MRI And Clinical Characteristics Of Different Pathological Subtype Of Focal Cortical Dysplasias

Objective: The purpose of this study is to summarize MRI fingdings of focal cortical dysplasias(FCD), analyze MRI characteristics ,clinical datas and surgical outcomes of different pathological subtype of focal cortical dysplasias.Methods: The study object was 44 patients between December, 2005 and December 2008, who have been proven of FCD by pathology. In according to pathologic findings, these patients have been separated into FCD type I group (30 cases) and FCD type II group (14 cases), which have been further separated into FCD type I A group (12 cases) , FCD type I B group (18 cases), FCD type II A group (8 cases) and FCD type II B group (6 cases).Collected the clinical information of these patients and chose age at surgery, age at epilepsy onset, central nervous system(CNS) infections history , febrile seizures history and surgical outcome as analyzed targets. Scanning conditions was as follows: Head coil,SE sequence: axial T1WI(TR 380-500 ms/TE 9-15 ms), T2WI(TR 3400 ms/TE 90-110 ms), 8mm- section thickness, 2mm-intersection gap; sagittal T1WI(TR 380-500 ms/TE 9-15 ms ) , 5mm- section thickness, 1 mm-intersection gap; coronal T1WI(TR 380-500 ms/TE 9-15 ms), 4mm- section thickness, 1.5mm-intersection gap. Axial FLAIR(TR 8002 ms, TE 105 ms, TI2000ms), 8mm- section thickness, 2mm-intersection gap; coronal FLAIR(TR 8002 ms, TE 105 ms, TI2000ms ) , 4mm- section thickness, 1.5mm-intersection gap. 240×180mm field of view, 256×192 matrix. 9 kinds of MRI findings were estimated, such as focal thickening of the cortex, blurring of the gray matter–white matter junction, tapering of white matter signal intensity alteration toward the ventricle, focal brain hypoplasia, increased signal intensity of gray matter and subcortical white matter on T2WI and FLAIR, decreased signal intensity of subcortical white matter on T1WI.Statistical analyses were performed by SAS 8.1 software, andΧ~2 tests, CorrectedΧ~2 tests, Fisher's exact test , exact test for r×c table and Wilcoxon rank sum tests were used. P<0.05 was considered to indicate a statistically significant difference, P>0.05 was indicated no statistically significant difference.Results:1 The analyses of Clinical information The average age at surgery were 23.4±9.0 years in FCD type I group (type I A 25.3±10.2 years, type I B 22.2±8.2 years) and 25.7±10.6 years in FCD type II group (type II A 28.2±7.9 years, type II B23.2±13.0 years). There was no statistically significant difference between FCD type I group and FCD type II group (P=0.2136), and among FCD type I A, I B, II A and II B group (P=0.3416).The average age at epilepsy onset were 12.4±9.7 years in FCD type I group (type I A 12.8±10.4 years, type I B 12.1±9.6 years) and 11.2±8.0 years in FCD type II group (type II A 15.4±8.2 years, type II B7.0±5.6 years). There was no statistically significant difference between FCD type I group and FCD type II group (P=0.9002), and among FCD type I A, I B, II A and II B group (P=0.4372).There were 9 patients with CNS infections in this study, 6 cases in FCD type I group and 3cases in FCD type II group; There were also 9 patients with febrile seizures , 7 cases in FCD type I group and 2 cases in FCD type II group. For these targets, There was no statistically significant difference between FCD type I group and FCD type II group .2 MRI findings FCD was identified by MRI in 32 cases (72.7%),21 cases in FCD type I group (70.0%) and 11 cases in FCD type II group (78.6%). By statistical analyses, the P value was more than 0.05, indicated no statistically significant difference between FCD type I group and II group. There was also no statistically significant difference among FCD type I A group (9 cases), FCD type I B group (12 cases), FCD type II A group (5 cases) and FCD type II B group (6 cases).Focal thickening of the cortex has been found in 47.7% of all the cases, which covered 36.7% in FCD type I group and 71.4% in FCD type II group ; Blurring of the gray matter–white matter junction has been found in 52.3% of all the cases , which covered 50.0% in FCD type I group and 57.1% in FCD type II group; Tapering of white matter signal intensity alteration toward the ventricle was found in 9.1% of all the cases, all in FCD type II B group(66.7%); Focal brain hypoplasia have been found in 25.0% of all the cases, all in FCD type I group(36.7%); Increased signal intensity of gray matter on FLAIR has been found in 29.5% of all the cases, which covered 23.3% in FCD type I group and 42.9% in FCD type II group; Increased signal intensity of gray matter on T2WI has been found in 22.7% of all the cases, which covered 16.7% in FCD type I group and 35.7% in FCD type II group; Increased signal intensity of subcortical white matter on FLAIR has been found in 36.4% of all the cases, which covered 23.3% in FCD type I group and 64.3% in FCD type II group; Increased signal intensity of subcortical white matter on T2WI has been found in 29.5% of all the cases, which covered 23.3% in FCD type I group and 42.9% in FCD type II group; Decreased signal intensity of subcortical white matter on T1WI has been found in 20.5% of all the cases, which covered 20.0% in FCD type I group and 21.4% in FCD type II group.By statistical analyses, 4 kinds of MRI finding indicated statistically significant difference between FCD type I group and FCD type II group. These were focal thickening of the cortex, tapering of white matter signal intensity alteration toward the ventricle, focal brain hypoplasia, and increased signal intensity of subcortical white matter on FLAIR. All of the MRI findings indicated no statistically significant difference between FCD type I A group and FCD type I B group. There was statistically significant difference between FCD type II A group and FCD type II B group in tapering of white matter signal intensity alteration toward the ventricle.3 Localization of lesions :There were 34 cases in temporal lobe( 77.3%) and 10 cases in extrotemporal lobes(4 cases in frontal lobe,1 cases in occipital lobe, 2 cases in occipital lobe ,3 cases in Multilobar). There was statistically significant difference between non-FCD type II B group (33 cases) and FCD type II B group (1 cases)(P=0.0010).4 Dual pathology( FCD plus ipsilateral hippocampal sclerosis): Dual pathology has been found in 10 cases(3 inⅠA group,6 inⅠB group , 0 inⅡA group and 1 inⅡB group). There is no statistically significant difference among the 4 groups。5 Surgical outcome: There were 38 cases that had been followed up successfully. In FCD typeⅠgroup, 25 cases in all, 20 patients were seizure-free; In FCD typeⅡgroup, 13 cases in all, 8 patients were seizure-free. In MRI positive group, 29 cases in all, 21 patients were seizure-free; In MRI negative group, 9 cases in all, 7 patients were seizure-free. There was no statistically significant difference between FCD type I group and FCD type II group (P=0.2629), and between MRI positive group and MRI negative group (P=1.0000).Conclusion:1 It is difficult to distinguish FCD type I group from FCD type II group by Clinical information discussed in this study.2 FCD has the following MRI characteristics:①Blurring of the gray-white matter junction is the most common marker of FCD and is found in both FCD type I and FCD type II;②Focal brain hypoplasia is typical in FCD type I ;③Increased cortical thickness, tapering of white matter signal intensity alteration toward the ventricle, increased signal intensity of subcortical white matter on FLAIR are features of FCD type II;④No MRI features was found that distinguish FCD type I A from FCD type I B in this study. Tapering of white matter signal intensity alteration toward the ventricle may facilitate distinguishing FCD type II A from FCD type II B.3 The MRI of a patient with FCD may be normal, which has no obvious relationship with pathological type. FCD can not be ruled out when a patient with intractable epilepsy and normal MRI.4 FCD type II B is found in temporal lobe at most, and the other subtypes in extra-temporal lobe most. There is no difference between FCD type I group and FCD type II group in Dual pathology .5 There is no significant relationship between the pathologic types of FCD and surgical outcome. MRI performances could not be viewed as predictors of postoperative curative effect.