Median Nerve Entrapment: Beyond Carpal Tunnel Syndrome

General Overview

Time and time again, the Occupational Therapists in my clinic get referrals for Carpal Tunnel Syndrome (CTS). In some of these cases, the patients also have cervical pain, shoulder pain, proximal forearm weakness, and/or palmar paresthesias. While these individuals may have compression within the carpal tunnel, many of them are suffering from nerve entrapment proximal to the carpal tunnel. Many develop adverse neural tension caused by postural dysfunctions, muscle imbalances, and systemic comorbidities which cause a breakdown of the nervous system. 

Am I saying CTS is over-diagnosed? That is exactly what I am saying. It has become a blanket term for pain in the wrist and hand just as lateral epicondylagia has at the elbow. Many times, the cause of someone's symptoms is not consistent with the referring diagnosis. In this mini-review, I will break down a few areas of entrapment of the median nerve and how to assess for adverse neural tension within the median nerve. 

Median Nerve Pathway

The median nerve is formed from contributions of the spinal nerve roots C5-T1. After originating from the brachial plexus in the axilla, the medial nerve travels down the arm to the cubital fossa. Next, the nerve travels through the two heads of the pronator teres and between the flexor digitorum superficialis and flexor digitorum profundus muscles. At this point the median nerve splits into the anterior interosseous nerve (AIN) and palmar cutaneous nerve. Finally, the nerve travels through the carpal tunnel space. (Be aware there are many alternative anatomy presentations; this is simply one of the most common ones).

As you can see there are many points of entrapment for the median nerve: the cervical spine, interscalene musculature, between the heads of the pronator teres, and within the carpal tunnel (among other less common ones). The patient's subjective reports and your clinical examination will point you to the correct structure and location of dysfunction. When suspecting neural tension, a clinical examination measure you should utilize is the Median Nerve ULTT. 

Assessing for Adverse Neural Tension & Different Sites of Entrapment

We have discussed adverse neural tension several times before on The Student Physical Therapist (How to assess neural tension, Differential Dx in neural tension). At the Harris Health Orthopedic Residency, I use 3 distinguishing criteria for positive adverse neural tension testing. The symptom(s) must reproduce the patient's primary complaint, it must change by moving a component at a joint proximal or distal to the complaint, and it must be different side to side. To see the full test for adverse neural tension of the median nerve, click HERE. This test will not tell you the exact location of symptoms, but it will give you an understanding of the sensitivity of the nerve.


In addition to performing neural tensioning tests, it is important to perform a thorough assessment of other potential areas of entrapment. For example, if you find muscle wasting in the FPL, pronator quadratus, and/or radial half of the FDP, the involved nerve is likely the AIN being compressed in the proximal forearm. Additionally, if the patient has comorbidities that affect the nervous system, such as a history of uncontrolled DM, this can significantly alter your patient presentation. Several clinicians I work with relate this to a form of double crush injury: the nerve is being mechanically entrapped and is also receiving compression from other intrinsic sources.

Continue to use your differential diagnosis skills to determine the source of one's symptoms. It may save your patient from an unnecessary surgery.

-Jim      

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