Elsevier

World Neurosurgery

Volume 113, May 2018, Pages e309-e313
World Neurosurgery

Original Article
Awake Microvascular Decompression for Trigeminal Neuralgia: Concept and Initial Results

https://doi.org/10.1016/j.wneu.2018.02.019Get rights and content

Highlights

  • This is the first reported series of “awake” microvascular decompression (MVD).

  • Intraoperative awake testing for pain relief following MVD may mitigate insufficient decompression, which may be responsible for some failures of MVD.

  • A subset of patients are not considered for MVD due to age or medical comorbidities, and rather are referred for percutaneous or radiosurgery procedures. Awake MVD may expand the indications for the procedure.

Background

In this initial series, we evaluated the use of microvascular decompression (MVD) under an awake anesthesia protocol (“awake” MVD) to assess whether intraoperative pain evaluation can identify and mitigate insufficient decompression of the trigeminal nerve, improving surgical outcomes, and possibly expand the indications of MVD in patients with comorbidities that would preclude the use of general endotracheal anesthesia (GEA).

Methods

An Institutional Review Board–approved prospective study of 10 consecutive adults who underwent MVD for trigeminal neuralgia (TN) was conducted. The primary outcome measure was postoperative TN pain quantified on the Barrow Neurological Institute (BNI) Pain Severity Scale.

Results

The median patient age was 65.5 years, with a female:male ratio of 6:4. All 10 patients tolerated the procedure well and did not require GEA intraoperatively or postoperatively. Nine patients had a successful surgical outcome (BNI score I, n = 5; BNI score II, n = 4). One patient did not have pain relief (BNI score IV). This same patient also developed a pseudomeningocele, which was the sole surgical complication observed in this series. One patient experienced recurrence of pain at 11 months, with BNI score increasing from I to II. The median duration of follow-up was 16.5 months. Two patients did not experienced resolution of evoked pain during intraoperative awake testing following decompression. Further intraoperative exploration revealed secondary offending vessels that were subsequently decompressed, leading to resolution of pain.

Conclusions

Intraoperative awake testing for treatment efficacy may increase the success rate of MVD by rapidly identifying and mitigating insufficient cranial nerve V decompression.

Introduction

The facial pain syndrome consistent with what we now know as trigeminal neuralgia (TN) was first described by Avicenna in 1037 AD.1 Some 700 hundred years later, Nicolas André coined the term “tic douloureux” in 1756 to describe the same pain syndrome, believing the intractable facial pain to be a consequence of compression of the facial sensory nerves.2 However, it was not until the early 20th century that Walter E. Dandy correlated the facial pain initially described by Avicenna and André to vascular compression of cranial nerve (CN) V.3

Dandy's discovery instigated numerous advances in the surgical management of TN, including the introduction of stereotactic radiosurgery (RS) by Lars Leksell in 19514 and of microvascular decompression (MVD) by Peter Jannetta in 1967.1 However, stereotactic RS did not truly become a feasible treatment option until the advent of the gamma knife in 1968. Since then, MVD has been established as the most efficacious treatment for TN.5

In this study, we assessed whether intraoperative pain evaluation under an awake anesthesia protocol (“awake MVD”) can identify and mitigate insufficient decompression of the trigeminal nerve, improving surgical outcomes. In addition, we evaluated whether awake MVD could expand the indications for this procedure in a subset of patients who are deemed too high risk for MVD based on their medical comorbidities and are referred for percutaneous procedures or RS.

Awake craniotomy is a well-established procedure that has been widely used for glioma resection and functional procedures that involve neurologic monitoring of eloquent cortical and subcortical areas.6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 Awake procedures also have been used for similar purposes in cerebrovascular surgery, specifically in carotid endarterectomy.25, 26, 27 Multiple case reports describing the use of awake craniotomy for aneurysms have also been presented in the literature, including 3 cases of distal vessel occlusion for mycotic aneurysm,28 ophthalmic artery aneurysm clipping with intraoperative visual testing,29 giant fusiform middle cerebral artery aneurysm trapping,30 and anterior choroidal artery aneurysm clipping.31 We recently published the first prospective series (n = 30) of awake clipping of unruptured intracranial aneurysms and compared our results with those of our own controls (retrospective series; n = 30) who underwent standard unruptured intracranial aneurysm clipping under general endotracheal anesthesia (GEA).32 The median length of stay was reduced from 5 days in our GEA control group to 3 days in our prospective awake craniotomy group. In addition, the rate of procedure-related stroke was reduced from 10% in the GEA control group to 3% in the prospective awake craniotomy group.32

We also recently published our experience in performing awake high-flow extracranial-to-intracranial bypass for complex aneurysms. We compared outcomes with those of our historical cohort who underwent the procedure under GEA. Absolute risk reduction in the awake craniotomy group (n = 30) relative to the historical control group (n = 110) was 7% for cerebrovascular accident, 9% for discharge to rehabilitation, and 10% for graft patency.33

Section snippets

Methods

We conducted a prospective study of 10 consecutive patients undergoing awake MVD for TN between August 2015 and August 2016. This report included all patients who underwent awake MVD for TN performed by the senior author (S.I.A.). During this interval, no patients underwent MVD with GEA. Pain outcomes were quantified using the Barrow Neurological Institute (BNI) Pain Intensity Scale34 (Table 1), with efficacious relief of pain defined as a score of I or II. Preoperatively, all patients were

Results

In this series, the median patient age was 65.5 years, with a female:male ratio of 6:4. All 10 patients tolerated the procedure well, and none required GEA intraoperatively or postoperatively. The study group included 3 patients who were initially being assessed for RS due to age and medical comorbidities. Nine patients had a successful surgical outcome (BNI Score I: n = 5, BNI Score II: n = 4). One patient did not experience pain relief (BNI Score IV); that patient also developed a

Discussion

In a recent meta-analysis investigating the safety and efficacy of MVD and RS for TN, Gubian and Rosahl reported initial success rates of 86.9% for MVD and 71.1% for RS.5 Based on these data and the literature, it is well established that MVD is the first-line treatment option for TN in younger patients and patients free of comorbidities. Comorbidities affecting the safety of GEA for MVD have historically excluded a subset of patients from undergoing this highly efficacious procedure,

Conclusions

Awake intraoperative testing for pain relief may be a powerful tool for identifying and mitigate incomplete decompression of CN V, potentially resulting in higher rates of successful MVD for TN. The subset of patients with TN who cannot tolerate GEA due to age or medical comorbidities may be candidates for awake MVD.

Acknowledgments

We thank Dr Wolf Stapelfeldt, Chair, Department of Anesthesiology, Saint Louis University, for his support of the pioneering concept of awake craniotomy for complex lesions.

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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