Spinal puncture

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A spinal puncture, also called a spinal tap, lumbar puncture, or LP is "tapping of the subarachnoid space in the lumbar region, usually between the third and fourth lumbar vertebrae.[1][2][3][4]

Procedure

Positioning

Sitting with hips flexed may best open the interspinous spaces, at least in children.[5]

Choice of needle

Use of an 'atraumatic needle' may reduce the chance of headache, although this needle is more difficult to use and may increase the number attempts needed before successful puncture.[2] Reinsertion of the stylet before needle removal decreases headache.[2]

Measurement of CSF pressure

The normal opening pressure is 6 to 18 cm of H2O or 0.4 to 1.3 cm Hg (mercury is 13.6 times more dense than water).[2] To accurately measure the opening pressure of the cerebrospinal fluid:

  • The patient should be laying (not sitting)[6][7] Sitting may increase the pressure by 40 cm H2O.[8] In the sitting position, CSF pressure ranges from 32 to 63 cm H2O with a mean of 49 cm H2O.[9]
  • The patient's neck should be relaxed as fully flexing the neck ('chin on chest') can raise pressure by 12 cm H2O[10][11] This may be due to the patient inadvertently performing Queckenstedt's maneuver or similar. Flexing the neck to only 30° may not matter.[12]
  • The position of the lower extremities does not matter.[12]

Laboratory tests

Interpretation

"No xanthochromia and red blood cell count <2000×10(6)/L reasonably excludes the diagnosis of aneurysmal subarachnoid hemorrhage" according to a prospective cohort study.[14]

References

  1. Anonymous (2023), Spinal puncture (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. 2.0 2.1 2.2 2.3 Straus SE, Thorpe KE, Holroyd-Leduc J (October 2006). "How do I perform a lumbar puncture and analyze the results to diagnose bacterial meningitis?". JAMA 296 (16): 2012–22. DOI:10.1001/jama.296.16.2012. PMID 17062865. Research Blogging. Cite error: Invalid <ref> tag; name "pmid17062865" defined multiple times with different content
  3. Ellenby MS, Tegtmeyer K, Lai S, Braner DA (September 2006). "Videos in clinical medicine. Lumbar puncture". N. Engl. J. Med. 355 (13): e12. DOI:10.1056/NEJMvcm054952. PMID 17005943. Research Blogging.
  4. Marton KI, Gean AD (1986). "The spinal tap: a new look at an old test.". Ann Intern Med 104 (6): 840-8. PMID 3518565.
  5. Abo A, Chen L, Johnston P, Santucci K (2010). "Positioning for lumbar puncture in children evaluated by bedside ultrasound.". Pediatrics 125 (5): e1149-53. DOI:10.1542/peds.2009-0646. PMID 20403933. Research Blogging.
  6. Becht FC (1920) Studies on the cerebrospinal fluid. Am J Physio 1920;51(1):1-125**
  7. Loman J, Myerson A, Goldman D. Effects of alterations in posture on the cerebrospinal fluid pressure. Arch Neurol Psych. 1934:1279-1295.**
  8. Magnaes B (1976). "Body position and cerebrospinal fluid pressure. Part 1: clinical studies on the effect of rapid postural changes.". J Neurosurg 44 (6): 687-97. DOI:10.3171/jns.1976.44.6.0687. PMID 1271089. Research Blogging. **
  9. Magnaes B (1976). "Body position and cerebrospinal fluid pressure. Part 2: clinical studies on orthostatic pressure and the hydrostatic indifferent point.". J Neurosurg 44 (6): 698-705. DOI:10.3171/jns.1976.44.6.0698. PMID 1271090. Research Blogging.
  10. Dinsmore J, Bacon RC, Hollway TE (1998). "The effect of increasing degrees of spinal flexion on cerebrospinal fluid pressure.". Anaesthesia 53 (5): 431-4. PMID 9659014.
  11. Deliyannakis E (1971). "Influence of the position of the head on the cerebrospinal fluid pressure. Variations of the Queckenstedt sign.". Mil Med 136 (4): 370-2. PMID 5005427. **
  12. 12.0 12.1 Abbrescia KL, Brabson TA, Dalsey WC, Kelly JJ, Kaplan JL, Young TM et al. (2001). "The effect of lower-extremity position on cerebrospinal fluid pressures.". Acad Emerg Med 8 (1): 8-12. PMID 11136140.
  13. Pai M, Flores LL, Pai N, Hubbard A, Riley LW, Colford JM (2003). "Diagnostic accuracy of nucleic acid amplification tests for tuberculous meningitis: a systematic review and meta-analysis.". Lancet Infect Dis 3 (10): 633-43. PMID 14522262.
  14. Perry JJ, Alyahya B, Sivilotti ML, Bullard MJ, Émond M, Sutherland J et al. (2015). "Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study.". BMJ 350: h568. DOI:10.1136/bmj.h568. PMID 25694274. Research Blogging.