CT negative subarachnoid hemorrhage in emergency department

Background: Subarachnoid hemorrhage (SAH) is rare but potentially life-threatening cause of acute headache. First diagnostic test performed in the Emergency Department (ED) for acute “thunderclap” headache is computed tomography of the head (CT) without contrast enhancement. Negative non-contrast head CT may be erroneously interpreted as an exclusion of SAH and lead to ED discharge. The consequences of overlooking SAH are of special interest to the Emergency Physician. The aim of this study was to assess prevalence and clinical picture of CT-negative cases of SAH admitted to the ED. Material and methods: Retrospective analysis of charts of patients admitted to the ED and diagnosed with SAH during 18 consecutive months. Results: Our data gives information about clinical picture of patients with CT-negative SAH and their further clinical course. Out of 126 patients diagnosed with SAH, 5 (4.0%) were diagnosed with SAH despite negative non-contrast head CT scan. All cases were diagnosed by means of lumbar puncture and analysis of cerebrospinal fluid. In all patients with CT-negative SAH computed tomographic angiography (CTA) was performed and no vascular abnormalities were found. In one case digital subtraction angiography was performed due to equivocal CTA picture and it demonstrated small unruptured aneurysm of the medial cerebral artery. All patients with CT-negative SAH were admitted to a neurological ward and later discharged from the hospital without neurological deficit. There were no episodes of clinical deterioration and none of the patients required an urgent neurosurgical intervention. Conclusions: Although lumbar puncture remains a gold standard in exclusion of SAH, head CT scan without contrast enhancement appears to be a satisfying diagnostic tool in ED.