False‐negative Interpretations of Cranial Computed Tomography in Aneurysmal Subarachnoid Hemorrhage

Abstract

Objectives: Prior studies examining the sensitivity of cranial computed tomography (CT) for the detection of subarachnoid hemorrhage (SAH) have used the final radiology report as the reference standard. However, optimal sensitivity may have been underestimated due to misinterpretation of reportedly normal cranial CTs. This study aims to estimate the incidence of missed CT evidence of SAH among a cohort of patients with aneurysmal SAH (aSAH).Methods: We performed a retrospective chart review of emergency department (ED) encounters within an integrated health delivery system between January 2007 and June 2013 to identify patients diagnosed with aSAH. All initial noncontrast CTs from aSAH cases diagnosed by lumbar puncture (LP) and angiography following a reportedly normal noncontrast cranial CT (CT-negative aSAH) were then reviewed in a blinded, independent fashion by two board-certified neuroradiologists to assess for missed evidence of SAH. Reviewers rated the CT studies as having definite evidence of SAH, probable evidence of SAH, or no evidence of SAH. Control patients who underwent a negative evaluation for aSAH based on cranial CT and LP results were also included at random in the imaging review cohort.Results: A total of 452 cases of aSAH were identified; 18 (4%) were cases of CT-negative aSAH. Of these, seven (39%) underwent cranial CT within 6 hours of headache onset, and two (11%) had their initial CTs formally interpreted by board-certified neuroradiologists. Blinded independent CT review revealed concordant agreement for either definite or probable evidence of SAH in nine of 18 (50%) cases overall and in five of the seven (71%) CTs performed within 6 hours of headache onset. Inter-rater agreement was 83% for definite SAH and 72% for either probable or definite SAH.Conclusions: CT evidence of SAH was frequently present but unrecognized according to the final radiology report in cases of presumed CT-negative aSAH. This finding may help explain some of the discordance between prior studies examining the sensitivity of cranial CT for SAH.ACADEMIC EMERGENCY MEDICINE 2016;23:591-598

CT negative subarachnoid hemorrhage in emergency department

“…Our study revealed that 4.0% of patients diagnosed with SAH at ED had a normal non-contrast head CT. This result is slightly lower than previously published findings showing percentage of CT-negative SAH between 4-20% [9][10][11]. The discrepancies may be partially explained with differences in parameters of CT scanner and in experience of radiologists describing the images.…”

“…Optimizing the quality of diagnostics and care of patients with suspected SAH is an important issue in recent Emergency Nedicine and Neurology literature. One of the solutions for prolonged diagnostics of headache in ED is extending imaging after originally negative non-contrast head CT scan to include CT-angiography if SAH remains part of the differential diagnosis, which may significantly reduce the risk of overlooking aneurysmal SAH [11]. Another approach is to focus on assessment of initially performed non-contrast head CT scan, as radiological evidence of SAH is frequently unrecognized [7].…”

Erythrophages do not develop when lumbar CSF and blood samples are mixed in vitro

“…Cerebrospinal fluid analysis is a crucial method in the diagnostic process if a subarachnoid hemorrhage (SAH) is clinically suspected but findings from cerebral imaging are negative or inconclusive. This is especially important in cases with an increased time interval between the suspicious clinical event and the cerebral imaging as the sensitivity of cerebral imaging declines significantly over time [ 1 , 2 ]. When faced with prolonged time intervals between a suspicious event with acute severe headache and clinical examination, CSF analysis may be the only diagnostic tool to verify a SAH [ 3 ].…”

Diagnosis of a subarachnoid hemorrhage with only mild symptoms using computed tomography in Japan

“…However, even in such cases, it might not be possible to clearly observe hematoma. Patients with small hemorrhages, who are the most likely to receive an incorrect clinical diagnosis, are also more likely to have negative results or misinterpretation on CT [ 17 , 18 ]. Although magnetic resonance technology is continually advancing and can detect aneurysms, standard magnetic resonance imaging (MRI) is inferior to CT in terms of detecting acute SAH [ 19 ].…”