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When to Order a CT Angiogram of the Head

Jessica Mason, MD and Ali Raja, MD
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Nurses Edition Commentary

Kathy Garvin, RN and Lisa Chavez, RN
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EMRAP 2019 04 April Written Summary 439 KB - PDF

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Patrick T. -

Sensitivity of early CT for diagnosing SAH has also been studied via meta-analysis: https://www.ncbi.nlm.nih.gov/pubmed/26797666.

john s. -

What about doing a CT angiogram in patients who refuse the LP to see if there is any sign of aneurysm that might have caused the bleed?
Also, how common are SAH if the patient has no signs of aneurysm on CT angio? Thanks.. JD

Whit F., M.D. -

I have the same question as John S. From a medical-legal perspective, can you be sued for not doing a CT angio if you do a non-con CT which is negative, but the patient refuses LP? It seems an attorney would argue that if you were worried enough about the condition, it was a dereliction to not perform an alternative test (CT angio) even with the theoretical risk of false positives.

I used to get stuck n this situation *constantly* for patients beyond the 6 hour mark. My solution has been to tell the patient I will not get the CT unless they agree to sign consent for the lumbar puncture ahead of time. Psychologically it commits the patient and it has made a big difference. Some of them still refuse the LP later, and I always sign them out AMA with scary discharge instructions after a very comprehensive discussion. Too much?

SHIH-CHIN C. -

I would do the best for the patient. If the patient does not look well, admit obs, CTA, neuro consult. After all, there are many other differentials for a severe headache besides SAH, such as meningitis, encephalitis, small mass, acute ischemic stroke, acute coronary syndrome, UTI.
At a comprehensive stroke center, we order CTAs many times a day, as most patients with NIHSS >=6 will require a CTA. So here, we don't worry about using CTAs.

Whit F., M.D. -

Yeah, it's pretty much a no-brainer (ha ha) for a patient who does not look well - after all, the risks of radiation, contrast, and excessive testing for incidental aneurysms can be justified if they look bad clinically.

It gets a little more difficult when you have someone who looks well but says "I got this horrible headache all of a sudden" in their triage note, but they are outside the non-con window and they refuse an LP. For someone who looks great, what IS "best for the patient?" The risks of CTA (which are small but not zero) become a little harder to justify. I mean, if we're going to argue that CT/LP should be the standard, we should consider a uniform approach for patients who refuse that standard...because it happens a LOT.

SHIH-CHIN C. -

The neurointerventional surgeons at our center prefer CTA brain/neck over MRA brain/neck. For vascular occlusions, UpToDate cites CTA sensitivities of 92-100%, and MRA sensitivities of 86-97%.

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