Paroxysmal Sympathetic Hyperactivity (PSH) aka Sympathetic Storm

Synonyms:

Diencephalic autonomic epilepsy (Penfield 1929), Paroxysmal autonomic dysreflexia, midbrain dysregulatory syndrome, paroxysmal autonomic instability, storming (Thorley,wertsch, & Klingbeil, 2001),.

What is sympathetic storming:

Was originally described by Penfield in 1929 in a patient who had a tumor pressing on the hypothalamus. Sympathetic storming is a potentially serious sequelae of any type of severe brain injury. PSH is primarily a clinical diagnosis of excluison and it is likely this condition often goes unrecognized. The episodes appear unprovoked and can last for hours and end abruptly. Characterized by agitation or restlessness that is associated with posturing, tachycardia (HR>130), hypertension (SBP>140mmHg), hyperthermia (>38.5 degree celsius), dystonia, tachypnea, and diaphoresis. An element may be present individually or as a constellation of symptoms. Diagnosis of PSH is more definitive  If 5/7 of the aforementioned criteria present.

Etiology:

Any type of severe brain injury, drug overdose, anoxic brain injury, traumatic brain injury and also after discontinuation of administration of sedatives and narcotics in the ICU. Occurs in 15-33% of patients with severe traumatic brain injury with GCS<8. No specific location of injury or pattern of neuronal injury is apparent on imaging, although its more common in patients with diffuse axonal injury (DAI)

Pathophysiology:

Release phenomenon secondary to the loss of cortical and subcortical control. Increase in sympathetic nervous system activity due to loss of balance between the sympathetic and parasympathetic nervous system. Normally the parasympathetic nervous system dampens the effects of increased activity of the sympathetic nervous system and maintains the homeostasis. In sympathetic storming this feedback is lost and individual is in an uncontrolled state of stress.

Timing:  

Can occur within the first 24hrs after injury or up to weeks later.

Treatment:

Prevention of secondary injury is a primary goal in the treatment of brain injury. Effects of prolonged sympathetic overactivity can increase the risk of secondary brain injury. Energy needs can be increased by 100-200% in the presence of storming (Baguley etal., 1999; Strum 2002). Medications that depress the CNS thus suppressing the sympathetic nervous system are most commonly used. Opiate receptor agonists, dopamine agonists, beta blockers alpha blockers ,GABA agonists and sedatives are used . Enteral routes are preferred but IV routes used in ICU with caution to avoid risk of respiratory depression.

Currently the most frequently used regimen is bromocriptine and oxycodone. If the episodes are associated with severe hypertension and tachycardia, or if oxycodone and bromocriptine do not provide control , beta blockers and alpha blockers can be used.

Bromocriptine (a dopamine receptor agonist), acts at the hypothalamic level, lowering the temperature thresold, decreasing diaphoresis, and decreasing the blood pressure. To begin with 2.5-5mg PO q8hr to a max of 30-40mg daily.

Propranolol, a nonselective beta-blocker, blocks sympathetic activity thereby decreasing neuronal activity. It also decreases serum catecholamines decreases cardiac workload and inhibits central fever by acting directly in the CNS.  Dosing starts at 10mg PO q12hr gradually increase dose per clinical response.

Extreme hyperthermia can be treated with chlorpromazine but fever workup is mandatory to rule out meningitis, pneumonia, UTI and DVT.  Dantrolene  can be added to regimen if there is persistent contracture or dystonia

References:

1.Perkes et al: A review of PSH Brain Inj, 2011;25(10):925-32

2. Bauguley IJ Semin Neurol. 2008 Nov ;28(5):716-25

3.Lemke DM Crit Care Nurse. 2007 Feb;27(1):30-7

4. Thorley RR, Wertsch JJ, Klingbeil GE. Acute hypothalamic instability in traumatic brain injury: a case report.Arch Phys Med Rehabil 2001;82:246-249

Thanks to Dr. Kamlesh Jha for this post.