Immediate Outcomes: Case Fatality Rates
One immediate outcome after brain injury is death.
Whereas the fatality rates (see Figure 1–2) provide an idea of the level or magnitude of severity in the general popu-lation, the case fatality rates after hospital admission mea-sure the immediate gross consequences of the trauma.
Case fatality data are available from eight United States population-based incidence studies and one esti-mate based on the NHDS for 1994–1995 (Figure 1–12).
Case fatality rates range from approximately 3 per 100 hospitalized cases in Rhode Island (Fife et al. 1986) to ap-proximately 8 per 100 hospitalized cases in the Bronx, New York (Cooper et al. 1983). However, these case fatal-F I G U R E 1 – 1 0 . Percentage of brain injury hospital discharges by diagnoses (any listed diagnoses): United States 1998. All listed diagnoses.
Source. Reprinted from Popovic JR, Kozak LJ: “National Hospital Discharge Survey: Annual Summary, 1998.” Vital and Health Statistics 13:1–194, 2000. Used with permission.
ity rates were not severity adjusted, which precludes ade-quate comparison across studies. Hospitals that admit a high proportion of patients with severe or moderate brain injury would be expected to have higher case fatality rates compared with those admitting a large proportion of pa-tients with MTBI, who sustain fewer deaths. Figure 1–12 also shows a case fatality rate from a report from Taiwan (Lee et al. 1990). This high case fatality rate illustrates further the difficulties in comparing rates across study centers where severity mixes in patient populations have not been standardized. For this reason, it is not appropri-ate to suggest that differences in outcome after hospital-ization relate to differences in quality of care.
Measurement of Long-Term Consequences
One widely used scale in assessing outcome of acute brain injury is the Glasgow Outcome Scale (GOS; Jennett and Teasdale 1981). The GOS is a crude indicator of medical (neurological) complications or residual effects at time of discharge from the primary treatment center. The major classifications of the GOS are 1) death, 2) persistent veg-etative state (i.e., no cerebral cortical function as judged
behaviorally), 3) severe disability (conscious but depen-dent on 24-hour care), 4) moderate disability (disabled but capable of independent care), and 5) good recovery (mild impairment with persistent sequelae but able to participate in a normal social life).
The major difficulty with the GOS is the inability to properly classify patients because of the lack of specific objec-tive criteria that separate severe from moderate or moderate from good recovery. Good recovery does not mean, nor was it intended to mean, complete recovery. Hence, it is impor-tant to assess GOS findings with some degree of caution.
Consequences of Mild TBI
Understanding the outcomes of MTBI is complicated by the many differences among research investigations. Study differences include how the sample was identified and drawn, how MTBI was defined, the length of follow-up, and what outcome measures were used. As shown in Figures 1–13 and 1–14, in research reports from 1984 to early 1991, definitions for MTBI in children, adolescents, and adults encompassed broad ranges of the length of loss of conscious-ness (from none to 60 minutes) and the GCS scores (from 15 F I G U R E 1 – 1 1 . Percentage of fractures by brain lesion type.
only to a range of 8–15). Injury severity varied considerably across these studies of “mild” brain injury. The variation is regrettable, given that the severity of the injury appears to be a primary factor in long-term recovery. It is hoped that the CDC National Center for Injury Prevention and Control Expert Working Group on Mild Traumatic Brain Injury will arrive at a consensus definition of MTBI for surveillance and clinical purposes.
Evidence on the frequency and nature of negative cognitive outcomes after MTBI is far from clear. As shown in Figure 1–15, most reports have assessed motor skills or a combination of learning and motor skills. A re-view of 13 outcome studies (Bassett and Slater 1990;
Bawden et al. 1985; Costeff et al. 1988; Dennis and Barnes 1990; Ewing-Cobbs et al. 1985, 1987; Gulbrand-son 1984; Hannay and Levin 1988; Jordan and Murdoch 1990; Jordan et al. 1988; Levin et al. 1987, 1988; Tomp-kins et al. 1990) indicated that children with MTBI
scored worse than their noninjured counterparts on mea-sures of general intelligence, language, and a combination of learning and motor skills. In contrast, most studies in-dicated that adults with MTBI did not differ from nonin-jured individuals on measures of motor and spatial skills.
Also, results were not consistent for mental functioning among skills as diverse as language, learning and memory, motor skills, and spatial skills. Furthermore, these studies are plagued by a common threat to validity—all assess-ments were made postinjury, so the groups may have dif-fered on the variables of interest before the brain injury occurred. In addition, preinjury information on inherent host factors (e.g., behavior) compromise the ability to as-certain postinjury changes in function.
The current scientific literature contains studies with small numbers of subjects, retrospective study designs, and inadequate control or comparison groups. Small numbers of study subjects and many different outcome F I G U R E 1 – 1 2 . Case fatality rate for brain injuries: selected studies.
A=Bronx, NY, 1980–1981 (Cooper et al. 1983); B=Virginia 1978 (Jagger et al. 1984); C=Utah 1990–1992 (Thurman et al. 1996);
D=San Diego County, CA, 1981 (Kraus et al. 1986); E=Maryland 1986 (MacKenzie et al. 1989); F=Colorado, Missouri, Oklahoma, Utah 1990–1992 (Centers for Disease Control and Prevention 1997); G=United States estimate 1980–1995 (Thurman and Guerrero 1999); H=San Diego County, CA, 1978 (Klauber et al. 1981); I=Rhode Island 1979–1980 (Fife et al. 1986); J=Taiwan 1977–1987 (Lee et al. 1990) (case series).
measures compromise the researcher’s ability to detect differences in risks or outcomes. Almost no studies were designed to adequately identify differences between peo-ple who had sustained MTBI and those who had not.
Given that there is not a sufficient body of literature from which to draw conclusions with confidence about the negative consequences of MTBI, the task of future re-search is to use sufficiently sophisticated rere-search meth-ods to detect these consequences if they exist. It is hoped that the work of the International Task Force on Mild Traumatic Brain Injury (source: H. von Holst, Stock-holm, Sweden) will synthesize the world’s literature to give the best insights yet on these issues.
Predicting Initial Consequences of Brain Injury
It would be useful to know which factors predict unfavor-able consequences after acute brain injury. Not all of the potential predictive factors from the moment of injury through emergency transport, emergency department treatment, and definitive care have been adequately mea-sured or evaluated. A few factors, however, are available to help predict severe outcome after trauma. For this discus-sion, we divide outcomes into three general categories:
1) death; 2) an unfavorable GOS score of moderate dis-ability, severe disdis-ability, or persistent vegetative state; and
3) presence of any neurological deficit or limitation on discharge. As mentioned in the section Consequences of Mild TBI, it is difficult to evaluate all variables in cross-F I G U R E 1 – 1 3 . Mild brain injury: loss of consciousness criterion.
F I G U R E 1 – 1 4 . Mild brain injury: Glasgow Coma Scale (GCS) criterion (Jennett and Teasdale 1981).
institutional comparisons because they have not been assessed in a similar way. Hence, for this discussion, we use the information from the 1981 San Diego County brain injury cohort study (Kraus et al. 1984). Variables which were confirmed in the hospital record include age, sex, GCS score, Maximum Abbreviated Injury Scale (MAIS; Association for the Advancement of Automotive Medicine 1990) for non-head injury, fracture status, and type of brain lesion (i.e., concussion, hemorrhage, contu-sion, laceration, or other intracranial injury).
Figures 1–16 and 1–17 provide adjusted odds ratios (the ratio of unfavorable outcome [e.g., death] to a favor-able outcome when injury severity, age, sex, etc., are controlled) for an unfavorable outcome (see preceding paragraph). The adjusted odds ratios show that hemor-rhage and fracture are important predictive factors for all unfavorable outcome measures. Increasing age (in 10-year increments), low GCS score, and high MAIS score are other factors that independently predict an unfavorable outcome. Although these data are not likely to apply to all brain injury populations, they illustrate the potential for
using patient descriptive and diagnostic measures to assist in identifying factors that need increased clinical attention in the effort to improve current outcomes for brain injury.
Published guidelines for treatment of severe TBI (Bullock et al. 1996) have concluded, based on the pub-lished evidence, that older age, hypotension, CT scan ir-regularities, abnormal pupillary responses, and GCS score of 3–5 are reasonably predictive of a poor outcome after TBI. However, the specific cutoff points in age and level of hypotension are not known. Information on other factors is incomplete, and data for predictive factors for moderate and mild forms of TBI are not available.
Estimating Brain Injury Disability in the Population
Estimation of the Number of New Disabilities Several assumptions are necessary to devise an estimate of the number of new disabilities (i.e., neurological deficits or limitations) each year after brain injury (the incidence F I G U R E 1 – 1 5 . Consequences of mild traumatic brain injury: summary of findings from 13 studies.
Source. Bassett and Slater 1990; Bawden et al. 1985; Costeff et al. 1988; Dennis and Barnes 1990; Ewing-Cobbs et al. 1985, 1987;
Gulbrandson 1984; Hannay and Levin 1988; Jordan and Murdoch 1990; Jordan et al. 1988; Levin et al. 1987, 1988; Tompkins et al. 1990.
rate was based on a pooled estimate from all incidence studies reported earlier in this chapter):
1. Brain injury incidence=120/100,000
2. United States population size, 2000=280 million 3. Total new cases in 2000=(120 × 2,800)=336,000 4. Prehospital brain injury deaths=(0.0001 ×
280,000,000)=28,000
5. Total cases admitted to hospital alive=308,000 6. United States hospital admissions by severity:
Mild: 50% × 308,000=154,000 Moderate: 30% × 308,000=92,400 Severe: 20% × 308,000=61,600
7. Discharge rate (alive) (Kraus et al. 1984; Levin et al.
1987; MacKenzie et al. 1989) by severity of brain injury:
Mild=100%
Moderate=93%
Severe=42%
If 50% of all new hospital-admitted patients have mild injuries, 154,000 (100% × 154,000) are discharged alive.
If 30% of all new hospital-admitted cases have moderate injuries, 92,400 (30% × 308,000) are admitted to a hospi-tal, and 85,932 (93% × 92,400) are discharged alive. If 20% of all brain injuries are severe, 61,600 (20% × 308,000) are admitted to a hospital annually, but only 25,872 (42% × 61,600) are discharged alive. Hence, the total pool of people discharged alive from a hospital by se-verity of admission is 265,804 (154,000 [mild] + 85,932 [moderate] + 25,872 [severe]).
The disability rate varies by severity of brain injury.
If we assume that 10% of those with MTBI have some neurological limitation, then 15,400 people are afflicted.
Also, if two-thirds of those with moderate brain injury are disabled, 57,288 have some disability. Finally, if 100% of severely injured patients have residual effects, 25,872 can be expected to have some form of disability.
The total number of new disabilities from brain injuries for 2000 is approximately 98,560, a rate of approxi-mately 35 per 100,000 population.
This estimating procedure can be summarized as fol-lows (model, Figure 1–18):
F I G U R E 1 – 1 6 . Adjusted odds ratios for predictor variables for outcome: death after brain injury.
MAIS=Maximum Abbreviated Injury Scale (Association for the Advancement of Automotive Medicine 1990); GCS=Glasgow Coma Scale (Jennett and Teasdale 1981).
Source. Unpublished data from the San Diego County Brain Injury Cohort Study (see Kraus et al. 1984).
Let BID equal the number of brain-injured patients who are discharged alive from hospitals each year with disability
n = size of population (i.e., United States 2000, 280,000,000)
H=hospitalization admission rate of brain injury pa-tients in the population (i.e., 0.0011/year)
pi=proportion of brain injury patients in the i-th se-verity group
(i=1...k, where k=3), where p1=0.50, p2=0.30, p3=0.20 Fi= cumulative hospital fatality for the i-th group where
F1=0, F2=0.07, F3=0.58
Pi=posthospital prevalence of disability in the i-th group where
P1=0.1, P2=0.667, P3=1.0 Hence
BID=HnΣpk i(1 – Fi)Pi i=1
that is,
BID=0.0011 (280,000,000) [0.5(1 – 0)(0.1) + 0.3(1 – 0.07)(0.667) + 0.2(1 – 0.58)(1)]=98,560
Cost of Head Injury
Almost no information was available on the cost of head injuries until Max et al. (1991) provided the first insights into the financial impact of head injuries in the population.
The data show that the average lifetime cost for head injury was approximately $85,000 per person during 1985. Max et al. pointed out that the lifetime costs for minor, moderate, F I G U R E 1 – 1 7 . Adjusted odds ratios for predictor variables for outcome: Glasgow Outcome Scale (Jennett and Teasdale 1981) less than good recovery.
MAIS=Maximum Abbreviated Injury Scale (Association for the Advancement of Automotive Medicine 1990); GCS=Glasgow Coma Scale (Jennett and Teasdale 1981).
Source. Unpublished data from the San Diego County Brain Injury Cohort Study (see Kraus et al. 1984).
F I G U R E 1 – 1 8 . Estimating model.
and severe head injury are surprisingly close, ranging from approximately $77,000 to $93,000 (Figure 1–19). This find-ing illustrates the problem associated with mild head injury, namely, that specific treatment costs are nearly as high as those for moderate and severe brain injury because the mild injury incurs other associated treatment costs and affects full-time employment. The lifetime cost for a brain injury fatality is approximately $357,000, a figure not much higher than the $325,000 for a very severe nonfatal brain injury.
The lifetime costs of head injury by age (Figure 1–20) are much higher for people between the ages of 15 and 44 years than for those in younger or older age groups. Al-though the data have not been severity adjusted, they re-flect costs associated with loss of productivity (and physi-cal, as well as psychosocial, limitations) during the middle, most productive years.
Total costs for all 328,000 head injuries that occurred in 1985 were estimated to be $37.8 billion (Max et al.
1991). Approximately 65% of the total costs were accrued among those who survived a head injury; the remainder were associated with head injury deaths.
Miller and associates (1995) gave additional information on comprehensive costs in 1989 dollars for hospital and non-hospital costs per case. The costs were approximately
$337,000 and $53,000 per case, respectively. The total com-prehensive costs per year in 1989 dollars were $4.1 billion and $154.9 billion for hospital and nonhospital, respectively.
Another estimate provided by Lewin-ICF (1992) found direct and indirect costs of TBI in the United States (in 1991 dollars) totaled more than $48 billion per year, with $32 bil-lion for survivors and $16 bilbil-lion for fatal brain injuries. Av-erage medical and nonmedical costs for each fatal TBI case ($450,000) were three times higher than for TBI survivors ($150,000). The lifetime costs for one person surviving a se-vere TBI, however, can be as high as $4 million (National Institute of Neurological Disorders and Stroke 1989).