In a manner relating to, characteristic of, or affected by an aneurysm; describing actions or conditions in aneurysm-related terms.
From aneurysmal (the adjective) plus the adverb suffix -ly, which converts the adjective into an adverbial form for describing how something occurs or manifests.
This is an extremely technical and rarely-used adverb—modern doctors would never write 'the artery expanded aneurysmally,' they'd just say 'aneurysm formation occurred,' showing how medical language has evolved to be clearer and more direct.
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