Which diagnostic procedure is commonly used to evaluate suspected multiple sclerosis by analyzing cerebrospinal fluid?

• A. MRI scan
• B. CT scan
• C. Spinal tap
• D. Electroencephalography

Answer: (C)

When multiple sclerosis is suspected, examining the cerebrospinal fluid through a spinal tap (lumbar puncture) is used to look for markers of immune activity in the CNS. The CSF often shows oligoclonal bands of IgG and an increased IgG index, which indicate intrathecal IgG production and support the diagnosis in the right clinical and imaging context. This direct analysis of CSF complements MRI, which is the primary imaging tool for identifying demyelinating lesions. CT is much less sensitive for MS lesions, and EEG isn’t useful for diagnosing MS. So, collecting CSF via a spinal tap to analyze its composition is the procedure commonly used to evaluate suspected MS.