Which dermatome covers sensation from the lateral shoulder tothe dorsal and palmer surface of the thumb? A. C6B. C5C. C7D. C4

To determine which dermatome covers sensation from the lateral shoulder to the dorsal and palmar surface of the thumb, we can analyze the options provided.

1. Understanding Dermatomes: Dermatomes are specific areas of skin that are mainly supplied by a single spinal nerve root. Knowing which spinal nerve corresponds to each dermatome will help us identify the correct answer.

2. Dermatome Mapping:

   • C4: Covers the area around the shoulder and the upper chest.
   • C5: Covers the lateral aspect of the arm and a part of the shoulder.
   • C6: Covers the lateral forearm and the thumb (dorsal and palmar surface).
   • C7: Covers the middle finger and parts of the hand.

3. Identification: The question specifies the area from the lateral shoulder to the thumb. The lateral shoulder corresponds to C5, but the thumb sensation is covered by C6.

Final Answer

The correct option is A. C6, as it covers sensation from the lateral shoulder to the dorsal and palmar surface of the thumb.