Second-impact syndrome is a rare traumatic brain injury occurs in athletes receiving a second head injury while still symptomatic from a prior head injury.
Second-impact syndrome is common in young athletes.
The typical second-impact syndrome scenario occurs usually when an athlete sustains an initial head injury with post-concussion symptoms such as a headache, dizziness and vertigo, then he suffers a second head injury before the symptoms associated with the first impact have cleared.
The athlete during the second head injury precipitously lapses into a coma with signs of brain herniation.
The pathophysiology of second-impact syndrome is poorly understood. However, it is presumed to be secondary to loss of autoregulation of the cerebrovasculature which leads to hyperemic brain swelling which in turn increases intracranial pressure, brain herniation and death.
Following an initial insult, there is characteristic ionic fluxes, acute metabolic changes, and cerebral blood flow alterations that occur immediately after cerebral concussions. Extracellular potassium concentration can increase massively in the brain, followed by hypermetabolism which can last up to ten days. This makes the brain more vulnerable and susceptible to death after a second sub-lethal insult of even less intensity.
CT and MRI can demonstrate the cerebral hyperemic swelling, brain herniation and post-herniation ischemia.
Intracranial (thin subdural hemorrhage) may be seen yet with severe midline shift and mass effect that appear disproportionate to the size of the hematoma
Treatment and prognosis
The treatment usually indicates decompressive craniectomy and evacuation of the SDH.
The use of mannitol in the treatment of intracranial pressure (ICP).
Any athlete who shows signs of concussion should not resume playing with appropriate outpatient follow up by a neurosurgeon.
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