Thecal sac

**Thecal Sac**

The thecal sac is a protective membrane that surrounds the spinal cord and the cauda equina, containing cerebrospinal fluid (CSF) which cushions and nourishes these vital structures. It is composed of the dura mater, one of the three layers of the meninges, and extends from the brain’s dura mater down through the vertebral canal. The thecal sac plays a crucial role in spinal health, providing a barrier against injury and infection while allowing nerve roots to exit through the vertebrae. Understanding the thecal sac is important in the context of spinal conditions, imaging, and surgical procedures.