“Head CT ruled out stroke.”
It happens multiple times each week. A patient arrives for a consultation, bringing outside medical records from the emergency department where his or her initial evaluation took place. Inevitably I will find the above statement, or some slight variation of it, stated in the notes, as if serving as a justification for why it was okay to send the patient home. Often the patient wonders why he developed partial visual loss for 30 minutes, or why the left side of her body was tingling for hours even prior to the decision to seek medical attention. After all, the symptoms seemed real at the time, but how to explain what happened since the head CT ruled out a stroke?
From my own experience caring for young stroke patients, I hear the same themes reiterated:
- “Everyone tells me that I don’t look like I’ve had a stroke, but I have never felt like the same person since my stroke.”
- “I have so much difficulty focusing and concentrating since my stroke, and I’m worried about my short term memory.”
- “I was told that I shouldn’t still be experiencing pain now that my vertebral artery dissection has healed, but my headaches are still awful.”
I could list at least 20 bulleted themes commonly heard when talking with young stroke patients, but perhaps the most common one that I hear is: “The first time I went to the ER, I was sent home.”
There are, of course, significant concerns about a young stroke patient seeking medical attention in the ER with stroke-like symptoms, and then being discharged home. The most critical reason to identify early ischemic stroke symptoms in a patient of any age is to take advantage of the only FDA-approved medication in the treatment of acute ischemic stroke – IV t-PA. As mentioned in a previous post, t-PA is a “clot-busting” medication. When a clot blocks blood from flowing in an artery, the administration of t-PA can dissolve the clot, relieving the obstruction and allowing blood to start flowing again. In acute stroke, every minute that passes equates to the death of approximately 1.5 to 2 million neurons (cells in the brain or spinal cord).
With each passing minute that blood is not flowing to part of the brain, the likelihood of a good functional recovery decreases. In addition to the decreasing benefit of t-PA with the passage of time during those first hours of an ischemic stroke, the risk of cerebral hemorrhage from giving t-PA increases. As tissue in the brain sustains injury from this lack of blood flow, the tissue becomes “leaky” and starts swelling, and giving a clot-busting medication like t-PA to a patient with brain tissue that has already died raises the risk that the drug could cause a brain hemorrhage.
This graph appeared in the paper that outlined the results of a stroke clinical trial known as the ECASS 3 study. ECASS 3 was a trial that demonstrated that some patients benefitted in terms of functional recovery from receiving t-PA out to four and a half hours after the start of their stroke symptoms. Prior to this trial, the “window” for giving t-PA to an ischemic stroke patient was three hours after stroke symptoms began. The FDA in the United States has not approved t-PA for use beyond three hours into an ischemic stroke, although in other parts of the world t-PA has been approved for up to 4.5 hours based on this data. I include the graph from that paper to demonstrate that minutes do count. The higher the solid line is on the graph, the better the likelihood of a good functional outcome without significant disability after a stroke. As time passes on the x-axis (numbers on the x-axis represent the number of minutes that have passed since a stroke began), one can see the line trending down, indicating smaller chances of seeing a good outcome. Once the line crosses at 1.0, this is the time point at which is becomes more dangerous to give t-PA because the risk of bleeding is no longer outweighed by the benefit. At this point, for the majority of patients, brain tissue has died, and there is no more benefit to be gained.
When the assumption is made that a patient with stroke-like symptoms is not having a stroke, a CT scan of the head is usually obtained to confirm this assumption. This is flawed reasoning though. The sensitivity of a CT scan without contrast within the first 12-24 hours of an ischemic stroke is around 65%. This means that 35% of patients presenting 12-24 hours after a stroke has started will have essentially normal head CT scans. Now, consider patients who are within the time window for consideration for t-PA. The sensitivity of a head CT scan during the first three to four and a half hours of a stroke is even lower.
A head CT scan is a very good tool for diagnosing bleeding that occurs in the brain, and this is the reason why patients presenting with stroke symptoms are supposed to have a CT scan – to look for blood. The purpose of a CT scan should not be to diagnose an ischemic stroke. The likelihood of detecting hemorrhage in the brain is around 90-95% with a CT scan. Since 20% of strokes are of the hemorrhagic type, but it is impossible to determine based on a patient’s symptoms alone whether a stroke is ischemic (due to a blood clot blocking blood flow) or hemorrhagic, a CT scan clarifies the stroke type.
When I am seeing an acute stroke patient in the ER, I expect to see one of three things on the head CT: 1) evidence of bleeding (hemorrhagic stroke), 2) evidence of ischemic stroke (which means swelling and cell death has already occurred), or 3) a normal head CT scan. It is the patient with the normal head CT scan who should receive t-PA, because this is the patient who is very early into an ischemic stroke. An early stroke can be a treatable stroke, but if a patient is sent home on the assumption that a normal CT scan “ruled out” a stroke, then the only evidence-supported medical therapy for treatment has been denied to that person.