Findings: Image #1 is an axial T2 WI of the head demonstrating a lesion with homogeneously increased signal intensity within the sella turcica.
Image # 2 is a coronal T1 WI of the sella region. In this image, the lesion is decreased in signal intensity at the anterior aspect of the sella.
Image #3 is a coronal T1 WI post gadolinium of the same region as image #2, in which the lesion does not enhance. The lesion does not appear to be a part of the adeno or neurohypophysis.
Diagnosis: Rathke's cleft cyst.
Discussion: Rathke's cleft cysts (RCC) are non-neoplastic and are derived from the embryonic remnants of Rathke's pouch. The majority of RCC are asymptomatic and are incidental findings in 10-23% of autopsies. The most common clinical symptoms are those due to mass effect and include visual deficits, pituitary dysfunction, as well as headaches.
The MRI appearance of symptomatic RCC is variable, although most can be divided into two groups. Both are high signal on T2 and WI. However, the first group is low on T1 WI and typically has a more insidious onset, presents at a later age, usually with compressive symptoms of the optic tract.
The second group is iso-high signal intensity on T1 and WI and presents at an earlier age, usually with headache. The difference in T1 WI is thought to be due to high protein content of the cystic contents or hemorrhage.
Less likely etiologies would include arachnoid, epidermoid, or dermoid cysts, pituitary adenoma, or craniopharyngioma.
References:
Mukherjee N, et al. Clinical, Radiological and Pathological Features of patients
with Rathke's Cleft Cyst: Tumors That May Recur. The Journal of Clinical Endocrinology
and Metabolism. 1997;82(7):2357-2362.
Saeki N, et al. MRI Findings and Clinical Manifestations in Rathke's Cleft Cyst.
Acta Neurochirurgica. 1999;141:1055-1061.
Shin JL. Cystic Lesions of the Pituitary: Clincopathological Features Distinguishing
Craniopharyngioma, Rathke's Cleft Cyst, and Arachnoid Cyst. 1999; 84(21):3972-3982.
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