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Neurology (Expert Forum)
Variability of Different MRI images
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Variability of Different MRI images
by arndins, Mar 22, 2007 12:00AM
I'm 35 male, take Prilosec OTC, 75 mcg synthroid, and 162 mg aspirin (PFO). I have not has a stroke before or a DVT...
In 2005, had complaints of numbness in my extremities. Had brain MRI, spine MRI, and spinal tap. Spine MRI and lumbar puncture normal, but brain MRI revealed small area in right midbrain that was suspicious, although it didn't show any effects of the contrast material. Followed-up with a Multiple Sclerosis doc who said he didn't think it was MS. I met with a brain tumor doc/oncologist who ran Pet Scan, which ruled out neoplasm. He said go to an MS doctor...!
I've been seeing a regular neuro ever since, and have had more MRI's in 2005 and 2006. My symptoms of numbness have dissipated (in my opinion) because I'm now being treated for hypothyroidism with Synthroid, which was untreated at the time of the first MRI. I have occasional bouts of "vertigo" which last for only a few minutes in the morning, then go away and are followed by nausea for a few days afterward. This has happened about 3 times in the last 20 months and might be unrelated. Otherwise, no other symptoms. For all I know, I was born with this area on my midbrain, for I have no baseline to compare it to. However...
The midbrain spot was "measured" at 9.5 millimeters in November of 2005. It was "measured" at 10 millimeters in November of 2006. This was the same facility, same machine, same doc reading it. My neuro says don't worry, it's a normal variation in measurement.
1. What do you think? Is this .5 mm difference anything to stress about? I thought that the same machine, same interpreter would mean any change would be suspicious, but perhaps it's not that simple.
In 2005, had complaints of numbness in my extremities. Had brain MRI, spine MRI, and spinal tap. Spine MRI and lumbar puncture normal, but brain MRI revealed small area in right midbrain that was suspicious, although it didn't show any effects of the contrast material. Followed-up with a Multiple Sclerosis doc who said he didn't think it was MS. I met with a brain tumor doc/oncologist who ran Pet Scan, which ruled out neoplasm. He said go to an MS doctor...!
I've been seeing a regular neuro ever since, and have had more MRI's in 2005 and 2006. My symptoms of numbness have dissipated (in my opinion) because I'm now being treated for hypothyroidism with Synthroid, which was untreated at the time of the first MRI. I have occasional bouts of "vertigo" which last for only a few minutes in the morning, then go away and are followed by nausea for a few days afterward. This has happened about 3 times in the last 20 months and might be unrelated. Otherwise, no other symptoms. For all I know, I was born with this area on my midbrain, for I have no baseline to compare it to. However...
The midbrain spot was "measured" at 9.5 millimeters in November of 2005. It was "measured" at 10 millimeters in November of 2006. This was the same facility, same machine, same doc reading it. My neuro says don't worry, it's a normal variation in measurement.
1. What do you think? Is this .5 mm difference anything to stress about? I thought that the same machine, same interpreter would mean any change would be suspicious, but perhaps it's not that simple.
Doctor's Answer
by Forum-M.D.-SH, Apr 13, 2007 12:00AM
First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes.
The symptoms that you describe are non-specific, but I suspect the numbness in your extremities was not due to the midbrain lesion for several reasons. First, you mentioned 'numbness in your extemities' which is very general but I assume you are referring to the hands on both sides and the feet/legs on both sides were effected equally. This is consistent with a systemic problem (such as hypothyroidism, diabetes, alcoholism, etc) rather than a focal lesion. If the numbness were due to the right sided midbrain lesion I would expect that you would have left sided problems only. Second when a lesion occurs in the brain stem where many important 'wires' are in tight quarters with each other (such as a MS lesion or a fast growing tumor) then a number of things would be affected (causing double vision, facial weakness, slurred speech, etc), while when a lesion has been in the brain stem for a very long time (such as a congential lesion, or a very slow growing lesion)then the brain stem structures are able to develop oaround the lesion or move out of the way if it occurs slowly over many years (and causes no symptoms). I suspect that you may have a very slow growing tumor (which can be PET negative) or a congential lesion (such as a hamartoma). There is a sampling error that can cause a slight variation in measured size even with the same machine. The images are aquired in slices which are 0.5-5mm apart (depending on the desired resoultion). The exact slicing pattern cannot be reproduced, so that the second time you have the scan you may get a slic that is a few mm off from the slice acquired last year and that particular slice may be a slightly different size. However, that being said, the most important thing is to get more imformation (continue getting MRIs). If the lesion continues to grow 0.5mm every year then you will know this is not random sampling variability of slices, but is real growth. If the the yearly measurements are some up some down, but the average is roughly the same then this is consistent with sampling error and does not indicate lesion growth.
I hope this has been helpful.
The symptoms that you describe are non-specific, but I suspect the numbness in your extremities was not due to the midbrain lesion for several reasons. First, you mentioned 'numbness in your extemities' which is very general but I assume you are referring to the hands on both sides and the feet/legs on both sides were effected equally. This is consistent with a systemic problem (such as hypothyroidism, diabetes, alcoholism, etc) rather than a focal lesion. If the numbness were due to the right sided midbrain lesion I would expect that you would have left sided problems only. Second when a lesion occurs in the brain stem where many important 'wires' are in tight quarters with each other (such as a MS lesion or a fast growing tumor) then a number of things would be affected (causing double vision, facial weakness, slurred speech, etc), while when a lesion has been in the brain stem for a very long time (such as a congential lesion, or a very slow growing lesion)then the brain stem structures are able to develop oaround the lesion or move out of the way if it occurs slowly over many years (and causes no symptoms). I suspect that you may have a very slow growing tumor (which can be PET negative) or a congential lesion (such as a hamartoma). There is a sampling error that can cause a slight variation in measured size even with the same machine. The images are aquired in slices which are 0.5-5mm apart (depending on the desired resoultion). The exact slicing pattern cannot be reproduced, so that the second time you have the scan you may get a slic that is a few mm off from the slice acquired last year and that particular slice may be a slightly different size. However, that being said, the most important thing is to get more imformation (continue getting MRIs). If the lesion continues to grow 0.5mm every year then you will know this is not random sampling variability of slices, but is real growth. If the the yearly measurements are some up some down, but the average is roughly the same then this is consistent with sampling error and does not indicate lesion growth.
I hope this has been helpful.
About the change of 0.5mm in the midbrain spot, its not a significant thing even if the MRI was done in the same lab, but what is really imprtant , your MRI with contrast (Gadilinium) ,PET, and the spinal tap were negative (I'm sure they did what is called IgG index and Oligoclonal banding)
In Meidcine , if you blame almost any thing on hypothyroidism ,you could be right, because it causes so many things including the numbness (affect the axons of the long nerves), or the vertigo/tinnitus (fluid accomulation in the inner ear) ...ext
But what caused the hypothyroidism is important (is it a primary..if it is ..is it due to autoimmune thyroiditis?), because it may associate with other autoimmune diseases like diabetes, Perncous anemia, addison disease, MS....ext..
Could this be MS? No,according to the MS clinical and MRI criterias.
About the vertigo? though, they mainly seemed to have happened after your last MRI? but they can not be called MS attacks since they are shorter than 24 hr, but MS specialist call these episodes " Brainstem Paroxysm" and consider them reliable signs..so talk to your MS specialist and see if a repeate MRI with conrtast(GD) is worthdoing?
I hope you find this helpful (Sorry for my English, its my 3rd language)
Bob