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. Opisthotonus in the neonate may be a symptom of meningitis, tetanus, severe kernicterus, or the rare maple syrup urine disease. This marked extensor tone can cause infants to "rear backwards" and stiffen out as the mother or nurse attempts to hold or feed them. Individuals with opisthotonus are quite challenging to position, especially in wheelchairs and car seats.Opisthotonus can be triggered by any attempt at movement, such as smiling, feeding, speech, or by involuntary movement, such as seizures. A similar tonic posturing may be seen in Sandifer syndrome. Poisoning
Opisthotonus can sometimes be seen in lithium intoxication.
Azithromycin is an antibiotic medication used for the treatment of a number of bacterial infections. This includes middle ear infections, strep throat, pneumonia, travelers diarrhea, and certain other intestinal infections. Along with other medications, it may also be used for malaria. It can be taken by mouth or intravenously with doses once per day.Common side effects include nausea, vomiting, diarrhea and upset stomach. An allergic reaction, such as anaphylaxis, QT prolongation, or a type of diarrhea caused by Clostridium difficile is possible. No harm has been found with its use during pregnancy. Its safety during breastfeeding is not confirmed, but it is likely safe. Azithromycin is an azalide, a type of macrolide antibiotic. It works by decreasing the production of protein, thereby stopping bacterial growth.Azithromycin was discovered in 1980 by the Croatian pharmaceutical company Pliva and approved for medical use under the brand name Sumamed in 1988. It is on the World Health Organizations List of Essential Medicines. The World Health Organization classifies it as critically important for human medicine. It is available as a generic medication and is sold under many trade names worldwide. In 2019, it was the 48th most commonly prescribed medication in the United States, with more than 15 million prescriptions. Medical uses
Azithromycin is used to treat diverse infections, including:

Prevention and treatment of acute bacterial exacerbations of chronic obstructive pulmonary disease due to H. influenzae, M. catarrhalis, or S. pneumoniae. The benefits of long-term prophylaxis must be weighed on a patient-by-patient basis against the risk of cardiovascular and other adverse effects.