What sensation is affected with an axillary nerve injury?

An axillary nerve injury specifically affects the sensory innervation of the skin overlying the deltoid muscle, also referred to as the deltoid patch on the upper arm. This area corresponds to the region that the axillary nerve supplies, making it crucial in both sensation and motor function. The axillary nerve provides motor innervation to the deltoid muscle and teres minor, which are important for shoulder abduction and external rotation. However, its sensory branch supplies the skin over the deltoid region, highlighting the importance of this nerve in sensory perception in that specific area.

In contrast, the other options refer to sensations that are supplied by different nerves: the lateral aspect of the forearm is primarily supplied by the musculocutaneous nerve, the dorsal web space between the thumb and index finger is innervated by the radial nerve, and the palmar aspect of the hand is served by the median and ulnar nerves. Therefore, the correct choice emphasizes the specific sensory disruption caused by axillary nerve injury, particularly in the area relevant to deltoid muscle innervation.