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What is Opisthotonus and explain in detail?
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 individuals head, neck and spinal column enter into a complete "bridging" or "arching" position.This extreme arched pose is an extrapyramidal effect and is caused by spasm of the axial muscles along the spinal column. It has been shown to occur naturally in birds, snakes suffering from advanced boid inclusion body disease, and placental mammals, among existing animals; it is observed in some articulated dinosaur fossils.

Causes
Opisthotonus is a symptom of some cases of severe cerebral palsy and traumatic brain injury or as a result of the severe muscular spasms associated with tetanus. It can be a feature of severe acute hydrocephalus, poisoning, and drowning.

Infants
Opisthotonus is more pronounced in infants