The term opisthotonos comes from the Greek words opisthen, meaning “behind,” and tonos, meaning “tension.” It describes a specific type of abnormal posturing known as a dystonic reaction, where sustained, involuntary muscle contractions cause twisting and repetitive movements or abnormal postures. In opisthotonos, the spasms primarily affect the powerful extensor muscles of the neck and back.

To understand why this happens, it is helpful to think of your body’s muscles as being arranged in two opposing groups:

• The flexor muscles at the front of the body, which allow you to bend forward.
• The extensor muscles along the back, which allow you to straighten up and arch backward.

Normally, the brain and spinal cord maintain a perfect, balanced control over these opposing muscle groups, allowing for smooth, coordinated movement. Opisthotonos occurs when there is a severe disruption to the central nervous system, particularly the parts of the brain (like the brainstem and cerebellum) that regulate muscle tone and posture. This disruption removes the brain’s normal inhibitory signals, effectively “cutting the brakes” on the muscles. The stronger extensor muscles of the back are then unleashed, contracting powerfully and without opposition, forcing the body into the characteristic, rigid arch. The spasm can be so intense that only the person’s head and heels are touching the surface they are lying on.

I’ve often seen opisthotonos in emergency settings, especially in children with underlying neurological or infectious issues. When I see that characteristic arched posture, it immediately signals a potential central nervous system emergency.

Opisthotonos is always caused by a severe underlying medical condition that is disrupting the central nervous system’s ability to regulate motor control. The conditions that can cause this are serious and often life-threatening.

Severe Infections

Infections affecting the central nervous system are a leading cause of opisthotonos, particularly in infants and young children.

• Tetanus: This is the most classic cause. Tetanus is a bacterial infection caused by Clostridium tetani, a bacterium found in soil and animal feces. The bacterium produces a powerful neurotoxin called tetanospasmin. This toxin travels to the central nervous system and blocks the release of the neurotransmitters that normally allow muscles to relax after contracting. This leads to generalized, excruciatingly painful muscle spasms throughout the body, including the severe arching of opisthotonos. Neonatal tetanus, caused by contamination of the umbilical stump in newborns of unimmunized mothers, is a major cause of infant mortality in many parts of the world and a primary cause of opisthotonos in this age group.
• Meningitis: This is an inflammation of the meninges, the protective membranes surrounding the brain and spinal cord. Severe bacterial meningitis, in particular, can cause significant irritation and inflammation of the nervous system, leading to opisthotonos, especially in infants.
• Other Severe Infections: Any severe systemic infection (sepsis) can potentially lead to neurological complications that include abnormal posturing.

Brain Injury and Damage

• Traumatic Brain Injury: Severe head trauma that causes bleeding, swelling, or direct damage to the brainstem can disrupt motor control pathways.
• Hypoxic Brain Injury: A lack of oxygen to the brain, such as can occur during a difficult birth (birth asphyxia), near-drowning, or cardiac arrest, can cause widespread brain damage that leads to this type of posturing.
• Kernicterus: This is a form of brain damage in newborns caused by extremely high levels of bilirubin, a substance produced during the normal breakdown of red blood cells. Severe, untreated jaundice can allow bilirubin to cross into the brain and cause permanent damage to areas that control movement, leading to opisthotonos (World Health Organization [WHO], 2023).

Toxins and Drug Reactions

• Strychnine Poisoning: Strychnine is a potent poison that causes violent, convulsive muscle spasms very similar to those seen in tetanus.
• Neuroleptic Malignant Syndrome: A rare but life-threatening reaction to certain antipsychotic medications can cause muscle rigidity and abnormal posturing.

In my experience, tetanus remains the classic textbook cause of opisthotonos, but I’ve also seen it arise in newborns with kernicterus or in cases of untreated meningitis. Regardless of the cause, it’s always a red flag for significant brain or brainstem involvement.

Opisthotonos develops as a secondary complication of another condition affecting the central nervous system. Therefore, the risk factors are those that predispose an individual to these specific medical emergencies.

• For Tetanus: The primary risk factor is being unvaccinated or inadequately vaccinated against tetanus. The bacteria enter the body through a contaminated wound, which can include puncture wounds, burns, crush injuries, or, in the case of neonatal tetanus, an unhygienic cut of the umbilical cord.
• For Bacterial Meningitis: Risk factors include being unvaccinated against the preventable causes of meningitis, such as Haemophilus influenzae type b (Hib) and certain strains of Streptococcus pneumoniae.
• For Neonatal Conditions: Risk factors include a traumatic birth, severe prematurity which can lead to bleeding in the brain, and severe, unmonitored jaundice in the first days of life.
• For Traumatic Brain Injury: Risk factors include involvement in severe accidents or falls without proper safety precautions.

I’ve encountered opisthotonos most often in under-vaccinated infants or those with a complicated birth history. It’s heartbreaking to see, especially knowing that many of the causes like tetanus or kernicterus are preventable with early care.

The hallmark feature of opisthotonos is a severe arching of the back, accompanied by other symptoms that reflect the underlying cause. The associated symptoms depend on the underlying cause.

When seen in an infant or newborn, it is often accompanied by:

• Extreme irritability and a high-pitched, inconsolable cry.
• Difficulty feeding.
• Fever.
• A tense or bulging fontanelle (the “soft spot” on the baby’s head).
• Seizures.

When seen in older children or adults, it is often accompanied by:

• High fever.
• Severe headache.
• A stiff neck.
• Sensitivity to light (photophobia).
• Altered mental status, such as confusion, delirium, or progressing to a coma.
• Seizures.
• Difficulty breathing.

In cases of tetanus, the opisthotonos is often accompanied by other specific signs, such as trismus (lockjaw) and a characteristic facial grimace that looks like a fixed smile, known as risus sardonicus.

One of the most alarming things for families is watching their loved one arch uncontrollably with extreme stiffness, it’s distressing and often painful. In newborns, I always look for feeding issues or eye movement changes in addition to the posturing.

The appearance of opisthotonos is a clinical sign that signals a dire medical emergency. The diagnostic process is an urgent race to find the underlying cause. All diagnostic tests are performed in a hospital emergency department or intensive care unit (ICU).

The immediate diagnostic steps include:

1. Rapid Clinical Assessment: A doctor will perform a quick physical and neurological examination to assess the patient’s level of consciousness, breathing, and vital signs.
2. History Taking: The doctor will urgently try to get a history from family members about any recent injuries, infections, fevers, headaches, or the patient’s vaccination status. In a newborn, the birth history and the mother’s tetanus immunization status are critically important.
3. Lumbar Puncture (Spinal Tap): If meningitis is suspected, this is an essential test. A needle is inserted into the lower back to collect a sample of cerebrospinal fluid (CSF). The fluid is immediately analyzed for signs of infection, such as a high white blood cell count, and sent for culture to identify the specific bacterium.
4. Neuroimaging: A Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI) of the head will be performed to look for evidence of bleeding, swelling, or other injuries to the brain.
5. Blood Tests: Blood will be drawn for a complete blood count and cultures to look for signs of a systemic infection or sepsis.

When faced with opisthotonos, I start with a wide differential, imaging, infection screening, and labs. The urgency depends on context, but rapid testing is crucial because the underlying cause is often life-threatening.

There is no treatment for the opisthotonic posture itself. All treatment is directed urgently at the life-threatening underlying cause. All patients exhibiting opisthotonos require immediate hospitalization and intensive care.

The treatment plan is entirely dependent on the diagnosed cause:

• For Tetanus: Treatment is complex and involves several components:
  • Tetanus Immune Globulin (TIG) to neutralize the circulating tetanus toxin.
  • Antibiotics (like metronidazole) kill bacteria and stop further toxin production.
  • Muscle Relaxants and Sedatives (such as benzodiazepines) to try to control the severe muscle spasms.
  • Often requires mechanical ventilation (a breathing machine) and a temporary tracheostomy to protect the airway during the prolonged spasms.
• For Bacterial Meningitis: Treatment involves high doses of intravenous antibiotics started immediately.
• For Brain Injury: Treatment may require neurosurgical intervention to relieve pressure on the brain, such as by draining a hematoma.
• For Kernicterus: In a newborn, treatment involves intensive phototherapy to break down the bilirubin and, in severe cases, an exchange transfusion, where the baby’s blood is replaced with donor blood.

The first priority is stabilizing the patient, especially if breathing or feeding is compromised. Then we work quickly to treat the root cause. In cases like tetanus, it’s a race against time. But early, aggressive care can turn things around.

Supportive Care

Regardless of the cause, intensive supportive care is vital for survival. This includes maintaining an open airway, providing oxygen or mechanical ventilation, giving IV fluids to support blood pressure, and providing nutrition.

Opisthotonos is not a disease but one of the most serious and dramatic warning signs in all medicine. The rigid, arched-back posture is a clear indication of a severe insult to the central nervous system, most commonly caused by life-threatening conditions like tetanus and bacterial meningitis. While the sight of it is frightening, the most important takeaway is that opisthotonos signals a true medical emergency. Anyone exhibiting this posture requires immediate, urgent transportation to the nearest hospital emergency department for life-saving care. Furthermore, its strong link to preventable diseases underscores the critical public health importance of routine vaccinations for tetanus and the bacteria that cause meningitis, which are the most powerful tools we have to prevent this terrifying neurological crisis from ever occurring.

National Institute of Neurological Disorders and Stroke (NINDS). (2023). Tetanus. Retrieved from https://www.ninds.nih.gov/health-information/disorders/tetanus

World Health Organization (WHO). (2023). Meningitis. Retrieved from https://www.who.int/news-room/fact-sheets/detail/meningitis

Centers for Disease Control and Prevention (CDC). (2022). Tetanus for clinicians. Retrieved from https://www.cdc.gov/tetanus/clinicians.html