Gamma knife radiosurgery for trigeminal neuralgia mechanism

Gamma knife radiosurgery for trigeminal neuralgia mechanism

Gamma Knife radiosurgery for trigeminal neuralgia (GKRS) is a noninvasive surgical treatment option. The long-term microstructural consequences of radiosurgery and their association with pain relief remain unclear.

Studies focusing on the electrophysiology properties of partially demyelinated trigeminal nerves submitted to radiosurgery are vital to truly advance our current knowledge in the field 1).

To better understand this topic, Shih-Ping Hung et al., used diffusion tensor imaging (DTI) to characterize the effects of GKRS on trigeminal nerve microstructure over multiple posttreatment time points.

Ninety-two sets of 3-T anatomical and diffusion weighted MR images from 55 patients with TN treated by GKRS were divided within 6-, 12-, and 24-month posttreatment time points into responder and nonresponder subgroups (≥ 75% and < 75% reduction in posttreatment pain intensity, respectively). Within each subgroup, posttreatment pain intensity was then assessed against pretreatment levels and followed by DTI metric analyses, contrasting treated and contralateral control nerves to identify specific biomarkers of successful pain relief.

GKRS resulted in successful pain relief that was accompanied by asynchronous reductions in fractional anisotropy (FA), which maximized 24 months after treatment. While GKRS responders demonstrated significantly reduced FA within the radiosurgery target 12 and 24 months posttreatment (p < 0.05 and p < 0.01, respectively), nonresponders had statistically indistinguishable DTI metrics between nerve types at each time point.

Ultimately, this study serves as the first step toward an improved understanding of the long-term microstructural effect of radiosurgery on TN. Given that FA reductions remained specific to responders and were absent in nonresponders up to 24 months posttreatment, FA changes have the potential of serving as temporally consistent biomarkers of optimal pain relief following radiosurgical treatment for classic TN 2).

Histopathology examination of the trigeminal nerve in humans after radiosurgery is rarely performed and has produced controversial results.

There is evidence of histological damage of the trigeminal nerve fibers after radiosurgery therapy. Whether or not the presence and degree of nerve damage correlate with the degree of clinical benefit and side effects are not revealed and need to be explored in future studies 3).

Existing studies leave important doubts as to optimal treatment doses or the therapeutic target, long-term recurrence, and do not help identify which subgroups of patients could most benefit from this technique 4).



Gorgulho A. Radiation mechanisms of pain control in classical trigeminal neuralgia. Surg Neurol Int. 2012;3(Suppl 1):S17-25. doi: 10.4103/2152-7806.91606. Epub 2012 Jan 14. PubMed PMID: 22826806; PubMed Central PMCID: PMC3400477.

Shih-Ping Hung P, Tohyama S, Zhang JY, Hodaie M. Temporal disconnection between pain relief and trigeminal nerve microstructural changes after Gamma Knife radiosurgery for trigeminal neuralgia. J Neurosurg. 2019 Jul 12:1-9. doi: 10.3171/2019.4.JNS19380. [Epub ahead of print] PubMed PMID: 31299654.

Al-Otaibi F, Alhindi H, Alhebshi A, Albloushi M, Baeesa S, Hodaie M. Histopathological effects of radiosurgery on a human trigeminal nerve. Surg Neurol Int. 2014 Jan 18;4(Suppl 6):S462-7. doi: 10.4103/2152-7806.125463. eCollection 2013. PubMed PMID: 24605252.

Varela-Lema L, Lopez-Garcia M, Maceira-Rozas M, Munoz-Garzon V. Linear Accelerator Stereotactic Radiosurgery for Trigeminal Neuralgia. Pain Physician. 2015 Jan-Feb;18(1):15-27. PubMed PMID: 25675056.

Percutaneous trigeminal rhizotomy

Percutaneous trigeminal rhizotomy

Percutaneous trigeminal rhizotomy are invasive percutaneous techniques for trigeminal neuralgia that remain safe, simple, and effective for achieving good pain control while minimizing procedural risk 1).

It has been associated with serious complications related to the cannulation of the foramen ovale. Some of these complications, such as internal carotid artery injury, are potentially lethal.

Neuronavigation was proposed as a method to increase the procedure’s safety. All of the techniques described so far rely on pre- or intraoperative computed tomography scanning. Lepski et al. present a simple method based on magnetic resonance imaging (MRI) (radiation free) used to target the foramen ovale under navigation guidance.

This method proved to be safe and effective, and it is especially recommended for young, inexperienced neurosurgeons. 2).


Percutaneous radiofrequency trigeminal rhizotomy

Percutaneous balloon compression trigeminal rhizotomy

Percutaneous glycerol trigeminal rhizotomy.

Although all 3 techniques are generally safe, efficient, and effective, a clear consensus has not been reached regarding their specific indications and degree of efficacy 3).

They differ in method and specificity of nerve injury. BC selectively injures larger pain fibers while sparing small fibers and does not require an awake, cooperative patient. Pain control rates up to 91% at 6 months and 66% at 3 years have been reported. RF allows somatotopic nerve mapping and selective division lesioning and provides pain relief in up to 97% of patients initially and 58% at 5 years. Multiple treatments improve outcomes but carry significant morbidity risk. GR offers similar pain-free outcomes of 90% at 6 months and 54% at 3 years but with higher complication rates (25% vs 16%) compared with BC. Advantages of percutaneous techniques include shorter procedure duration, minimal anesthesia risk, and in the case of GR and RF, immediate patient feedback 4).

In a systematic review and meta-analysis Percutaneous radiofrequency trigeminal rhizotomy is associated with statistically significant higher odds for immediate pain relief and anesthesia and lower risk for post-operative herpes eruption as compared to Percutaneous glycerol trigeminal rhizotomy. Patients in the Percutaneous balloon compression trigeminal rhizotomy group had a statistically significant higher risk to develop post-operative mastication weakness and diplopia when compared to Percutaneous glycerol trigeminal rhizotomy 5).


A real-time augmented reality simulator for percutaneous trigeminal rhizotomy was developed using the ImmersiveTouch platform. Ninety-two neurosurgery residents tested the simulator at American Association of Neurological Surgeons Top Gun 2014. Postgraduate year (PGY), number of fluoroscopy shots, the distance from the ideal entry point, and the distance from the ideal target were recorded by the system during each simulation session. Final performance score was calculated considering the number of fluoroscopy shots and distances from entry and target points (a lower score is better). The impact of PGY level on residents’ performance was analyzed.

Seventy-one residents provided their PGY-level and simulator performance data; 38% were senior residents and 62% were junior residents. The mean distance from the entry point (9.4 mm vs 12.6 mm, P = .01), the distance from the target (12.0 mm vs 15.2 mm, P = .16), and final score (31.1 vs 37.7, P = .02) were lower in senior than in junior residents. The mean number of fluoroscopy shots (9.8 vs 10.0, P = .88) was similar in these 2 groups. Linear regression analysis showed that increasing PGY level is significantly associated with a decreased distance from the ideal entry point (P = .001), a shorter distance from target (P = .05), a better final score (P = .007), but not number of fluoroscopy shots (P = .52).

Because technical performance of percutaneous rhizotomy increases with training, we proposed that the skills in performing the procedure in our virtual reality model would also increase with PGY level, if our simulator models the actual procedure. Our results confirm this hypothesis and demonstrate construct validity 6).



Cheng JS, Lim DA, Chang EF, Barbaro NM. A review of percutaneous treatments for trigeminal neuralgia. Neurosurgery. 2014 Mar;10 Suppl 1:25-33; discussion 33. doi: 10.1227/NEU.00000000000001687. Review. Erratum in: Neurosurgery. 2014 Jun; 10 Suppl 2:372. PubMed PMID: 24509496.

Lepski G, Filho PM, Ramina K, Bisdas S, Ernemann U, Tatagiba M, Morgalla M, Feigl G. MRI-Based Radiation-Free Method for Navigated Percutaneous Radiofrequency Trigeminal Rhizotomy. J Neurol Surg A Cent Eur Neurosurg. 2015 Jan 16. [Epub ahead of print] PubMed PMID: 25594821.

Missios S, Mohammadi AM, Barnett GH. Percutaneous treatments for trigeminal neuralgia. Neurosurg Clin N Am. 2014 Oct;25(4):751-62. doi: 10.1016/ Epub 2014 Aug 3. PubMed PMID: 25240662.

Cheng JS, Lim DA, Chang EF, Barbaro NM. A Review of Percutaneous Treatments for Trigeminal Neuralgia. Neurosurgery. 2013 Sep 23. [Epub ahead of print] PubMed PMID: 24064481.

Texakalidis P, Xenos D, Tora MS, Wetzel JS, Boulis NM. Comparative safety and efficacy of percutaneous approaches for the treatment of trigeminal neuralgia: A systematic review and meta-analysis. Clin Neurol Neurosurg. 2019 May 14;182:112-122. doi: 10.1016/j.clineuro.2019.05.011. [Epub ahead of print] Review. PubMed PMID: 31121470.

Shakur SF, Luciano CJ, Kania P, Roitberg BZ, Banerjee PP, Slavin KV, Sorenson J, Charbel FT, Alaraj A. Usefulness of a Virtual Reality Percutaneous Trigeminal Rhizotomy Simulator in Neurosurgical Training. Neurosurgery. 2015 Sep;11 Suppl 3:420-5; discussion 425. doi: 10.1227/NEU.0000000000000853. PubMed PMID: 26103444.

Handbook of Trigeminal Neuralgia

Handbook of Trigeminal Neuralgia

Girija Prasad Rath (Editor)

Price: $149.99


This book covers all aspects of trigeminal neuralgia (TGN) which is a common yet very painful condition of face and scalp. Chapters include historical perspective of the condition, clinical presentations, diagnosismanagement strategy, drug therapy, different interventional techniques utilized, and non-invasive modalities offered. The book has ample images to explain three main percutaneous procedures carried out for this condition such as radiofrequency thermocoagulation, glycerol rhizolysis and balloon microcompression in detail. It also covers open neurosurgical procedures including microvascular decompression and certain non-conventional and non-invasive methods.

This book provides assistance to pain physicians to have a comprehensive knowledge of trigeminal neuralgia. It is also relevant to neurosurgeons, neurologists, anesthesiologists, dental surgeons and resident doctors.

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