A choroidal fissure cyst refers to a benign intracranial cyst occurring at the level of the choroidal fissure. They frequently represent either an arachnoid cyst, neuroglial cyst or a neuroepithelial cyst 2. They are therefore a location-based diagnosis rather than a distinct pathological entity.
They are usually asymptomatic and discovered incidentally. Very rarely they may cause seizures of mass effect within the temporal lobe 3.
They are usually small and range around about 1-2 centimetres in diameter. Occasionally, larger cysts may be seen. The cysts are usually round on axial and coronal scans, with a characteristic spindle or ovoid shape paralleling the long axis of the temporal lobe and choroid fissure on sagittal images.
CT scans show a well-delineated homogeneous low density mass with attenuation characteristics similar to CSF. Calcification and contrast enhancement are absent.
MR signal characteristics are similar to CSF on all sequences. The cyst walls are thin. Contrast enhancement, surrounding oedema and gliosis are absent.
Treatment and prognosis
They are almost always benign with interval follow up (not required) showing no imaging changes. As such no treatment is required 1.
General imaging differential considerations include
- a solitary enlarged perivascular space
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