**Core Concept**
Intramedullary spinal cord lesions (SOL) refer to abnormalities within the spinal cord itself, which can be caused by various factors such as tumors, infections, or vascular events. Accurate diagnosis of these lesions is crucial for determining the appropriate treatment approach.

**Why the Correct Answer is Right**
Magnetic Resonance Imaging (MRI) is the investigation of choice for intramedullary spinal cord lesions due to its excellent soft tissue resolution and ability to distinguish between different types of lesions. MRI can provide detailed images of the spinal cord, enabling the identification of lesions such as syringomyelia, intramedullary tumors, or spinal cord infarction. The use of contrast agents can further enhance the diagnostic capabilities of MRI by highlighting areas of contrast uptake or enhancement.

**Why Each Wrong Option is Incorrect**
**Option A:** CT scans may be useful for detecting bony abnormalities or calcifications but are not the best modality for visualizing soft tissue lesions within the spinal cord.
**Option B:** Myelography involves injecting a contrast agent into the spinal canal to visualize the spinal cord and nerve roots, but it is less sensitive than MRI for detecting intramedullary lesions.
**Option C:** Plain X-rays are not useful for diagnosing intramedullary spinal cord lesions, as they lack the resolution to visualize soft tissue abnormalities.

**Clinical Pearl / High-Yield Fact**
When evaluating patients with suspected intramedullary spinal cord lesions, it is essential to consider the patient's symptoms, such as sensory or motor deficits, and to perform a thorough neurological examination. MRI should be performed promptly to guide further management and treatment.

**Correct Answer:** C.