Rathke cleft cyst: MR and biomedical analysis of cyst content

Purpose: At least one type of Rathke cleft cyst has unique MR findings, spe cifically, high intensity on T1-weighted images and iso- to low intensity o n T2-weighted images relative to white matter. To clarify the influence of cyst content on MR images, we analyzed the cyst content by biomedical metho ds after surgical removal. Method: We studied five patients diagnosed with Rathke cleft cyst, whose MR images showed high intensity on T1-weighted images and iso- to low intensi ty on T2-weighted images. After surgery, total protein and cholesterol leve ls were quantified, and correlations of protein and cholesterol content wit h T1 and T2 signal intensities were performed in vitro. Results: All five cysts had very high concentrations of protein (11,700-26, 600 mg/dl mean 17,940 mg/dl) with nearly no cholesterol (at most 2.0 mg/dl) . Along with increases in protein concentration in vitro, the signal intens ity of T1-weighted images increased, while that of T2-weighted images decre ased. In contrast, the cholesterol concentration sequence influenced the si gnal intensity of neither T1- nor T2-weighted images. Conclusion: The unique MR finding of Rathke cleft cysts-high signal intensi ty on T1-weighted images and low signal intensity on T2-weighted images-mig ht depend mainly on protein concentration, not on cholesterol.