Apparent diffusion coefficient of subcutaneous epidermal cysts in the head and neck: Comparison with intracranial epidermoid cysts

Rationale and Objectives. Subcutaneous epidermal cysts and intracranial epidermoid cysts are pathologically identical. Although diffusion-weighted imaging (DWI) studies of intracranial epidermoid cysts have been numerously reported, those of subcutaneous epidermal cysts have not been sufficiently investigated. Our hypothesis for this study is that the apparent diffusion coefficient (ADC) values of subcutaneous epidermal cysts and intracranial epidermoid cysts are not different. This study was intended to evaluate the ADC of subcutaneous epidermal cysts of the head and neck in comparison with that of intracranial epidermoid cysts. Materials and Methods. The MR studies were performed in 14 patients with head and neck, subcutaneous epidermal cysts and 10 patients with intracranial epidermoid cysts using line scan DWI (LSDWI). The ADC was measured and compared between the two types of cyst. Results. The ADC values (mean +/- SD) were 0.81 +/- 0.14 X 10(-3) mm(2)/s in subcutaneous epidermal cysts and 1.06 +/- 0.12 X 10(-3) mm(2)/S in intracranial epidermoid cysts. A significant difference was found in ADC values between the two types (P =.0019). Conclusion. Our preliminary study has shown that the ADC provides useful information regarding tissue characterization of subcutaneous epidermal cysts. However, the ADC of subcutaneous epidermal cysts was significantly lower than that of intracranial epidermoid cysts.