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USMLE Step 1 Bits & Pieces High yield short focused points, monographs, charts, illustrations, tables, and other stuff related to the USMLE Step 1 Exam.


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  #1  
Old 11-15-2009
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Anatomy Lumbar Puncture Layers

A very high yield anatomical question, What layers does the spinal needle traverse when we do lumbar puncture?

Have a look at this illustration
Lumbar Puncture Layers-lumbarlayers.jpg
Original image from wikimedia commons

As per the numbers in the illustration
1- Skin
2- Facia and SC fat
3- Surpaspinous ligament
4- Interspinous ligament
5- Ligamentum flavum
6- Epidural space and fat (epidural anesthesia needle stops here)
7- Dura

Right after that the needle pops into the subarachnoid space where the CSF is swimming.

Important Notes:
  • 3,4, and 5 are collectively occuring in the interlaminar space.
  • There's no subdural space (as FA is saying), it's a potential space that can be filled by fluid but normally it's empty.
  • The best intervertebral space is between L3/L4 or L4/L5 usually lower levels in children.

Last edited by lee-usmle; 09-12-2010 at 08:25 AM.
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  #2  
Old 03-21-2010
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Default Mnemonic of lumber puncture layers..

I posted a mnemonic about this here
Mnemonic of Lumbar Puncture Layers..

Last edited by shaheer; 03-21-2010 at 06:04 AM. Reason: just to add mnemonic..
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Old 09-03-2010
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Smile

Hi,

just a correction, the best space for adults is l2-l3 and for children l4-l5 as their spinal cord ends lower.

thanks
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Old 09-03-2010
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Thumbs Up Thanks for the feedback

Quote:
Originally Posted by freda View Post
Hi,

just a correction, the best space for adults is l2-l3 and for children l4-l5 as their spinal cord ends lower.

thanks
Thanks, it was corrected.
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  #5  
Old 04-01-2013
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Default

Quote:
Originally Posted by Evelina Todd View Post
I was learning from HY Gross Anatomy
Lumbar puncture:
1. Skin-----------------------Spune-le
2. Superficial fascia----------Sa
3. Supraspinous ligament---Studieze
4. Interspinous ligament----In
5. Ligamentum flavum------Laborator
6. Epidural space containing the internal vertebral venous plexus -E
7. Dura mater D
8. Arachnoid A
9. Subarachnoid space containing cerebrospinal fluid.
S



Spune-le Sa Studieze In Lab EDA; Hope it works
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  #6  
Old 06-17-2013
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Default

y is that nobody mentions about DEEP FASCIA??? plz enligten
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  #7  
Old 06-30-2013
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Default Clarifying The Safe Level for Lumbar Puncture and Presence of Subdural Space

Howdy,

I am going to comment on two points regarding Lumbar Puncture:

1- In adults, spinal cord ends at the LOWER border of L1. Thus, the level at which we can insert the needle in ADULTS could be L2-L3 or lower, i.e., as long as you avoid the first lumbar space (L1-L2), you are good. In children and infants, spinal cord ends at a lower level so going for L4-L5 is wise.

2- Regarding the presence or absence of a Subdural space; in fact this space is present but in LIVING ADULTS the pressure of CSF pushes the Arachnoid against Dura thus obliterating this space, so practically once the tip of the needle hits Dura, you have already hit arachnoid and now the needle is swimming in CSF. We have two "give" s when we do Lumbar Puncture; first "give" is when the needle pierces Ligamentum Flavum, second "give" is when the needle pierces Dura.
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