ZocdocAnswersHow big do brain lesions need to be for them to show up on an MRI?

Question

How big do brain lesions need to be for them to show up on an MRI?

How big does a brain lesion have to be to show up on an MRI? I'm a 55 year old woman who was just examined for MS, and my doctor found no lesions - but I have the symptoms and I'm wondering if they could be so small that they're just not showing up on the scan.

Answer

Currently MRI is the most sensitive technique for viewing MS lesions and infrequently misses active lesions. In addition, active MS lesions that result in symptoms are usually not small, or at least not small enough to be missed by MRI. However, MRI is not perfect and can, in some cases miss inactive or old lesions. Plus MRI evidence of disease is not required for diagnosis. Let me explain. MS can actually be diagnosed with only symptoms. If you have a characteristic neurological symptom such as temporary vision loss, numbness, tingling, weakness, that goes away only to return a second time, you can be diagnosed with MS. The second flair is necessary for diagnosis. Since most patients present to a doctor after the first set of symptoms, then another test is needed for diagnosis. In addition to MRI, a very sensitive test is looking for specific proteins in the Cerebral Spinal Fluid. If you are still worried you may have MS, then you could ask for a spinal tap to collect cerebral spinal fluid for analysis. Either way, I suggest you schedule an appointment with your doctor that is testing you for MS. You may ask for a referral to a neurologist, if you haven't seen one yet. Good luck.

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