Will A Stroke Show Up On A CT (CAT) Scan?

The diagnosis of stroke usually involves several procedures. One of the common ones is with an imaging test called CT scan or CAT scan. Accurate diagnosis is necessary to help determine the most appropriate medication for best outcome and prognosis. But does a stroke always show up on CAT /CT scan?

What actually is Computerized Tomography (CT) scan?

Brain imaging test is often used to diagnose a stroke, including the type of damage (whether it is ischemic or hemorrhage stroke).

CT scan is one of common procedures used to analyze the brain damage due to stroke. It is a large medical device that uses a series of appropriate X-ray radiation to make a detailed picture of the brain so doctors can analyze the brain’s anatomy of patient through a series of thin slices of images.

Sometimes it is also followed with the injection of contrast dye in order to provide more detailed pictures of the brain for clearly diagnosis. The dye injection can help define tissues and blood vessels of the brain.

The procedure of CT scan with the injection of a contrast dye is medically called computerized tomography angiography.

How does it work?

In general, the working principle of CT scan is similar to most regular X-ray devices . The appropriate X-rays are radiated by the device and then will be absorbed by the body.

The absorption can vary in each part of the body. Water in the body absorbs little X-rays. Therefore it appears black on the image. On the other hand, the rays are mostly absorbed by the bones. That’s why bones usually show up ‘white’.

How about the brain? The brain usually appears grey on the image, because it has intermediate density in absorbing X-rays.

Area of the brain with hemorrhage usually appears white and denser than normal brain. And if there is an ischemic damage, this usually appears darker and less dense than other parts of the brain.

How long does the test take? The answer varies, but mostly about 20-60 minutes.

Will stroke always show up on CT scan?

The device for CT-scan test is commonly available in emergency rooms. In general, this test is the standard procedure used to diagnose a stroke. The next question, is accurate enough to diagnose the disease?

It is also not effective to diagnose transient ischemic stroke (TIA) or often familiar called as an impending stroke. TIA usually doesn’t appear with CT scan or MRI test.

When a true stroke doesn’t show up on CT scan?

There are some reasons, but many times this occurs when the test is performed too soon after the attack.

Another reason is when the damage region in the brain is too small to get captured during the test. That’s why TIA or mini-stroke usually doesn’t appear with the test, as noted before.

Furthermore, the location of damage may have an effect. For instance, when the damage occurs in small part of the brain (such as cerebellum or brain stem), it may not image well!

For these reasons, sometimes the diagnosis of stroke can involve numerous different tests and procedures. If necessary, doctors may consider using additional tests for accurate diagnosis.

What are the side effects of CT scan?

The test is not painful, instead it is painless. However, there are a few side effects that may occur after the procedure. 

The radiation of X-rays during the test is safe because it uses very light x-ray radiation.

But if the test also uses contrast dye, an allergic reaction may occur. Sometimes allergic reaction may become serious and require appropriate treatment.

Is MRI-scan test more accurate than CT-scan test?

As mentioned before, the drawback of CT-scan is less accurate when the test is performed for the first several hours after the first stroke symptoms appear.

What’s more?