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Awake microvascular decompression with fat-teflon sandwich technique: Clinical implications of a novel approach for cranial nerve neuralgias
Journal of Clinical Neuroscience 64 (2019) 77–82
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Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Clinical study
Awake microvascular decompression with fat-teflon sandwich technique: Clinical implications of a novel approach for cranial nerve neuralgias q Vishwaraj Ratha a,⇑, V.R. Roopesh Kumar a, Sudhakar Subramaniam b, Senthil Kumar b, Vijay Sankaran a, K.R. Suresh Bapu a a b
Department of Neurosurgery, SRM Institute of Medical Sciences and Hospital, Chennai, India Department of Neuroanaesthesia, SRM Institute of Medical Sciences and Hospital, Chennai, India
a r t i c l e
i n f o
Article history: Received 20 November 2018 Accepted 12 April 2019
Keywords: Awake anaesthesia Microvascular decompression (MVD) Glossopharyngeal neuralgia (GPN) Trigeminal neuralgia (TN) Internal neurolysis
a b s t r a c t Re-appearance of trigeminal neuralgia (TN) pain following microvascular decompression (MVD) is a challenging issue. A selective ablation with MVD provides the best response in such recurrences. The absence of intra-operative indicator for immediate correction of sub-optimal decompression is the primary factor for failure. We analysed the effectiveness and safety of awake MVD in minimizing failure, by tailoring the procedure according to intra-operative response with re-exploration or additional procedure like internal neurolysis in the same setting, especially in patients without vascular compression and those unfit for General Anesthesia (GA). The prospective study from June 2016 to June 2017 includes one glossopharyngeal neuralgia (GPN) and 6 trigeminal neuralgia (TN). Five cases responded with immediate complete pain relief but in 2 cases, incomplete pain relief resulted in alteration of intraoperative decision. In one case, a partial pain relief, mandated an additional internal neurolysis in the same setting, resulting in complete pain relief while in the other, re-exploration revealed a hidden venous conflict, not identified on MRI following which an additional IN was performed. All cases were followed up with BNI PIS for a minimum of one year without recurrence. Awake MVD is safe and reliable intraoperative neurophysiological prognostic marker of immediate pain relief and provides a window for an immediate correction of sub-optimal decompression with Internal Neurolysis when needed, in the same setting, especially in neuroimaging negative and elderly cases unfit for GA. It has the potential to reduce the rate of reintervention and increase the overall effectiveness of MVD by specifically ameliorating the pain burden and quality of life. Ó 2019 Published by Elsevier Ltd.
1. Introduction
Abbreviations: TN, trigeminal neuralgia; MVD, microvascular decompression; GPN, glossopharyngeal neuralgia; TREZ, trigeminal root entry zone; BNI PIS, barrow neurological institute pain intensity scale; IN, internal neurolysis; MAC, monitored anesthesia care; NRS, numeric rating scale; VRS, verbal rating scale; RS, radiosurgery; NVC, neurovascular conflict; SCA, superior cerebellar artery; AICA, anterior inferior cerebellar artery; PICA, posterior inferior cerebellar artery; GA, General Anesthesia. q A preliminary analysis was presented in Neurological society of India (NSI) Annual conference in Dec 2016. ⇑ Corresponding author at: Institute of Neurosciences, SRM Institute of Medical Sciences and Hospital, Vadapalani, Chennai 600026, India. E-mail address: [email protected] (V. Ratha).
https://doi.org/10.1016/j.jocn.2019.04.007 0967-5868/Ó 2019 Published by Elsevier Ltd.
The pioneering work of Gardner and later Janneta in the late 1950s–60s demonstrated the immense success of microvascular decompression (MVD) in trigeminal neuralgia (TN) pain and after 4 decades of scientific experience, it is currently recognized as the primary therapeutic option and gold standard in the treatment of TN [1–4]. However, despite the tremendous strides in neurosurgery, the management of neuralgia recurrence following a primary MVD has proven to be a contentious issue along with the fact that the one-year pain relief post MVD has remained around 80–85% and not significantly improved even after 4 decades from its inception [1,5].
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Recently, Tung-Han Wu et al have shown an excessive risk of psychiatric disorders among patients with untreated TN [6]. Persistence or recurrence of symptoms following a failed primary MVD not only severely affects the Quality-of-life (QoL) but further burdens them with additional financial and psycho-social infliction especially for patients from developing nations. One of the reasons for the failure of MVD has been the absence of any immediate intra-operative neurophysiological marker to ascertain any sub-optimal decompression and nonresponsiveness to optimal decompression who may benefit with an additional ablative procedure. Awake craniotomy has been extensively used in the resection of eloquent region gliomas and epilepsy surgeries [7]. Abdulrauf et al. have been instrumental in pushing the traditional boundaries of awake anesthesia and have successfully used it in cerebrovascular and skull-base lesions [8]. A further push has come from their 2018 seminal paper ‘‘Awake Microvascular Decompression for Trigeminal Neuralgia: Concept and Initial Results” wherein awake MVD was conceptualized and explored in 10 consecutive patients [9]. In early 2016, we, independently and uninfluenced by the just published work of Abdulrauf et al. [9], had a similar concept and proposed to amalgamate the awake anaesthesia protocol with MVD to enhance its effectiveness in immediate pain relief and reduce recurrence especially in those with doubtful neuroimaging and cases unfit for GA. Along with its use in TN, we had the opportunity to establish its role in glossopharyngeal neuralgia (GPN) as well. The emphasis was to establish the usefulness of awake MVD as an intra-operative neurophysiological prognostic marker of immediate response and its use in tailoring the need and extent of internal neurolysis or partial selective rhizotomy in addition to MVD, especially in patients without any obvious vascular compression to avoid immediate re-intervention and failure. Thus, our series re-strengthens the usefulness of awake anesthesia in MVD as proposed by Abdulrauf et al. [9].
2. Methods and materials This is an analysis of our initial experience of an ongoing prospective study (IRB approved) of Awake craniotomy in MVD for patients with cranial nerve neuralgia treated at S.I.M.S. Hospital from June 2016 till June 2017. All cranial nerve neuralgias and only Type 1 burchiel TN with an elicitable trigger point who were followed up for a minimum of 1 year, were considered. A thorough neurological evaluation was carried out categorizing each case with the identified cranial nerve neuralgia along with MRI with constructive interference in steady-state (CISS) sequence. A written informed consent was obtained explaining in detail about the principles and expectations of awake anaesthesia and the possible complications. The awake anaesthesia protocol utilized in our institute has been awake-awake-awake (A-A-A) rather the sleep-awake-sleep (S-A-S) which has relatively more risks [10]. The efficacy of communication in A-A-A approach is significantly better due to the avoidance of sedative agents and reduced need for opioids [10,11]. Scalp block was performed by using 20–40 ml 0.5% bupivacaine along with epinephrine to ensure long duration block. (Fig. 1) Five minutes before head pinning, 0.5% bupivacaine was infiltrated at each pin-insertion site [10]. A trial positioning was done to ascertain the most comfortable position which was determined by allowing the patient in one position for 10 min and assessing the ease of communication. Fig. 2(A) The trigger point was elicited, and baseline response was documented. Fig. 2(B). In our institute’s A-A-A protocol, dexmedetomidine was used with a loading dose of 0.5–1.0 mg kg 1 over 20 min followed by
Fig. 1. Scalp block.
an infusion rate of 0.2–0.7 mg kg 1 h 1 depending on the level of sedation required. Only if the patient requested, sedation was deepened after skin incision till removal of the bone flap and was always stopped for pre-procedure assessment [11]. Monitored anaesthesia care (MAC) protocol was followed and Operating room (OR) was re-organized to keep an unhindered communication line between the patient and anesthetist. Standard mini retrosigmoid craniotomy was performed in all cases centering the asterion. After identifying the neurovascular conflict, neuralgia was triggered by the anesthetist and the response was documented. We modified our MVD technique with Fat-teflon sandwich technique i.e. used Teflon pledget to push the vascular conflict away from the nerve while a small fat globule is inserted between the shredded teflon and the Vth nerve (Fig. 3). If the compression was by one or more unnamed veins; they were coagulated and sacrificed. After the decompression, patient’s neuralgia was again triggered and a composite of 4 point categorical Verbal rating scale (VRS) and a 11 point Numeric Rating scale (NRS) was used for intra-operative assessment of MVD. This was further categorized as (a) Complete relief {NRS: 0–1 and VRS: None} (b) Partial {NRS: 2–6 and VRS: Mild to Moderate} and (c) Poor relief {NRS: 7–10 and VRS: Severe}. If the response was anything other than complete relief, the trigeminal nerve root entry zone (TREZ) was re-explored for any hidden offending vessel. If no new conflict was found, either an internal neurolysis (i.e. dividing of all or portions of trigeminal nerve fibers longitudinally between the pons and the porous trigeminus) or partial selective rhizotomy (dividing the caudal two-thirds to one-half portion of the trigeminal nerve sensory root) was performed according to patient’s pain relief response in real time. Post procedure, anesthesia satisfaction was assessed by 1) Highly satisfied, 2) Some dissatisfaction and 3) Highly dissatisfied, remark. We utilized benefit assessment score for analyzing the usefulness of awake MVD, by categorizing the intraoperative decisions into (a) 1: No benefit, (b) 2: Useful but without any change in decision, (c) 3: Useful and changed decision and (d) 4: False reassurance of benefit. All patients were periodically reviewed for a minimum period of 1 year to understand the usefulness and to accurately get an assessment for comparison with world literature. Follow up pain outcome was assessed by the Barrow Neurological Institute Pain Intensity Score (BNI PIS). We purposefully decided 1 year as the appropriate follow up time for data analyses as we understand
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Fig. 2. (A) Comfortable patient positioning, (B) Eliciting the Trigger Point.
Table 1 The demographic and clinical characteristics of patients. Number of patients Average Age Male (n = 4) Female (n = 3) Sex ratio (F/M) Type of Neuralgia Burchiel Type 1 TN Glossopharyngeal Neuralgia Average duration of symptoms Side of neuralgic pain Right Left Distribution of neuralgia V1-2 V2-3 V1-2-3 IX
Fig. 3. Awake MVD with fat globule sandwiched between shredded Teflon pledget and NVC. White arrow denotes Shredded Teflon pledget, * denotes Vth nerve and Black arrow represents the fat globule sandwiched between Teflon and NVC.
the limitations of an immediate post-op response can be biased and many recurrences are delayed. This is our first phase analyses and we would follow up all the patients for 5 years. All patients consented to the chart review and, in addition, were contacted by telephone for the current follow-up and pain relief outcome was assessed by both BNI PIS and NRS-VRS response.
3. Results Out of the total 21 consecutive MVD for cranial nerve neuralgia done in our institute from June 2016 till June 2017, 7 patients (33%) agreed for awake MVD and have completed a minimum of oneyear follow-up. The patient population consisted of 4 males and 3 females. Their age ranged from 52 to 67 years (mean 58 years). In our series, majority were Type 1 Burchiel TN (6 cases) and one case was of classical Glossopharyngeal neuralgia (GPN). The duration of symptoms ranged from 6 months to 5 years. The demographic and clinical characteristics of patients are listed in Table 1. MRI with CISS sequence was performed in all 7 cases (Fig. 4A & B) with no identifiable secondary causes and neurovascular conflict was well observed in 6 of the 7 cases (Table 2). All 7 patients were co-operative and preferred lateral position. Hemodynamic and respiratory behavior and patient response time
7 58 years 57 years 59.5 years 2:3 6 1 2 years (6 months to 5 years) 3 4 1 2 3 1
was satisfactory, and no case required conversion to GA. Intraoperative assessment of pain relief post MVD with complete relief {NRS: 0–1 and VRS: None} was observed in 5 cases while in 2 cases, a further re-exploration and internal neurolysis respectively reduced the response from partial to complete pain relief. The follow up was done at 3, 6 and 12 months. There have been no clinical recurrences seen till now at 1 year follow up and all had excellent surgical outcome (BNI score I: n = 6, BNI score II: n = 1). Our first case was of classical GPN and awake protocol and offending vessel was identified to be Posterior Inferior Cerebellar artery (PICA). MVD provided an immediate complete relief of otalgia as assessed by VRS and NRS score on triggering swallowing action, although a transient difficulty in swallowing and coughing was observed in immediate post-operative period which improved in 6 weeks. Out of the 6 TN cases, 4 had complete pain relief after MVD, however in one TN case, a poor pain relief response after MVD on eliciting the trigger point, resulted in immediate reexploration and identification of an additional venous conflict near TREZ which was missed out in neuroimaging. An adequate and appropriate MVD was performed but persistence of pain prompted an additional internal neurolysis which resulted in complete relief. The trigger point elicitation was done twice more to confirm the pain relief. The second patient was without MRI proven neuro-vascular conflict (NVC) and intra-operative finding revealed only approximation of Superior Cerebellar Artery (SCA) without significant compression but with arachnoidal band adhesions. MVD provided only partial pain relief response, thus an additional internal
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Fig. 4. MRI CISS sequence showing (A) Right sided PICA compressing the Lower Cranial nerves in GPN, (B) Left sided SCA compressing the Vth Cranial nerve in TN.
Table 2 Neuroimaging details. MRI imaging: Diagnosis Primary Neurovascular compression Normal Secondary Offending vessel Superior cerebral artery Anterior inferior cerebellar artery Posterior inferior cerebellar artery Veins Basilar artery
Table 3 Details of the intraoperative findings. 7 patients 7 1 6 0 4 1 1 0 0
neurolysis performed in the same setting, resulted in complete pain relief. However, he had transient minimal partial facial numbness which fully recovered by 12 weeks but his BNI score remained II till his last follow up at 1 year. In all the cases, we noticed that the movement of CSF in the cisternal spaces was more pronounced (influenced by the breathing pattern), making the delicate dissection for MVD more tedious. There were no complications observed and details of the intraoperative findings are mentioned in Table 3. On immediate post op assessment, all were highly satisfied with the awake anesthesia with none experiencing any position related discomfort. All our 7 patients were kept awake through-out the procedure and all had an uneventful post-operative recovery, without any surgical complications. Benefit assessment score was documented for all cases. In our preliminary experience, Awake MVD proved to be beneficial in all cases and it proved to be a decision changer in 1 patient. The numbers are small to draw any decisive conclusion yet, but it still provides an insight into awake MVDs usefulness (Table 4).
4. Discussion Prior to the pioneering work from Gardner and Janneta, ablative procedure was the norm for TN [1,12,13]. It took almost 20 more years to establish MVD as the ‘‘Gold Standard” and first line of curative treatment in TN [1,3,14,15]. The recent meta-analysis by
Characteristic
No.
Offending NVC identified on first inspection Superior cerebral artery Anterior inferior cerebellar artery Posterior inferior cerebellar artery Basilar artery Re-inspection Unnamed vein in addition to SCA No NVC Location of neurovascular compression TREZ Middle 1/3 Lateral Intra-operative pain relief response Complete Partial (additional Internal Neurolysis) Poor Post operative patient satisfaction Highly satisfied Some dissatisfaction Highly dissatisfied Peri-operative complication GA conversion CSF leak Cranial nerve deficit Transient Permanent
6 4 1 1 2 1 1 6 1 0 4 2 0 7 0 0 0 0 2 0
Gubian and Rosahl demonstrated an initial success rate of 86.9% for MVD and further strengthened the position of MVD [14]. However, on reviewing the world literature on MVD, one cannot miss to observe the fact that the long term complete pain relief has remained around 80–85% all over the world since Janneta first published his results [1,5,14]. We took the liberty in viewing this data from a different vantage and realized the existence of lacunae in literature in addressing the issue of recurrences and reinterventions for a subset of patients who remain inflicted with pain even after MVD, especially in neuroimaging negative cases and also the subset who are deemed unfit for GA, subsequently getting sub-optimal therapeutic interventions with second line of treatment. The literature provides few possible preventable primary risk factors for persistence or recurrence of pain following MVD like
V. Ratha et al. / Journal of Clinical Neuroscience 64 (2019) 77–82 Table 4 Benefit assessment score. DIAGNOSIS
SCORE: 1
SCORE:2
SCORE:3
SCORE:4
TOTAL
TN GPN TOTAL
0 0 0
5 1 6 (85.7%)
1 0 1 (14.3%)
0 0 0
6 1 7
Scores (1): No benefit, (2): Useful but without any change in decision, (3): Useful and changed decision and (4): False reassurance of benefit.
inadequate exposure and inspection of the REZ especially in neuroimaging negative cases, along with undetected venous compression [15,16]. An uncommon and underestimated reason described is, improper and overindulgent use of Teflon for decompression [17]. It has been convincingly shown that the Teflon is not absolutely inert and can induce an inflammatory giant-cell foreign body reaction (Teflon granuloma) which can cause a delayed recurrence [17]. Although ‘‘technique related” factors are the most important reasons, but despite the best of surgical practices, the recurrence and persistence of pain in few case, constitutes a significant burden even in centers of excellence. The other under-analyzed factors affecting outcome are (a) neuralgia in absence of NVC and (b) subset of patients not eligible for GA. As literature has shown not all patients with TN demonstrate NVC at the TREZ, and many asymptomatic patients do. A recent large case series found that 28.8% of patients with Type 1 TN exhibit no NVC. Moreover, the review of long-term recurrence rates of TN after successful MVD has been estimated at 4%–5% per year, which likewise occurs in the absence of NVC [18]. Thus, MVD will prove ineffective in this subset of cases with no significant NVC. This subset would be immensely benefited from partial sensory rhizotomy or Internal neurolysis [18] but are mostly managed with the less effective second line options. The management of recurrent neuralgia is challenging. Even though literature favors a re-exploration and re-MVD [19], most opt for less invasive procedures to achieve pain relief. This is primarily due to (a) success rate of repeat MVD being significantly lower with increased risk of complications [20,21] and more importantly (b) the apprehension of second brain surgery with possible poor outcome. This makes it paramount to get the maximum benefit from the first MVD itself and reduce all the factors for possible re-intervention later as invariably, these recurrent cases are provided second line options [22]. Despite the plethora of literature on MVD suggesting improper and inadequate technique being the most important factor for failure, very few have attempted to refine or improvise the technique of MVD. The recent advances have been confined to the use of endoscopy [23–25] or advances in neuroimaging and neuromonitoring [26]. Broggi et al. reported 8.5% of cases in whom conflict was not clearly visible with the microscope but revealed and solved with the endoscope [23]. However, the pain outcome and rate of complications of a fully endoscopic MVD was comparable to microscopic MVD if not superior. Surprisingly, in their paper Sandell et al suggested the performance of a neurolytic procedure (rhizotomy) was the strongest predictor of success [24]. Hence, an ideal procedure for neuralgia should include a proper and thoroughly exposed TREZ and MVD with adequate teflon for TN with NVC and internal neurolysis or partial rhizotomy for those without NVC or non-improvement after MVD, in the same setting. On reviewing these factors, we found that except for teflon granuloma, rest all factors are essentially due to absence of any intraoperative neurophysiological prognostic indicator which could caution immediately about sub-optimal decompression during the surgery itself, thereby avoiding recurrences and reinterventions.
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As a solution to these factors, we have tried to amalgamate the advantages of awake anesthesia with the minor refining (fat-teflon sandwich instead of Teflon alone) of the Gold standard technique MVD to increase the success rate. Abdulrauf et al. were the first to report on the concept and utility of awake MVD [9] and with our series, its usefulness has been further strengthened. In their series, the median patient age was 65.5 years while in our series, the average age was 58 years. In their cohort, nine patients had a successful surgical outcome (BNI Score I: n = 5, BNI Score II: n = 4) with one not getting any pain relief (BNI Score IV). In 3/10 patients, intraoperative decision was altered based on failure of pain relief during the awake testing period. The one failure did not improve even with IN as well [9]. While in our series, of the 7 cases, one patient’s intra-op response guided us to re-explore and discover an additional vein as the main offending vessel despite an obvious arterial compression while in another case, the partial pain relief after MVD required an additional internal neurolysis for complete pain relief. We believe that awake MVD helped us in these two cases in avoiding immediate recurrences and possible re-intervention, thereby improving the efficacy of MVD immensely. There have been no clinical recurrences seen till now at 1 year follow up and all had excellent surgical outcome (BNI score I: n = 6, BNI score II: n = 1). Re-analysing, Abdulrauf et al. series and our findings, we believe, awake MVD has the potential to provide a real time assessment of effectiveness of decompression and guide for a tailored response like re-exploration and Internal neurolysis when MVD alone is suboptimal and additional ablative procedure is mandated. In addition, we also attempted to find a solution for Teflon slippage/granuloma issue by modifying the standard Teflon insertion with Fat-Teflon sandwich technique. Our preliminary experience with awake MVD supports the safety, feasibility, and potential benefits of this approach for cranial nerve neuralgias. Our initial experience has been encouraging, where patients own response during awake MVD guides the further management. It also helps in tailoring the need and extent of selective partial rhizotomy/Internal neurolysis as an adjunct to the definitive procedure of MVD in providing complete pain relief in patients especially useful in those without any NVC or are unfit for GA. We also believe that it has the potential to increase the detection rate of NVC in MRI negative cases for hidden offending vessels. 5. Limitations We understand the cohort is very small (n = 7) to extract any definitive conclusion. Absence of a reliable trigger point in many TN patients and the fear of enduring triggered neuralgia pain during the procedure is a major deterrent in limiting the recruitment of more patients for awake MVD. We also believe that Teflon granuloma is an under estimated factor in recurrences, as very few undergo redo-MVD to prove or disprove this issue and our modification of standard MVD technique has the potential to mitigate this issue. Our benefit assessment score has provided enough encouragement to validate its usefulness and superiority as an adjunct to MVD. With this push, a subsequent larger cohort and inclusion of more elderly patients can substantiate the findings and can change the way we evaluate cases for MVD. 6. Conclusion Awake MVD is a safe, feasible and effective adjunct to conventional MVD and improves its efficacy in the management of cranial nerve neuralgias. It has the potential to act as an intraoperative
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neurophysiological indicator of immediate success or failure and allows tailoring of the procedure for additional internal neurolysis, as per the responses, especially useful in MRI negative cases or in detecting the often missed out hidden offending vessels. We also believe that fat –teflon sandwich method for MVD can potentially prevent Teflon granuloma and combining this modification in awake MVD with or without IN will greatly reduce the burden of re-intervention and will be useful in increasing its overall success. However, a longer follow-up and a larger number of patients will enable us to validate our initial findings. Sources of support This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Conflict of interest All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent Informed consent was obtained from all individual participants included in the study. Acknowledgments None. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jocn.2019.04.007. References [1] Barker FG, Jannetta PJ, Bissonette DJ, Larkins MV, Jho HD. The long-term outcome of microvascular decompression for trigeminal Neuralgia. N Engl J Med 1996;334(17):1077–84. https://doi.org/10.1056/nejm199604253341701. [2] Hitotsumatsu T, Matsushima T, Inoue T. Microvascular decompression for treatment of trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia: three surgical approach variations: technical note. Neurosurgery 2003;53(6):1436–41. discussion 1442-3. [3] McLaughlin MR, Jannetta PJ, Clyde BL, Subach BR, Comey CH, Resnick DK. Microvascular decompression of cranial nerves: lessons learned after 4400 operations. J Neurosurg 1999;90(1):1–8. https://doi.org/10.3171/ jns.1999.90.1.0001.
[4] Broggi G, Broggi M, Ferroli P, Franzini A. Surgical technique for trigeminal microvascular decompression. Acta Neurochir 2012;154(6):1089–95. https:// doi.org/10.1007/s00701-012-1324-2. [5] Tyler-Kabara EC, Kassam AB, Horowitz MH, et al. Predictors of outcome in surgically managed patients with typical and atypical trigeminal neuralgia: comparison of results following microvascular decompression. J Neurosurg 2002;96(3):527–31. https://doi.org/10.3171/jns.2002.96.3.0527. [6] Wu TH, Hu LY, Lu T, et al. Risk of psychiatric disorders following trigeminal neuralgia: a nationwide population-based retrospective cohort study. J Headache Pain 2015;16:64. https://doi.org/10.1186/s10194-015-0548-y. [7] De Benedictis A, Moritz-Gasser S, Duffau H. Awake mapping optimizes the extent of resection for low-grade gliomas in eloquent areas. Neurosurgery 2010;66(6):1074–84. [8] Abdulrauf S. Awake craniotomies for aneurysms, arteriovenous malformations, skull base tumors, high flow bypass, and brain stem lesions. J Cranioverteb Junct Spine 2015;6(1):8. [9] Abdulrauf SI, Urquiaga JF, Patel R, et al. Awake microvascular decompression for trigeminal neuralgia: concept and initial results. World Neurosurg 2018;113:e309–13. https://doi.org/10.1016/j.wneu.2018.02.019. [10] Hansen E, Seemann M, Zech N, Doenitz C, Luerding R, Brawanski A. Awake craniotomies without any sedation: the awake-awake-awake technique. Acta Neurochir 2013;155(8):1417–24. [11] Stevanovic A, Rossaint R, Veldeman M, Bilotta F, Coburn M. Anaesthesia management for awake craniotomy: systematic review and meta-analysis. PLoS ONE 2016;11(5). [12] Apfelbaum R. Trigeminal and glossopharyngeal neuralgia and hemifacial spasm. Principles of neurosurgery. 2nd ed. Philadelphia: Lippincott-Raven; 1999. p. 19. [13] Cole CD, Liu JK, Apfelbaum RI. Historical perspectives on the diagnosis and treatment of trigeminal neuralgia. Neurosurg Focus 2005;18(5):1–10. [14] Gubian A, Rosahl SK. Meta-analysis on safety and efficacy of microsurgical and radiosurgical treatment of trigeminal neuralgia. World Neurosurg 2017;103:757–67. [15] Cohen-Gadol AA. Microvascular decompression surgery for trigeminal neuralgia and hemifacial spasm: naunces of the technique based on experiences with 100 patients and review of the literature. Clin Neurol Neurosurg 2011;113(10):844–53. [16] Kabatas S, Karasu A, Civelek E, Sabanci AP, Hepgul KT, Teng YD. Microvascular decompression as a surgical management for trigeminal neuralgia: long-term follow-up and review of the literature. Neurosurg Rev 2009;32(1):87. [17] Chen J-F, Lee S-T, Lui T-N, Yeh Y-S, Chen T-Y, Tzaan W-C. Teflon granuloma after microvascular decompression for trigeminal neuralgia. Surg Neurol 2000;53(3):281–7. [18] Ko AL, Ozpinar A, Lee A, Raslan AM, McCartney S, Burchiel KJ. Long-term efficacy and safety of internal neurolysis for trigeminal neuralgia without neurovascular compression. J Neurosurg 2015;122(5):1048–57. [19] Kang IH, Park BJ, Park CK, Malla HP, Lee SH, Rhee BA. A clinical analysis of secondary surgery in trigeminal neuralgia patients who failed prior treatment. J Korean Neurosurg Soc 2016;59(6):637. [20] Bakker NA, Van Dijk JMC, Immenga S, Wagemakers M, Metzemaekers JD. Repeat microvascular decompression for recurrent idiopathic trigeminal neuralgia. J Neurosurg 2014;121(4):936–9. [21] Barker FG, Jannetta PJ, Bissonette DJ, Jho HD. Trigeminal numbness and tic relief after microvascular decompression for typical trigeminal neuralgia. Neurosurgery 1997;40(1):39–45. [22] Rath SA, Klein HJ, Richter H-P. Findings and long-term results of subsequent operations after failed microvascular decompression for trigeminal neuralgia. Neurosurgery 1996;39(5):933–40. [23] Broggi M, Acerbi F, Ferroli P, Tringali G, Schiariti M, Broggi G. Microvascular decompression for neurovascular conflicts in the cerebello-pontine angle: which role for endoscopy? Acta Neurochir 2013;155(9):1709–16. [24] Sandell T, Ringstad GA, Eide PK. Usefulness of the endoscope in microvascular decompression for trigeminal neuralgia and MRI-based prediction of the need for endoscopy. Acta Neurochir 2014;156(10):1901–9. [25] Bohman L-E, Pierce J, Stephen JH, Sandhu S, Lee JY. Fully endoscopic microvascular decompression for trigeminal neuralgia: technique review and early outcomes. Neurosurg Focus 2014;37(4):E18. [26] Ruiz-Juretschke F, Guzmán-de-Villoria J, García-Leal R, Sañudo J. Predictive value of magnetic resonance for identifying neurovascular compressions in trigeminal neuralgia. Neurologia (Barcelona, Spain) 2017.
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Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Clinical study
Awake microvascular decompression with fat-teflon sandwich technique: Clinical implications of a novel approach for cranial nerve neuralgias q Vishwaraj Ratha a,⇑, V.R. Roopesh Kumar a, Sudhakar Subramaniam b, Senthil Kumar b, Vijay Sankaran a, K.R. Suresh Bapu a a b
Department of Neurosurgery, SRM Institute of Medical Sciences and Hospital, Chennai, India Department of Neuroanaesthesia, SRM Institute of Medical Sciences and Hospital, Chennai, India
a r t i c l e
i n f o
Article history: Received 20 November 2018 Accepted 12 April 2019
Keywords: Awake anaesthesia Microvascular decompression (MVD) Glossopharyngeal neuralgia (GPN) Trigeminal neuralgia (TN) Internal neurolysis
a b s t r a c t Re-appearance of trigeminal neuralgia (TN) pain following microvascular decompression (MVD) is a challenging issue. A selective ablation with MVD provides the best response in such recurrences. The absence of intra-operative indicator for immediate correction of sub-optimal decompression is the primary factor for failure. We analysed the effectiveness and safety of awake MVD in minimizing failure, by tailoring the procedure according to intra-operative response with re-exploration or additional procedure like internal neurolysis in the same setting, especially in patients without vascular compression and those unfit for General Anesthesia (GA). The prospective study from June 2016 to June 2017 includes one glossopharyngeal neuralgia (GPN) and 6 trigeminal neuralgia (TN). Five cases responded with immediate complete pain relief but in 2 cases, incomplete pain relief resulted in alteration of intraoperative decision. In one case, a partial pain relief, mandated an additional internal neurolysis in the same setting, resulting in complete pain relief while in the other, re-exploration revealed a hidden venous conflict, not identified on MRI following which an additional IN was performed. All cases were followed up with BNI PIS for a minimum of one year without recurrence. Awake MVD is safe and reliable intraoperative neurophysiological prognostic marker of immediate pain relief and provides a window for an immediate correction of sub-optimal decompression with Internal Neurolysis when needed, in the same setting, especially in neuroimaging negative and elderly cases unfit for GA. It has the potential to reduce the rate of reintervention and increase the overall effectiveness of MVD by specifically ameliorating the pain burden and quality of life. Ó 2019 Published by Elsevier Ltd.
1. Introduction
Abbreviations: TN, trigeminal neuralgia; MVD, microvascular decompression; GPN, glossopharyngeal neuralgia; TREZ, trigeminal root entry zone; BNI PIS, barrow neurological institute pain intensity scale; IN, internal neurolysis; MAC, monitored anesthesia care; NRS, numeric rating scale; VRS, verbal rating scale; RS, radiosurgery; NVC, neurovascular conflict; SCA, superior cerebellar artery; AICA, anterior inferior cerebellar artery; PICA, posterior inferior cerebellar artery; GA, General Anesthesia. q A preliminary analysis was presented in Neurological society of India (NSI) Annual conference in Dec 2016. ⇑ Corresponding author at: Institute of Neurosciences, SRM Institute of Medical Sciences and Hospital, Vadapalani, Chennai 600026, India. E-mail address: [email protected] (V. Ratha).
https://doi.org/10.1016/j.jocn.2019.04.007 0967-5868/Ó 2019 Published by Elsevier Ltd.
The pioneering work of Gardner and later Janneta in the late 1950s–60s demonstrated the immense success of microvascular decompression (MVD) in trigeminal neuralgia (TN) pain and after 4 decades of scientific experience, it is currently recognized as the primary therapeutic option and gold standard in the treatment of TN [1–4]. However, despite the tremendous strides in neurosurgery, the management of neuralgia recurrence following a primary MVD has proven to be a contentious issue along with the fact that the one-year pain relief post MVD has remained around 80–85% and not significantly improved even after 4 decades from its inception [1,5].
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Recently, Tung-Han Wu et al have shown an excessive risk of psychiatric disorders among patients with untreated TN [6]. Persistence or recurrence of symptoms following a failed primary MVD not only severely affects the Quality-of-life (QoL) but further burdens them with additional financial and psycho-social infliction especially for patients from developing nations. One of the reasons for the failure of MVD has been the absence of any immediate intra-operative neurophysiological marker to ascertain any sub-optimal decompression and nonresponsiveness to optimal decompression who may benefit with an additional ablative procedure. Awake craniotomy has been extensively used in the resection of eloquent region gliomas and epilepsy surgeries [7]. Abdulrauf et al. have been instrumental in pushing the traditional boundaries of awake anesthesia and have successfully used it in cerebrovascular and skull-base lesions [8]. A further push has come from their 2018 seminal paper ‘‘Awake Microvascular Decompression for Trigeminal Neuralgia: Concept and Initial Results” wherein awake MVD was conceptualized and explored in 10 consecutive patients [9]. In early 2016, we, independently and uninfluenced by the just published work of Abdulrauf et al. [9], had a similar concept and proposed to amalgamate the awake anaesthesia protocol with MVD to enhance its effectiveness in immediate pain relief and reduce recurrence especially in those with doubtful neuroimaging and cases unfit for GA. Along with its use in TN, we had the opportunity to establish its role in glossopharyngeal neuralgia (GPN) as well. The emphasis was to establish the usefulness of awake MVD as an intra-operative neurophysiological prognostic marker of immediate response and its use in tailoring the need and extent of internal neurolysis or partial selective rhizotomy in addition to MVD, especially in patients without any obvious vascular compression to avoid immediate re-intervention and failure. Thus, our series re-strengthens the usefulness of awake anesthesia in MVD as proposed by Abdulrauf et al. [9].
2. Methods and materials This is an analysis of our initial experience of an ongoing prospective study (IRB approved) of Awake craniotomy in MVD for patients with cranial nerve neuralgia treated at S.I.M.S. Hospital from June 2016 till June 2017. All cranial nerve neuralgias and only Type 1 burchiel TN with an elicitable trigger point who were followed up for a minimum of 1 year, were considered. A thorough neurological evaluation was carried out categorizing each case with the identified cranial nerve neuralgia along with MRI with constructive interference in steady-state (CISS) sequence. A written informed consent was obtained explaining in detail about the principles and expectations of awake anaesthesia and the possible complications. The awake anaesthesia protocol utilized in our institute has been awake-awake-awake (A-A-A) rather the sleep-awake-sleep (S-A-S) which has relatively more risks [10]. The efficacy of communication in A-A-A approach is significantly better due to the avoidance of sedative agents and reduced need for opioids [10,11]. Scalp block was performed by using 20–40 ml 0.5% bupivacaine along with epinephrine to ensure long duration block. (Fig. 1) Five minutes before head pinning, 0.5% bupivacaine was infiltrated at each pin-insertion site [10]. A trial positioning was done to ascertain the most comfortable position which was determined by allowing the patient in one position for 10 min and assessing the ease of communication. Fig. 2(A) The trigger point was elicited, and baseline response was documented. Fig. 2(B). In our institute’s A-A-A protocol, dexmedetomidine was used with a loading dose of 0.5–1.0 mg kg 1 over 20 min followed by
Fig. 1. Scalp block.
an infusion rate of 0.2–0.7 mg kg 1 h 1 depending on the level of sedation required. Only if the patient requested, sedation was deepened after skin incision till removal of the bone flap and was always stopped for pre-procedure assessment [11]. Monitored anaesthesia care (MAC) protocol was followed and Operating room (OR) was re-organized to keep an unhindered communication line between the patient and anesthetist. Standard mini retrosigmoid craniotomy was performed in all cases centering the asterion. After identifying the neurovascular conflict, neuralgia was triggered by the anesthetist and the response was documented. We modified our MVD technique with Fat-teflon sandwich technique i.e. used Teflon pledget to push the vascular conflict away from the nerve while a small fat globule is inserted between the shredded teflon and the Vth nerve (Fig. 3). If the compression was by one or more unnamed veins; they were coagulated and sacrificed. After the decompression, patient’s neuralgia was again triggered and a composite of 4 point categorical Verbal rating scale (VRS) and a 11 point Numeric Rating scale (NRS) was used for intra-operative assessment of MVD. This was further categorized as (a) Complete relief {NRS: 0–1 and VRS: None} (b) Partial {NRS: 2–6 and VRS: Mild to Moderate} and (c) Poor relief {NRS: 7–10 and VRS: Severe}. If the response was anything other than complete relief, the trigeminal nerve root entry zone (TREZ) was re-explored for any hidden offending vessel. If no new conflict was found, either an internal neurolysis (i.e. dividing of all or portions of trigeminal nerve fibers longitudinally between the pons and the porous trigeminus) or partial selective rhizotomy (dividing the caudal two-thirds to one-half portion of the trigeminal nerve sensory root) was performed according to patient’s pain relief response in real time. Post procedure, anesthesia satisfaction was assessed by 1) Highly satisfied, 2) Some dissatisfaction and 3) Highly dissatisfied, remark. We utilized benefit assessment score for analyzing the usefulness of awake MVD, by categorizing the intraoperative decisions into (a) 1: No benefit, (b) 2: Useful but without any change in decision, (c) 3: Useful and changed decision and (d) 4: False reassurance of benefit. All patients were periodically reviewed for a minimum period of 1 year to understand the usefulness and to accurately get an assessment for comparison with world literature. Follow up pain outcome was assessed by the Barrow Neurological Institute Pain Intensity Score (BNI PIS). We purposefully decided 1 year as the appropriate follow up time for data analyses as we understand
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Fig. 2. (A) Comfortable patient positioning, (B) Eliciting the Trigger Point.
Table 1 The demographic and clinical characteristics of patients. Number of patients Average Age Male (n = 4) Female (n = 3) Sex ratio (F/M) Type of Neuralgia Burchiel Type 1 TN Glossopharyngeal Neuralgia Average duration of symptoms Side of neuralgic pain Right Left Distribution of neuralgia V1-2 V2-3 V1-2-3 IX
Fig. 3. Awake MVD with fat globule sandwiched between shredded Teflon pledget and NVC. White arrow denotes Shredded Teflon pledget, * denotes Vth nerve and Black arrow represents the fat globule sandwiched between Teflon and NVC.
the limitations of an immediate post-op response can be biased and many recurrences are delayed. This is our first phase analyses and we would follow up all the patients for 5 years. All patients consented to the chart review and, in addition, were contacted by telephone for the current follow-up and pain relief outcome was assessed by both BNI PIS and NRS-VRS response.
3. Results Out of the total 21 consecutive MVD for cranial nerve neuralgia done in our institute from June 2016 till June 2017, 7 patients (33%) agreed for awake MVD and have completed a minimum of oneyear follow-up. The patient population consisted of 4 males and 3 females. Their age ranged from 52 to 67 years (mean 58 years). In our series, majority were Type 1 Burchiel TN (6 cases) and one case was of classical Glossopharyngeal neuralgia (GPN). The duration of symptoms ranged from 6 months to 5 years. The demographic and clinical characteristics of patients are listed in Table 1. MRI with CISS sequence was performed in all 7 cases (Fig. 4A & B) with no identifiable secondary causes and neurovascular conflict was well observed in 6 of the 7 cases (Table 2). All 7 patients were co-operative and preferred lateral position. Hemodynamic and respiratory behavior and patient response time
7 58 years 57 years 59.5 years 2:3 6 1 2 years (6 months to 5 years) 3 4 1 2 3 1
was satisfactory, and no case required conversion to GA. Intraoperative assessment of pain relief post MVD with complete relief {NRS: 0–1 and VRS: None} was observed in 5 cases while in 2 cases, a further re-exploration and internal neurolysis respectively reduced the response from partial to complete pain relief. The follow up was done at 3, 6 and 12 months. There have been no clinical recurrences seen till now at 1 year follow up and all had excellent surgical outcome (BNI score I: n = 6, BNI score II: n = 1). Our first case was of classical GPN and awake protocol and offending vessel was identified to be Posterior Inferior Cerebellar artery (PICA). MVD provided an immediate complete relief of otalgia as assessed by VRS and NRS score on triggering swallowing action, although a transient difficulty in swallowing and coughing was observed in immediate post-operative period which improved in 6 weeks. Out of the 6 TN cases, 4 had complete pain relief after MVD, however in one TN case, a poor pain relief response after MVD on eliciting the trigger point, resulted in immediate reexploration and identification of an additional venous conflict near TREZ which was missed out in neuroimaging. An adequate and appropriate MVD was performed but persistence of pain prompted an additional internal neurolysis which resulted in complete relief. The trigger point elicitation was done twice more to confirm the pain relief. The second patient was without MRI proven neuro-vascular conflict (NVC) and intra-operative finding revealed only approximation of Superior Cerebellar Artery (SCA) without significant compression but with arachnoidal band adhesions. MVD provided only partial pain relief response, thus an additional internal
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Fig. 4. MRI CISS sequence showing (A) Right sided PICA compressing the Lower Cranial nerves in GPN, (B) Left sided SCA compressing the Vth Cranial nerve in TN.
Table 2 Neuroimaging details. MRI imaging: Diagnosis Primary Neurovascular compression Normal Secondary Offending vessel Superior cerebral artery Anterior inferior cerebellar artery Posterior inferior cerebellar artery Veins Basilar artery
Table 3 Details of the intraoperative findings. 7 patients 7 1 6 0 4 1 1 0 0
neurolysis performed in the same setting, resulted in complete pain relief. However, he had transient minimal partial facial numbness which fully recovered by 12 weeks but his BNI score remained II till his last follow up at 1 year. In all the cases, we noticed that the movement of CSF in the cisternal spaces was more pronounced (influenced by the breathing pattern), making the delicate dissection for MVD more tedious. There were no complications observed and details of the intraoperative findings are mentioned in Table 3. On immediate post op assessment, all were highly satisfied with the awake anesthesia with none experiencing any position related discomfort. All our 7 patients were kept awake through-out the procedure and all had an uneventful post-operative recovery, without any surgical complications. Benefit assessment score was documented for all cases. In our preliminary experience, Awake MVD proved to be beneficial in all cases and it proved to be a decision changer in 1 patient. The numbers are small to draw any decisive conclusion yet, but it still provides an insight into awake MVDs usefulness (Table 4).
4. Discussion Prior to the pioneering work from Gardner and Janneta, ablative procedure was the norm for TN [1,12,13]. It took almost 20 more years to establish MVD as the ‘‘Gold Standard” and first line of curative treatment in TN [1,3,14,15]. The recent meta-analysis by
Characteristic
No.
Offending NVC identified on first inspection Superior cerebral artery Anterior inferior cerebellar artery Posterior inferior cerebellar artery Basilar artery Re-inspection Unnamed vein in addition to SCA No NVC Location of neurovascular compression TREZ Middle 1/3 Lateral Intra-operative pain relief response Complete Partial (additional Internal Neurolysis) Poor Post operative patient satisfaction Highly satisfied Some dissatisfaction Highly dissatisfied Peri-operative complication GA conversion CSF leak Cranial nerve deficit Transient Permanent
6 4 1 1 2 1 1 6 1 0 4 2 0 7 0 0 0 0 2 0
Gubian and Rosahl demonstrated an initial success rate of 86.9% for MVD and further strengthened the position of MVD [14]. However, on reviewing the world literature on MVD, one cannot miss to observe the fact that the long term complete pain relief has remained around 80–85% all over the world since Janneta first published his results [1,5,14]. We took the liberty in viewing this data from a different vantage and realized the existence of lacunae in literature in addressing the issue of recurrences and reinterventions for a subset of patients who remain inflicted with pain even after MVD, especially in neuroimaging negative cases and also the subset who are deemed unfit for GA, subsequently getting sub-optimal therapeutic interventions with second line of treatment. The literature provides few possible preventable primary risk factors for persistence or recurrence of pain following MVD like
V. Ratha et al. / Journal of Clinical Neuroscience 64 (2019) 77–82 Table 4 Benefit assessment score. DIAGNOSIS
SCORE: 1
SCORE:2
SCORE:3
SCORE:4
TOTAL
TN GPN TOTAL
0 0 0
5 1 6 (85.7%)
1 0 1 (14.3%)
0 0 0
6 1 7
Scores (1): No benefit, (2): Useful but without any change in decision, (3): Useful and changed decision and (4): False reassurance of benefit.
inadequate exposure and inspection of the REZ especially in neuroimaging negative cases, along with undetected venous compression [15,16]. An uncommon and underestimated reason described is, improper and overindulgent use of Teflon for decompression [17]. It has been convincingly shown that the Teflon is not absolutely inert and can induce an inflammatory giant-cell foreign body reaction (Teflon granuloma) which can cause a delayed recurrence [17]. Although ‘‘technique related” factors are the most important reasons, but despite the best of surgical practices, the recurrence and persistence of pain in few case, constitutes a significant burden even in centers of excellence. The other under-analyzed factors affecting outcome are (a) neuralgia in absence of NVC and (b) subset of patients not eligible for GA. As literature has shown not all patients with TN demonstrate NVC at the TREZ, and many asymptomatic patients do. A recent large case series found that 28.8% of patients with Type 1 TN exhibit no NVC. Moreover, the review of long-term recurrence rates of TN after successful MVD has been estimated at 4%–5% per year, which likewise occurs in the absence of NVC [18]. Thus, MVD will prove ineffective in this subset of cases with no significant NVC. This subset would be immensely benefited from partial sensory rhizotomy or Internal neurolysis [18] but are mostly managed with the less effective second line options. The management of recurrent neuralgia is challenging. Even though literature favors a re-exploration and re-MVD [19], most opt for less invasive procedures to achieve pain relief. This is primarily due to (a) success rate of repeat MVD being significantly lower with increased risk of complications [20,21] and more importantly (b) the apprehension of second brain surgery with possible poor outcome. This makes it paramount to get the maximum benefit from the first MVD itself and reduce all the factors for possible re-intervention later as invariably, these recurrent cases are provided second line options [22]. Despite the plethora of literature on MVD suggesting improper and inadequate technique being the most important factor for failure, very few have attempted to refine or improvise the technique of MVD. The recent advances have been confined to the use of endoscopy [23–25] or advances in neuroimaging and neuromonitoring [26]. Broggi et al. reported 8.5% of cases in whom conflict was not clearly visible with the microscope but revealed and solved with the endoscope [23]. However, the pain outcome and rate of complications of a fully endoscopic MVD was comparable to microscopic MVD if not superior. Surprisingly, in their paper Sandell et al suggested the performance of a neurolytic procedure (rhizotomy) was the strongest predictor of success [24]. Hence, an ideal procedure for neuralgia should include a proper and thoroughly exposed TREZ and MVD with adequate teflon for TN with NVC and internal neurolysis or partial rhizotomy for those without NVC or non-improvement after MVD, in the same setting. On reviewing these factors, we found that except for teflon granuloma, rest all factors are essentially due to absence of any intraoperative neurophysiological prognostic indicator which could caution immediately about sub-optimal decompression during the surgery itself, thereby avoiding recurrences and reinterventions.
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As a solution to these factors, we have tried to amalgamate the advantages of awake anesthesia with the minor refining (fat-teflon sandwich instead of Teflon alone) of the Gold standard technique MVD to increase the success rate. Abdulrauf et al. were the first to report on the concept and utility of awake MVD [9] and with our series, its usefulness has been further strengthened. In their series, the median patient age was 65.5 years while in our series, the average age was 58 years. In their cohort, nine patients had a successful surgical outcome (BNI Score I: n = 5, BNI Score II: n = 4) with one not getting any pain relief (BNI Score IV). In 3/10 patients, intraoperative decision was altered based on failure of pain relief during the awake testing period. The one failure did not improve even with IN as well [9]. While in our series, of the 7 cases, one patient’s intra-op response guided us to re-explore and discover an additional vein as the main offending vessel despite an obvious arterial compression while in another case, the partial pain relief after MVD required an additional internal neurolysis for complete pain relief. We believe that awake MVD helped us in these two cases in avoiding immediate recurrences and possible re-intervention, thereby improving the efficacy of MVD immensely. There have been no clinical recurrences seen till now at 1 year follow up and all had excellent surgical outcome (BNI score I: n = 6, BNI score II: n = 1). Re-analysing, Abdulrauf et al. series and our findings, we believe, awake MVD has the potential to provide a real time assessment of effectiveness of decompression and guide for a tailored response like re-exploration and Internal neurolysis when MVD alone is suboptimal and additional ablative procedure is mandated. In addition, we also attempted to find a solution for Teflon slippage/granuloma issue by modifying the standard Teflon insertion with Fat-Teflon sandwich technique. Our preliminary experience with awake MVD supports the safety, feasibility, and potential benefits of this approach for cranial nerve neuralgias. Our initial experience has been encouraging, where patients own response during awake MVD guides the further management. It also helps in tailoring the need and extent of selective partial rhizotomy/Internal neurolysis as an adjunct to the definitive procedure of MVD in providing complete pain relief in patients especially useful in those without any NVC or are unfit for GA. We also believe that it has the potential to increase the detection rate of NVC in MRI negative cases for hidden offending vessels. 5. Limitations We understand the cohort is very small (n = 7) to extract any definitive conclusion. Absence of a reliable trigger point in many TN patients and the fear of enduring triggered neuralgia pain during the procedure is a major deterrent in limiting the recruitment of more patients for awake MVD. We also believe that Teflon granuloma is an under estimated factor in recurrences, as very few undergo redo-MVD to prove or disprove this issue and our modification of standard MVD technique has the potential to mitigate this issue. Our benefit assessment score has provided enough encouragement to validate its usefulness and superiority as an adjunct to MVD. With this push, a subsequent larger cohort and inclusion of more elderly patients can substantiate the findings and can change the way we evaluate cases for MVD. 6. Conclusion Awake MVD is a safe, feasible and effective adjunct to conventional MVD and improves its efficacy in the management of cranial nerve neuralgias. It has the potential to act as an intraoperative
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neurophysiological indicator of immediate success or failure and allows tailoring of the procedure for additional internal neurolysis, as per the responses, especially useful in MRI negative cases or in detecting the often missed out hidden offending vessels. We also believe that fat –teflon sandwich method for MVD can potentially prevent Teflon granuloma and combining this modification in awake MVD with or without IN will greatly reduce the burden of re-intervention and will be useful in increasing its overall success. However, a longer follow-up and a larger number of patients will enable us to validate our initial findings. Sources of support This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Conflict of interest All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent Informed consent was obtained from all individual participants included in the study. Acknowledgments None. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jocn.2019.04.007. References [1] Barker FG, Jannetta PJ, Bissonette DJ, Larkins MV, Jho HD. The long-term outcome of microvascular decompression for trigeminal Neuralgia. N Engl J Med 1996;334(17):1077–84. https://doi.org/10.1056/nejm199604253341701. [2] Hitotsumatsu T, Matsushima T, Inoue T. Microvascular decompression for treatment of trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia: three surgical approach variations: technical note. Neurosurgery 2003;53(6):1436–41. discussion 1442-3. [3] McLaughlin MR, Jannetta PJ, Clyde BL, Subach BR, Comey CH, Resnick DK. Microvascular decompression of cranial nerves: lessons learned after 4400 operations. J Neurosurg 1999;90(1):1–8. https://doi.org/10.3171/ jns.1999.90.1.0001.
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