone (REZ) has been proposed to be an ideal stereotactic target because it is partially composed of centrally produced myelin, conferring a theoretical increased sensitivity to irradiation as well as increased susceptibility to neurovascular conflict, making it the site in which nociceptive signals likely arise. The aim of this study is to determine if there is a statistically and clinically significant difference in pain relief or facial hypesthesia following SRS based on distance of the stereotactic isocenter from REZ.


METHODS
Patients undergoing Novalis radiosurgery for the treatment of trigeminal neuralgia with at least 3 months' follow-up were included in this study. Postoperative outcomes were stratified by Barrow Neurological Institute (BNI) score for pain relief and BNI facial numbness score for facial hypesthesia.


RESULTS
Sixty-seven patients met inclusion criteria and were included in this study. BNI score of I-IIIa was attained in 82% of patients at 3 months and 65% at 1 year following SRS. Distance from isocenter to REZ varied from 0 to 8.6 mm, with a mean of 1.94 ± 1.62 mm. Logistic regression of target-REZ distance against pain relief outcome (patients with score I-IIIa and IIIb-V) was insignificant at 3 months (P = .988), 6 months (P = .925), 9 months (P = .845), and 12 months (P = .547) postoperatively. Furthermore, no significant correlation was found with logistic regression of target-REZ distance with pain relief outcome (patients with score I and score II-IV) (P = .544).


CONCLUSIONS
The current analysis suggests that distance from REZ does not correlate with degree of postoperative pain relief or facial hypesthesia; thus, targeting specific regions within the trigeminal nerve in relation to these anatomical characteristics may not afford any advantage from this perspective.
David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
Justin
J
Sharim
Department of Neurosurgery, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California; Division of Neurosurgery, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan; Doctoral Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University and National Health Research Institutes, Taipei, Taiwan.
Wei-Lun
WL
Lo
Department of Neurosurgery, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
Won
W
Kim
Department of Neurosurgery, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
Srinivas
S
Chivukula
Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
Stephen
S
Tenn
Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
Tania
T
Kaprealian
Department of Neurosurgery, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California; Department of Radiation Oncology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California; Brain Research Institute, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California; Neuroscience Interdepartmental Program, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California. Electronic address: npouratian@mednet.ucla.edu.
Nader
N
Pouratian
D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D016634:Radiosurgery / Q000379:methods*; D014277:Trigeminal Neuralgia / Q000601:surgery* / Q000628:therapy