Under what circumstances is lumbar puncture indicated in a patient with multiple sclerosis?
Lumbar puncture should certainly be done in all patients in whom Clinically Definite (CDMS) or Laboratory-Definite MS (LDMS) cannot be diagnosed on the basis of the history, neurologic examination, and MRI.
In many patients, possible MS is diagnosed on the basis of the clinical presentation and negative MRI scans. Since the MRI scan of the brain may be negative in 5 percent of patients with early MS (and may remain so for several years in some cases, despite microscopic demyelinating changes in the white matter), using all available diagnostic modalities to detect MS is important. It is surprising how many of these patients have not had a lumbar puncture to help clarify the diagnosis. In such patients, the lumbar puncture and MRI should be seen as complementary, not competitive, paraclinical examinations.
Lumbar puncture findings in MS include a normal opening cerebrospinal fluid (CSF) pressure, fewer than 20 mononuclear cells, a normal or slightly elevated protein level, a negative CSF VDRL test, and negative tests for bacteria and fungi. These findings rule out many infections that can mimic acute MS.
The myelin basic protein level is elevated during acute exacerbations of MS. Oligoclonal bands (OCBs) are found in 83 to 95 percent of patients in whom definite MS is eventually diagnosed.
OCBs are also seen in 25 to 50 percent of patients with other inflammatory diseases of the nervous system, including viral, bacterial, and fungal infections and CNS vasculitis. In addition, they can be found in patients with cancers of the nervous system, CNS syphilis, other demyelinating diseases, and some parasitic diseases. OCBs generally disappear in patients who are recovering from brain infections, but the unique pattern seen in MS patients does not change over time. It is important to perform simultaneous measurement of OCBs in the blood.
The CSF IgG index gives invaluable information about abnormal immunoglobulin synthesis in the brain. An abnormal index can be found in about 90 percent of patients with MS, but it is not disease specific and may also occur in more than 50 percent of patients with inflammatory and infectious disease of the CSF.
Many patients refuse a lumbar puncture because of fear of paralysis or severe headaches or other unjustified fears. Patient education materials, such as the accompanying guide to lumbar puncture, may help allay such fears.
Often, the more convenient MRI scans is performed instead of the lumbar puncture. While MRI has become the most commonly used surrogate marker for MS, it is neither 100 percent sensitive nor 100 percent specific. The lumbar puncture remains a simple examination that yields valuable information. Together, a negative MRI scan of the brain with contrast, a negative lumbar puncture with OCB and CSF index, and a negative evoked potentials study form a very powerful argument against a diagnosis of MS.
(Last reviewed 7/2009)