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)?

In his study of 762 spinal taps at an urban hospital, a total of 236 (31%) CSF samples were ‘‘champagne taps.  Onhundred seventy-three of these taps were attributed tthe ED, and 63 were attributed to all other locations ithe hospital. Mic drop. 

 

 

 

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