In part 1 of this 4-part series. Dr. Baugh discusses physical exam and CT signs of a hemorrhagic stroke (emphasis on subarachnoid hemorrhage)
Faculty: Christopher Baugh, MD, MBA
Vice Chair of Clinical Affairs Department of Emergency Medicine | Brigham and Women's Hospital Associate Professor | Harvard Medical School
Dr. Baugh has published on the clinical and administrative aspects of observation care in the New England Journal of Medicine, Health Affairs, Annals of Emergency Medicine, and Academic Emergency Medicine. He previously served as Chair of the Observation Medicine Section of the American College of Emergency Physicians.
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- Today, let's focus on spontaneous subarachnoid hemorrhage, soliciting a history of a sudden onset worst headache of life, also known as a thunderclap headache. You should place this into your differential diagnosis. On exam, patients may have elevated blood pressure, neck discomfort, and possibly even focal neurologic deficit, such as a cranial nerve palsy. A third-nerve palsy where the patient has double vision and the affected eye deviates downwards and outwards can be associated with subarachnoid hemorrhage, or more commonly with an expanding but unruptured aneurysm of the posterior communicating artery or superior cerebellar artery. The first step in the diagnosis is a CT scan of the head. CT scans are widely available and can be obtained and interpreted quickly. CT is also highly sensitive in the acute setting. Hemorrhages are evident almost instantly after onset as focal, white, hyperdense lesions within the brain parenchyma. However, the sensitivity of a non-contrast scan is time dependent due to the normal creation, flow, and replacement of CSF. As a result, the sensitivity is highest in the first six hours after the bleed starts, and then progressively declines over time. In addition, sensitivity may be reduced due to low volume bleeds, patients with severe anemia, and poor scan quality due to patient movement. On a positive scan, blood is usually found in the basal cisterns and can extend into the intraventricular or subdural spaces. The distribution of blood does provide clues whether the cause of the bleed is aneurysmal or not. In patients with a negative CT more than six hours from the headache onset, an LP is needed to effectively rule out subarachnoid hemorrhage. Red blood cells present in the CSF undergo lysis, resulting in breakdown products such as bilirubin and oxyhemoglobin, resulting in xanthochromia, which is not sensitive early, but becomes increasingly sensitive after a few hours. If the LP result is concerning, you'll want to pursue a CT angiogram to help identify an underlying aneurysm that needs emergent intervention, such as clipping or coiling in parallel with specialty consultation, blood pressure control, airway management, and possibly transferred to a higher level of care if that specialty care is unavailable locally.
