In this condition, the subarachnoid space is extended into the sella tursica through a partial defect in the diaphragma sellae. An enlarged sella is seen on skull x-ray, and a low density CSF filled cavity occupying most the sella is seen on CT. The remaining space contains pituitary gland, tumour or both.
The condition is thought to arise from a change in CSF circulation with subsequent cisternal herniation. There is progressive compression of the pituitary parenchyma and reduction in portal vessel perfusion.
It is usually found in obese, often hypertensive, females. Presenting symptoms tend to non-specific - frequent headache and transient visual problems. Endocrine disturbance is unusual but when present, includes amenorrhoea in one - third of cases, usually due to hypogonadotropism. However, many patients enjoy normal pituitary function.
There is a risk that aneurysms may develop within the dilated sella which should be examined for by angiography.
Pituitary replacement therapy is required. Occasionally, it may be necessary to decompress the chiasm surgically.
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