Happy New Year SinaiEM! In keeping with the holiday spirit, today’s pearl is a bit about spinal taps, aka Lumbar Puncture. First is a review of what findings you would see for our most common differential diagnosis, and it is followed by some literature published by our very own PD.
Bacterial Meningitis
Appearance
Cloudy & Turbid
White Cells
Raised neutrophils
Red Cells
Normal
Protein
High or Very High
Glucose
Very Low
Viral Meningitis
Appearance
Normal
White Cells
Raised lymphocytes
Red Cells
Normal
Protein
Normal or High
Glucose
Normal or Low
Tuberculous Meningitis
Appearance
Normal or Slightly Cloudy
White Cells
Raised lymphocytes
Red Cells
Normal
Protein
High or Very High
Glucose
Very Low
Subarachnoid Hemorrhage
Appearance
Usually blood stained
White Cells
Normal
Red Cells
Very High (sustained through 4th tube)
Protein
Normal or High
Glucose
Normal or Low
Guillan-Barré Syndrome
Appearance
Normal
White Cells
Normal
Red Cells
Normal
Protein
High (only after one week)
Glucose
Normal or Low
Multiple Sclerosis
Appearance
Normal
White Cells
Raised lymphocytes
Red Cells
Normal
Protein
High
Glucose
Normal
What does the pressure tell us?
In theory, if the pressure is out of the range of 8-15 cm CSF (with patient lying on side), it is considered abnormal. Whiteley et al. decided to investigate the accuracy of this but prospectively recording CSF opening pressure in 242 adults who had a lumbar puncture with concomitant measurement of weight and height to see if body mass index would be related. The 95% reference interval for lumbar CSF opening pressure was 10 to 25. BMI had a small but clinically insignificant influence on CSF opening pressure. The methods of the study are more relevant to our practice because all patients were tapped while on their side with legs drawn up (historically, the normal reference range was developed on patients whose legs were straightened out). Thus, intracranial hypertension should be diagnosed with caution in patients with CSF pressure less than 25 cm CSF (and in some patients, an opening pressure of up to 28 cm CSF is normal). Pressure measurement is useful when you suspect, idiopathic intracranial hypertension (formerly known as pseudotumor cerebri), cerebral venus sinus thrombosis, or CSF leak (pressure would be low, usually in the post operative setting).
What did Kaush have to say in 2003 about “champagne” spinal taps (zero RBCs in the first and last tubes)?
References
Doherty, C.M., R.B. Forbes. Diagnostic lumbar puncture. Ulster Med J, 83 (2014), pp. 93–102
Shah KH, Richard KM, Nicholas S, Edlow JA. Incidence of traumatic lumbar puncture. Acad Emerg Med. 2003;10:151-154
Whiteley, R. Al Shahi, C.P. Warlow, et al. CSF opening pressure: reference interval and the effect of body mass index. Neurology, 67 (2006), pp. 1690–169
http://www.osceskills.com/e-learning/subjects/cerebrospinal-fluid-results-interpretation/#sthash.fXZtYPoA.dpuf
