A 62 year old male patient presented with paraplegia, bilateral thermoanesthesia and analgesia below the level of the umbilicus, and loss of bowel and bladder movements. However, the proprioception and vibration senses are intact. Spinal angiography revealed thrombus in the anterior spinal aery. Which of the following regions of the spinal cord is likely to be affected?

**Core Concept**
The underlying principle being tested is the anatomy and blood supply of the spinal cord, specifically the **anterior spinal artery** and its distribution. This artery supplies the **anterior two-thirds of the spinal cord**, including the **corticospinal tract** and **spinothalamic tract**.

**Why the Correct Answer is Right**
The patient's symptoms, such as paraplegia, bilateral thermoanesthesia, and analgesia below the level of the umbilicus, and loss of bowel and bladder movements, are consistent with a lesion affecting the **anterior two-thirds of the spinal cord**, which is supplied by the **anterior spinal artery**. The intact proprioception and vibration senses suggest that the **posterior columns**, which are supplied by the **posterior spinal arteries**, are unaffected.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the posterior columns are responsible for proprioception and vibration sense, which are intact in this patient.
**Option B:** Incorrect as the patient's symptoms do not correlate with a lesion in this area.
**Option D:** Incorrect because the patient's symptoms suggest a more specific lesion than a general spinal cord injury.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **anterior spinal artery syndrome** typically presents with loss of motor function and sensation below the level of the lesion, while preserving proprioception and vibration sense.

**Correct Answer:** C. Anterior two-thirds of the spinal cord.

✓ Correct Answer: C. Anterior 2/3rd of the spinal cord