Paroxysmal sympathetic hyperactivity

Paroxysmal Sympathetic Hyperactivity (PSH) refers to a clinical syndrome characterized by episodic, excessive, and uncontrolled activation of the sympathetic nervous system. It is most commonly observed in individuals recovering from severe brain injury, including traumatic brain injury (TBI), hypoxic brain injury, and after severe infections or inflammation of the brain. PSH can significantly impact the recovery process, leading to prolonged hospital stays and increased need for therapeutic interventions.

Symptoms

The hallmark symptoms of PSH include sudden increases in heart rate, blood pressure, respiration rate, temperature, and sweating. These are often accompanied by posturing, agitation, and sometimes seizures. The episodes can vary in frequency and intensity and are typically triggered by nonspecific stimuli such as noise, movement, or light touch.

Pathophysiology

The exact mechanism underlying PSH is not fully understood, but it is believed to involve dysregulation of the autonomic nervous system (ANS), specifically an imbalance between the sympathetic and parasympathetic nervous systems. This imbalance leads to uncontrolled sympathetic outbursts. Damage to the parts of the brain that regulate the ANS, such as the hypothalamus, is thought to contribute to the development of PSH.

Diagnosis

Diagnosis of PSH is primarily clinical, based on the observation of symptoms and their episodic nature. There is no specific diagnostic test for PSH, but various scales and criteria, such as the PSH-Assessment Measure (PSH-AM), have been proposed to standardize the diagnosis. Differential diagnosis is crucial to exclude other conditions that can present with similar symptoms, such as sepsis, endocrine disorders, and medication side effects.

Treatment

Treatment of PSH focuses on managing symptoms and preventing triggers. Pharmacological interventions include the use of beta-blockers, anticonvulsants, and sedatives to control sympathetic outbursts. Non-pharmacological strategies involve minimizing environmental stimuli and providing a calm, structured environment. In some cases, physical restraints may be necessary to prevent injury during severe episodes.

Prognosis

The prognosis of PSH varies depending on the underlying cause and severity of the brain injury. While some patients experience a decrease in symptoms over time, others may have persistent symptoms that require long-term management. Early recognition and treatment of PSH are crucial to improving outcomes and reducing complications.

Epidemiology

The prevalence of PSH is not well-defined, as it largely depends on the population being studied and the diagnostic criteria used. It is most commonly reported in individuals with severe brain injury, with estimates suggesting that it occurs in 15-33% of this population.

History

The concept of PSH has evolved over time, with various terms used to describe the condition, including "diencephalic seizures," "autonomic storms," and "sympathetic storms." The term "Paroxysmal Sympathetic Hyperactivity" has been adopted to more accurately reflect the episodic nature and underlying autonomic dysfunction of the syndrome.