• Draw cerebrospinal fluid (CSF) and examine for infection, oligoclonal bands (OCBs), and intrathecal immunoglobulin G (IgG) production. OCBs are found in 90-95% of MS patients and intrathecal IgG production in 70-90%; however, these findings are not specific for MS.

Imaging Studies:

• MRI remains the imaging procedure of choice for diagnosing and monitoring disease progression in the brain and spinal cord. This test can show brain abnormalities in 90-95% of patients and spinal cord lesions in up to 75% of cases, especially in elderly patients. MRI alone cannot be used to diagnose MS. The brain shows a characteristic pattern of lesions, usually periventricular.

• New or newly active lesions in the CNS can be enhanced with gadolinium as a result of the breakdown of the blood brain barrier. They may be enhanced from days to several weeks. These enhancing lesions have been seen even without clinical signs of disease activity. This finding is significant because it demonstrates that not all lesions result in neurologic deficits; however, it does demonstrate that the disease is widespread and present even during the periods previously believed to be silent.

• The T2-weighted images on MRI show edema and more chronic lesions. The T1-weighted images demonstrate cerebral atrophy and "black holes." These black holes represent areas of axonal death.

• With MRI, the lesion (plaque) burden, a measure of disease severity, can be determined. Unfortunately, the lesion burden is not well correlated with impairment or disability. MRI can help to determine cerebral and spinal cord atrophy, even early in the disease. This atrophy signifies widespread axonal loss in the brain and spinal cord even when active lesions are not identified. Atrophy in the spinal cord, cerebellum, and cerebral cortex has been correlated with disability.

• CT scan with enhancement has been used to identify acute lesions; however, it is not particularly helpful for patients with stable disease, as the lesions do not enhance.

• A newer neuroimaging technique, magnetic resonance spectroscopy (MRS), has been useful in following N-acetyl-aspartate (NAA) levels in patients with MS. NAA is an amino acid found in neurons and axons of the mature brain. In patients with relapsing-remitting MS, NAA levels are reduced, suggesting axonal loss; however, in patients with secondary progressive MS with more disability, the NAA levels are reduced more significantly. In fact, patients with MS had lower levels of NAA even in areas of the brain previously thought to be unaffected, when compared with levels in normal patients.

Other Tests:

• Evoked potentials have been the most useful neurophysiological studies for evaluation of MS. These tests include visual evoked potentials (VEPs), somatosensory evoked potentials (SSEPs), and brainstem auditory evoked potentials (BAEPs). These studies are used to identify subclinical lesions but are nonspecific for MS.

• VEPs are performed by having a patient focus on a reversing black and white checkerboard pattern. Delays in latencies indicate demyelination in the anterior visual pathways.

• SSEPs evaluate the posterior column of the spinal cord, the brainstem, and the cerebral cortex. Delays in latencies of various peaks indicate demyelination in the correlated pathway of the spinal cord or brain.

• BAEPs are performed to evaluate ipsilateral asymptomatic MS lesions in the auditory pathways but are less sensitive than VEPs and SSEPs.

• Electroencephalogram (EEG) results have been found to be outside the reference range in some patients with MS, but the findings are nonspecific. Nonspecific EEG abnormalities can be seen in normal individuals in the general population.

Procedures:

• Lumbar puncture is performed to evaluate CSF for the presence of OCBs and intrathecal IgG production.