Where is the terminal filum found?
The correct answer and explanation is:
Correct Answer:
The terminal filum (also called filum terminale) is found within the vertebral canal, extending from the conus medullaris (the tapered end of the spinal cord) down to the coccyx.
300-Word Explanation:
The terminal filum is a slender, thread-like extension of the pia mater, one of the three membranes (meninges) that surround the brain and spinal cord. It plays an essential structural role in anchoring the spinal cord in place.
The spinal cord ends at a point called the conus medullaris, usually around the L1 or L2 vertebra in adults. From this point downward, the terminal filum continues as a fibrous strand. It passes through the lumbar cistern, a space filled with cerebrospinal fluid (CSF) and nerve roots called the cauda equina.
The terminal filum has two parts:
- Filum terminale internum – the upper portion (about 15 cm long), located within the dural sac, surrounded by nerve roots of the cauda equina.
- Filum terminale externum – the lower portion (about 5 cm), outside the dural sac. This part attaches to the coccyx, anchoring the spinal cord and meninges to the vertebral column.
Functionally, the terminal filum prevents upward movement of the spinal cord and helps stabilize it within the vertebral canal. It does not contain nerve tissue, although it is surrounded by spinal nerves in the cauda equina.
Clinically, abnormalities in the terminal filum (like a thickened filum) can lead to conditions such as tethered cord syndrome, where the spinal cord is abnormally attached, causing stretching and neurological problems.
In summary, the terminal filum is a key structural feature of the spinal cord anatomy, extending from the conus medullaris to the coccyx, ensuring stability and proper placement of the spinal cord within the vertebral column.