Which of the following is spared in lumbar sympathectomy: September 2009

**Core Concept**
Lumbar sympathectomy is a surgical procedure that involves interrupting the sympathetic nerves in the lumbar region to relieve symptoms such as excessive sweating, pain, or hypertension. The procedure targets the sympathetic nervous system, which plays a crucial role in regulating various bodily functions, including vasomotor tone, sweat production, and pain perception.

**Why the Correct Answer is Right**
The sympathetic nervous system has a complex network of neurons that innervate various organs and tissues. During a lumbar sympathectomy, the goal is to interrupt the sympathetic nerves that supply the target area, thereby relieving symptoms. However, certain structures are spared from the sympathetic denervation due to their unique anatomical and physiological characteristics. In the context of lumbar sympathectomy, the parasympathetic nerves, which are responsible for promoting digestion, reducing heart rate, and facilitating other "rest and digest" functions, are spared. This is because the parasympathetic nervous system has a separate and distinct set of neurons that are not targeted by the sympathectomy procedure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the sympathetic nerves that innervate the skin are targeted during a lumbar sympathectomy, leading to a reduction in sweat production.
**Option B:** This option is incorrect because the sympathetic nerves that regulate vasomotor tone are interrupted during the procedure, leading to vasodilation and a decrease in blood pressure.
**Option C:** This option is incorrect because the sympathetic nerves that innervate the visceral organs are also targeted during the procedure, leading to changes in organ function and blood flow.

**Clinical Pearl / High-Yield Fact**
The parasympathetic nervous system is often referred to as the "rest and digest" system, and it plays a crucial role in regulating various bodily functions, including digestion, heart rate, and respiration. The parasympathetic nerves are spared during a lumbar sympathectomy due to their unique anatomical and physiological characteristics.

**Correct Answer:** C. The parasympathetic nerves are spared in lumbar sympathectomy.