Despite the decades of very extensive medical research literature on single occurrences of Traumatic Brain Injury (TBI), repeat injuries have been studied seriously in the West for only a few years1.
Previous episodes increase the probability of future TBI. Prevalence of a previous history in studies of unselected acutely injured patients varies from 8-31%1. Statistics for alcoholics2 are higher, whereas figures for children are significantly lower3.
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Recurrent Traumatic Brain Injury is relatively common, its effects cumulative |
The previously injured brain is more susceptible to subsequent brain injury. Russian research, otherwise inaccessible to most readers, is here1 summarised in some detail.
A 1989 paper noted that three-quarters of the series of patients with repeated MTBI had motor abnormalities, and over half had disturbances of intracranial pressure, portending a poor (treated) prognosis for return to work.
An earlier paper documents a magnitude of disability disproportionate to the severity of recurrent injury, and is corroborated by a British study4 of effects on cognitive function.
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The previously traumatised brain is more susceptible to new injury, particularly shortly thereafter |
However, this research on increased vulnerability has been misused to propose a major and permanent deterioration following Mild TBI years after incompletely recovered Severe TBI. There is no empirical support for this plaintiff strategy.
Similarly, a mythology has grown around Second Impact Syndrome5, such that sports concussion guidelines have been developed6 around the belief that a closely-spaced second MTBI will lead to diffuse cerebral swelling, with delayed catastrophic deterioration.
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Particularly because the medical research literature is relatively scant, "thin skull" arguments should be critically evaluated |
Although even mildly diminished blood-supply to the brain may be unusually destructive during the 24 hours following TBI, a recent critical review7 of the existing medical research literature refutes such extrapolation. Undoubtedly there is clinical evidence4, 5 for a greater cumulative effect if second injury occurs sooner rather than later, but the case may have been overstated.
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