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F r e e S O A P n o t e s w i t h M a s s a g e B o o k f o r A B M P m e m b e r s : a b m p . u s / M a s s a g e b o o k 93 Image 1 shows the dermatome region for the C8 nerve root (there is a C8 nerve root even though there are only seven cervical vertebra due to an odd naming convention). The C8 nerve root exits below the C7 vertebra, and some of the fibers in the C8 nerve root form the medial antebrachial cutaneous nerve and some become part of the ulnar nerve. Notice that the C8 dermatome covers the ulnar aspect of the hand, but it also extends into the forearm and back side of the arm. The fibers from the nerve roots branch out into the peripheral nerves. The area of skin that is innervated by a single peripheral nerve is referred to as that nerve's cutaneous innervation. A peripheral nerve may have fibers that originate from more than one nerve root, but a single nerve root can also branch into more than one peripheral nerve. Because the nerve could have fibers from more than one nerve root, the nerve's cutaneous innervation could be split across more than one dermatome. Thus, there is no one- to-one correspondence between a peripheral nerve and a dermatome. Image 2 shows the cutaneous innervation of several upper extremity nerves. In the image, you can see that the cutaneous innervation region for the medial antebrachial cutaneous nerve and the ulnar nerve are both contained within the C8 dermatome. Let's take a look at the symptom patterns in Monica's case to see how this anatomical information applies. The primary location of Monica's symptoms would indicate involvement of the ulnar nerve, as the symptoms are contained within the cutaneous innervation pattern for that nerve. However, you can't rule out nerve root involvement completely in Monica's case because her symptoms are still within the C8 dermatome, even if they don't extend throughout the entire dermatome. To determine nerve root involvement (radiculopathy), as opposed to injury farther along the nerve The location of symptoms is one of the most important clues as to where a predominant nerve injury is located. The C8 dermatome. Mediclip image copyright (1998) Williams & Wilkins. All Rights Reserved. C8 dermatome Ulnar nerve Medial antebrachial cutaneous nerve Cutaneous innervation in the upper extremity. Image courtesy Wikimedia Commons. 1 2 When working with nerve injuries, be sure to note any client symptoms or sensations that indicate you are putting additional pressure on the nerve and further aggravating existing nerve compression. Change your treatment strategy if there are neurological symptoms. CLINICAL APPS