An Investigation And Analysis Of In-patient Cerebral Infectious Disease On MRI

Background and Objective Cerebral infectious disease is a frequent group of disease, its morbidity and mortally is very high, and misdiagnosis still exists in clinic. Therefore, it is necessary to give prompt and accurate diagnosis and treatment to avoid severe complications that can lead to an undesired outcome. At present, magnetic resonance imaging (MRI) is the most sensitive imaging modality in detecting focal or diffuse parenchymal infection. However, there is no report about the in-patient distribution and MRI features of cerebral infectious diseases in Anhui province. This study was to explore the approximate constituent and MRI features of cerebral infectious diseases in our district to improve the accurate diagnostic rate of cerebral infectious diseases.Materials and Methods All the patients who have received MRI and hospitalized in the First Affiliated Hospital of Anhui Medical University with the final diagnosis of cerebral infectious diseases from January 2005 to December 2007 were reviewed retrospectively. Detail data of all subjects were recorded, which include medical record, laboratory examination and the findings of MRI. All MRI scans were obtained with a GE Signa Horizon 1.5T MRI Scanner. The MRI protocol was identical for all patients and included three axial sequences: T1-weighted sequence, T2-weighted sequence and fluid-attenuated inversion recovery (FLAIR). Partial patients also underwent coronal and sagittal T1-weighted sequence, T2-weighted sequence, and diffusion weighted imaging (DWI), contrast enhanced T1WI. The following parameters were observed, which included constitution ratio of cerebral infections, the lesion location, the distribution, the shape, the edge, the number, peripheral edema, the characteristics of signal intensity, the extent of space-occupied effect and enhancement.Results There are 131 cases (1.64%) hospitalized patients with the diagnosis of cerebral infection among 7989 patients underwent brain MRI. Cerebral viral infections were present in 96 patients (73.3%). In addition, there are 20 cases of cerebral nonspecific pyogenic infection (15.3%), 1 case of cerebral Whipple's disease (0.76%), 10 cases of cerebral tuberculosis (7.6%), 3 cases of cerebral schistosomiasis (2.3%) and 1 case of cerebral cryptococcosis (0.76%). Sixty five of 96 cases with virus encephalitis were diagnosed by MRI, and the positive detection rate of MRI was 67.7%. In these cases the specific etiology still remains unknown for 85.4%. Multiple lesions were demonstrated in most patients with viral encephalitis. The lesions located mainly in the cortical, subcortical areas of temporal lobe (53.8%), frontal lobe (44.6%), parietal lobe (33.8%), and appeared as patchy or gyrus-like. All the lesions showed iso- or hypo-intense signal on T1WI, hyperintense signal on T2WI, FLAIR and DWI. On contrast-enhanced MRI, no-enhancement was found in 40% of viral infection, and spot-patchy enhancement in 27.7%. Cerebral pyogenic infection included pyogenic encephalitis in 10 cases, abscess in 10 cases and cerebral pyogenic infection accompanied meningitis in 3 cases. Single lesion was found in most patients with nonspecific pyogenic infection. No difference about the conventional MRI signal was found between pyogenic and viral encephalitis. However, there is significant difference between viral encephalitis and pyogenic encephalitis in location, distribution, number of the lesions, extension and type of contrast enhancement (P<0.05). The lesion of pyogenic infection appear as patchy or round. DWI is useful in differentiating it from tumors. More than half(58.6%) of the lesions showed ring-like enhancement. In a case with cerebral Whipple's disease, MR imaging demonstrated that multiple foci appeared as slightly long T1 and T2 signal with homgenous nodular enhancement and marked peri-lesion edema at onset. As the time went on, the number of the lesion increased and the extent became wide, some of which had necrosis. At last, the imaging data showed that all the lesions transformed into stroke-like, cortical hemorrhage appeared and meningeal enhancement was demonstrated. Eight of 10 cases with cerebral tuberculosis were diagnosed by MRI, and the positive detection rate of MRI was 80%. Cerebral tuberculoma included mature tuberculoma in 3 cases, non-mature tuberculoma in 5 cases and tuberculoma accompanied tuberculous meningitis in 6 cases. Multiple foci were found in all patients with cerebral tuberculosis, 87.5% of which located in the parietal lobe, and appeared as round. The lesions showed isointense or hypo-intense signal on T1WI, hypo- or slightly hyperintense signal on T2WI and FLAIR. On contrast-enhanced MRI, the lesions showed ring-like or nodular and leptomeningeal enhancement. In 3 patients with cerebral schistosomiasis, multiple lesions were found in all patients. The lesions located in the parietal lobe, occipital lobe, frontal lobe, basal ganglia, and appeared to be nodular or conglomeration. The lesions showed isointense or slightly hypointense signal on T1WI, isointense or slightly hyperintense signal on T2WI, FLAIR and DWI. On contrast-enhanced MRI, the lesions showed nodular enhancement and cluster nodular enhancement is its feature in characteristic diagnosis. In a patient with cerebral cryptococcosis, single lesion in the right cerebral hemisphere, basal ganglia was demonstrated on MRI. The lesion appeared as heterogeneously iso-and hypointense signal on T1WI, iso- and hyperintense signal on T2WI and FLAIR. On contrast-enhanced MRI, the lesions showed marked heterogeneous and meningeal enhancement.Conclusions Cerebral viral infection was the commonest, followed by nonspecific pyogenic infection, cerebral tuberculosis, cerebral schistosomiasis and cryptococcosis in the local area in-patient. The etiology still remains unknown in 85.4% cases of viral infection in our study and more sensitive diagnostic methods for viruses are needed to provide useful etiological evidence for diagnosis and treatment. There were some false-negative cases with cerebral viral infection and cerebral tuberculosis with conventional MRI. In order to improve the detection of these lesions, a combination of DWI and contrast-enhanced MRI is necessary. The MRI features including location, distribution, number of the lesions and contrast enhancement are useful and important for distinguishing viral encephalitis from pyogenic encephalitis. MRI is one of the important methods in diagnosis of cerebral infectious diseases, it can provide evidencesfor early diagnosis and differentiation in certain degree.