Body spasm in which the head and heels are bent backward while the trunk is arched forward. When lying down, a patient suffering from opisthotonus may actually have his buttocks, back, and thighs off the ground, resting instead on his heels and the back of his head. In severe cases, the knees may be bent so that the heels are touching the patient's buttocks. It's an extrapyramidal effect caused by spasm of axial muscles along the spine; it may be seen in tetanus, cerebral palsy, traumatic brain injury, and meningitis (in which it may serve to reduce pain by immobilizing the spine). Newborns occasionally manifest opisthotonus, but it does not necessarily indicate pathology of any kind; it may just be a reflection of their relatively immature nervous system.
Occasionally spelled opisthotonos.