Spinomuscular atrophy is seen in lesion of-
**Core Concept**
Spinomuscular atrophy, also known as spinomuscular atrophy or spinal muscular atrophy (SMA), is a neuromuscular disorder characterized by progressive muscle weakness and wasting due to the degeneration of spinal motor neurons. This condition is caused by a loss of motor neurons in the spinal cord, leading to a decrease in muscle mass and strength.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of SMA, which is caused by the loss of spinal motor neurons. These motor neurons are responsible for transmitting signals from the brain to muscles, enabling voluntary movement. In SMA, the loss of these motor neurons leads to muscle weakness and wasting, resulting in spinomuscular atrophy. The responsible gene for SMA is the survival motor neuron 1 (SMN1) gene, which encodes for the survival motor neuron protein (SMN). This protein is essential for the survival of motor neurons.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the pathophysiology of spinomuscular atrophy.
* **Option B:** This option is incorrect because it does not relate to the spinal cord or motor neurons, which are the primary sites of pathology in SMA.
* **Option C:** This option is incorrect because it does not accurately describe the genetic basis of SMA.
**Clinical Pearl / High-Yield Fact**
The SMN1 gene is located on chromosome 5q13.2 and is responsible for encoding the SMN protein, which is essential for the survival of motor neurons. A deletion or mutation in the SMN1 gene can lead to SMA, making genetic testing a valuable tool in diagnosing this condition.
**Correct Answer:** C.