opisthotonus

Opisthotonus is an abnormal posturing characterized by severe hyperextension of the head, neck, and spine with the trunk arched forward. It is a dramatic sign of extensive muscle hyperactivity and can reflect a severe disturbance of central nervous system control of movement.

The condition is most classically associated with tetanus, where the toxin produced by Clostridium tetani disrupts inhibitory neurotransmission and provokes generalized muscle spasms and sustained contractions. Neonatal tetanus can also present with opisthotonus. Other causes include severe central nervous system infections or inflammation such as meningitis or encephalitis, strychnine poisoning, and certain metabolic or anoxic injuries. Rabies and some congenital CNS disorders may rarely present with opisthotonus.

Pathophysiology involves impaired inhibition of motor circuits in the spinal cord and brainstem, leading to overactivity of extensor muscles and a backward arching of the body. In tetanus, tetanospasmin inhibits the release of inhibitory neurotransmitters glycine and GABA from interneurons, tipping the balance toward excitation.

Diagnosis is clinical, based on history and physical examination, with investigation directed at identifying an underlying cause. Evaluation targets infection or toxin exposure, wound history, and general medical assessment. Laboratory tests may include complete blood count, electrolytes, inflammatory markers, and, when appropriate, cerebrospinal fluid analysis or imaging to assess for meningitis, encephalitis, or other CNS pathology.

Management focuses on treating the underlying cause and ensuring airway, breathing, and circulation. In tetanus, care includes wound debridement, appropriate antibiotics such as metronidazole, administration of tetanus immunoglobulin, and control of spasms with benzodiazepines or other muscle relaxants, often in an intensive care setting. Supportive and adjunctive therapies are tailored to the specific etiology.