**Question:** Test used for prolapsed lumbar intervertebral disc is -

A. Discography
B. X-ray
C. Magnetic Resonance Imaging (MRI)
D. Electromyography (EMG)

**Core Concept:** A prolapsed lumbar intervertebral disc is a condition characterized by an herniation of the gel-like nucleus pulposus from the central portion of the intervertebral disc, leading to pressure on the spinal nerve roots or spinal cord. This can cause back pain, sciatica, and radiculopathy. Diagnosing the condition involves identifying the specific affected disc and assessing the severity of the herniation.

**Why the Correct Answer is Right:** Discography is the most specific test for diagnosing a prolapsed lumbar intervertebral disc. It involves injecting dye into the affected disc and observing the response, which helps determine the location and severity of the disc herniation. This test is crucial for determining the exact disc affected and the extent of its involvement, enabling targeted treatment planning.

**Why Each Wrong Option is Incorrect:**

1. **X-ray (B)**: X-rays are essential for evaluating bone structure but provide limited information regarding soft tissues like discs or nerve root compression. X-rays lack sensitivity in detecting disc protrusion and herniation.

2. **Electromyography (EMG) (D)**: EMG is primarily used to evaluate the function of motor and sensory nerves, not to diagnose disc herniation. Although EMG can detect nerve root compression, it is not specific to disc herniation and is not a direct test for disc herniation.

3. **Magnetic Resonance Imaging (MRI) (C)**: MRI is a powerful imaging modality that can visualize soft tissues, including discs and nerve roots. However, MRI is not specifically designed for disc herniation diagnosis. Discography is more sensitive and specific for diagnosing disc herniation, given that MRI can also demonstrate nerve root compression but lacks the ability to directly visualize the disc herniation and its relation to nerve roots.

**Clinical Pearl:** In clinical practice, a combination of clinical examination findings and MRI may be used to suspect a lumbar disc herniation. However, discography remains the gold standard for confirming the diagnosis and defining the extent of disc herniation. This test is crucial for precise treatment planning and avoiding unnecessary surgeries or inadequate treatments targeting adjacent structures.