Differences between irritated meninges and inflamed meninges? - Do their symptoms present the same? I have possible meningeal irritation after a blood patch. Are there tests to know the difference?

No difference. When you doctor uses the word irritated he's using a common word to approximate the meaning of inflammation, which is a medical term for a protective/reparative process that occurs when parts of the body have been infected or injured. The inflammatory response can involve white blood cells, lymphocytes, chemical mediators working together to remove injurious substances and heal the affected tissue.