After a systematic, yet focused history and physical exam, the treating provider must make decisions about appropriate diagnostic testing for the person with suspected MBI. For a diagnostic test to yield reliable information, it must be relatively free of bias and random error. The test must also be sensitive enough to detect an intracranial lesion, yet safe and cost-effective. The World Health Organization Collaborating Centre Task Force recently conducted a systematic review concerning the evidence about diagnostic tools available to detect MBI (Borg et al., 2004). A summary of their findings follows.
Twenty-nine studies provided evidence for the use of CT scans as a diagnostic tool in cases of MBI. Only injured persons who were hospitalized were included in this review, thus not fully representing persons with MBI. The review reported that CT scans can detect unsuspected lesions in patients with MBI. However, pediatric facilities and community and teaching hospitals were noted to have variability in their use of CT testing. Only 8% of those with GCS scores of 15 had abnormal CT results. As the GCS score declined, the likelihood of abnormal CT results increased. For example, 30% of patients with GCS scores of 13 had abnormal CT results. Similar prevalence rates were reported in CT studies with children.
The use of skull X rays was also considered in this review. Fifteen studies reported the use of skull X rays to detect lesions in MBI. X rays were capable of detecting skull fractures known to increase the likelihood of an intracranial lesion. When a depressed skull fracture was present along with vomiting, nausea, and headache, there was increased likelihood of intracranial lesions. No conclusions about the diagnostic value of MRI in detecting abnormalities among those with MBI were delineated in this review.
The review also considered whether cognitive assessments were sensitive in the detection of MBI. Reviewers concluded that although there is limited evidence supporting the benefit of specific cognitive assessments in the detection of MBI, there is beginning evidence that specific cognitive tests may detect sport-related concussive injuries (Lovell & Collins, 2002).
Reviewers also concluded that for persons with MBI, there was good evidence predicting those at risk for complications. Surgical intervention was more likely within 2 hours of admission for those with MBI who were 65 years of age or older, vomiting twice or more, with evidence of basal skull fracture, suspected open or depressed skull fracture, dangerous injury mechanism, or anterograde amnesia of more than 30 minutes (Borg et al., 2004). Consequently, careful clinical assessment coupled with diagnostic tests can predict those patients likely to have MBI complications.
There are studies correlating more sensitive diagnostic tests, such as MRI, single photon emission computed tomography (SPECT), and quantitative magnetic resonance (QMR) imaging with brain abnormalities in those with milder injuries (Kesler, Adams, & Bigler, 2000; Umile, Plotkin, & Sandel, 1998; Wallesch et al., 2001). However, findings are unclear about their sensitivity and relevance because of limited ability to recruit persons with similar injuries and length of time since the injury. Gowda and associates (2006) suggested that SPECT was able to detect significant hypoperfusion in the frontal lobes of adults who had evidence of PTA, loss of consciousness, or PCS. In addition, it is likely that persons with milder injuries and persistent symptoms have increased likelihood of temporal lobe injury as evidenced with animals and human studies of MBI (Umile, Sandel, Alavi, Terry, & Plotkin, 2002). Further research is being conducted about these relationships.
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