Subarachnoid hemorrhage (SAH) cannot be ruled out by CT scan or history with physical examination alone, according to a recent study published in Annals of Emergency Medicine. A lumbar puncture with examination of the cerebrospinal fluid is the only way to rule subarachnoid bleeding. Previous studies have reported that a clinical decision rule can rule out SAH with 100% sensitivity. Other studies have reported that a CT scan of the brain within 6 hours can rule SAH out with 100% accuracy. This study says otherwise. The researchers retrospectively looked at cases of SAH in patients with normal neurological exams and also looked at the accuracy of the clinical rule test and the CT imaging test. Sixty two percent (62%) of these patients had cerebral aneurysms and were presenting with signs of small early sentinel bleeds. This important proper diagnosis allows treatment time prior to catastrophic rupture.
The clinical decision rule was positive for SAH if there was any combination of an age of 40 years or more, neck pain or stiffness, loss of consciousness, or headache onset during exertion. This clinical decision rule missed 3% of SAH patients. This also means that 2% of all patients with cerebral aneurysms who present with headache from a sentinel bleed will go undiagnosed and likely suffer subsequent catastrophic rupture if only the clinical rule is used. The CT imaging test required a CT scan of the brain within 6 hours of headache onset. The CT imaging test missed 20% of SAH patients. This means that 12% of patients with cerebral aneurysms presenting as headache will go undiagnosed and suffer subsequent catastrophic rupture if only the CT scan is relied upon. The use of these two tests together without a lumbar puncture will still miss approximately 1 in 165 cases of SAH, and approximately 1 in 500 patients with small early sentinel aneurysm bleeds will go undiagnosed.
Sadly, this study shows that a lumbar puncture is the only way to definitively rule out subarachnoid hemorrhage. Britcher Leone & Roth understands the importance of prompt and proper diagnosis in the emergency room to prevent catastrophic injury. Emergency room errors can lead to otherwise avoidable injury. Only careful evaluation of the medical facts can tell if proper care was rendered.