What is the purpose of testing cutaneous innervation, what sensations are tested, and how is it clinically relevant for diagnosing nerve damage?

The provided text explains the importance of understanding cutaneous innervation for physical examination. Purpose: Sensory testing of the upper limb skin is performed when damage to nerves from the C3 to T2 spinal segments is suspected. Sensations Tested: Routinely, light touch and pinprick are assessed. In special cases, temperature, two-point discrimination, and vibration* are also tested. Diagnosis: Areas of anesthesia (loss of sensation) or paresthesia* (abnormal sensation) are mapped and compared to the dermatomal distribution to identify the affected nerve segment. Clinical Relevance: For example, if nerve roots from C3 to T2 are compressed (e.g., due to spondylitis), pain is referred to the specific dermatomes supplied by those nerves.