Letter to the Editor. Microvascular decompression for trigeminal neuralgia: does it matter whether the view is through a microscope or via an endoscope?

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TO THE EDITOR: I read with great interest the article by Zagzoog and colleagues2 (Zagzoog N, Attar A, Takroni R, et al: Endoscopic versus open microvascular decompression for trigeminal neuralgia: a systematic review and comparative meta-analysis. J Neurosurg [epub ahead of print December 7, 2018; DOI: 10.3171/2018.6.JNS172690]). They performed a systematic review to compare the efficacy and the complications of traditional microvascular decompression (MVD) and totally endoscopic MVD (E-MVD) for trigeminal neuralgia (TN). The resolution available with endoscopic systems is improving, and 4K cameras have been introduced to the neurosurgical field as well as other fields.1 With high-magnification endoscopic imaging systems and the use of a high-definition monitor, surgeons can grasp minute details of anatomical structure that are sometimes difficult to discern with a surgical microscope, and this advantage can compensate for the lack of depth.

Zagzoog et al. collected data from articles with clinical results of each procedure in at least 10 patients and showed that E-MVD was associated with pain relief comparable to that achieved with traditional MVD, but with fewer complications. They also compared the recurrence of TN in articles published after 2000 with log-rank analysis, and they found no major difference between the 2 modalities. In this survival analysis, they used only data from articles published after 2000 to ensure an equivalent state of health care and medical technology between the 2 comparison groups. However, the authors also note that their comparison of MVD and E-MVD outcomes “includes MVD articles dating from 1995 to 2017.” It seems odd to compare surgical results of MVD before 2000, since the modern-day craniotomy resulted in the small surgical corridor size comparable to those needed for E-MVD, as the authors describe in the introduction to their article. Moreover, E-MVD would have been performed after some experience with traditional MVD or with supervision of a surgeon with enough experience with traditional MVD, which should create a bias toward better results for E-MVD. Or there could have been publication bias if severe morbidity or mortality occurred when surgeons had just started to perform E-MVD and had not yet had experience with a sufficient number of cases. In TN surgery, the working space is so small that if bleeding occurs under a small craniotomy just large enough for an endoscope, it can be quite difficult to control and can easily end in a critical condition. This situation is different from that of abdominal endoscopic surgery, where the surgeon is operating in a large cavity and can easily obtain a wide opening in an emergency. Hence, we have to be careful to interpret the results of Zagzoog and colleagues’ study.

In addition, there are some differences among E-MVD articles, and in some of them the craniotomy that was used is larger than in traditional keyhole MVD; and in such cases, it is not clear what “less invasive” means. Zagzoog et al. concisely depicted the complications of each group in Fig. 4, and it is interesting to see that the incidence of complications is quite different between articles. This suggests that differences between institutions may be more important than differences between E-MVD and traditional MVD. Facial palsy and hearing loss could occur as a result of retracting the cerebellum in the wrong direction, and what we have to consider may be not the question of whether to see the lesion through the microscope or via the endoscope, but rather to see it from a correct and safe direction.

Last, I wonder whether E-MVD can be performed through a 1-cm incision, as described in the authors’ introduction. Is this measurement correct?

Because Gamma Knife surgery and nerve block as well as medical therapy can be alternative options for TN, we should focus more on improving the safety of surgery rather than focusing on the pursuit of new devices.

Nevertheless, we do appreciate the authors’ effort to clarify the current status of MVD and E-MVD through an extensive analysis.

Disclosures

The author reports no conflict of interest.

References

  • 1

    Rigante MLa Rocca GLauretti LD’Alessandris GQMangiola AAnile C: Preliminary experience with 4K ultra-high definition endoscope: analysis of pros and cons in skull base surgery. Acta Otorhinolaryngol Ital 37:2372412017

  • 2

    Zagzoog NAttar ATakroni RAlotaibi MBReddy K: Endoscopic versus open microvascular decompression for trigeminal neuralgia: a systematic review and comparative meta-analysis. J Neurosurg [epub ahead of print December 7 2018; DOI: 10.3171/2018.6.JNS172690]

INCLUDE WHEN CITING Published online March 22, 2019; DOI: 10.3171/2019.2.JNS1977.

Response

We are grateful to Dr. Kimura for his interest in our work. We appreciate his thorough review and the excellent points he raises regarding our methodologies and conclusions.

Most of the comments he has set forth are in regard to whether the differences noted between traditional microscope-assisted MVD (M-MVD) or E-MVD used to treat TN are truly due to differences purely in the surgical procedures or due to compounding factors and whether our study selection criteria may have led to unintentional bias that could have affected our conclusions. We agree that the points that Dr. Kimura raises should be considered when evaluating clinical studies on this topic.

One of the first points that Dr. Kimura raises is the discrepancy in publication years between the M-MVD and E-MVD articles. For our discussion, we wished to perform a perfunctory examination of current techniques used in MVD for treatment of TN, for which modern methods were used in the mid-1990s. The 2 papers included from 19953 and 19961 varied widely on either side of the M-MVD average for both postsurgical complications and recurrence of pain, with neither skewing the average for the group dramatically. Nevertheless, all statistical comparisons between M-MVD and E-MVD were performed using papers from concurrent years, starting with the year 2000.

The issue of surgeon experience is interesting, and we agree that it should be important to consider. Unfortunately, most of the articles reviewed for both M-MVD and E-MVD made no mention of surgeon experience, either in years or in numbers of cases previously performed. It is possible that there could be a bias toward more experienced surgeons performing E-MVD procedures. This would be a very interesting topic for future research, if it is possible to attain information on surgical expertise and correlate that to incidence of complications or TN recurrence. If surgeon inexperience is a primary contributing factor to higher rates of complications and unsuccessful operations, then this would be especially important to determine. Likewise, the factors contributing to the variation in complication and recurrence rates from within the E-MVD or M-MVD groups should be examined as well (these could be related to experience or possibly reflect minor differences in technique) in order to inform best practices for such procedures.

Finally, with regard to Dr. Kimura’s question about incision size—this is perhaps a matter of the terminology used in our manuscript. For example, the procedure described by Halpern et al. in Minimally Invasive Surgery in 2013 uses a 1-cm incision in the dura through which the endoscope is capable of operating, although the initial skin/musculature incision is 4–6 cm.2 We hope this helps clear up any confusion.

Once again, we would like to thank Dr. Kimura for reading our work and for his supportive comments. The considerations raised in our manuscript and in the issues he has mentioned will hopefully lead to standardized practices that improve the safety of TN treatments for patients.

References

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Article Information

Correspondence Toshikazu Kimura: tkim-tky@umin.ac.jp.

INCLUDE WHEN CITING Published online March 22, 2019; DOI: 10.3171/2018.12.JNS183574.

Disclosures The author reports no conflict of interest.

© AANS, except where prohibited by US copyright law.

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References

  • 1

    Rigante MLa Rocca GLauretti LD’Alessandris GQMangiola AAnile C: Preliminary experience with 4K ultra-high definition endoscope: analysis of pros and cons in skull base surgery. Acta Otorhinolaryngol Ital 37:2372412017

  • 2

    Zagzoog NAttar ATakroni RAlotaibi MBReddy K: Endoscopic versus open microvascular decompression for trigeminal neuralgia: a systematic review and comparative meta-analysis. J Neurosurg [epub ahead of print December 7 2018; DOI: 10.3171/2018.6.JNS172690]

  • 1

    Barker FG IIJannetta PJBissonette DJLarkins MVJho HD: The long-term outcome of microvascular decompression for trigeminal neuralgia. N Engl J Med 334:107710831996

  • 2

    Halpern CHLang SSLee JYK: Fully endoscopic microvascular decompression: our early experience. Minim Invasive Surg 2013:7394322013

  • 3

    Mendoza NIllingworth RD: Trigeminal neuralgia treated by microvascular decompression: a long-term follow-up study. Br J Neurosurg 9:13201995

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