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Dr. Andrew Rynne

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What Is The Reason Of Negative CAT Scan In Case Of Stroke?

51, 5 7, 185, single bypass heart at age 44, recently have had a stroke on June 27, 2011, with parisse to my left arm and leg, however the cat scan was negative in its showings and I can not have an mri due to metal in my face. why would the cat scan not show anything.
Mon, 7 Jul 2014
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Neurologist,  's  Response
Hi,

Thank you for posting your query.

I have noted your symptoms and the fact that CAT scan was negative, even though you had paresis (weakness) of left arm and leg.

This can happen because of two reasons:

1. Very small infarct (area of reduced blood flow to brain)- CT scan is not sensitive to pick up very small infarcts (especially those below 10 mm in size).

2. Very early after the stroke onset- the changes on CT scan takes a few hours to develop after ischemic stroke. So, in the first 4-6 hours, CAT scan may be negative even in the presence of paresis.

It should be noted, however, that the CAT scan is positive very early after a bleed in the brain (brain hemorrhage). Therefore, CAT scan is often used to detect bleeding in brain.

I hope my reply has helped you.

I would be pleased to answer, if you have any follow up queries or if you require any further information.
     
Best wishes,
Dr Sudhir Kumar MD (Internal Medicine), DM (Neurology)
Senior Consultant Neurologist
Apollo Hospitals, Hyderabad,
For DIRECT QUERY to me: http://bit.ly/Dr-Sudhir-kumar
My blog: http://bestneurodoctor.blogspot.com/
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What Is The Reason Of Negative CAT Scan In Case Of Stroke?

Hi, Thank you for posting your query. I have noted your symptoms and the fact that CAT scan was negative, even though you had paresis (weakness) of left arm and leg. This can happen because of two reasons: 1. Very small infarct (area of reduced blood flow to brain)- CT scan is not sensitive to pick up very small infarcts (especially those below 10 mm in size). 2. Very early after the stroke onset- the changes on CT scan takes a few hours to develop after ischemic stroke. So, in the first 4-6 hours, CAT scan may be negative even in the presence of paresis. It should be noted, however, that the CAT scan is positive very early after a bleed in the brain (brain hemorrhage). Therefore, CAT scan is often used to detect bleeding in brain. I hope my reply has helped you. I would be pleased to answer, if you have any follow up queries or if you require any further information. Best wishes, Dr Sudhir Kumar MD (Internal Medicine), DM (Neurology) Senior Consultant Neurologist Apollo Hospitals, Hyderabad, For DIRECT QUERY to me: http://bit.ly/Dr-Sudhir-kumar My blog: http://bestneurodoctor.blogspot.com/