martedì 11 aprile 2006

Pineal cyst







Findings

A cystic lesion (2.0 x 1.8 x 1.2 cm) with thin and well-defined enhancing walls (Figure 1 and Figure 2) places mild mass-effect on the tectum. No hydrocephalus is present. The cystic lesion (Figure 1, Figure 2, Figure 3 and Figure 4) is homogeneously isointense to CSF on T1-weighted imaging, uniformly hyperintense on FLAIR sequences, and isointense to CSF on T2-weighted imaging. No diffusion restriction is seen on diffusion-weighted imaging. These findings are most compatible with a pineal cyst. Less likely, this may represent a pinecytoma.

Differential diagnosis:
- Pineal cyst
- Normal pineal
- Pineocytoma
- Epidermoid cyst
- Arachnoid cyst
- Germ cell neoplasm


Diagnosis: Pineal cyst


Pineal cysts are usually asymptomatic and are often discovered incidentally. They have been discovered in up to 40% of patients on autopsy studies. Patients with large pineal cysts may experience headaches secondary to obstructive hydrocephalus. Rarely, pineal cysts can produce Parinaud syndrome (paralysis of upward gaze, lid retraction, and abnormal pupillary movements). If the cyst is hemorrhagic, acute hydrocephalus can develop. Young females (aged 21-30) are affected more than males (female to male ratio is 3:1). The cysts commonly enlarge with puberty and then regress with age.

On CT, the pineal cyst contents are usually isodense relative to CSF. The wall may be calcified. The cyst wall (nodular or thin) may enhance with contrast. Pineal cysts have a variable appearance with MR. Cystic contents are most often hyperintense relative to CSF, but may be isointense on T1-weighted imaging. On T2-weighted sequences, the cystic contents are either isointense or hypointense to CSF. On FLAIR sequences, the cystic contents are hyperintense. No restriction is seen with diffusion-weighted imaging. The cyst walls may enhance (60%). On delayed images, the cystic contents may enhance.

The key management issue regarding a pineal cyst, is the fact that they can be indistinguishable from a pinecytoma. Therefore, a histological diagnosis may be needed to make the distinction. If biopsy or surgery is not performed, long-term follow-up imaging should be obtained. Some suggest that clinical follow-up without imaging is an acceptable alternative. In one follow-up series, the cysts did not change in size in 75% of patients.

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