Part 1: Do nerves get pinched?


​What prompted this article was some discussion in the social media along these lines:

"People don't get pinched nerves so we should not be telling patients they have one."

​Pinched nerves is an ambiguous and unfortunate term because it can conjure all sorts of negative connotations andemotions in patients with pain problems  So here is a clarification in more scientific terms.
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"There is no evidence for stuck nerves so we should not be telling patients they have one."











"The strength of neurodynamic tests is their sensitivity and ability to eliminate neurodynamic problems when compared to gold standards ...".
 Whether nerves get pinched is a very important question because we have a professional responsibility to be clinically accurate and make our explanations to our patients factual, which must include the evidence.

Hence, there are three parts to this article:

1. Do nerves get pinched?

Here is some research that you should know about as it basically validates the idea that nerve roots can get pinched.

2. The statement "There is no evidence ...".

Discussed is the idea that 'lack of evidence' is misunderstood and often used incorrectly to justify not doing something.  Also, the decision to ​NOT do something can itself be based on a lack of evidence.

3. Integration of evidence

This section discusses that integration of documented evidence is important but it has its limitations.
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So, what is the evidence for 'pinched nerves'?
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First, we should define what we mean by 'pinched'. There is no doubt that nerves and nerve roots can become compressed and they malfunction as a result, producing all sorts of pain problems.  The classical and well-recognised examples are cervical and lumbar radiculopathy and peripheral nerve entrapment, such as carpal tarsal, supinator, pronator and cubital tunnel syndromes.

So, if we consider that 'pinched' means compressed, then there should be no dispute.  And if you still think there is a lack of evidence, please read the literature on the subject, particularly the surgical reports and radiology and electrophysiology studies as these are the gold standards for diagnosis. There are hundreds of such studies in the peer-reviewed literature.
If the patient has no clinical features of a pinched nerve, we should certainly not tell them they have one. But, rather than relying on the research literature to know if the patient has one, it is critical that any clinical decisions are based on detailed and skilled examination, particularly with neurodynamic tests, nerve palpation and neurological evaluation and sometimes quantitative sensory testing.

Furthermore, if the clinician does not do a subjective or physical examination designed to eliminate such nerve problems (elimination tests), it may not always be justified to tell the patient that they don't have one.  This is because no negating evidence has been sought and a decision of 'no pinched nerve' is also based on a 'lack of evidence'.  So it's about testing and including or eliminating the problem with testing that includes a balance of confirming and negating evidence

Clinically, it is imperative that the clinician searches for both supporting and negating evidence in an unbiased fashion so decisions are influenced primarily by what is found in the patient.

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If 'stuck' means the nerve can't move adequately, then this is more complex.  There is quite a lot of valuable research on this now in the form of ultrasound imaging of longitudinal nerve movement but I don't refer to it here as it's a large subject and validity comes into discussion, too much for here.

Instead, here are two examples of a stuck nerve, when it means loss of movement, alias 'mechanical impairment'.

Clinical example: Athlete - hamstring injury and sciatic nerve
 I saw an elite athlete a while ago who had pain in the posterior thigh which co-existed with scarring around, and degeneration of, his hamstring tendon as it inserted into the ischial tuberosity, found on MRI.  The slump test reproduced his pain and it changed with cervical movements, supporting a neural element to the problem.  At surgery, the smart surgeon did a straight leg raise to observe behaviour of the sciatic nerve in the ischial region.  Even after freeing it surgically by removing the scar tissue and manually mobilising it, it was noticed that the nerve remained tight, compared with what the surgeon had noticed in other patients with similar testing.  The conclusion was that the nerve is intrinsically tight and just can't move normally.  That is a stuck nerve.

Lumbar nerve root
There are certainly studies that show loss of lumbar nerve root movement in patients with radiculopathy due to disc protrusion.  It has been found at surgery that the lumbosacral nerve roots lack movement when tested neurodynamically with the straight leg raise (SLR). When the nerve roots are 'freed up' surgically by removal of the disc protrusion and scar tissue, the nerve root movement improves, along with the intraneural blood flow and the neurodynamic test (SLR) response.  In this study by Kobayashi et al (2003), the more restricted was the nerve root movement, the worse the clinical features, particularly the SLR.

Before removal of the disc protrusion and adherent scar tissue, the S1 nerve root could only move in the foramen 0.5 mm on average.  After release, this increased to 4.1 mm and correlated with improvements in nerve root blood flow, SLR angle and patient responses (See figure - left, from Kobayashi et al 2003, 2010).  

In this study, the nerve roots lost as much 85% of their excursion!

That is a stuck nerve.

Now that we have evidence for stuck lumbar nerve roots, how effective can neurodynamic tests be in diagnosis when compared with a gold standard such as MRI showing nerve root compression by disc protrusion?

Majlesi et al (2008) showed that the slump test produced the sensitivity and specificity ratings below, when reproduction of clinical symptoms was used as the key diagnostic criterion:

Sensitivity - 0.52
Specificity - 0.89
Positive likelihood ratio - 4.73
Negative likelihood ratio - 0.54
N = 77

If you think a patient does NOT have a neurodynamic problem
Ask yourself - "Have I tested for it properly in my subjective and physical examinations and found negating evidence that outweighs any supporting evidence?".

If you think a patient DOES have a neurodynamic problem
Ask yourself -  "Have I found supporting evidence in my subjective and physical examinations that outweighs any negating evidence, including:

Subjective - radiating pain and pins and needles or numbness, muscle weakness and/or wasting.
Medical tests - radiology, neurophysiology, surgical, haematological, metabolic, genetic
Physical - neurodynamic test responses, nerve palpation and neurological testing?"

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SUMMARY POINTS
'Lack of evidence' is often used incorrectly to justify excluding a diagnosis.

Lack of evidence is NOT negating evidence.

Just as supporting evidence can implicate a diagnosis, negating evidence helps to exclude it.

Clinical decisions are based on searching for both supporting and negating evidence, balancing the two.

NEXT:
Part 2 - "There is no evidence for that ..."

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REFERENCES
Kobayashi S, Shizu N, Suzuki Y, Asai T, Yoshizawa H 2003 Changes in nerve root motion and intraradicular blood flow during an intraoperative straight-leg-raising test. Spine 28 (13):1427-34 
See abstract

Kobayashi S, Takeno K, Yayama T, Awara K, Miyazaki T, Guerrero A, Baba H 2010 Pathomechanisms of sciatica in lumbar disc herniation: effect of periradicular adhesive tissue on electrophysiological values by an intraoperative straight leg raising test. Spine 35(22): 2004-2014
See abstract

Majlesi J, Togay H, Ünalan H, Toprak S 2008 The sensitivity and specificity of the slump and the straight leg raising tests in patients with lumbar disc herniation. Journal of Clinical Rheumatology (2): 87-91
See abstract

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