|History: Patient 01: female, 20 years;Patient 02: female, 36 years;Patient 03: male, 48 years.|
|Findings: Figure 01 (patient 01): CT scan shows a well delineated homogeneous low density cyst-like mass, without enhancement, located in the medial left temporal lobe. (red arrows). Figure 02 (patient 02): Axial T2-weighted MR demonstrates a small cystic appearing image with signal characteristics similar to CSF, located at the left medial temporal lobe (red arrow). Figure 03 (patient 02): Coronal T2-weighted MR shows the small left choroidal fissure cyst (red arrow), without surrounding edema and gliosis. Figure 04 (patient 03): Axial T2-weighted MR shows a cyst-like mass in the medial right temporal lobe (red arrow). Figure 05 (patient 03): Coronal T1-weighted MR demonstrates a CSF space located between the fimbria of the hippocampus and diencephalon, at the choroidal fissure (red arrow). Figure 06 (patient 03): Coronal T2-weighted MR shows the classic aspect of choroidal fissure cyst (red arrow).|
|Diagnosis: Choroidal Fissure Cyst.|
|Discussion: The choroidal fissure is a CSF space between the fimbria of the hippocampus and diencephalon that curves postero-superiorly from the anterior temporal lobe to the atrium of the lateral ventricle. The choroidal fissure is a common site for neuroepithelial or arachnoid cysts. Choroidal fissure cysts are usually asymptomatic and discovered incidentally. Interval follow up examinations disclose no clinical or imaging changes. 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 edema and gliosis are absent. The cysts are usually quite 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. They are often about one centimeter in diameter, but may be two or three times this size. A variety of pathologies can cause a cyst-like mass in the medial temporal lobe as follows: choroidal fissure cyst; parasitic cyst; epidermoid cyst; low grade glioma. Recognition of choroid fissure cyst as a developmental variant is important to avoid mistaking them for other lesions.|
|References: 1. Osborn AG. Diagnostic Neuroradiology. St. Louis, MO. Mosby - Year Book, Inc. 1994. 2. Yock DH. Magnetic Resonance Imaging of CNS Disease - A Teaching File. 2nd ed. St. Louis, MO. Mosby, Inc. 2003.|
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Case Number: 35509939Last Updated: 01-18-2010 The reader is fully responsible for confirming the accuracy of this content.
The reader is fully responsible for confirming the accuracy of this content.