What is a Kernohan?
Duane E. HAINES1, J.A. LANCON2, and
There are a number of clinical examples to which the name of the discoverer/describer is applied that are especially interesting or instructive. Perhaps one of the more interesting is what is called the Kernohan notch phenomenon. This brainstem syndrome characteristically may include long tract and cranial nerve signs, but in contrast to the general rule of alternating deficits, these deficits are on the same side of the head and body.
In 1929 James Watson Kernohan (b. 1896, d. 1981) offered an explanation for the observation that some patients have a hemiplegia of the extremities that is ipsilateral to a brain tumor located in a supratentorial location. In general, the tumor mass displaces the brainstem at the midbrain-thalamus junction such that the crus cerebri on the opposite side is forced against the edge of the tentorium cerebelli. This creates a "notch" and consequent damage to the corticospinal fibers in the crus; the result is a hemiplegia on the side of the lesion.
Kernohan was born and received his Medical training (in Obstetrics, Medicine and Surgery) in Northern Ireland. He came to the US, and to the Mayo Clinic, in 1922 and stayed at the Mayo until his retirement in 1962. Although his interest started in general pathology, he soon devoted his energies to the new field of neuropathology. His interests encompassed neuropathology as broadly defined, but focused on tumors of the spinal cord, brain abscesses, metastatic brain lesions, and vascular lesions/tumors of the spinal cord. One of his most significant contributions was the development of a classification system for brain tumors.
This paper reviews the unique features of the cases described by Kernohan, reviews the man himself, and present the view that the combination of deficits described are more appropriately called the Kernohan syndrome rather than the Kernohan notch phenomenon.
Session XII -- Brain Trauma and Death
Montreal, Quebec, Canada