II. Definitions
- Second Impact Syndrome
- Following a first Minor Head Injury, a second significant Head Injury results in severe neurologic injury
III. Epidemiology
- Uncommon to rare, but with devastating consequences
- Appears limited to children and adolescents
- Although adults with multiple Concussions may develop chronic Traumatic encephalopathy (CTE)
- CTE, by contrast, results in a chronic neurodegenerative disorder with Dementia and Parkinsonism features
IV. Pathophysiology
- Results from repeated Concussions over a short period of time
- Initial Traumatic Brain Injury initiates an inflammatory response and altered cerebral autoregulation
- Subsequent head injuries result in cerebral edema without physiologic compensatory mechanisms
- Rapid and diffuse cerebral edema with no effective treatment (does not respond to manitol)
- Reduced cerebral Blood Flow or fluctuating cerebral flow, varying with systemic perfusion
V. Signs
- Rapid neurologic decline following repeated Head Injury
VI. Imaging
-
CT Head
- Cerebral edema
- Small Cerebral Ventricles
- Loss of cerebral sulci
- Loss of subarachnoid space
VII. Management
- See Increased Intracranial Pressure in Closed Head Injury
- See Severe Head Injury Management
- See Status Epilepticus
VIII. Prevention
- Helmets should not offer a false sense of security against Second Impact Syndrome
- Helmets do not prevent Second Impact Syndrome in those with unresolved prior Concussion-related symptoms
- Prevention of Second Impact Syndrome is the primary focus of post-Concussion guidelines in sports
IX. Course
- Mortality approaches 50% with severe neurologic sequelae in the other 50%
X. References
- Dreis (2020) Crit Dec Emerg Med 34(7):3-21
- McCrory (2012) Br J Sports Med 47(5): 250-8 [PubMed]