A Second Head Injury
syndrome (SIS) occurs when an athlete who sustains a head injury -
often a concussion or worse injury, such as a cerebral contusion
(bruised brain) - sustains a second head injury before symptoms
associated with the first have cleared.
Typically, the athlete suffers post-concussion signs and symptoms after the first head injury, such as headache, visual, motor or sensory
changes or mental difficulty, especially with the thought and memory process.
Before these symptoms have cleared, which may take minutes, hours, days
or weeks, the athlete returns to competition and receives a second blow
to the head.
Onset Is Sudden
The second blow may be
unremarkable, perhaps only involving a blow to the chest that jerks the
athlete's head and indirectly sends accelerating forces to the brain.
Affected athletes may appear stunned, but do not suffer loss of
consciousness (LOC) and often complete the play. They usually remain
alert on their feet for 15 seconds to 1 minute or so but seem dazed,
like someone suffering from a Grade 1 (mild) concussion (one without loss of consciousness).
Often, affected athletes remain on the playing field or
walk off under their own power. Usually within seconds to minutes of
the second impact, the athlete - conscious but stunned - suddenly
collapses to the ground, semi-conscious with rapidly dilating
(widening) pupils and loss of eye movement, and stops breathing.