The ganglion to be avoided while doing cervical sympathectomy to avoid Horner syndrome

**Core Concept**
The question is testing the understanding of the anatomy and innervation of the sympathetic nervous system in the neck, specifically the ganglia involved in cervical sympathectomy and their relationship to the development of Horner syndrome.

**Why the Correct Answer is Right**
Horner syndrome is a condition characterized by ptosis, miosis, and anhidrosis, resulting from disruption of the sympathetic nerves supplying the eye. During cervical sympathectomy, the surgeon aims to interrupt the sympathetic outflow to the upper limb, but must avoid damaging the sympathetic nerves that run to the eye. The superior cervical ganglion (SCG) is the primary ganglion involved in the sympathetic innervation of the eye. If the SCG is damaged during surgery, it can lead to Horner syndrome.

**Why Each Wrong Option is Incorrect**
**Option A:** The middle cervical ganglion is not primarily involved in the sympathetic innervation of the eye and is not the primary ganglion to be avoided during cervical sympathectomy.

**Option B:** The inferior cervical ganglion is also not primarily involved in the sympathetic innervation of the eye and is not the primary ganglion to be avoided during cervical sympathectomy.

**Option C:** The stellate ganglion is a fusion of the inferior cervical ganglion and the first thoracic ganglion, and is involved in the sympathetic innervation of the upper limb, but is not the primary ganglion to be avoided during cervical sympathectomy.

**Clinical Pearl / High-Yield Fact**
The superior cervical ganglion is the primary ganglion to be avoided during cervical sympathectomy to prevent Horner syndrome.

**Correct Answer:** C. The stellate ganglion.