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Table of Contents    
NI FEATURE: THE EDITORIAL DEBATE V-- PROS AND CONS
Year : 2019  |  Volume : 67  |  Issue : 2  |  Page : 412-413

Radiosurgery for the management of intractable trigeminal neuralgia


Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

Date of Web Publication13-May-2019

Correspondence Address:
Dr. Ajay Niranjan
Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.258017

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How to cite this article:
Niranjan A. Radiosurgery for the management of intractable trigeminal neuralgia. Neurol India 2019;67:412-3

How to cite this URL:
Niranjan A. Radiosurgery for the management of intractable trigeminal neuralgia. Neurol India [serial online] 2019 [cited 2019 Jul 19];67:412-3. Available from: http://www.neurologyindia.com/text.asp?2019/67/2/412/258017




Akdag et al., retrospectively evaluated 21 patients treated with gamma knife radiosurgery (GKS) for trigeminal neuralgia (TN).[1] The authors used the visual analog scale for the pre- and post-radiosurgery assessment of facial pain. At a median follow-up of 11 months, the pain decreased in 16 (76%) and remained unchanged in 5 (24%) patients. One patient developed facial sensory dysfunction and one patient developed facial paresis. The authors have not reported rates of initial pain relief and durable pain relief or recurrence rate. In the figure, the authors have shown the 80% isodose line (not the 50% isodose line, which was mentioned in the method section). Overall, this is a small study with a limited follow-up, which confirms that radiosurgery is a minimally invasive surgical alternative for the management of intractable facial pain.

The outcome of radiosurgery for TN has been extensively reported in literature worldwide. Radiosurgery is now an established procedure for the management of TN. More than 500 peer-reviewed articles evaluating the safety and efficacy of radiosurgery in the treatment of face pain have been published. Pain relief, defined as Barrow Neurological Institute (BNI) grades I–IIIb, can be achieved in 75%–90% of patients after radiosurgery for type 1 TN.

In a long-term outcome study involving 497 patients with classical TN treated with radiosurgery, Régis et al., reported that 92% of patients were initially pain-free in a median time of 10 days.[2] However, about one-third of patients experienced recurrence of pain within 2 years. In our study involving 503 patients, the initial pain relief rate after TN radiosurgery was 89%.[3] The BNI I–IIIa pain relief was 73%, 65%, and 41% at 1, 2, and 3 years, respectively. The BNI I–IIIb pain control was 80%, 71%, and 46% at 1, 2, and 3 years, respectively. The recurrence of facial pain over time highlights the importance of long-term follow-up assessment, as pain may recur in about half of the patients by the third year. A majority of these patients are eligible for a second session of radiosurgery for the management of intractable pain. A repeat radiosurgery is associated with BNI I–IIIb pain control in 88%, 70%, and 44% patients at 1, 2, and 5 years, respectively.[4]

The predictors of durability of pain control after radiosurgery include the type of facial pain (typical vs atypical), the post-radiosurgery BNI score, and the presence of post-radiosurgery sensory dysfunction. Post-radiosurgery sensory loss (numbness) has been identified as a major predictor of durable pain relief. The type or character of TN is also an important consideration. Patients with type 2 TN (those with “atypical features”) are at a greater risk of pain relapse after GKS. More than 70% of patients had an excellent response to radiosurgery if they had no prior surgical intervention, in contrast to 40% patients who had a prior surgical intervention.

In one of our recent studies, we reported that the duration of symptoms of TN prior to radiosurgery was a significant predictor of durable pain relief. We retrospectively evaluated 121 patients with refractory TN and reported a shorter time to pain relief, a longer pain-free interval, and a longer time off medications if the patients were treated within 3 years of TN onset, and GKS was used as an initial surgical procedure.[5]

Although most studies have used 80 Gy as the central dose for TN radiosurgery, the emphasis during dose planning should be on optimizing the treatment for the individual patient by evaluating the integral dose delivered to the nerve. We have reported that an integral dose between 1.4 and 2.7 mJ was associated with a high rate of pain control and a lower rate of facial dysfunction.[6] An integral dose higher than 2.7 mJ leads to higher rates of sensory loss without further improving pain outcome. Doses lower than 1.4 mJ were associated with lower rates of pain relief. Future studies are needed to determine whether customizing the integral dose to the trigeminal nerve will result in longer pain-free outcomes after radiosurgery.

Trigeminal nerve sensory dysfunction is the most common side effect of TN radiosurgery. The rates of persistent sensory dysfunction vary from 10% to 40%. We reported a sensory dysfunction rate of 10.5% for the initial radiosurgery and a rate of 21% for the repeat radiosurgery. The location of the target isocenter may determine the extent of sensory dysfunction after radiosurgery. Radiosurgical targets in the anterior cisternal portion of the nerve are associated with lower rates of numbness (10%), whereas higher radiation doses to the nerve and the brain-stem edge are associated with higher rates of facial numbness. A longer length of the nerve included within the target zone has been shown to result in a higher complication rate with no significant difference in pain freedom rates. Facial numbness, predictive of long-term response to radiosurgery, is generally not bothersome to patients. However, severe trigeminal sensory dysfunction may be bothersome to some patients.

Radiosurgery is an effective treatment approach for the management of TN, and its results are comparable to that of other ablative techniques. Overall, radiosurgery for TN has a lower rate of complications, the most common of which is trigeminal nerve dysfunction. Although microvascular decompression is considered the best management option in eligible patients due to higher rates of durable pain relief, an increasing number of physicians and patients prefer radiosurgery to avoid complications related to invasive surgical procedures. Radiosurgery is an ideal option for elderly or high surgical risk patients with intractable TN.



 
  References Top

1.
Akdag H, Comert D, Akdur K, Sakarcan A, Seyithanoglu H, Hatiboglu MA. The efficacy of gamma knife radiosurgery in patients with trigeminal neuralgia: The initial experience of the Bezmialem Vakif University. Neurol India 2019;67:476-80.  Back to cited text no. 1
  [Full text]  
2.
Régis J, Tuleasca C, Resseguier N, Carron R, Donnet A, Gaudart J, et al. Long-term safety and efficacy of Gamma knife surgery in classical trigeminal neuralgia: A 497-patient historical cohort study. J Neurosurg 2016;124:1079-87.  Back to cited text no. 2
    
3.
Kondziolka D, Zorro O, Lobato-Polo J, Kano H, Flannery TJ, Flickinger JC, et al. Gamma knife stereotactic radiosurgery for idiopathic trigeminal neuralgia. J Neurosurg 2010;112:758-65.  Back to cited text no. 3
    
4.
Park KJ, Kondziolka D, Berkowitz O, Kano H, Novotny J Jr, Niranjan A, et al. Repeat gamma knife radiosurgery for trigeminal neuralgia. Neurosurgery 2012;70:295-305.  Back to cited text no. 4
    
5.
Mousavi SH, Niranjan A, Huang MJ, Laghari FJ, Shin SS, Mindlin JL, et al. Early radiosurgery provides superior pain relief for trigeminal neuralgia patients. Neurology 2015;85:2159-65.  Back to cited text no. 5
    
6.
Mousavi SH, Niranjan A, Akpinar B, Monaco EA, Cohen J, Bhatnagar J, et al. Aproposed plan for personalized radiosurgery in patients with trigeminal neuralgia. J Neurosurg 2018;128:452-9.  Back to cited text no. 6
    




 

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