Opisthotonos is a clinical sign of severe meningeal irritation, characterized by a severely arched back, hyperextended neck, heels bent back, and flexed arms and hands. It occurs spontaneously and may be aggravated by movement. The posture likely represents a protective reflex that immobilizes the spine, reducing the pain associated with meningeal irritation.

Opisthotonos is most commonly caused by meningitis, but it may also result from subarachnoid hemorrhage, Arnold-Chiari syndrome, tetanus, and, occasionally, as a reaction to antipsychotic medications. The sign is more common and pronounced in children due to nervous system immaturity.

Pathophysiology

Opisthotonos results from excessive, sustained contraction of axial and limb muscles due to hyperexcitability of motor neurons. The mechanisms vary depending on the underlying cause:

1. Meningeal irritation (e.g., meningitis, subarachnoid hemorrhage)

   • Inflammation of the meninges leads to irritation of the spinal cord and brainstem motor neurons.

   • This triggers reflex hypertonia of the extensor muscles of the back and neck, resulting in the characteristic arched posture.

   • Cranial nerve involvement may accompany this, producing diplopia, photophobia, or other neurologic deficits.

2. Tetanus (Clostridium tetani infection)

   • Tetanospasmin toxin blocks inhibitory neurotransmitters (GABA and glycine) in the spinal cord.

   • Loss of inhibitory input causes uncontrolled excitatory discharge in motor neurons, producing muscle rigidity, trismus, and opisthotonos.

   • The spasms may involve the respiratory muscles, leading to life-threatening respiratory compromise.

3. Arnold-Chiari malformation

   • Structural displacement of the cerebellar tonsils through the foramen magnum can compress the brainstem and cervical spinal cord, causing abnormal motor reflexes and posturing.

   • Associated hydrocephalus increases intracranial pressure (ICP), further aggravating axial muscle hypertonia.

4. Drug-induced dystonia (e.g., phenothiazines)

   • Acute dystonic reactions result from dopamine receptor blockade in the basal ganglia.

   • Imbalance between excitatory and inhibitory motor pathways produces sustained involuntary muscle contractions, including the opisthotonic posture.

Emergency interventions

• Immediately evaluate vital signs if the patient is stuporous or comatose.

• Implement resuscitative measures if needed.

• Place the patient safely in bed or crib with side rails padded.

• Monitor airway and respiratory function, especially in tetanus or severe meningeal irritation.

History and Physical Examination

History

• For infants/children, consult parents or guardians.

• Ask about recent infection, hypertension, cerebral aneurysm, or arteriovenous malformations.

• Explore associated symptoms: headache, chills, vomiting, irritability.

Physical Examination

• Assess neurologic status: level of consciousness, sensorimotor function, cranial nerves.

• Check for meningeal irritation signs: Brudzinski’s sign, Kernig’s sign, nuchal rigidity.

• Observe posture and severity of muscle spasms.

Medical causes

Special considerations

• Monitor neurologic status and vital signs frequently.

• Ensure patient comfort with side-lying position and supportive pillows.

• If meningitis is suspected, initiate respiratory isolation.

• Prepare for diagnostic tests: lumbar puncture, CT scan, or MRI as indicated.

Patient counseling

• Explain opisthotonos and its treatment to the patient and family.

• Provide emotional support and referrals to support groups or community resources.

• Educate on preventive measures for infectious causes (e.g., tetanus vaccination).

References

1. Sommers MS, Brunner LS. Pocket diseases. Philadelphia, PA: F.A. Davis; 2012.

2. StatPearls. Opisthotonus. Treasure Island, FL: StatPearls Publishing; 2025. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559170/

3. MedlinePlus. Opisthotonos. Bethesda, MD: U.S. National Library of Medicine; 2023. Available from: https://medlineplus.gov/ency/article/003195.htm

4. Healthline. Opisthotonos: Causes, Treatments, and Prevention. New York, NY: Healthline Media; 2024. Available from: https://www.healthline.com/health/opisthotonos

5. Cleveland Clinic. Opisthotonos: What It Is, Causes, Symptoms & Treatment. Cleveland, OH: Cleveland Clinic; 2024. Available from: https://my.clevelandclinic.org/health/symptoms/opisthotonos

6. Tubbs RS, Loukas M, Shoja MM. Arnold-Chiari malformation. Neurosurg Clin N Am. 2011;22(3):381–400.

7. Milhorat TH, et al. Chiari type I malformation redefined: clinical and radiographic findings in 364 symptomatic patients. Neurosurgery. 1999;44(5):1005–1017.

8. Koyama J, et al. Chiari malformation presenting with subarachnoid hemorrhage: a case report. J Neurol Sci. 2023;448:120–127.

9. Farrar JJ. Tetanus. In: Bennett JE, Dolin R, Blaser MJ, editors. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 9th ed. Philadelphia: Elsevier; 2020. p. 2877–2884.

10. Jankovic J. Pathophysiology and treatment of dystonia. Lancet Neurol. 2006;5(10):864–872.