That's called opisthotonos -- typical of this condition. ".    From Wordnik.com.  [Every living thing]

He was motionless, his legs extended stiffly, his back arched in a dreadful opisthotonos, his eyes staring.    From Wordnik.com.  [Every living thing]

Oculogyric crisis, blepharospasm, respiratory stridor with cyanosis, torticollis, and opisthotonos can occur, as well as slow, writhing movements of the extremities.    From Wordnik.com.  [The Neuropsychiatric Guide to Modern Everyday Psychiatry] Reference

The past was a dim montage of life at the agency and the treatment center and the ranch, a recollection of lying on the river bank with women in attitudes of opisthotonos or of lying against the boulders with a rifle.    From Wordnik.com.  [This Crowded Earth] Reference

According to the muscles involved, it is styled trismus, emprosthotonos, opisthotonos and pleuristhotonos.    From Wordnik.com.  [An Epitome of Practical Surgery, for Field and Hospital.] Reference

At one moment the patient was extended at full length with her body arched forward in a state of opisthotonos.    From Wordnik.com.  [Primitive Love and Love-Stories] Reference

Epileptic convulsions, as the emprosthotonos and opisthotonos, with the cramp of the calf of the leg, locked jaw, and other cataleptic fits, appear to originate from pain, as some of these patients scream aloud before the convulsion takes place; which seems at first to be an effort to relieve painful sensation, and afterwards an effort to prevent it.    From Wordnik.com.  [Zoonomia, Vol. I Or, the Laws of Organic Life] Reference

“Then, I presume it is not true, ” Coictier went on with rising hear, “that gout is an internal eruption; that a shotwound may be healed by the outward application of a roasted mouse; that young blood, injected in suitable quantities, will restore youth to aged veins; it is not true that two and two make four, and that emprosthotonos follows upon opisthotonos?.    From Wordnik.com.  [I. The Abbot of St.-Martin’s. Book V] Reference

And in this they differ from the successive dissimilar exertions of the retina, mentioned in this section, which resemble in miniature the more violent agitations of the limbs in convulsive diseases, as epilepsy, chorea S. Viti, and opisthotonos; all which diseases are perhaps, at first, the consequence of pain, and have their periods afterwards established by habit.    From Wordnik.com.  [Zoonomia, Vol. I Or, the Laws of Organic Life] Reference

The restlessness in some fevers is an almost perpetual exertion of this kind, excited to relieve some disagreeable sensations; the reciprocal opposite exertions of a wounded worm, the alternate emprosthotonos and opisthotonos of some spasmodic diseases, and the intervals of all convulsions, from whatever cause, seem to be owing to this circumstance of the laws of animation; that great or universal exertion cannot exist at the same time with great or universal sensation, though they can exist reciprocally; which is probably resolvable into the more general law, that the whole sensorial power being expended in one mode of exertion, there is none to spare for any other.    From Wordnik.com.  [Zoonomia, Vol. I Or, the Laws of Organic Life] Reference