Nerve decompression
[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.
Diagnostic nerve blocks can confirm the clinical diagnosis for chronic pain as well as identify the entrapment site.
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] 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.
An advancement of MRI that takes advantage of the tissue properties of nerves, called MR neurography (MRN), provides more detail.
[9] MRT uses diffusion tensor imaging to visualize the directional movement of water molecules along nerve tracts.
MRT has been used to identify sacral nerve entrapment by the piriformis muscle, which would otherwise only be diagnosable with exploratory surgery.
[15] 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.
[34] 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.
[36] Studies that have compared migraine surgery to a control group have found similarly low placebo cure rates, both at 4%.
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.
[47] A study on Meralgia Paraesthetica found higher success rates for nerve resection and that most patients were not bothered by numbness following the procedure.
The development of carpal tunnel syndrome to explain idiopathic tardy median nerve palsy formalized the concept of nerve compression at anatomic areas of narrowing, and influenced the development of other tunnel syndromes.
[7][55] The use of magnetic resonance neurography (MRN) and diffusion tensor imaging (DTI) have allowed better visualization of nerves, at times identifying the site of entrapment without the need for extensive surgical exploration.
[64][65] 1994: Diffusion tensor imaging described[66] 1997 endoscopic pudendal nerve decompression[67] 2000: correlation found between brow lifts and migraine reduction.
[71][73] In diabetic peripheral neuropathy (treatable in some cases with multiple nerve decompressions[73]) and migraines (migraine surgery is a nerve decompression[74]), critics dispute the interpretation of the results because the majority of studies are of retrospective case series (reports of surgeries performed in the past) rather than prospective randomized controlled trials (RCTs), and so any positive results of surgery could be influenced by methodological flaws such as lack of proper control groups.
[71] Proponents have alleged that the success of treating previously untreatable patients validates decompression as a treatment.
[78] That the improvement from surgery is clearly much larger than the studied magnitude of the placebo effect, and so cannot be explained by it.
