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Objective:To describe the manifestations of demyelinating pseudotumor lesions on MRI, discuss the diagnostic value of the open-ring sign in this disease entity, to enhance the realization of demyelinating pseudotumor lesions and improve the diagnostic accuracy.Methods:1.I collected 10 cases with intracranial space occupying lesions and unclear pathological diagnosis from neurosurgery of our hospital, maked myelin staining for their paraffin specimens with the help of pathology department, judged whether they were demyelinating pseudotumor lesions and analysed the value of myelin staining for demyelinating pseudotumor lesions.2.An analysis was done in 30 cases of pathology-proved demyelinating pseudotumor lesions, consisted of one case from the First Affiliated Hospital of Guangxi Medical University and twenty-nine cases from on-line MEDLARS. Their MRI manifestations (distribution, quantity, mass effective, surrounding edema, contrast enhancement) and the specificity of open-ring sign were studied in contrast to pathology-proved 30 cases of gliomas (named control group 1),30 cases of brain abscess(named control group 2) and 16 cases of PCNSL (named control group 3),with the help of two experienced neuroradiologists, reading the images as closed-ring or open-ring enhancement together, blinded to the pathologic diagnosis. Then we calculated the sensitivity, specificity, positive predictive value and negative predictive value of the open-ring sign, discussed the diagnostic value of the open-ring sign in demyelinating pseudotumor lesions .Results:1.In 10 cases with myelin staining, 4 cases were normal brain tissue,with no loss of myelin; the other 6 cases were all with loss of myelin, they were 1 case demyelinating disease, 1case inflammatory granuloma, 1 case retrogression brain tissue, 1case parasitic infection, 1 case PCNSL and 1 case scathing brain tissue after radiotherapy for NPC.2.In case group with pathology-proved, there were 8 cases whose lesions w- ere circumscribed to white matter and 22 cases whose lesions distributed between white matter and grey matter; there were 19 cases with only one lesion and 11 ca- ses with more than two lesions, including 3 cases with 2 lesions,5 cases with 3 l- esions, 3 cases with 4 lesions; there were 22 cases with no or mild mass effective and surrounding edema, 8 cases with obvious mass effective and surrounding ed- ema; there were 2 cases with no contrast enhancement and 28 cases with obvious contrast enhancement; there were 20(67%) cases with contrast enhancement sha- ped as an open ring, 2(7%) cases shaped as a closed ring, 4(13%) cases shaped as a block mass, 1(3%) case shaped as a taper perpendicular to paracele and 1(3%) case with nonuniform contrast enhancement. The clinical manifestation was obv- iously improved or the lesions was reduced in size or in enhanced effects after hormone treatment in 20 cases.3. The number of cases with open-ring sign was 20 in case group, 6 in con- trol group 1, 2 in control group 2 and 2 in control group 3. We found statistically significant difference about the open-ring sign between case group and control group 1 (p<0.05), case group and control group 2 (p<0.05), the same with it be- tween case group and control group3 (p<0.05).4.The number of cases whose gaps of open-ring sign was opposite to grey m- atter , white matter and paracele was 17(85%), 0(0%)and 3(15%)in case group; 4(66%), 1(17%)and 1(17%)in control group 1; 1(50%), 0(0%)and 1(50%)in control group 2; 0(0%),1(50%)and 1(50%)in control group 3.5.The characteristic of demyelinating pseudotumor lesions on MRI,especial- ly the open-ring sign had significant value in differentiating the disease from gli- omas, brain abscess and PCNSL. The sensitivity, specificity, positive predictive value and negative predictive value of the open-ring sign were 66.67%, 80.00%, 76.92%,70.59% versus control group 1; 66.67%,93.33%, 90.91%, 73.68% versus control group 2; 66.67%, 87.50%, 90.91%, 58.33% versus control group3; 66.67 %, 86.84%, 66.67%, 86.84% versus three control groups.Conclusions:1.The loss of myelin in pathology was not the only defining characteristic for demyelinating pseudotumor lesions after myelin staining. To make correct diagnosis, we should consider other pathologic features, clinical manifestations, imaging features and so on. 2.The characteristic of demyelinating pseudotumor lesions on MRI were as follows: The lesions were often circumscribed to white matter and the junctional zone between white matter and grey matter. The number of lesions was maybe only one or more. The lesions were usually with no or mild mass effective and surrounding edema. Most of them showed obvious contrast enhancement on MRI, the open-ring sign was common. The gaps of most lesions with open-ring sign were opposite to grey matter . Most lesions could be reduced in size or in enhan- ced effects after hormone treatment.3. We found statistically significant difference about the open-ring sign between case group and control group 1 (p<0.05), case group and control group 2(p<0.05), the same with it between case group and control group 3(p<0.05).4. The specificity and positive predictive value of the open-ring sign were relatively high, and the gaps of open-ring sign were usually opposite to grey matter. These characteristic had significant value in differentiating the disease from gliomas , brain abscess and PCNSL, which could improve the diagnosetic accuracy, avoiding unnecessary radiotherapy and surgery to patients.
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