Nerve decompression

Short description: Surgical procedure

A nerve decompression is a neurosurgical procedure to relieve chronic, direct pressure on a nerve to treat nerve entrapment, a pain syndrome characterized by severe chronic pain and muscle weakness. In this way a nerve decompression targets the underlying pathophysiology of the syndrome and is considered a first-line surgical treatment option for peripheral nerve pain.[1] Despite treating the underlying cause of the disease, the symptoms may not be fully reversible as delays in diagnosis can allow permanent damage to occur to the nerve and surrounding microvasculature. Traditionally only nerves accessible with open surgery have been good candidates, however innovations in laparoscopy and nerve-sparing techniques made nearly all nerves in the body good candidates, as surgical access is no longer a barrier.

## Contents

* 1 Surgical planning
* 1.1 Diagnostic blocks
* 1.2 Imaging
* 2 Surgical outcomes
* 2.1 Carpal tunnel release
* 2.2 Sciatic nerve decompression
* 2.3 Migraine surgery
* 3 Complications
* 4 Other procedures
* 5 See also
* 6 References

## Surgical planning

Surgical planning is distinct from diagnosis of entrapment. Diagnosis will focus on a binary decision: does the patient have entrapment or not? A diagnosis may not be enough information for surgery on its own as the area to explore may be too large. Surgical planning seeks to localize the specific area of entrapment to improve surgical outcomes. Identifying the level of entrapment is an important consideration for surgery as decompressing the wrong area will lead to a failed surgery (e.g. performing back surgery for extra-spinal sciatica),[2][3] failure to treat nerve entrapment early can lead to permanent nerve injury,[4] and the patient may be unnecessarily exposed to surgical complications.

### Diagnostic blocks

Diagnostic nerve blocks can confirm the clinical diagnosis for chronic pain as well as identify the entrapment site.[5] A diagnostic block is like an inverted palpation in the sense that palpation will cause a sensory nerve to send a signal (action potential) and a block will prevent a sensory nerve from sending a signal. By blocking nerve signals, the pain-contributing nerves can be identified or ruled out. Nerves are predisposed to entrapment in certain anatomical regions such as in an osteofibrous tunnels, through a muscle, adjacent to fibrous tissue.[6] Consequently, knowledge of these anatomical regions as well as peripheral nerve anatomy is an essential component to planning successful diagnostic blocks.[5] Ultrasound is a common form of image-guidance to place the needle properly, but it faces limitations visualizing small and deep nerves.[7] CT\- or MRI\- guidance are better positioned to access deep nerves as well as identify the anatomic level of the needle.[7]

### Imaging

MRI may be used to identify certain causes of entrapment such as a structural lesions pressing on a nearby nerve, but is prone to false negatives/positives and has poor correlation with the clinical examination.[8] A major limitation with MRI is that nerve tissue is resistant to imaging. An advancement of MRI that takes advantage of the tissue properties of nerves, called MR neurography (MRN), provides more detail. MR tractography (MRT) can also be of use in surgical planning as it can identify peripheral nerve abnormalities with a high correlation to intraoperative findings and has higher accuracy than MR neurography alone.[9] MRT uses diffusion tensor imaging to visualize the directional movement of water molecules along nerve tracts. Often an abnormality can be identified along tracts of nerve where water is not diffusing normally along the axis. MRT has been used to identify sacral nerve entrapment by the piriformis muscle, which would otherwise only be diagnosable with exploratory surgery.[10]

## Surgical outcomes

Nerve decompressions are still a relatively new surgery, however a picture emerges from looking at the outcomes of some of the most studied nerve decompressions: carpal tunnel release, sciatic nerve decompression, and migraine surgery. Even within these commonly performed surgeries, the measurement of outcomes is not always standardized. Common ways of measuring outcomes are syndrome-specific disability questionnaires (e.g. Boston Carpal Tunnel Questionnaire,[11] Oswestry low back disability questionnaire,[12] and the migraine disability assessment[13]); visual analog scale (VAS);[14] physical examination findings;[15] and subjective patient satisfaction[16]

### Carpal tunnel release

Further information: Medicine:Carpal tunnel surgery

Carpal tunnel surgery has a clinical success rate of 75-90%.[17] Success is most frequently measured with the Boston Carpal Tunnel Questionnaire, physical examination (sensory function, motor function, pain, electrodiagnostic, trophic function), and patient self-assessments. One study found that while 86% of patients improved, only 26% had complete recovery of clinical and electrodiagnostic findings. Of the functional assessments, pain showed the greatest improvements following surgery.[18] Another study compared carpal tunnel syndrome patients who elected surgery with those who chose not to. 77% of the surgery group said they were cured compared to 16% who did not elect surgery.[19] While some of the success of surgery may just be due to the natural history of the disease, the surgery groups still have an improvement in outcomes over conservative measures. A systematic review found that surgical treatment outweighed the benefits over conservative treatment overall all outcome measures, however conservative treatment caused fewer complications.[20]

### Sciatic nerve decompression

A systematic review has found that 90% of surgery patients see improved pain scores with scores improving on average from 6.7 preoperatively to 2.1 postoperatively.[21] In the literature, the most common outcome measurement for sciatic nerve decompressions is the visual analog scale, where patients rate their pain on a 100mm horizontal line that gets converted into a numeric score from 0-10 or 0–100. The main disability questionnaires used are the modified Harris Hip score (mHHS) and the Oswestry low back disability questionnaire. One study found that all deep gluteal syndrome surgery patients who were taking narcotics for pre-operative pain (n = 21) no longer needed narcotics for the initial complaint after decompression surgery.[22]

### Migraine surgery

Further information: Medicine:Migraine surgery

A systematic review has found that the improvement is seen in 68-100% of surgery patients and complete migraine elimination is seen in 8-86% of surgery patients.[23] The outcomes are usually measured in migraine intensity, frequency, and duration (an early measurement, the migraine headache index, was just the product of these numerical values). The most common migraine disability questionnaires are the migraine disability assessment (MIDAS), headache impact test (HIT), and migraine specific quality of life questionnaire (MSQ).[24]

One randomized study compared the efficacy of migraine surgery to pharmacologic treatment and found that surgical treatment had a significantly higher success rate than medical treatment. Notably, 36% of patients in the surgical treatment group experienced complete elimination of migraine headaches, compared to and 4% in the medical treatment group.[25] Another randomized study compared surgery to sham surgery. 57% of the surgery group experienced complete elimination of migraine headaches, compared on only 4% of the sham surgery group.[26] A separate study examining outcomes found that there was a bimodal distribution (two main outcomes), where approximately >80% of patients saw either at least an 80% reduction in symptoms or less than 5% reduction. Of the patients seeing significant improvement, the mean improvement was 96%. Of the patients seeing minimal improvement, the average improvement was 0%.[27]

Paying special attention to complete elimination of migraines or measuring outcomes after long follow ups (e.g. years) may be important for assessing the efficacy of migraine surgery because headache research has found a strong placebo effect.[28] A large meta-analysis found that the placebo effect in acute migraine treatments was greatly reduced when the treatment outcome was "pain-free" (9% of patients) compared to "improved" (30% of patients).[29] Studies that have compared migraine surgery to a control group have found similarly low placebo cure rates, both at 4%.[25][26]

## Complications

Complications can be perioperative or postoperative. Among the generic set of surgical complications such as bleeding, infection, scarring, complications from general anesthesia, etc. nerve decompressions come with a risk of nerve injury. A nerve can be directly injured due to transection (cutting), traction (pulling), crush injuries (squeezing), destroying a blood vessel that supplied the nerve, etc. While nerve sparing techniques have been developed to mitigate nerve injury,[30][31] the radical nature of decompression surgeries cannot eliminate the risk.

In a large national study of carpal tunnel decompression postoperative complications, the serious complications seen were wound dehiscence, wound infection, tendon injury, and neurovascular injury. Serious postoperative complications, defined as requiring re-admittance to a hospital within 90 days, was relatively rare, at 0.1% over approximately 850,000 surgeries.[32]

Endoscopic sciatic nerve decompression has similarly low rates of complication. Two studies with a combined 95 patients found no complications.[33][22] A systematic review also found a 0% major complication rate and a 1% minor complication rate for the endoscopic approach.[21]

A systematic review on migraine surgeries found a major complication rate of 1% and a liberal estimate on the minor complication rate of approximately 32%. The most common complications were numbness/paresthesia and itching.[23] Another systematic review found the adverse event rate to be 11.6%.[34] One of the challenges in cataloging the complication rate of migraine surgery is that it's a relatively new surgery and so the surgical treatment can be extremely heterogeneous across different surgeons (e.g. remove artery, remove muscle, decompress nerve, remove nerve all across one or more trigger sites).[34]

## Other procedures

An alternative to a decompression is a nerve resection.[1] When the nerve does not have any motor fibres and loss of sensation is acceptable, removing the nerve in its entirety may be a more "complete" solution as it will address a much wider dermatome (all distal nerve fibres from the point of excision). Nerve decompressions, in contrast, cannot explore the entire course of a nerve and all its branches and so may potentially miss the true entrapment point. For this reason, a nerve resection may be considered after a failed decompression. Examples of nerves that may be good candidates for resection are lateral femoral cutaneous nerve,[35] zygomaticotemporal branch of the trigeminal nerve,[36] the posterior femoral cutaneous nerve,[37][38] and the middle/superior cluneal nerves[39]

It's not clear whether a nerve resection is superior to a nerve decompression when both treatments may be suitable. A study on occiptal neuralgia in 2017 found that there was not enough data to make a determination.[40] A study on Meralgia Paraesthetica found higher success rates for nerve resection and that most patients were not bothered by numbness following the procedure.[41]

## See also

* Nerve compression syndrome
* Nerve block
* Neurectomy
* Laparoscopy
* Arthroscopy
* Endoscopy

## References

1. ↑ 1.0 1.1 Lipinski, L. J.; Spinner, R. J. (2014). "Neurolysis, neurectomy, and nerve repair/Reconstruction for chronic pain". Neurosurgery Clinics of North America 25 (4): 777–787. doi:10.1016/j.nec.2014.07.002. PMID 25240664.
2. ↑ Siddiq, Md Abu Bakar; Clegg, Danny; Hasan, Suzon Al; Rasker, Johannes J. (2020). "Extra-spinal sciatica and sciatica mimics: a scoping review". The Korean Journal of Pain 33 (4): 305–317. doi:10.3344/kjp.2020.33.4.305. PMID 32989195.
3. ↑ Kulcu, Duygu Geler; Naderi, Sait (2008). "Differential diagnosis of intraspinal and extraspinal non-discogenic sciatica". Journal of Clinical Neuroscience 15 (11): 1246–1252. doi:10.1016/j.jocn.2008.01.017. PMID 18789864.
4. ↑ MacKay, B. J.; Cox, C. T.; Valerio, I. L.; Greenberg, J. A.; Buncke, G. M.; Evans, P. J.; Mercer, D. M.; McKee, D. M. et al. (2021). "Evidence-Based Approach to Timing of Nerve Surgery: A Review". Annals of Plastic Surgery 87 (3): e1–e21. doi:10.1097/SAP.0000000000002767. PMID 33833177.
5. ↑ 5.0 5.1 Wiederhold BD, Garmon EH, Peterson E, et al. Nerve Block Anesthesia. [Updated 2023 Apr 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK431109/
6. ↑ Muniz Neto, F. J.; Kihara Filho, E. N.; Miranda, F. C.; Rosemberg, L. A.; Santos DCB; Taneja, A. K. (2018). "Demystifying MR Neurography of the Lumbosacral Plexus: From Protocols to Pathologies". BioMed Research International 2018: 1–20. doi:10.1155/2018/9608947. PMID 29662907.
7. ↑ 7.0 7.1 Wadhwa, V.; Scott, K. M.; Rozen, S.; Starr, A. J.; Chhabra, A. (2016). "CT-guided Perineural Injections for Chronic Pelvic Pain". Radiographics 36 (5): 1408–1425. doi:10.1148/rg.2016150263. PMID 27618322.
8. ↑ Schmid, A. B.; Fundaun, J.; Tampin, B. (2020). "Entrapment neuropathies: A contemporary approach to pathophysiology, clinical assessment, and management". Pain Reports 5 (4): e829. doi:10.1097/PR9.0000000000000829. PMID 32766466.
9. ↑ Lemos, N.; Melo HJF; Sermer, C.; Fernandes, G.; Ribeiro, A.; Nascimento, G.; Luo, Z. C.; Girão MJBC et al. (2021). "Lumbosacral plexus MR tractography: A novel diagnostic tool for extraspinal sciatica and pudendal neuralgia?". Magnetic Resonance Imaging 83: 107–113. doi:10.1016/j.mri.2021.08.003. PMID 34400289.
10. ↑ Sermer, Corey; Li, Adrienne L K.; Fernandes, Gustavo L.; Ribeiro, Augusta M.; Polesello, Giancarlo; Tokechi, Denise; Cancelliere, Laura; Lemos, Nucelio (2021). "Intrapelvic entrapment of sacral nerve roots by abnormal bundles of the piriformis muscle: Description of an extra-spinal cause of sciatica and pudendal neuralgia". Journal of Hip Preservation Surgery 8 (1): 132–138. doi:10.1093/jhps/hnab041. PMID 34567608. PMC 8460165. https://doi.org/10.1093/jhps/hnab041.
11. ↑ Multanen, J.; Ylinen, J.; Karjalainen, T.; Ikonen, J.; Häkkinen, A.; Repo, J. P. (2020). "Structural validity of the Boston Carpal Tunnel Questionnaire and its short version, the 6-Item CTS symptoms scale: A Rasch analysis one year after surgery". BMC Musculoskeletal Disorders 21 (1): 609. doi:10.1186/s12891-020-03626-2. PMID 32919457.
12. ↑ Fairbank, J. C.; Pynsent, P. B. (2000). "The Oswestry Disability Index". Spine 25 (22): 2940–52; discussion 2952. doi:10.1097/00007632-200011150-00017. PMID 11074683.
13. ↑ Stewart, W. F.; Lipton, R. B.; Dowson, A. J.; Sawyer, J. (2001). "Development and testing of the Migraine Disability Assessment (MIDAS) Questionnaire to assess headache-related disability". Neurology 56 (6 Suppl 1): S20-8. doi:10.1212/wnl.56.suppl_1.s20. PMID 11294956.
14. ↑ McCormack, H. M.; Horne, D. J.; Sheather, S. (1988). "Clinical applications of visual analogue scales: A critical review". Psychological Medicine 18 (4): 1007–1019. doi:10.1017/s0033291700009934. PMID 3078045.
15. ↑ Rosales, R. S.; Atroshi, I. (2020). "The methodological requirements for clinical examination and patient-reported outcomes, and how to test them". The Journal of Hand Surgery, European Volume 45 (1): 12–18. doi:10.1177/1753193419885509. PMID 31722640.
16. ↑ Anufriyeva, V.; Pavlova, M.; Stepurko, T.; Groot, W. (2021). "The validity and reliability of self-reported satisfaction with healthcare as a measure of quality: A systematic literature review". International Journal for Quality in Health Care 33 (1). doi:10.1093/intqhc/mzaa152. PMID 33306791.
17. ↑ Louie, D.; Earp, B.; Blazar, P. (2012). "Long-term outcomes of carpal tunnel release: A critical review of the literature". Hand 7 (3): 242–246. doi:10.1007/s11552-012-9429-x. PMID 23997725.
18. ↑ Haupt, W. F.; Wintzer, G.; Schop, A.; Löttgen, J.; Pawlik, G. (1993). "Long-term results of carpal tunnel decompression. Assessment of 60 cases". Journal of Hand Surgery 18 (4): 471–474. doi:10.1016/0266-7681(93)90149-a. PMID 8409659.
19. ↑ Kouyoumdjian, J. A.; Morita, M. P.; Molina, A. F.; Zanetta, D. M.; Sato, A. K.; Rocha, C. E.; Fasanella, C. C. (2003). "Long-term outcomes of symptomatic electrodiagnosed carpal tunnel syndrome". Arquivos de Neuro-Psiquiatria 61 (2A): 194–198. doi:10.1590/s0004-282x2003000200007. PMID 12806496.
20. ↑ Klokkari, D.; Mamais, I. (2018). "Effectiveness of surgical versus conservative treatment for carpal tunnel syndrome: A systematic review, meta-analysis and qualitative analysis". Hong Kong Physiotherapy Journal 38 (2): 91–114. doi:10.1142/S1013702518500087. PMID 30930582.
21. ↑ 21.0 21.1 Kay, J.; De Sa, D.; Morrison, L.; Fejtek, E.; Simunovic, N.; Martin, H. D.; Ayeni, O. R. (2017). "Surgical Management of Deep Gluteal Syndrome Causing Sciatic Nerve Entrapment: A Systematic Review". Arthroscopy 33 (12): 2263–2278.e1. doi:10.1016/j.arthro.2017.06.041. PMID 28866346.
22. ↑ 22.0 22.1 Martin, H. D.; Shears, S. A.; Johnson, J. C.; Smathers, A. M.; Palmer, I. J. (2011). "The endoscopic treatment of sciatic nerve entrapment/Deep gluteal syndrome". Arthroscopy 27 (2): 172–181. doi:10.1016/j.arthro.2010.07.008. PMID 21071168.
23. ↑ 23.0 23.1 Elhawary, H.; Barone, N.; Baradaran, A.; Janis, J. E. (2022). "Efficacy and Safety of Migraine Surgery: A Systematic Review and Meta-analysis of Outcomes and Complication Rates". Annals of Surgery 275 (2): e315–e323. doi:10.1097/SLA.0000000000005057. PMID 35007230.
24. ↑ Albano, N. J.; Israel, J. S.; Carbullido, M. K.; Stilp, E. K.; Leverson, G.; Voils, C. I.; Afifi, A. M. (2023). "Measuring Success in Headache Surgery: A Comparison of Different Outcomes Measures". Plastic and Reconstructive Surgery 151 (3): 469e–476e. doi:10.1097/PRS.0000000000009930. PMID 36730226.
25. ↑ 25.0 25.1 Omranifard, M.; Abdali, H.; Ardakani, M. R.; Talebianfar, M. (2016). "A comparison of outcome of medical and surgical treatment of migraine headache: In 1 year follow-up". Advanced Biomedical Research 5: 121. doi:10.4103/2277-9175.186994. PMID 27563631.
26. ↑ 26.0 26.1 Guyuron, B.; Reed, D.; Kriegler, J. S.; Davis, J.; Pashmini, N.; Amini, S. (2009). "A placebo-controlled surgical trial of the treatment of migraine headaches". Plastic and Reconstructive Surgery 124 (2): 461–468. doi:10.1097/PRS.0b013e3181adcf6a. PMID 19644260.
27. ↑ Gfrerer, L.; Hulsen, J. H.; McLeod, M. D.; Wright, E. J.; Austen Jr, W. G. (2019). "Migraine Surgery: An All or Nothing Phenomenon? Prospective Evaluation of Surgical Outcomes". Annals of Surgery 269 (5): 994–999. doi:10.1097/SLA.0000000000002697. PMID 29394166.
28. ↑ Diener, H. C.; Schorn, C. F.; Bingel, U.; Dodick, D. W. (2008). "The importance of placebo in headache research". Cephalalgia 28 (10): 1003–1011. doi:10.1111/j.1468-2982.2008.01660.x. PMID 18727647.
29. ↑ MacEdo, A.; Farré, M.; Baños, J. E. (2006). "A meta-analysis of the placebo response in acute migraine and how this response may be influenced by some of the characteristics of clinical trials". European Journal of Clinical Pharmacology 62 (3): 161–172. doi:10.1007/s00228-005-0088-5. PMID 16402240.
30. ↑ Tavukçu, H. H.; Aytac, O.; Atug, F. (2016). "Nerve-sparing techniques and results in robot-assisted radical prostatectomy". Investigative and Clinical Urology 57 (Suppl 2): S172–S184. doi:10.4111/icu.2016.57.S2.S172. PMID 27995221.
31. ↑ Michl, U.; Tennstedt, P.; Feldmeier, L.; Mandel, P.; Oh, S. J.; Ahyai, S.; Budäus, L.; Chun FKH et al. (2016). "Nerve-sparing Surgery Technique, Not the Preservation of the Neurovascular Bundles, Leads to Improved Long-term Continence Rates After Radical Prostatectomy". European Urology 69 (4): 584–589. doi:10.1016/j.eururo.2015.07.037. PMID 26277303.
32. ↑ Lane JCE; Craig, R. S.; Rees, J. L.; Gardiner, M. D.; Green, J.; Prieto-Alhambra, D.; Furniss, D. (2021). "Serious postoperative complications and reoperation after carpal tunnel decompression surgery in England: A nationwide cohort analysis". The Lancet. Rheumatology 3 (1): e49–e57. doi:10.1016/S2665-9913(20)30238-1. PMID 33381769.
33. ↑ Ham, D. H.; Chung, W. C.; Jung, D. U. (2018). "Effectiveness of Endoscopic Sciatic Nerve Decompression for the Treatment of Deep Gluteal Syndrome". Hip & Pelvis 30 (1): 29–36. doi:10.5371/hp.2018.30.1.29. PMID 29564295.
34. ↑ 34.0 34.1 Wormald JCR; Luck, J.; Athwal, B.; Muelhberger, T.; Mosahebi, A. (2019). "Surgical intervention for chronic migraine headache: A systematic review". Jpras Open 20: 1–18. doi:10.1016/j.jpra.2019.01.002. PMID 32158867.
35. ↑ Son, Byung-Chul; Kim, Deok-Ryeong; Kim, Il-Sup; Hong, Jae-Taek; Sung, Jae-Hoon; Lee, Sang-Won (2012). "Neurolysis for Megalgia Paresthetica". Journal of Korean Neurosurgical Society 51 (6): 363–366. doi:10.3340/jkns.2012.51.6.363. PMID 22949966. PMC 3424177. https://doi.org/10.3340/jkns.2012.51.6.363.
36. ↑ Guyuron, B.; Harvey, D.; Reed, D. (2015). "A Prospective Randomized Outcomes Comparison of Two Temple Migraine Trigger Site Deactivation Techniques". Plastic and Reconstructive Surgery 136 (1): 159–165. doi:10.1097/PRS.0000000000001322. PMID 25829156.
37. ↑ Kachniarz, B.; Dellon, A. L. (2021). "Relief of Sitting Pain by Resecting Posterior Femoral Cutaneous Nerve, and Elucidation of Its Anatomical Branching Pattern". Journal of Reconstructive Microsurgery 37 (8): 687–693. doi:10.1055/s-0041-1726027. PMID 33757132.
38. ↑ Dellon, A. L. (2015). "Pain with sitting related to injury of the posterior femoral cutaneous nerve". Microsurgery 35 (6): 463–468. doi:10.1002/micr.22422. PMID 25917688.
39. ↑ Karl, H. W.; Helm, S.; Trescot, A. M. (2022). "Superior and Middle Cluneal Nerve Entrapment: A Cause of Low Back and Radicular Pain". Pain Physician 25 (4): E503–E521. PMID 35793175.
40. ↑ McNutt, S.; Hallan, D. R.; Rizk, E. (2020). "Evaluating the Evidence: Is Neurolysis or Neurectomy a Better Treatment for Occipital Neuralgia?". Cureus 12 (11): e11461. doi:10.7759/cureus.11461. PMID 33329959.
41. ↑ De Ruiter, Godard C. W.; Wurzer, Johannes A. L.; Kloet, Alfred (2012). "Decision making in the surgical treatment of meralgia paresthetica: Neurolysis versus neurectomy". Acta Neurochirurgica 154 (10): 1765–1772. doi:10.1007/s00701-012-1431-0. PMID 22766927. https://doi.org/10.1007/s00701-012-1431-0.

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