"The subarachnoid tissue is not as abundant here as in the normal subarachnoid space and cerebrospinal fluid (CSF) gathers to form pools or cisterns (Latin: "box"). As they are interconnected, the patency is essential for CSF circulation."

https://radiopaedia.org/articles/subarachnoid...

There are clues in the archives:

Siehe Wörterbuch: entfaltet

It basically means that the cisterns are clearly seen and not obstructed => patent

Any ideas on this one, Marianne?

Siehe auch: inhaltliches und formales Denken

It doesn't have a [Med.] tag, partially because the thread was revived. It's also for a Befund.