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Does change in arm position affect MRI results of the spinal cord?

DOCTOR OF THE MONTH - May 2014
May 2014
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Radiologist
Practicing since : 2002
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Hello, 10 days ago I had an MRI of the cervical area done because I have been having neck and right shoulder pain. I swim a great deal and thought it was probably a muscle, or other soft tissue issue. When the MRI began, I asked the technician to take me out of the tube because when both of my hands were on my chest, my right shoulder and arm hurt too much in that position. After withdrawing from the tube, I put my right arm straight back behind my head, with the fist clinched and it relieved the pain and I was able to continue. My left arm remained relaxed with my hand on my chest. When the MRI results were reviewed with me by a surgeon, who I was referred to by the pain anesthesiologist who initially ordered the MRI, he stated that my spinal cord was "very tight", and that I had a congenitally small spinal passage way. I have never had spinal problems before and I believe improper breathing technique while swimming long distances may have caused, or contributed to two herniated discs I now have. My question is this: Can the fact that my right arm was held straight behind my head influence the impression that this surgeon had when reviewing the MRI? The radiologist mentioned nothing about a congenitally small spinal passage way, he simply characterized my situation as degeneratative. I do not want this to sound silly; yet since the MRI, I have laid on a flat surface and put both hands on my chest, as was my initial position during the MRI, and then felt my vertebrae area and it is loose and relaxed. Then I have put my right arm behind my head and the vertebrae tighten and narrow as would have been the case during the recent MRI. Could my right arm clinched position have influenced the surgeon's impression that I have a "tight spinal passage way? Once again, the MRI report indicated nothing about a congenitally narrow spinal canal, and neither did the X-ray report, which was also done. The surgeon was the person that stated this impression to me. Since this conversation, I have curtailed my swimming and the pain and shoulder discomfort is reduced significantly. The surgeon did not recommend surgery; yet he did leave an impression my congenitally narrow spinal passage way may be an issue in the future. My question is could my arm position, rigidly behind my head in a clinch, during the MRI, have given him an inaccurate impression? Thank you for your time and expertise.
Posted Fri, 21 Mar 2014 in X-ray, Lab tests and Scans
 
 
Answered by Dr. Vivek Chail 1 hour later
Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXX Thanks for writing in to us. I appreciate the query raised by you. To the best of my knowledge, change in arm position or clenching the fist will not cause any difference in spinal canal measurement in the cervical region. Though there is significant amount of comfort/ discomfort in some patients associated with change in arm position while lying down flat as in the MRI scanner tube. Speaking about cervical spine X rays, it is usually done in the neutral position. However when required, X rays in bending the neck forwards (flexion) and bending backwards (extension) are done in few patients. This is done to assess the spinal canal space in various positions. In MRI scan, all tissue layers are clearly visible and there is no significant variation in the cervical spinal canal due to positioning. The pain that is felt is essentially due to pressure on nerve roots that emerge from the spinal cord. Degenerative discs and bones may cause significant pain due to pressure. This pain is dependent on position of arms in some patients. Hope your query is answered. Do write back if you have any doubts. Regards, Dr.Vivek
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Follow-up: Does change in arm position affect MRI results of the spinal cord? 12 hours later
Thank you for your quick response, in follow up, while I understand the fact that the MRI illustrates all layers of tissue, I still wonder if the surgeon whose diagnosis is that I have a congenitally small spinal passage way could had his perspective influenced by the fact that when my arm is straight behind my head, it is like pulling a passage way that "does have some expansion and contraction capability", taut. He was reviewing the MRI when it was as taut as it could possibly be. I have never had back, or neck problems until very recently. I plan to have another MRI, with my hands relaxed on my chest, in the next few months. Once again the radiologist that reported on the MRI and on the X-rays done the same day said nothing about a small passage way, he simply indicated degenerative change. My symptoms have already improved in the last 10 days, since I have altered my swimming technique and made a few other changes. Please let me know if you believe the surgeon could possibly be misinterpreting my MRI results based on the information I have shared. Thank you again. PS Please have an MRI specialist respond as well.
 
 
Answered by Dr. Vivek Chail 7 hours later
Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXX Thanks for writing back with an update. The cervical spinal canal diameter is measured mathematically to avoid any errors due to subjective variability. Two methods are in use. 1. The Torg ratio is determined by dividing the sagittal spinal-canal diameter by the corresponding sagittal vertebral-body diameter. 2. The space available for the cord SAC was determined by subtracting the sagittal spinal-cord diameter from the corresponding sagittal spinal-canal diameter. Research shows that the SAC measure relies more on the spinal canal compared with the Torg ratio and, therefore, may be a more effective indicator of spinal stenosis. The above factors are independent of position of the arm in any patient. However, there can be erroneous measurement of the cervical spinal canal due to susceptibility artifacts related to osseous and calcified structures and gradient-echo images tend to result in slight overestimations of the degree of stenosis in the lateral recesses and neuroforaminal spaces. Therefore the matter is very technical and sometimes the canal diameter may appear less in particular series of images which is entirely due to technical factors. Hope I have been able to answer your query to the best of my knowledge. Further doubts welcome. Regards, Dr.Vivek
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Follow-up: Does change in arm position affect MRI results of the spinal cord? 2 hours later
I understand your expertise, and I understand my intuitive impressions. If I question the surgeons conclusions, not knowing how he arrived at his conclusion, what type of diagnostic test could I do to get a unreffutable answer. I believe the surgeon is wrong and once again the radiologist that summarized the MRI and x-rays did not indicate a congenitally small passage way, shouldn't that conclusion be the radiologist job, rather than a surgeon? Thank you, XXXXXXX
 
 
Answered by Dr. Vivek Chail 2 hours later
Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXXXXX Thanks for writing back. I do respect your intuitive impressions on hearing the surgeon's opinion. The surgeon has examined you clinically but at the same time further clarification is important should there be any confusion between image interpretation and clinical problems. In my opinion, I believe your MRI scan was done on a scanner with magnet strength 1.5T or 3T. Nowadays 3T scanner is used in most places. If your MRI scan was done using a 1.5T machine then the best alternative would be getting a scan done on a 3T machine after a while, if you do not recover completely. If your scan has been already done using a 3T machine then we have to accept the radiological report showing no significant cervical spinal canal stenosis. Hope I have been able to answer your query to the best of my knowledge. Further doubts welcome. Regards, Dr.Vivek
Above answer was peer-reviewed by
 
Follow-up: Does change in arm position affect MRI results of the spinal cord? 3 hours later
Thank you, my MRI was done on a 1.5 Tesla magnet. Please explain, in layman's terms, why this could be significant in all possible ways. I greatly appreciate the time you have spent considering and answering my questions. Let me ask the question in a better way, why would a 3.0 machine provide more clarity on whether, or not my spinal passage way is congenitally small? What other information, or clarity could a 3.0 machine provide vs a 1.5 magnet in relation to the various questions I have been asking, or my overall situation. Please keep it simple; yet be through, I am trying to understand all the possibities here. Thank you again, XXXXXXX
 
 
Answered by Dr. Vivek Chail 1 hour later
Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXXXXX Thanks for writing in with queries. A 3.0 T machine will have double the magnet strength than a 1.5 T machine. Therefore tissue contrast and resolution of images will be analyzed in greater detail. Earlier, about 10 years back 0.23 T machines were in use and in them cervical spine was difficult to assess. Soon we had 0.5 T machines which allowed the cervical spine to be seen slightly better. Then came the 0.75 T and 1.0 T machines which gave a better view. In the last 5 years 1.5 T has been used extensively. In the last three years 3.0 T machines have been installed in many hospitals for clinical use. As you can see the stronger the magnet, better is the signal received. MRI scan works on principle of radio frequency waves. This translates to better images with less ambiguities in a MRI machine having 3.0 T magnet. Hope I have been able to answer your query. Further doubts welcome. Regards, Dr.Vivek
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