Inflammation of the arachnoid membrane, which is a thin layer of tissue surrounding the brain and spinal cord, causing pain and neurological problems.
From Greek 'arachne' (spider) + '-oid' (like) + '-itis' (inflammation). Named because the arachnoid membrane resembles a spider's web under a microscope. The term emerged in the 1800s.
Arachnoiditis is devastatingly difficult to treat because the arachnoid membrane's spider-web structure can scar and stick to the spinal cord, potentially causing permanent nerve damage—which is why doctors try so hard to prevent it!
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