MRI characteristics of various pathological subtypes of focal cortical dysplasia

Objective To summarize MRI findings of focal cortical dysplasia (FCD), analyze MRI characteristics of various pathological subtypes of focal cortical dysplasia. Methods Forty-four patients with FCD were collected. Their MRI findings were analyzed retrospectively. According to pathologic findings, these patients were divided into FCD type Ⅰ group and FCD type Ⅱ group. The following MR signs were observed in the two types of FCD: ( 1 ) Focal thickening of the cortex. ( 2 ) Blurring of the gray matter-white matter junction. ( 3 ) Tapering of white matter signal intensity alteration toward the ventricle on FLAIR and on T2WI. (4)Focal brain hypoplasia. (5)Increased signal intensity of gray matter on FLAIR. (6)Increased signal intensity of gray matter on T2 WI. ( 7 ) Increased signal intensity of subcortical white matter on FLAIR.(8) Increased signal intensity of subeortical white matter on T2WI. (9) Decreased signal intensity of subcortical white matter on T1 WI. The χ2 tests and corrected χ2 tests were used for comparison between the two groups. Results In the 44 cases, there were 30 cases with FCD type Ⅰ and 14 cases with FCD type Ⅱ. FCD was identified by MRI in 32 cases. Blurring of the gray-white matter junction is the most common sign of FCD (23 cases). There were 21 cases identified by MRI in FCD type Ⅰ group. Focal brain hypoplasia is a typical sign of FCD type Ⅰ , which was found in 11 cases in FCD type Ⅰ group but none in FCD type Ⅱ group. There was statistically significant difference between the two groups (continuity corrected χ2 =5. 0286,P =0. 0249) . In FCD type Ⅱ group, 11 cases were identified by MRI. Increased cortical thickness was found in 10 eases in FCD type Ⅱ group and 11 cases in FCD type Ⅰ group ( χ2 =4. 6234 ,P =0. 0315). Increased signal intensity of subcortical white matter on FLAIR was found in 9 cases in FCD type Ⅱ group and 7 cases in FCD type Ⅰ group (χ2 =6.9180,P =0.0085). Tapering of white matter signal intensity alteration toward the ventricle was found in 4 cases in FCD type Ⅱ group and none in FCD type Ⅰ group ( continuity corrected χ2 = 6. 2883, P = 0. 0122). The above-mentioned three MRI findings showed statistically significant difference between the two groups and were features of FCD type Ⅱ.All of the other MRI findings showed no statistically significant difference between the two groups. Conclusions Different pathological subtypes of FCD have different MRI characteristics. It is helpful to make preoperative diagnosis and planning. Key words: Cerebral cortex;  Nervous system abnormalities;  Magnetic resonance imaging