Dermatome in the thumb and index finger region is supplied by
**Core Concept**
The dermatomes are areas of skin supplied by nerves that arise from specific spinal nerve roots, which are part of the peripheral nervous system. Dermatomes are essential in diagnosing nerve root lesions or damage.
**Why the Correct Answer is Right**
The dermatome in the thumb and index finger region is primarily supplied by the C6 spinal nerve root. This is because the C6 nerve root gives rise to the lateral antebrachial cutaneous nerve, which supplies the skin on the lateral aspect of the forearm and the palmar surface of the thumb and index finger. The C6 dermatome is crucial in diagnosing nerve root lesions, especially those affecting the cervical spine.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a particular dermatome. Dermatomes are specific areas of skin supplied by nerves that arise from specific spinal nerve roots.
**Option B:** This option is incorrect because it is not specific to the thumb and index finger region. The dermatome for the middle finger is typically supplied by the C7 spinal nerve root.
**Option C:** This option is incorrect because it is not accurate. The dermatome for the little finger is typically supplied by the C8 spinal nerve root.
**Clinical Pearl / High-Yield Fact**
It is essential to remember the dermatomal distribution of the skin to diagnose nerve root lesions or damage. A thorough understanding of dermatomes can help clinicians identify the affected spinal nerve root and guide further management.
**Correct Answer: C. C7 spinal nerve root.**