Earliest sign in X-ray in TB spine is: March 2011
**Core Concept**
TB spine, also known as Pott's disease, is a form of tuberculosis that affects the spine. It is a type of osteoarticular tuberculosis, which is a form of extrapulmonary tuberculosis. The disease is characterized by the destruction of the vertebral bodies and the intervening discs due to caseation necrosis caused by the Mycobacterium tuberculosis bacteria.
**Why the Correct Answer is Right**
The earliest sign in X-ray in TB spine is the loss of the normal lordosis of the spine, leading to a gibbus deformity. This occurs due to the destruction of the vertebral bodies, which causes the spine to become kyphotic. The loss of the normal lordosis is often seen in the early stages of the disease, even before any visible changes in the vertebral bodies can be seen on X-ray.
**Why Each Wrong Option is Incorrect**
* **Option A:** Destruction of the vertebral bodies is a characteristic feature of TB spine, but it is not the earliest sign. Destruction of the vertebral bodies is a late sign and occurs after the loss of the normal lordosis.
* **Option B:** Erosion of the superior endplate of the vertebra is a feature of TB spine, but it is not the earliest sign. Erosion of the superior endplate occurs after the loss of the normal lordosis.
* **Option C:** The "ring sign" or "double density sign" is a feature of TB spine, but it is not the earliest sign. The ring sign occurs due to the preservation of the calcified nucleus pulposus surrounded by the inflammatory tissue and is seen in the later stages of the disease.
* **Option D:** The "vertebral body collapse" is a feature of TB spine, but it is not the earliest sign. Vertebral body collapse occurs after the destruction of the vertebral bodies and is a late sign.
**Clinical Pearl / High-Yield Fact**
The earliest sign of TB spine is often missed on X-ray, and the diagnosis is often delayed. Therefore, a high index of suspicion is required to diagnose TB spine, and other imaging modalities such as MRI may be required to confirm the diagnosis.
**Correct Answer:** A. Loss of normal lordosis.