James Watson Kernohan (1896–1981): Frontiers in neuropathology

As one of the early pioneers of the field of neuropathology, James Watson Kernohan contributed immensely to our understanding of tumors in the nervous system. Kernohan was born in Moyasset, County Antrim, North Ireland (1 October 1896) and received his medical training at Queen's University, Belfast—where he earned a bachelor's in obstetrics (B.A.O.), medicine (M.B.) and surgery (B.Ch.) in 1921. During his time at Queen's University, he also earned a diploma in public health (D.P.H.) and a bachelor of science (B.Sc.) degree with first class honors. Following his medical training, Kernohan spent one year at the Crichton Royal Institute in Dumfries, Scotland, as a clinical pathologist and subsequently migrated to the United States in 1922 to become a fellow in pathology at the Mayo Graduate School of Medicine, Minnesota. This fellowship afforded him the opportunity to also train in the Department of Pathology at the University of Minnesota, from which he earned a master's degree (M.A.) in anatomy and pathology in 1924. The thesis of his master's degree was The Ventriculus Terminalis: Its Growth and Development. His dissertation on this ependymally lined space within the conus medullaris laid the groundwork for future study of tumors within the central and peripheral nervous systems (Dahlin,1984). Kernohan's 40-year career as a fellow and consultant at the Mayo Clinic proved to be propitious, yielding major contributions to the fields of pathology and neuropathology. In 1925, Kernohan joined the Department of Anatomic Pathology at Mayo Clinic as a consultant (Sayre,1982; Dahlin,1984). Under the distinguished leadership of H.E. Robertson, Kernohan was allowed to progressively handle more neuropathology—resulting in the coauthoring of the classic article entitled Incisura of the Crus due to Contralateral Brain Tumor in 1929 (Kernohan and Woltman,1929). In this article, the authors described a paradoxical phenomenon involving the crus cerebri in which the neurological deficit remained ipsilateral to the side of the expanding lesion (a false localizing sign). This finding is commonly referred to today as the Kernohan–Woltman notch phenomenon (Pearce,2006; Eesa and Bell,2010). Although remaining active in general pathology (with notable publications on hypertension and systemic vascular disease throughout the latter half of the 1920s), he progressively found himself immersed in neuropathological investigation. In this endeavor, he collaborated with colleagues from both the fields of neurology and neurosurgery. By 1931, Kernohan coauthored his first article on spinal tumors, which was to be the first among many on this subject (Rasmussen et al.,1940; Sayre,1982). This study described common manifestations of a variety of spinal extradural tumors, including lymphoma, myeloma, and metastatic carcinoma. Important correlations between glioma type and location in the spinal cord served as the basis of his 1964 monograph. Undoubtedly, the vast breadth of material covered by Kernohan was augmented by the abundant surgical specimens accessible at Mayo Clinic—one of the leading centers for brain tumors worldwide (Dahlin,1984). Kernohan succeeded Robertson as the head of the Section of Anatomic Pathology from 1943 to 1955. It was during this period that he developed a new system of classification for brain tumors, publishing his landmark article in 1949 entitled—A Simplified Classification of the Gliomas (Kernohan et al.,1949). In it, he suggested a new scheme for grading astrocytomas, ependymomas, oligodendrogliomas, and neuroastrocytomas from 1 to 4 (in ascending order of malignancy), much like the system developed by Broders for grading malignancies outside the central nervous system. This grading classification simplified many of the older designation schemes and correlated well with the clinical course and prognosis (Kernohan et al.,1949; Svien et al.,1949). Kernohan's contribution to our understanding of spinal cord tumors culminated in the publication of the Armed Forces Fascicle on Tumors of the Central Nervous System in 1952. In later years, he reclassified some previously undesignated specimens as sarcomas of the brain using this system. These findings were published during the 1960s and included in his monograph on sarcomas of the brain, coauthored by Uihlein in 1962 (Kernohan and Uihlein,1962; Sayre,1982). Kernohan's other neuropathological interests included the study of metastatic carcinoma to the brain (which his studies revealed to most commonly arise from lung neoplasms), localized pressure on the optic chiasm and optic nerves, meningiomas, hemangiomas, pituitary tumors, brain abscesses, cerebral inflammation and edema, vascular malformations as well as vascular neoplasms affecting the spinal cord. He also explored a wide range of topics in general pathology such as carcinoma of the liver, arterial embalming, age related changes of the intervertebral disc, the myenteric plexus in ulcerative colitis, congenital hypertrophic pyloric stenosis, Hirschsprung's disease, periarteritis nodosa, glomus tumors, and retroperitoneal ganglioneuromas. An avid educator, Dr. Kernohan supervised numerous trainees in pathology, surgery, and internal medicine, endeavoring to impart to them the basic principles of pathology and neuropathology (Dahlin,1984). Kernohan was elected president of the Staff of the Mayo Clinic in 1952—a position he held until his retirement in 1962. In addition to a successful career at the Mayo Clinic, Kernohan also held prominent positions within the societies of pathology, neuropathology, and neurology. In 1938 and 1939, he was elected president of the American Association of Neuropathologists (AANP) and was appointed the vice president of the American Neurological Association in 1955. Kernohan was also among the individuals representing the United States in London at the Second International Congress on Neuropathology in 1955. He was a member of the American Board of Pathology (ABP) from 1946 to 1960—serving as the president from 1957 to 1959. It was during his time on the ABP that Kernohan made significant strides toward the establishment of subspecialty certification in neuropathology. He also served as chairman of the Scientific Advisory Board of the Armed Forces Institute of Pathology in 1954. Quite befitting of his contributions to science, in 1966 he was accorded an honorary degree of doctor of science (D.Sc.) from Queen's University, his alma mater. Kernohan was also presented with the award for Meritorious Contributions to Neuropathology by the AANP in 1971; the plaque for this award reads “in grateful recognition of his dedication and contribution to Neuropathology” (Bailey,1972; Dahlin,1984). Following his retirement from the Mayo Clinic in 1962, Kernohan became a consultant at the Barrow Neurological Institute in Phoenix, Arizona from 1962 to 1964. This period allowed him to publish his monographs on sarcomas of the brain (1962) and tumors of the spinal cord and filum terminale (1964) (Bailey,1972). These monographs were the culmination of his life's work, representing material collected and analyzed over a 40-year period. Following retirement, he returned to his home in Rochester, MN, where he continued to publish on neuropathology into the 1970s (Haines et al.,2005). An avid golfer since his youth in Ireland, Kernohan was known for turning in respectable scores on the course. Many long-life friendships were also formed on the golf course. In 1932, Kernohan married Eleanor Fletcher of Winnipeg, a former fellow in pathology. Together, the Kernohan's warm hospitality made their home a welcomed respite for students and colleagues alike. Aside from his amiable nature, Dr. Kernohan was also known for his characteristically Irish brogue and wit (Bailey,1972). James Watson Kernohan died on May 5, 1981 at the age of 84, leaving behind an enduring legacy of excellence in his field as well as ∼170 articles, 11 book chapters and 3 books (Bailey,1972; Sayre,1982; Haines et al.,2005).

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