Opisthotonus

Etiology

Several entities can lead to generalized stiffness and spasms. However, the typical opisthotonus, risus sardonicus, and trismus are found in tetanus.[2] Opisthotonos occurs in a wide variety of disorders. It can manifest at any stage of the disorder and, on some occasions, maybe the only symptom that will point to identify the correct disease.

Infectious

1. Meningitis[3]
2. Encephalitis[4]
3. Tetanus[2][5][6]
4. Rabies[7]
5. Cerebral malaria[8]
6. Neurosyphilis[9]

Poisoning

Strychnine, phencyclidine, and other drugs including phenothiazines, lignocaine, methoxphenidine, adrenergic bronchodilator overdose, and rarely propofol.[10][11]

Developmental and Metabolic

Cerebral palsy, Krabbe disease, hyperbilirubinemia, and kernicterus, Gaucher disease, adenylosuccinate lyase deficiency, infant alcohol withdrawal syndrome, which is more commonly seen in neonates.[12][13][14]

Increased Intracranial Pressure

Intracranial hemorrhage, subarachnoid hemorrhage, hydrocephalus, or a space-occupying lesion

Neurodegenerative Syndromes

This includes neurodegeneration with brain iron accumulation, Wilson disease, cerebral palsy, and Parkinson disease. It has been described in neurometabolic disorders like maple syrup urine disease, glutaric aciduria, Lesch Nehan syndrome, dopa-responsive dystonias.[15]

Psychogenic Dystonia

Hysteria[16][17]

Anoxic Injury

After near-drowning, cardiac arrest, suffocation, or birth asphyxia[1][18]

Miscellaneous

1. Stiff person syndrome
2. Growth hormone deficiency
3. Dandy-Walker malformation[19]

Epidemiology

Opisthotonus is relatively rare. It is a sign that may be present in a wide variety of disorders. It can affect infants (e.g.neonatal tetanus), children, or adults. There is no gender predilection. It is indeed difficult to diagnose in the younger age group. As opisthotonus is not a disorder nor a disease, the incidence and prevalence are not reported.

Pathophysiology

The typical posture occurs due to the simultaneous mass contraction of agonist and antagonist muscle groups along with increased tone. There is an imbalance between facilitatory and inhibitory neurologic pathways innervating the muscle groups involved. It is possible that the secretion of inhibitory neurotransmitters, such as glycine and gamma-aminobutyric acid, plays a role. Consequently, there is uncontrolled activity of alfa and gamma motor neurons. The segmental reflex loop keeps active, perpetuating a sustained state of muscle contraction. In tetanus, the toxin blocks the presynaptic spinal inhibitory neurons.

History and Physical

The principal postural abnormality is the arching of the back and extension of extremities. It occurs due to spastic, sustained dystonic contraction of spinal muscles leading to dorsal extension movement of the spine. There is a rigid backward extension of the head, neck, and trunk. This typical posture occurs due to the simultaneous mass contraction of agonist and antagonist muscle groups along with increased tone.

Symptoms associated with opisthotonos are representative of the causative disease. Fever may be present in tetanus and meningitis, while hydrophobia may be seen in rabies. Tachycardia, pupillary abnormalities, hyperhidrosis, cardiac arrhythmias, fluctuating blood pressure, respiratory abnormalities due to autonomic or muscular pathology can occur. Altered consciousness, vomiting, seizures are not uncommon. Patients may complain of pain or discomfort due to spastic contraction of muscles. Patients may develop fatigue due to multiple factors like poor oral intake, increased muscle activity, fever, and vomiting. Opisthotonus is difficult to be diagnosed in children as they are crying, restless or may develop intermittent contraction of muscle groups.

Evaluation

Opisthotonus frequently poses a diagnostic dilemma. The patients may exhibit non-specific signs and symptoms. The cause of opisthotonus may be due to a myriad of diagnoses, including infectious, metabolic, developmental, degenerative, neurologic, environmental etiologies. While the physical exam may reveal that the patient has generalized stiffness and spasms, the cause is difficult to know without proper imaging studies and metabolic and hematological studies. Due to wide variations in presentation, diagnosis may be delayed if patients are not specifically screened for specific diseases.

It is extremely important to make an early and correct diagnosis of the etiology producing opisthotonus. Delay in the diagnosis can produce devastating outcomes and even death. It is important to attempt the prevention of causative agents. Collaboration in care is an integral component of delivering efficient and effective health care. While the responsibility for screening rests mainly among primary care providers, most do not consistently assess metabolic problems due to various barriers such as lack of time and more pressing health issues.

Tests to confirm the underlying cause, complications and for monitoring the disease activity are performed. They include complete blood counts, metabolic profile, renal and hepatic functions. Brain magnetic resonance imaging and/or computed tomography scan is performed to confirm the presence of lesions causing raised intracranial pressure. A lumbar puncture can be performed after a normal neuroimaging study and is likely to reveal a raised opening pressure. The fluid obtained undergoes relevant tests like glucose, protein, cell count to rule out infections.

Treatment / Management

Treatment includes the management of the underlying pathology. Depending on the underlying cause, appropriate antimicrobial agents and tetanus immune globulins are administered if the disease is suspected or confirmed. Deep brain stimulation for dystonic opisthotonos associated with Parkinson’s disease has produced variable outcomes.[20] Enzyme replacement therapy is used for Gaucher disease.(A1)

Supportive measures include maintenance of fluid and electrolyte balance and ventilatory support, nutritional support, either parenteral or enteral. Avoidance of triggers like noise in tetanus or the sound of water in rabies reduces precipitation of the spasms. A dark, soundproof room is preferred. Oral administration of medication such as benzodiazepines and baclofen can be administered to improve the spasms. Intrathecal baclofen can reduce spasticity/dystonia.[13][18][21] Analgesics are given to reduce the pain. Anticholinergics agents are administered intramuscularly or intravenously.(B2)

It is important to educate patients, caretakers, and colleagues about opisthotonus and its many consequences. Successful interventions with early identification and treatment may help to slow progression and improve the quality of life. Older adults should pay attention to their ability to prevent some of the associated causes, especially tetanus. It is important to maintain adequate tetanus prophylaxis on all older patients (age 60 and beyond) as they forget about preventive immunization.

Differential Diagnosis

• Dystonia
• Decerebrate posturing
• Hysteria
• Catatonia[7]

Prognosis

Opisthotonus can be life-threatening if left untreated. When the primary etiology is controlled or eliminated, patients will no longer present opisthotonus. The prognosis of the patient will depend on the disorder causing it. Intrathecal baclofen to reduce spasticity/dystonia in children and deep brain stimulation for dystonic opisthotonos in Parkinson disease produce good results to improve the quality of life.

Complications

• Neurological manifestations
• Extreme pain and soreness in the muscles 
• Trouble breathing
• Difficulty swallowing
• Delayed development
• Malnutrition
• Ulcers
• Chronic spasticity
• Contractures
• Scoliotic deformities
• Coma
• Death