E-Pearl of the Week: Kernohan-Woltman Notch Phenomenon (KWNP)

December 20, 2012


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December 20, 2012

Kernohan–Woltman Notch Phenomenon (KWNP)

Lesions above the pyramidal decussation usually cause contralateral symptoms on the body. In KWNP, hemiparesis is ipsilateral to the supratentorial lesion. It results typically from an advanced brain tumor, severe head injury, or rarely, intracerebral hemorrhage causing transtentorial herniation. The contralateral pyramidal tract is pressed against the tentorial incisum and resultant hemiparesis is found on the same side of the lesion. KWNP implies a false–localizing sign because clinical findings lead the examiner to an incorrect neuroanatomical diagnosis.


  1. Fujimoto A, Sato H, Katayama W, et al.  Kernohan’s phenomenon associated with left ruptured occipital arteriovenous malformation.  J Clin Neurosci 2004 May; 11: 444–446.
  2. McKenna C, Fellus J, Barrett AM.  False localizing signs in traumatic brain injury.  Brain Inj 2009; 23: 597–601.

Submitted by: Ganesh Asaithambi, MD,  University of Minnesota.

Disclosure: Dr. Asaithambi reports no disclosures.

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