Commonest type of spinal T.B. is –
**Core Concept**
Spinal tuberculosis (TB) is a form of extrapulmonary TB that affects the vertebral column, leading to destruction of the intervertebral discs and adjacent vertebrae. The disease can cause significant morbidity and mortality if left untreated.
**Why the Correct Answer is Right**
The most common type of spinal TB is the **Pott's spine**, also known as tuberculous spondylitis. This condition typically affects the lower thoracic or upper lumbar spine, leading to vertebral body collapse and kyphosis (a forward curvature of the spine). The disease is caused by the bacterium *Mycobacterium tuberculosis*, which gains entry into the spine through hematogenous spread from a primary focus, often in the lungs.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a recognized type of spinal TB. Spinal TB can manifest in various forms, but Pott's spine is the most common.
**Option B:** This option is incorrect because it is not a recognized classification of spinal TB. While spinal TB can affect the cervical spine, it is not a distinct category.
**Option C:** This option is incorrect because it is not a valid type of spinal TB. Spinal TB can cause various complications, but this option does not accurately describe a recognized form of the disease.
**Clinical Pearl / High-Yield Fact**
Pott's spine is a classic example of a "collapsing vertebra" due to TB, often presenting with back pain, weakness, and neurological deficits. Early recognition and treatment are crucial to prevent long-term disability.
**Correct Answer: D. Pott's spine**