Isolated traumatic subarachnoid hemorrhage (tSAH) after traumatic brain injury (TBI) on head computed tomography (CT) scan is often regarded as a \"mild\" injury, with reduced need for additional workup. However, tSAH is also a predictor of incomplete recovery and unfavorable outcome. This study aimed to evaluate the characteristics of CT-occult intracranial injuries on brain magnetic resonance imaging (MRI) scan in TBI patients with emergency department (ED) arrival Glasgow Coma Scale (GCS) score 13-15 and isolated tSAH on CT. The prospective, 18-center Transforming Research and Clinical Knowledge in Traumatic Brain Injury Study (TRACK-TBI; enrollment years 2014-2019) enrolled participants who presented to the ED and received a clinically-indicated head CT within 24 h of TBI. A subset of TRACK-TBI participants underwent venipuncture within 24 h for plasma glial fibrillary acidic protein (GFAP) analysis, and research MRI at 2-weeks post-injury. In the current study, TRACK-TBI participants age ≥17 years with ED arrival GCS 13-15, isolated tSAH on initial head CT, plasma GFAP level, and 2-week MRI data were analyzed. In 57 participants, median age was 46.0 years [quartile 1 to 3 (Q1-Q3): 34-57] and 52.6% were male. At ED disposition, 12.3% were discharged home, 61.4% were admitted to hospital ward, and 26.3% to intensive care unit. MRI identified CT-occult traumatic intracranial lesions in 45.6% (26 of 57 participants; one additional lesion type: 31.6%; 2 additional lesion types: 14.0%); of these 26 participants with CT-occult intracranial lesions, 65.4% had axonal injury, 42.3% had subdural hematoma, and 23.1% had intracerebral contusion. GFAP levels were higher in participants with CT-occult MRI lesions compared with without (median: 630.6 pg/mL, Q1-Q3: [172.4-941.2] vs. 226.4 [105.8-436.1], p = 0.049), and were associated with axonal injury (no: median 226.7 pg/mL [109.6-435.1], yes: 828.6 pg/mL [204.0-1194.3], p = 0.009). Our results indicate that isolated tSAH on head CT is often not the sole intracranial traumatic injury in GCS 13-15 TBI. Forty-six percent of patients in our cohort (26 of 57 participants) had additional CT-occult traumatic lesions on MRI. Plasma GFAP may be an important biomarker for the identification of additional CT-occult injuries, including axonal injury. These findings should be interpreted cautiously given our small sample size and await validation from larger studies.

BACKGROUND: Computed tomographic angiography (CTA) tends to be overused in patients with traumatic subarachnoid hemorrhage (tSAH) to rule out intracranial aneurysmal disease. We hypothesized that there are two exclusive subsets of patients with tSAH that maybe at increased risk for aneurysm and thus should undergo CTA, those \"found down\" with an unknown mechanism of injury and those with \"central subarachnoid hemorrhage\" (CSH, in the subarachnoid cisterns and Sylvian fissures). This pilot study was performed to provide more information on the validity of our hypothesis.
METHODS: A retrospective analysis was performed on trauma patients with tSAH who underwent CTA of the brain. Patients presented to a level I trauma center from January 2008-December 2012. Our principal outcome was the diagnosis of an intracranial aneurysm. Student t-test, chi-squared test, Mann-Whitney U test, and binary logistic regression were used for statistical analysis, with significance set at alpha = 0.05.
RESULTS: Of 617 total patients with tSAH, 186 patients underwent CTA. Majority of patients were male (64%), with median age of 56 y. Median Glasgow coma scale on presentation was 15, and the median injury severity score was 16. Thirteen patients (6.99%) had an aneurysm on the follow-up CTA. Of those, 8 of 13 (61.5%) were felt to have presented with a ruptured aneurysm. Among those, 5 of 8 (62.5%) sustained a fall and 3 of 8 (37.5%) resulted from a motor vehicle crash. Among the 14 patients (7.5%) \"found down\", none had an aneurysm. All eight patients with a ruptured aneurysm (100%) had CSH, whereas none of the five patients with unruptured aneurysm had CSH. On multivariate analysis, suprasellar cistern hemorrhage was the most predictive noncontrast computed tomographic finding with regard to aneurysm presence (odds ratio, 4.78; 95% confidence interval, 1.33-17.1). Patients with an aneurysmal disease had a significantly higher mean arterial pressure on presentation (median, 115 mm Hg) than those without an aneurysm (median, 96 mm Hg, P < 0.05). Of the eight ruptured aneurysms, six underwent neurosurgical clipping or coiling, one underwent a ventriculostomy, and one underwent a craniotomy for evacuation of hemorrhage.
CONCLUSIONS: These preliminary data support a more selective approach to screening CTAs in patients with tSAH. CTA should be used in those patients with CSH regardless of mechanism of injury. A more restrictive approach should be used in patients with only peripheral subarachnoid hemorrhage.