From the notch to a glioma grading system: The neurological contributions of James Watson Kernohan

During his lifetime and a career spanning 42 years, James Watson Kernohan made numerous contributions to neuropathology, neurology, and neurosurgery. One of these, the phenomenon of ipsilateral, false localizing signs caused by compression of the contralateral cerebral peduncle against the tentorial edge, has widely become known as "Kernohan's notch" and continues to bear his name. The other is a grading system for gliomas from a neurosurgical viewpoint that continues to be relevant for grading of glial tumors 60 years after its introduction. In this paper, the authors analyze these two major contributions in detail within the context of Kernohan's career and explore how they contributed to the development of neurosurgical procedures.