Dubosh, Nicole M.

Abstract Background The objective was to systematically evaluate the sensitivity of diffusion‐weighted magnetic resonance imaging (DW‐MRI) for transient global amnesia (TGA) across various time frames compared to the reference‐standard clinical criteria. Methods All indexed publications related to TGA and MRI through June 2020 were retrieved by a medical librarian. Two independent reviewers identified original research studies of adults with a clinical diagnosis of TGA using Caplan and Hodges and Warlow criteria (reference standard) who were evaluated with DW‐MRI. Pooled estimates and its 95% confidence intervals (CI) for the proportion of acute TGA patients with positive DW‐MRI (i.e., sensitivity) were obtained using random‐effects meta‐analysis for various time frames. Quality assessment was performed using the revised Quality of Assessment of Diagnostic Accuracy Studies (QUADAS‐2) tool. Results After screening 665 reports, we identified 81 potentially relevant studies. Twenty‐three studies representing 1688 patients met eligibility criteria, but not all studies had data available for meta‐analysis. The pooled sensitivity (also described as positivity rate) of DW‐MRI was 15.6% (95% CI = 2.6%–35.0%) between 0 and 12 h from symptom onset, 23.1% (95% CI = 6.1%–45.7%) at 0–24 h, 72.8% (95% CI = 40.8%–96.3) at 12–24 h, 68.8% (95% CI = 44.8%–88.8%) at 24–36 h, 72.4% (95% CI = 59.8%–83.5%) at 36–48 h, 82.8% (95% CI = 54.7%–99.6%) at 48–60 h, 66.9% (95% CI = 47.5%–83.9%) at 60–72 h, and 72.0% (95% CI = 30.1%–100.0%) at 72–96 h. There was significant concern for risk of bias in the QUADAS‐2 domains of patient selection and index test, yielding a low level of certainty in the pooled estimates. Conclusion DW‐MRI lesions are uncommon in patients with TGA early after symptom onset, but the sensitivity (i.e., positivity rate) of DW‐MRI increases with time. Despite the limited quality of existing evidence, obtaining an early DW‐MRI in patients with clinical diagnosis of TGA in the acute setting is likely a low‐yield test.

Background and Purpose— Emerging evidence demonstrating the high sensitivity of early brain computed tomography (CT) brings into question the necessity of always performing lumbar puncture after a negative CT in the diagnosis of spontaneous subarachnoid hemorrhage (SAH). Our objective was to determine the sensitivity of brain CT using modern scanners (16-slice technology or greater) when performed within 6 hours of headache onset to exclude SAH in neurologically intact patients. Methods— After conducting a comprehensive literature search using Ovid MEDLINE, Ovid EMBASE, Web of Science, and Scopus, we conducted a meta-analysis. We included original research studies of adults presenting with a history concerning for spontaneous SAH and who had noncontrast brain CT scan using a modern generation multidetector CT scanner within 6 hours of symptom onset. Our study adheres to the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Results— A total of 882 titles were reviewed and 5 articles met inclusion criteria, including an estimated 8907 patients. Thirteen had a missed SAH (incidence 1.46 per 1000) on brain CTs within 6 hours. Overall sensitivity of the CT was 0.987 (95% confidence intervals, 0.971–0.994) and specificity was 0.999 (95% confidence intervals, 0.993–1.0). The pooled likelihood ratio of a negative CT was 0.010 (95% confidence intervals, 0.003–0.034). Conclusions— In patients presenting with thunderclap headache and normal neurological examination, normal brain CT within 6 hours of headache is extremely sensitive in ruling out aneurysmal SAH.