Diagnosing MS in Patients
If an evil doctor wanted to create a phrase to instill fear and horror in the heart of patients everywhere, he could design no better phrase than “spinal tap” or “lumbar puncture (LP).” Yet, this is a test that I find myself recommending for some terrified soul on an almost weekly basis. As I said in a previous post, the diagnosis of MS is primarily a clinical one, made by talking to and examining patients. All patients with a suspected diagnosis of MS will have at least a brain MRI as well. In those patients for whom the history, physical, and MRI are completely suggestive of MS, there is not much of a role for an LP.
However, there are many patients for whom the diagnosis of MS is far from a certainty, at least during the early stages of the illness. An LP is most useful for the following groups of patients:
- Patients with symptoms not usually seen as a first symptom of MS, such as depression or cognitive impairment. In this group of patients, a doctor may suggest a lumbar puncture, especially if the MRI results are also inconclusive.
- Patients with symptoms that are characteristic of MS, yet have either a completely normal MRI or an MRI that shows abnormalities that are not typical for MS.
- Patients with other “red flags” including a history of other illness that can mimic MS, such as lupus, or patients outside of the normal age range for MS.
So, how does an LP help a neurologist? First, it can help us decide if a patient has MS or not. In 90 percent of patients with MS, there is a marker of inflammation in the spinal fluid called oligoclonal bands. If oligoclonal bands are not detected in the spinal fluid, an alternative diagnoses to MS should be considered, especially if the history, neurological exam, or MRI are in any way atypical. Additionally, the LP should not show too many other abnormalities, like numerous white blood cells or high protein; if these are found, an alternative diagnosis should be sought.
Second, the presence or absence of oligoclonal bands may provide a clue, though a small one, about the clinical course of patients with MS. One study which investigated the spinal fluid of patients who had a single episode suggestive of MS found that patients with oligoclonal bands had twice the risk for having a second attack, regardless of the initial MRI. However, the presence of these bands did not seem to influence the development of disability. Another study found that patients with MS, but without oligoclonal bands, “were significantly more likely to exhibit neurological or systemic clinical features atypical of MS (headaches, neuropsychiatric features, and skin changes).” However, other studies have not identified a difference between MS patients with and without oligoclonal bands.
In summary, an LP is most useful in patients for whom the clinical diagnosis of MS is a possibility, but not a certainty. Although it is certainly not pleasant to undergo this procedure, it is worth doing if a doctor feels that it is necessary, given that it might make the difference between a diagnosis of MS or not.
I am available via e-mail at email@example.com and will try to answer all questions in future posts.