Case

A 43yo is involved in a motor vehicle accident. The driver used a standard three point restraint in a sedan vehicle and was impacted in the side by a pickup truck. The patient has multiple injuries including a displaced left arm mid-humeral fracture causing considerable mid-arm pain. The patient indicates an inability to open their left hand and loss of sensation to a portion of their left hand. Their hand is warm and the patient is able to grasp your hand with theirs

Question 3/3 - To further characterize possible radial nerve neuropathy, the physiatrist tests for sensory deficits.

To assess the radial nerve, sensation from which part of the upper limb would be tested?

Click on your selected option(s) below  (correct = 1, over-thinking = 2+)

Case Complete

Incorrect. While the radial nerve does innervate the posterior arm skin, these branches arise somewhat more proximal than the mid-arm location. Additionally, the patient reports considerable pain from the location of the mid-arm fracture so the patient is neurologically intact to at least the mid-arm.

Correct! The radial nerve is the posterior nerve of the upper limb, so sensation from the posterior (dorsal) hand arises from the radial nerve. 

The tip of the fingers (around the fingernail) is supplied by median/ulnar nerve so the physiatrist would test a little more proximally on the hand and not at the fingertips themselves for testing radial nerve function.

Incorrect. The palmar surface is supplied by the median nerve (digits 1-3 and half of 4) and the ulnar never (digit 5 and half of 4). Thus, this would not test radial nerve function.

Incorrect. The bulk of sensory innervation of the lateral thumb arises from branches of the median nerve, not the radial.

Incorrect. The anterior and much of the lateral side is supplied by the ulnar nerve. While the more posterior side of the little finger is radial nerve territory, and the boundaries between any dermatomes there can be some overlap in the fields. Thus, this would not be a reliable location for testing radial nerve function due to possible dermatome overlap by the ulnar distribution.

Incorrect. The medial forearm skin sensation is supplied by it's own nerve, the medial cutaneous nerve of the forearm, and not a branch of the radial nerve. 

Incorrect. The medial arm skin sensation is supplied by it's own nerve, the medial cutaneous nerve of the arm, and not a branch of the radial nerve.