Opisthotonus or opisthotonos, from Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 roots, opistho meaning "behind" and tonos meaning "tension", is a state of a severe hyperextension and spasticity

Spasticity

Spasticity is a feature of altered skeletal muscle performance in muscle tone involving hypertonia, which is also referred to as an unusual "tightness" of muscles...

 in which an individual's head, neck and spinal column enter into a complete "bridging" or "arching" position. This abnormal posturing

Abnormal posturing

Abnormal posturing is an involuntary flexion or extension of the arms and legs, indicating severe brain injury. It occurs when one set of muscles becomes incapacitated while the opposing set is not, and an external stimulus such as pain causes the working set of muscles to contract. The posturing...

 is an extrapyramidal

Extrapyramidal symptoms

The extrapyramidal system can be affected in a number of ways, which are revealed in a range of extrapyramidal symptoms , also known as extrapyramidal side-effects , such as akinesia and akathisia .Extrapyramidal symptoms are various movement disorders such as acute dystonic reactions,...

 effect and is caused by spasm

Spasm

In medicine a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. It is sometimes accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes...

 of the axial

Anatomical terms of location

Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...

 muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s along the spinal column.

Causes

It is seen in some cases of severe cerebral palsy

Cerebral palsy

Cerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....

 and traumatic brain injury

Traumatic brain injury

Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

 or as a result of the severe muscular spasms associated with tetanus

Tetanus

Tetanus is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani...

.

Opisthotonus can be produced experimentally in animals by transection of the midbrain (between the superior colliculus

Superior colliculus

The optic tectum or simply tectum is a paired structure that forms a major component of the vertebrate midbrain. In mammals this structure is more commonly called the superior colliculus , but, even in mammals, the adjective tectal is commonly used. The tectum is a layered structure, with a...

 and the inferior colliculus

Inferior colliculus

The inferior colliculus is the principal midbrain nucleus of the auditory pathway and receives input from several more peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex...

), which results in severing all the corticoreticular fibers. Hyperextension occurs due to facilitation of the anterior reticulospinal tract caused by the inactivation of inhibitory corticoreticular fibers, which normally act upon the pons

Pons

The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...

 reticular formation

Reticular formation

The reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...

. It has been shown to occur naturally only in bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s and placental mammals.

Opisthotonus is more pronounced in infants. Opisthotonus in the neonate may be a symptom

Symptom

A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

 of meningitis

Meningitis

Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...

, tetanus

Tetanus

Tetanus is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani...

, severe kernicterus

Kernicterus

Kernicterus is damage to the brain centers of infants caused by increased levels of unconjugated bilirubin. This may be due to several underlying pathologic processes. Newborn babies are often polycythemic. When they break down the erythrocytes, one of the byproducts is bilirubin, which circulates...

, or the rare Maple Syrup Urine Disease

Maple syrup urine disease

Maple syrup urine disease , also called branched-chain ketoaciduria, is an autosomal recessive metabolic disorder affecting branched-chain amino acids. It is one type of organic acidemia...

. This marked extensor tone can cause infants to "rear backwards" and stiffen out as the mother or nurse attempts to hold or feed them. Opisthotonus can be induced by any attempt at movement such as smiling, feeding, vocalization

Speech production

Speech production is the process by which spoken words are selected to be produced, have their phonetics formulated and then finally are articulated by the motor system in the vocal apparatus...

, or by seizure

Seizure

An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...

 activity. A similar tonic posturing may be seen in Sandifer syndrome

Sandifer syndrome

Sandifer syndrome is a rare paediatric medical disorder, characterised by gastrointestinal symptoms and associated neurological features There is a significant correlation between the syndrome and gastroesophageal reflux disease , however it is estimated to occur in less than 1% of children with...

. Individuals with opisthotonus are quite challenging to position, especially in wheelchairs and car seats.

Opisthotonus can sometimes be seen in lithium

Lithium pharmacology

Lithium pharmacology refers to use of the lithium ion, Li+, as a drug. A number of chemical salts of lithium are used medically as a mood stabilizing drug, primarily in the treatment of bipolar disorder, where they have a role in the treatment of depression and particularly of mania, both acutely...

 intoxication. It is a rare extrapyramidal

Extrapyramidal symptoms

The extrapyramidal system can be affected in a number of ways, which are revealed in a range of extrapyramidal symptoms , also known as extrapyramidal side-effects , such as akinesia and akathisia .Extrapyramidal symptoms are various movement disorders such as acute dystonic reactions,...

 side effect of phenothiazine

Phenothiazine

Phenothiazine is an organic compound that occurs in various antipsychotic and antihistaminic drugs. It has the formula S2NH. This yellow tricyclic compound is soluble in acetic acid, benzene, and ether. The compound is related to the thiazine-class of heterocyclic compounds...

s, haloperidol

Haloperidol

Haloperidol is a typical antipsychotic. It is in the butyrophenone class of antipsychotic medications and has pharmacological effects similar to the phenothiazines....

, and metoclopramide

Metoclopramide

Metoclopramide is an antiemetic and gastroprokinetic agent. It is commonly used to treat nausea and vomiting, to facilitate gastric emptying in people with gastroparesis, and as a treatment for the gastric stasis often associated with migraine headaches.-Medical uses:Metoclopramide is commonly...

.

Opisthotonus with the presence of the risus sardonicus

Risus sardonicus

Risus sardonicus is a highly characteristic, abnormal, sustained spasm of the facial muscles that appears to produce grinning.The name of the condition derives from the appearance of raised eyebrows and an open "grin" - which can appear malevolent to the lay observer - displayed by those suffering...

 is also a symptom of strychnine poisoning

Strychnine poisoning

Strychnine poisoning can be fatal to humans and other animals and can occur by inhalation, swallowing or absorption through eyes or mouth. It produces some of the most dramatic and painful symptoms of any known toxic reaction...

.

Opisthotonus is also described as a potential CNS symptom of heat stroke along with bizarre behavior, hallucination

Hallucination

A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...

s, decerebrate rigidity, oculogyric crisis

Oculogyric crisis

Oculogyric crisis is the name of a dystonic reaction to certain drugs or medical conditions. The term "Oculogyric" refers to rotating of eyeballs, but several other responses are associated with the crisis.-Causes:...

and cerebellar dysfunction.