The value of the "worst" computed tomographic scan in clinical studies of moderate and severe head injury

OBJECTIVE: Computed tomographic (CT) scanning can reveal the pattern and se verity of structural brain damage after head injury. With the proliferation of CT scanners in general hospitals, and with improvements in patient tran sport, the interval from injury to the first CT scan is decreasing. The pot ential result is an "admission" scan missing an evolving and potentially op erable lesion. Furthermore, the literature is confusing regarding the timin g and coding of CT findings. We sought to establish the frequency of deteri oration in CT appearance from an admission scan to subsequent scans and the prognostic significance of such deterioration. METHODS: In a survey organized by the European Brain Injury Consortium, dat a on initial severity, management, and subsequent outcome were gathered pro spectively for 1005 patients with moderate or severe head injury admitted t o one of 67 European neurosurgical units during a 3-month period in 1995. T he findings of the initial and the final ("worst") CT scan were classified according to the Traumatic Coma Data Bank system and were related to outcom e as assessed using the Glasgow Outcome Scale 6 months after injury. RESULTS: Data on an initial and a final CT scan were available for 897 pati ents; of these, 724 patients were assessed using the Glasgow Outcome Scare at 6 months. The initial CT findings were classified as a diffuse injury fo r 53% of the cohort, with 16% of these diffuse injuries demonstrating deter ioration on a subsequent scan. In 56 (74%) of 76 deteriorations, the change was from a diffuse injury to a mass lesion. When the initial CT scan demon strated a diffuse injury without swelling or shift, evolution to a mass les ion was associated with a statistically significant increase in the risk of an unfavorable outcome (62% versus 38%). When the initial scan demonstrate d evidence of swelling or shift, there was a nonsignificant trend in the op posite direction, although the numbers were limited. CONCLUSION: When an admission CT scan demonstrates evidence of a diffuse in jury, follow-up scans should be performed, because approximately one in six such patients will demonstrate significant CT evolution. In studies compar ing series of head-injured patients, correspondence of timing of CT scans i s necessary for valid comparison.