the medical term opisthotonos (backward bending tone) means
Opisthotonus Opisthotonus or opisthotonos, from Greek roots, ὄπισθεν, opisthen meaning "behind" and τόνος tonos meaning "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] This abnormal posturing is an extrapyramidal effect and is caused by spasm of the axial muscles along the spinal column.