Kernohan-Woltman notch phenomenon: a review article

Kernohan-Woltman notch phenomenon (KWNP) is a false localising sign which may still cause diagnostic confusion. It was first described by Kernohan and Woltman in 1929, through post-mortem studies on 297 patients following cases of false localisation. They proposed that raised intracranial pressure causes uncal herniation, which can compress the contralateral cerebral peduncle against the tough tentorium, manifesting as hemiparesis ipsilateral to the primary brain lesion. A number of case reports have been written since the original description of this phenomenon, primarily secondary to intracranial bleeds, and little has been written about long-term outcome of patients who develop KNWP. We performed a literature search of all published cases of KWNP, and reviewed its clinical, pathophysiological, imaging and neurophysiological characteristics. Furthermore, we summarise the long-term outcomes of these patients as described by case reports, with the aim to improve understanding of rehabilitation potential. Thirty-eight cases were found through a PubMed search. We also included a case from our own Trust, making the total number of cases in the analysis 39. Thirty-six cases were secondary to intracranial bleeds (22 of which were traumatic), the remainder were due to an arachnoid cyst, high grade glioma, and reabsorption bone syndrome. Additional clinical manifestations to hemibrachiocrural syndrome included third nerve palsy, mydriasis of the contralateral and ipsilateral pupils, facial nerve palsies, and parkinsonism. Twenty-six (67%) patients had improvement in motor function of varying degrees, with twelve (31%) patients attaining complete motor recovery or independence. More studies on long-term outcome of patients who develop KWNP are needed to understand rehabilitation potential.