Qualitative and quantitative evaluation for the heterogeneity of cortical tubers using structural imaging and diffusion-weighted imaging to predict the epileptogenicity in tuberous sclerosis complex patients

We aimed to evaluate whether the heterogeneity of tuber imaging features, evaluated on the structural imaging and apparent diffusion coefficient (ADC) map, can facilitate detecting epileptogenic tubers before surgery in tuberous sclerosis complex (TSC) patients. Twenty-three consecutive patients, who underwent tuber resection at our institute, were retrospectively selected. A total of 125 tubers (39 epileptogenic, 86 non-epileptogenic) were used for the analysis. Tuber heterogeneity was evaluated, using a 5-point visual scale and standard deviation of ADC values (ADC${}_{sd}$). A 5-point visual scale reflected the degree of T1/T2 prolongation, presence of internal cystic degeneration, and their spatial distribution within the tuber. These results were statistically compared between epileptogenic and non-epileptogenic groups, and their performance in predicting the epileptogenicity was also evaluated by receiver operating characteristic (ROC) analysis. A 5-point visual scale demonstrated that more heterogeneous tubers were significantly more epileptogenic (p < 0.001). Multiplicity of internal cystic degeneration moderately correlated with epileptogenicity (p < 0.03) based on the comparison between class 4 and class 5 tubers. ADC${}_{sd}$ was significantly higher in epileptogenic tubers (p < 0.001). ROC curves revealed that a 5-point visual scale demonstrated higher area under the curve (AUC) value than ADC${}_{sd}$ (0.75 and 0.72, respectively). Tuber heterogeneity may help identify the epileptogenic tubers in presurgical TSC patients. Visual assessment and standard deviation of ADC value, which are easier to implement in clinical use, may be a useful tool predicting epileptogenic tubers, improving presurgical clinical management for TSC patients with intractable epilepsy.