CHAPTER 2 OVERVIEW OF TB!
O- IAPTER 2 OVERVIEW OF TB
abnormalities prevalent in frontal and temporal regions of
mm head
injury patients (Wilberger, 1993).2.4.2 Second Impact Syndrome
(515)
Second impact syndrome results when an individual sustains a second trauma to the brain before symptoms associated with an initial brain injwy (most often mild in nature) have fully resolved (Cantu, 1992; Wilberger, 1993; Cantu & Voy, 1995; Kelly & Rosenberg,
1997). The second impact, in which consciousness can be retained (Wilberger, 1993), may lead to rapid cerebral swelling as a result of cerebrovascular congestion or a loss of
cerebrovascular autoregulation. Consequently, there is a marked increase in intracranial pressure (Kelly & Rosenberg, 1997) which invariably leads to brain herniation and coma (McCrory, 1997).
The concept of this syndrome, first described by Schneider in 1973 and again, a little over 10 years later by Saunders and Harbaugh (Cantu, 1992), rests solely on the
interpretation of anecdotal reports, with no case-control studies having been conducted to identify SIS risk factors (McCrory, 1997). However, examination of numerous case studies by Cantu and V oy (1995) has gone some way to reveal an established trend, giving some merit to SIS as an accepted entity. In the majority of these cases athletes have been shown to firstly experience residual post-concussive symptoms, including visual, sensory, or motor changes and difficulty with thought and memory. Secondly, after receiving a second blow the athlete would typically lapse into a coma with, as a consequence of brain herniation, massively increased intracranial pressure, and edema resulting in brain stem collapse (Cantu
& Voy, 1995). Despite appropriate treatment, this condition carries a high mortality rate (McCrory, 1997).
CHAPTER 2 OVERVIEW OF TBI
2.4.3 Cumulative Effects of MTBI
While the current rate of brain injury occurring in sports can be estimated, the
proportion of these brain injuries that are repeat injuries is not very well known (Wi1berger, 1993) although the risk of repetition does appear to be high in many sports (Kelly & Rosenberg, 1997). In an investigation involving injured college football players 24% reported having a recurrent injury to the head or neck in the same season as the original injury (Albright, Mcauley, Martin, Crowley, & Foster, 1985). Gerberich et al. (1983) reported that of 3,063 high-school American football players 14% reported having
experienced at least one previous episode of unconsciousness. A comparatively higher rate of repeat concussion was found in a study conducted by Bird et al. (1998Y with 30% of those sustaining rugby-related concUssion reporting a previous injury to the head, severe enough to warrant medical attention. It is generally accepted that once the first injury is sustained, the chance of the individual being subject to future brain injuries is four-to-six times greater (Kelly & Rosenberg, 1997; Marion, 1999).
In addition to placing an individual at greater risk of further injury, the likelihoqd of serious sequelae increases when MTBI is repeated (Kelly & Rosenberg, 1997). Gronwall and Wrightson (1975) identified significant and sustained neuropsychological abnormalities in individuals after a second MTBI in contrast to controls suffering only one MTBI. These authors later state that long term effects become more evident with repeat concussions, with memory and concentration deficits, personality changes, and diminished abilities becoming more evident to the individual, family, and friends (W rightson & Gronwall, 1983). Carlsson, Svardsodd and Welm (1987) reported that cumulative effects of repeated brain trauma are likely to play a significant role in the development and persistence of post concussive syndrome, having identified a strong correlation between the extent of post concussive symptoms and previous brain injury.
GIAPTER 2 OVERVIEW OF TB!
While repeated concussions can cause long-tenn functional impainnent for some individuals, knowledge of these effects for athletes are less well known (Nelson & Schoene, 1995a). A pilot study conducted by McCrory, Maddocks, and Dicker (1995) examining the cumulative effects of MTBI revealed that athletes do not n£IESSariJy suffer significant
impainnent as a consequence of multiple concussions. This study was limited, however, with respect to the number of players sustaining multiple injuries
(
n = � and the relatively short period of time over which they were monitored (5 years). More recently,Shuttleworth-Edwards, Border, and Radloff (in press) carried out an investigation with South African national and school level rugby players, revealing detrimental effects were more apparent for the older (national) players attributed to longer more intensive exposure to play and the additive effects of multiple brain trauma. Definitive conclusions regarding the effect of multiple concussions on outcome appear difficult to make on the basis of such investigations.
2.5 MEASURING INJURY SEVERITY
2.5.1 Measuring Severity of TB!
The severity of brain injury is typically gauged by evidence of loss of consciousness, duration of post-traumatic amnesia (PTA), and/or ratings on the Glasgow Coma Scale (GCS). The period of time an individual takes to regain consciousness is often used as an indicator of severity (Lucas, 1998), although the reliability of this infonnation is somewhat questionable unless a witness to the injury can give corroborating evidence of duration. In addition, there is no indication in the research literature that longer periods of
a-IAPTER 2 OVERVIEW OF TBI
The importance of measuring PTA cannot be understated as it provides a useful index
of severity and is one of the best predictors of recovezy (Wilson et al., 1999). A general
guide to severity and recovezy of function is presented in Table 1 . This classification
system suggests that a mild TB! is indicated by PTA lasting between 5 -60 minutes, with
recovezy possible in 3 months or less with the possibility of only a few residual deficits
thereafter (Kibby & Long, 1997).
Table 1.