Opisthotonos

Opisthotonos is a form of severe hyperextension posturing in which the head, neck, and spine arch backward. It is not a disease itself but a clinical sign indicating significant disturbance of the nervous system or muscular control. The posture arises from intense and sustained contraction of extensor muscles along the back and neck, and may be accompanied by rigidity of other muscle groups.

Common causes include tetanus, where neurotoxin-induced disinhibition leads to generalized muscle spasm; meningitis or other severe central nervous system infections causing meningeal irritation and reflexive extension; intracranial injury or hemorrhage; and metabolic or toxic states such as strychnine poisoning. Neonatal opisthotonos is often described in severe neonatal tetanus or certain inborn errors of metabolism. Less frequently, other severe CNS insults or diffuse encephalopathy can produce similar posturing.

Clinical features vary from intermittent spasm to sustained arching. Opisthotonos may occur with reduced consciousness, autonomic instability, fever, or signs specific to the underlying disease. It is a sign rather than a diagnosis and requires urgent evaluation to identify and treat the underlying cause.

Diagnosis relies on clinical observation supplemented by history and investigations directed at potential etiologies, including infectious workup, neuroimaging, and metabolic testing as appropriate.

Management targets the underlying condition and supportive care. In tetanus, treatment includes wound management, tetanus immunoglobulin, antibiotics, muscle relaxation, sedation, and airway support as needed. Prognosis depends on the cause, the rapidity of diagnosis, and the adequacy of treatment.