UMEM Educational Pearls

Category: Neurology

Title: What's the cause of this patient's hemiplegia?

Keywords: Uncal herniation, ipsilateral hemiplegia, Kernohan's notch, Kernohan's sign (PubMed Search)

Posted: 8/10/2016 by WanTsu Wendy Chang, MD
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Patient presents after a fall confused, not moving his right side, but moving his left side spontaneously.  What's the diagnosis?


  • The patient has a right subdural hematoma (SDH) with midline shift and right uncal herniation. 
  • The classic presentation of a cerebral lesion with uncal herniation is ipsilateral mydriasis, contralateral hemiparesis, and abnormal extensor posturing.
  • In this patient’s case, there is compression of the contralateral cerebral peduncle of the midbrain by the edge of the tentorium cerebelli producing an ipsilateral hemiplegia (see attachment for Figure 2).
  • This false localizing sign is named Kernohan’s notch syndrome, Kernohan’s notch phenomenon, or Kernohan’s sign.


Diagram modified from "Localised Neurological Disease and Its Management A Intracranial". Accessed 10 Aug 2016.


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1608101928_20160810_Figure_2.jpg (38 Kb)