martedì 28 aprile 2009
Rathke cleft cyst
Figure 1 and Figure 2: Sagittal and coronal T1 weighted images demonstrate a well-defined, high-signal round structure in the suprasellar region with a low signal mural nodule. The high signal material is likely due to hemorrhagic or proteinaceous material within the cyst.
Figure 3 and Figure 4: Axial and coronal T2 weighted images demonstrate an isotense suprasellar structure with a low signal mural nodule.
Figure 5: Post-contrast T1 weighted image demonstrates no enhancement of the Rathke cleft cyst with some lateral displacement of the enhancing stalk.
Diagnosis: Rathke Cleft Cyst
Rathke cleft cysts (RCC) are nonneoplastic cysts which arise from remnants of the Rathke pouch. The cyst is lined with a single layer epithelium. On pathlogy, inflammatory changes may be present. The cyst may contain cerebrospinal fluid density material as well as thick mucoid debris, hemorrhage, hemosiderin as well as colloid. RCCs stain positively for cytokeratins.
Most RCCs are found incidentally as they are asymptomatic. RCCs can produce symptoms by causing pituitary dysfunction, visual disturbance or headache. RCCs may rarely produce sphenoid sinusitis or compress the optic chiasm and/or hypothalamus. RCCs have a slight female predominance. Some RCCs will decrease in size or spontaneously resolve while others display stable size and MR signal over time. If RCCs are deemed to be symptomatic, cyst aspiration or excision may be necessary. They recur in up to 1/3 of patients.
CT imaging characteristics of RCCs are well defined intra- or suprasellar masses which are fluid attenuation or mixed density. Cyst wall calcification is present in 10-15% of patients. The T1 appearance of RCCs varies bases upon cyst content. Five to 10% may have a fluid-fluid level. Intracystic mural nodules are present in 75%. T2 signal characteristics also vary with cyst content, with 75% demonstrating a low signal intracystic nodule. RCCs do not demonstrate internal enhancement, however the adjacent compressed pituitary enhances.
Differential diagnostic considerations for Rathke cleft cysts include:
- Craniopharyngioma (differentiated by the degree of calcification and enhancement)
- Cystic pituitary adenoma (rarely have calcification, demonstrate heterogeneous signal intensity and may demonstrate rim and/or nodular enhancement)
- Colloid cysts as well as pars intermedia cysts are also diagnostic considerations
- Other non-neoplastic cysts derived from arachnoid, dermoid, or epidermoid elements