The cyst with dot sign is a commonly seen MRI feature of Rathke cleft cysts and is helpful in making the diagnosis with certainty on imaging features alone.
It should not be confused with the cyst with dot sign of neurocysticercosis.
Radiographic features
A cyst with dot sign is observed in 65-75% of Rathke cleft cysts. The dot is due to a non-enhanced intracystic nodule, which is usually hyperintense on T1 and hypointense on T2, within a fluid-intensity cyst. Its visibility may vary depending on the fluid's signal, potentially making it inconspicuous in one or more sequences 1-3.
The cyst with dot sign is said to be pathognomonic for Rathke cleft cyst if other appearances align 2. It's important to note that the dot can occasionally be quite large, occupying most of the cyst.
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