What's making my hand go numb? Part 3 - Peripheral Nerve Disorder


Author: Bryan Lang, PT, DPT, MHA, CSCS, Cert.DN: Doctor of Physical Therapy, Business Owner, Associate Professor, and Blog Contributor. Explores common client questions, helps find solutions for every day functional health concerns, and interprets difficult theories in healthcare rehabilitation. Committed to life-long learning and education. Learn more about Bryan on Google+.


Nerves are like highways transporting cars. In this case, “cars” are the action potentials that allow you to feel and to move throughout your body. If there is an accident on a road, cars won’t be able to get to their destination. This also happens with the action potentials in your nerves where there is a blockage along the length of a nerve. There are some common places that nerves get caught.

Median Nerve: This nerve is most famously known for creating the symptoms of Carpal Tunnel Syndrome. The most common area where the peripheral nerve is entrapped or inflamed at the meeting of the wrist and forearm under a tunnel of tissue called the flexor retinaculum.  Also, a couple of less common median nerve entrapment syndromes that can be equally disabling are knows as anterior interosseous nerve syndrome (AINS) and pronator teres syndrome. Interestingly, pronator teres syndrome can be easily represented as carpal tunnel syndrome. The most common difference is numbness into the forearm which does not occur with carpal tunnel syndrome [1].  AINS is a very rare condition. With this issue, there is no loss of sensation, but a patient will be unable to make the “OK” sign. This is because the nerves that innervate muscles in order to form that sign are impaired [2].

 Image courtesy of http://body-disease.com/wp-content/uploads/2013/01/A-The-cutaneous-distribution-and-B-course-of-the-median-nerve.jpg

Image courtesy of http://body-disease.com/wp-content/uploads/2013/01/A-The-cutaneous-distribution-and-B-course-of-the-median-nerve.jpg

These were only some common aspects of an entrapped median nerve. There are many places where the nerve itself can be pinched, and these areas are described below:

  • Cervical nerve root level – discussed previously in part 2
  • Against a cervical rib
  • Between the anterior and middle scalene muscles
  • Between the clavicle and first rib
  • Underneath the pectoralis minor muscle
  • Underneath the ligament of Struthers
  • Passing by the bicipital aponeurosis (lacertus fibrosus)
  • Between the two heads of the pronator teres
  • Compression in the carpal tunnel [3]

Ulnar Nerve: The main sites of compression with this nerve are in the forearm and wrist. Primarily, the entrapments are either in a structure called the cubital tunnel or, in less common instances, in the Guyon’s canal [4]. Both areas of entrapment can cause numbness and/or tingling into the hand, specifically into the 4th and 5th digit. It can also cause muscle weakness into the hand.  Sometimes an injury to the ulnar nerve is called a cyclist’s palsy because the compression of the nerve against the handlebar of a bicycle can begin causing symptoms.

 Image courtesy of https://www.dartmouth.edu/~humananatomy/figures/chapter_8/8-12_files/IMAGE001.JPG

Image courtesy of https://www.dartmouth.edu/~humananatomy/figures/chapter_8/8-12_files/IMAGE001.JPG

 

Radial Nerve: The most common area for radial nerve entrapment is at the elbow between the tendons of a muscle called the supinator. The name of this area is the arcade of Frohse. The syndromes associated with radial nerve entrapment are called radial tunnel and posterior interosseous syndrome [5].  Radial tunnel syndrome is often misdiagnosed as lateral epicondylitis, or tennis elbow, because the tests can easily mimic those specific symptoms. Entrapment of the radial nerve will cause numbness into the back of the hand that surround digits 3-5. It can also cause weakness of the muscles that extend to the wrist and fingers [4]. Like the ulnar nerve, injury to the radial nerve also has a nickname. It’s sometimes called the handcuff neuropathy because of the ease in which the nerve can be injured with tightly bound handcuffs [4].

 Image courtesy of https://www.dartmouth.edu/~humananatomy/figures/chapter_8/8-13_files/IMAGE001.JPG

Image courtesy of https://www.dartmouth.edu/~humananatomy/figures/chapter_8/8-13_files/IMAGE001.JPG

Sites of Radial Compression:

  •  Fibrous bands anterior to the radial head at the entrance of the radial tunnel
  • Radial recurrent vessels
  • Tendinous origin of the extensor carpi radialis brevis
  • Tendinous proximal border of supinator (arcade of Frohse) – the most common site for radial tunnel syndrome
  • Distal edge of the supinator at exit [6]

There are a plethora of ways that a nerve can become entrapped or pinched and that are not from any traumatic physical injury. In the three parts of this article, we looked at compression sites along the shoulder in thoracic outlet syndrome, sites in the neck with nerve root disorders, and sites in the forearms and hands with peripheral nerve compression. The next time you wake up with your hand asleep, be thankful that the symptoms dissipate within seconds. If you are someone who questions whether or not you may have a pinched nerve in your body, contact a physical therapist to have an initial consultation and talk about future plans for treatment.

 

References:

[1] Radswiki et al. (n.d.). Carpal tunnel syndrome | Radiology Reference Article | Radiopaedia.org. Retrieved July 24, 2015.

[2] Jones, J., & Gaillard, F. (n.d.). Anterior interosseous nerve syndrome | Radiology Reference Article | Radiopaedia.org. Retrieved July 24, 2015.

[3] Lowe, W. (2004, October 1). Median Nerve Compression Pathologies. Retrieved July 24, 2015.

[4] Ulnar Nerve Entrapment. (n.d.). Retrieved July 24, 2015, from http://www.physio-pedia.com/Ulnar_Nerve_Entrapment

[5] Neal, S., & Fields, K. (2015, January 15). Peripheral Nerve Entrapment and Injury in the Upper Extremity. Retrieved July 24, 2015.

[6] Wheeless, C. (2015, June 17). Radial Nerve. Retrieved July 24, 2015, from http://www.wheelessonline.com/ortho/radial_nerve 

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