Kernohan’s Notch Phenomenon

If you’re a clinical clerk or a junior intern in the radiology department specifically assigned in MRI division and you are on you’re very first day of duty but you wanted to make your residents or consultants have a “first impression to last”. But you do not know what to expect from your patient’s MRI result with a history of one-sided paralysis.

MRI of the headMRI of the head (image from

Well, here’s one thing that may help you to at least think of something to look for from your patient’s plates.

A cerebral peduncle indentation associated with some forms of transtentorial herniation or the so-called uncal herniation. Kernohan’s Notch. 

If you find one, and you are suspecting that it is really that feature, try to go back to your patient and do a detailed history taking and some sort of physical examination.

Kernohan’s notch is a result of a primary condition that may be caused by an injury to the opposite hemisphere of the brain. This means that when you examine your patient and you are seeing a left–sided motor weakness, you should be reading your findings from the right side of your patient’s MRI of the head plates or the other way around.

Aside from injury or head trauma, other cause of this Kernohan’s notch is a brain tumor which still need further investigation.

So, being the junior intern on duty, should you impress your consultant with your findings.

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