Opisthotonus … Opisthotonus or opisthotonos (from Ancient Greek: ὄπισθεν, romanized: opisthen, lit. ‘behind’ and τόνος, tonos, ‘tension’) is a state of severe hyperextension and spasticity in which an individual’s head, neck and spinal column enter into a complete “bridging” or “arching” position. [1][2]