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Sympathetic Storms - Fact Sheet

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Sympathetic Storms - Fact Sheet

Sympathetic Storms are a common complication following traumatic brain injury and is associated with a set of distressing and uncomfortable symptoms, including elevated body temperature, increased heart-rate and perspiration.


Briefly, sympathetic storming is excessive, uncontrolled activation ("storming") of the Sympathetic Nervous System (SNS). The SNS is responsible for the control of body arousal, which includes increasing heart-rate, respiration, perspiration, release of adrenaline and other activating hormones, which all characterise the bodies stress response. The Parasympathetic Nervous System (PNS) is responsible for de-arousal or relaxed states: lowering heart-rate, reduced adrenaline, etc. Sympathetic storming occurs when the SNS produces this stress response repeatedly and without further external stressors.


The brain's role in Sympathetic Storming

It is believed that the Hypothalamus, a small area above the Brain Stem, that regulates body temperature, appetite and the release of hormones, over-stimulates the sympathetic nervous system by flooding the bloodstream with chemicals normally associated with stress [1]. During this storm, the parasympathetic nervous system cannot cope and fails to control the arousal levels. The hypothalamus itself may be damaged, or it may be responding to damage in other areas of the brain. It is thought to be a stage in recovery from a severe traumatic brain injury [2].


A major problem with this condition is that there is not yet any one agreed-upon term for the same set of symptoms. For the purposes of this fact sheet we will be using the term 'sympathetic storms.'


Alternative Names: 

  • Acute midbrain syndrome
  • Autonomic Dysfunction Syndrome (ADS)
  • Autonomic storming
  • Brain-stem attacks
  • Central dysregulation
  • Diencephalic autonomic Epilepsy
  • Diencephalic Seizure
  • Dysautonomia
  • Hyperpyrexia associated with muscle contraction
  • Hypothalamic-midbrain dysregulation syndrome
  • Neurostorming
  • Paroxysmal autonomic instability with dystonia (PAID)
  • Sympathoadrenal response
  • Tonic cerebellar fits
  • Tonic decerebrate spasms
  • Traumatic apallic syndrome




The clinical description of sympathetic storming includes a temperature of 38.5C, Hypertension, a pulse of at least 130 beats per minute, a respiratory rate of at least 40 breaths per minute, intermittent agitation, disorientation, diaphoresis (profuse sweating) and dystonia (rigidity or decerebrate posturing for at least 3 days with at least 1 cycle per day) [3]. Decerebrate posturing is "an abnormal body posture indicated by rigid extension of the arms and legs, downward pointing of the toes, and backward arching of the head" [4]. They symptoms may vary among different individuals, along with the duration and intensity of the symptoms [1]. During an episode awareness levels are generally low.


Cause of Sympathetic Storming

There is no single agreed upon explanation for why sympathetic storming occurs. Traumatic brain injury (TBI) is not the only possible cause of sympathetic storming, but is the most common: Hydrocephalus, brain tumours, subarachnoid haemorrhaging and intracerebral haemorrhaging may also result in sympathetic storming. 15-33% of patients with a brain injury develop sympathetic storming [1]. It appears to be more common following diffuse axonal injury (injury to neurons throughout the brain) and injury to the brainstem, which is responsible for controlling fundamental life processes such as breathing, heartbeat and the sleep-wake cycle. One study found 'Dysautonomia' to be particulary associated with severe diffuse axonal injury, preadmission hypoxia, younger age and brain stem injury [5].



Although sympathetic storming is rare without an identified cause, there is no simple process of diagnosis and it is often a diagnosis of exclusion and careful assessment by medical staff. Diagnosis of exclusion means that other, testable, causes need to be considered and ruled our before a diagnosis of sympathetic storming can be made. It is considered important to rule our other possible diagnoses because treatment may differ between sympathetic storming and other, similar-looking conditions. Other problems that need to be considered are meningitis, infection, serotonin syndrome and thyroid storming, which can produce similar symptoms [3].


Treatment of Sympathetic Storming

Treatment for sympathetic storming is symptomatic. As with many other ABI-related conditions, the symptoms are treated independently and there is no specific treatment for the underlying cause (neural damage). Temperature can be addressed by doctors using a range of medications that directly influence body temperature or that influences underlying causes, such as inflammation or decreased Cerebral blood flow or by using external methods to cool the patient down. Beta-blockers or other heart medications may be used to treat arrhythmia or Tachycardia.


Risks and outcomes associated with Sympathetic Storming

Sympathetic storming is associated with increased risks of death, cardiac arrest, cerebral haemorrhage or elevated cerebral temperature, which can itself lead to secondary injury. Severe muscle rigidity can result in muscle rupture or the breakdown of muscle fibres, a process called rhabdomyolysis. Sympathetic storming is also associated with an increased length of stay in rehabilitation services and less favorable rehabilitation outcomes. The symptoms of sympathetic storming can interfere with physical, occupational or speech therapy due to their unpredictability and physical nature, and this delay in rehabilitation can adversely Affect progress.


References and further information





[5]Baguley, I. J., Nicholls, J. L., Felmingham, K. L., Crooks, J., Gurka, J. A., & Wade, L. D. (1999). Dysautonomia after traumatic brain injury: a forgotten syndrome? Journal of Neurology, Neurosurgery & Psychiatry, 67, 39-43.



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