Inflammation of the basal layer of the arachnoid membrane, which is one of the protective membranes surrounding the brain and spinal cord.
From 'basial' (base) + 'arachnid' (from Greek 'arachne' meaning spider, because the membrane is web-like) + '-itis' (inflammation). A medical term combining anatomy with a suffix indicating disease.
Your brain floats in a protective fluid surrounded by three membrane layers—the arachnoid is the middle cobweb-like one, and basiarachnitis is when the base of that delicate spider-web membrane gets inflamed.
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