Neuro-Ortho overlap

[Elizabeth Powers]

For your powerpoint on neuro-ortho overlap, you discuss that below the c-spine, the spinal nerve is named for the vertebra ABOVE. So at L5/S1, I would assume that the L5 spinal nerve exits at this level… However, when you give an example of common disc herniations, you say that a disc herniation at L5/S1 would lead to S1 impairments (PF weakness, dec sensation at posterior and lateral LE). Can you explain this? Am I misunderstanding?

Thanks!

[Chrissy Durrough]

Hi Elizabeth!

Thank you for this question! As an NCS, orthopedics is not my specialty, so I had to do some digging to confirm. The website below does a nice job of explaining the difference between “exiting” and “traversing” nerve roots at each spinal level. At the L5-S1 level, the L5 nerve root is exiting the spinal column while the S1 nerve root is crossing the disc to exit at the next level below. In the lumbar spine, disc herniations tend to affect the traversing nerve root due to the most common direction of herniations (posterolateral). In the cervical spine, disc herniations usually affect the exiting nerve root (lateral herniations).

https://www.spine-health.com/conditions/spine-anatomy/radiculopathy-radiculitis-and-radicular-pain#:~:text=Traversing%20nerve%20root.&text=It%20is%20called%20the%20%E2%80%9Ctraversing,at%20the%20L5%2DS1%20level.

Hope this helps!

Chrissy

[Suzanne Atcavage]

That was greate information, thank you!

[Elizabeth Powers]

Gotcha! Yes that makes sense!
Thank you for that link.

Lizzy

[Margaret Frank]

Hi Chrissy, this all makes sense so thank you. However, On exam #2 – There was a question about a disc herniation (described as severe) at L4/5 spinal level – asking which spinal nerve distribution might you notice strength and/or sensation changes. I put L5 as L5 is the “transverse” nerve root – however, the answer was L4, L5 and S1. Is this only because it is described as “severe”? I found it to be a trick question. If the question did not label the severity of the herniation – then would L5 make the most sense as the correct answer? Thank you so much for your feedback!

[Chrissy Durrough]

Hi Margaret! Yes, this is because the disc herniation is severe and at the L4-5 spinal level. The spinal cord ends at approximately L1-2 spinal level. The associated lower spinal nerves travel distally and exit several levels below. A disc herniation at L4-5 may come in contact with any of the above listed nerves as they travel distally prior to exiting the spinal column.

Let me know if you have any other questions, and happy Thanksgiving!

Chrissy

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