The Lumbar Puncture – When and Why is it Necessary?

An unpopular but necessary procedure in the diagnosis of Multiple Sclerosis is the removal of cerebrospinal fluid, the lumbar puncture. The diagnosis of MS is made today using the so-called McDonald criteria. These criteria are based primarily on the findings of cranial and spinal magnetic resonance imaging, which confirm the clinical suspicion. With a certain constellation of findings, the diagnosis of a confirmed MS can then also be made in many cases.Well-informed MS patients who have looked more closely at the diagnostic criteria may have noticed that the analysis of cerebrospinal fluid (cerebrospinalis) does not really appear within the McDonald criteria. This may have led to the rumor that the lumbar puncture is dispensable nowadays.

This can be countered by the fact that the McDonald criteria clearly state that no other conditions except MS could be identified as the cause of neurological symptoms in an individual. However, this requirement can only be fulfilled if appropriate differential diagnostic investigations were carried out before the diagnosis – and a cerebrospinal fluid diagnosis is indispensable for this careful differential diagnostic clarification.

The cerebrospinal fluid finding of Multiple Sclerosis is characteristic: Often there is a slight increase in cell count. Normal is the detection of about 4 leukocytes per µl (microliter = 0.001 ml) of cerebrospinal fluid. In MS, a slight increase in cell count to 10 – 50 cells per µl is found. A normal cell count does not argue against MS; a cell count > 50/µl is compatible with Multiple Sclerosis, but should prompt further thought.

Another important parameter is the protein content in the cerebrospinal fluid. This value is usually completely normal in MS patients. Therefore, an increased cerebrospinal fluid protein should also give pause for thought. Finally, the cerebrospinal fluid is examined for signs of chronic immune activation, which is typical for MS. For this, the presence of so-called oligoclonal bands (OB) is determined. However, these bands are not specific to Multiple Sclerosis, but are also found in other inflammatory CNS diseases. In MS, however, they are found in about 95% of cases. Therefore, the detection of bands is very typical, but the absence of OB does not argue against MS, as in 5% of all MS cases no bands are found. However, the absence of bands should give pause for thought.

After these explanations, it is clear that not a single value is decisive, but rather the combination of various measured values speaks for or against the presence of MS. So, in my view, it is quite clear that a thorough MS diagnosis cannot ignore the analysis of the cerebrospinal fluid.

However, this means that even if a lumbar puncture is indispensable from my point of view for the diagnosis of MS, a careful analysis is ultimately sufficient. Repeated cerebrospinal fluid punctures are not useful and not necessary in MS.

Of course, it can still happen that cerebrospinal fluid is taken again during the course of an MS disease. This measure is often associated with the monitoring of a specific Multiple Sclerosis therapy. An example is the detection of progressive multifocal leukoencephalopathy, which can occur as a side effect of Natalizumab (Tysabri) therapy and can only be reliably ruled out or detected by a lumbar puncture.

And then there are of course various “experts” who offer cerebrospinal fluid analyses for supposed special examinations – here, for example, the performance of lymphocyte transformation tests or the determination of not yet validated immune parameters are to be mentioned. These offers should be treated with great caution. In any case, a consultation with an experienced neurologist and MS therapist should take place beforehand. Better to coordinate beforehand than to engage in such examination methods.