Prevalence of herniation and intracranial shift on cranial tomography in patients with subarachnoid hemorrhage and a normal neurologic examination.

OBJECTIVES: Patients frequently present to the emergency department (ED) with headache. Those with sudden severe headache are often evaluated for spontaneous subarachnoid hemorrhage (SAH) with noncontrast cranial computed tomography (CT) followed by lumbar puncture (LP). The authors postulated that in patients without neurologic symptoms or signs, physicians could forgo noncontrast cranial CT and proceed directly to LP. The authors sought to define the safety of this option by having senior neuroradiologists rereview all cranial CTs in a group of such patients for evidence of brain herniation or midline shift.

METHODS: This was a retrospective study that included all patients with a normal neurologic examination and nontraumatic SAH diagnosed by CT presenting to a tertiary care medical center from August 1, 2001, to December 31, 2004. Two neuroradiologists, blinded to clinical information and outcomes, rereviewed the initial ED head CT for evidence of herniation or midline shift.

RESULTS: Of the 172 patients who presented to the ED with spontaneous SAH diagnoses by cranial CT, 78 had normal neurologic examinations. Of these, 73 had initial ED CTs available for review. Four of the 73 (5%; 95% confidence interval [CI] = 2% to 13%) had evidence of brain herniation or midline shift, including three (4%; 95% CI = 1% to 12%) with herniation. In only one of these patients was herniation or shift noted on the initial radiology report.

CONCLUSIONS: Awake and alert patients with a normal neurologic examination and SAH may have brain herniation and/or midline shift. Therefore, cranial CT should be obtained before LP in all patients with suspected SAH.