From the Guidelines
The conus medullaris typically ends at the level of the L1-L2 vertebral interspace. This is based on the most recent and highest quality study available, which indicates that by 2 months after birth, the conus medullaris ends most commonly opposite the disc space between the first and second lumbar vertebrae (L1-L2 disc space) 1. The study also notes that the lowest normal level, with 95% confidence limits, is opposite the L1-L2 disc space.
Key Points to Consider
- The conus medullaris is the lower end of the spinal cord, and its position is crucial for spinal procedures and diagnosis of conditions like tethered cord syndrome.
- The position of the conus medullaris changes during fetal development, ascending relative to the vertebral column as growth occurs, and reaches its adult position around birth or shortly thereafter.
- Understanding the normal anatomical variation is essential, as the conus occasionally ends slightly higher (at T12-L1) or lower (at L2-L3).
- Clinicians should be aware of the typical ending point of the conus medullaris to avoid damaging the spinal cord during procedures like lumbar punctures, which are typically performed below L3.
Clinical Implications
The knowledge of the conus medullaris ending at the L1-L2 vertebral interspace has significant implications for clinical practice, particularly in procedures involving the spinal cord and in the diagnosis of spinal cord-related conditions. As noted in the study, the conus medullaris ends at a level that is higher than the levels mentioned in options A, B, C, and D, which are not supported by the most recent and highest quality evidence 1.
From the Research
Conus Medullaris Levels
The level at which the conus medullaris typically ends is a subject of medical study. According to the provided evidence:
- The conus medullaris terminates at the second lumbar vertebra, as stated in the literature 2.
- However, the termination level can vary, with some studies suggesting that it can end at levels ranging from L1 to L3 2, 3.
- One study found that the conus medullaris ended at the L-1 or L-2 vertebral level in all 13 specimens examined 3.
- Another study suggested that the conus medullaris can be found below the vertebra L3 in infants without recognized spinal pathology 2.
Key Findings
- The level of the conus medullaris can vary between individuals, with a range of normal positions 4, 5.
- The conus medullaris is not always a fixed structure and can move with positional changes 5.
- The presence of a conus medullaris at a normal position does not necessarily rule out the possibility of tethered cord syndrome 4, 6.
Relevant Studies
- A study published in the Journal of Korean Neurosurgical Society found that the conus medullaris terminates at the second lumbar vertebra 2.
- A study published in Neurological Research suggested that the conus medullaris can be tethered even if it is in a normal position 4.
- A study published in Clinical Anatomy found that high lumbar punctures may be safer than previously thought due to the movement of the conus medullaris with positional changes 5.
- A study published in the Journal of Neurosurgery: Pediatrics found that the filum terminale may contain functional neural elements 3.
- A study published in Neurosurgery found that tethered cord syndrome can occur even if the conus medullaris is in a normal position 6.