Meaning

noun anesthesia of the lower half of the body; caused by injury to the spinal cord or by injecting an anesthetic beneath the arachnoid membrane that surrounds the spinal cord

adjective of or relating to the spine or spinal cord

originBorrowed from Late Latin spīnālis (“of or belonging to the spine”), from spīna (“a prickle, spine”) + -ālis (“-al”, adjectival suffix). By surface analysis, spine + -al.

Etymology from Wiktionary, CC BY-SA 3.0