Print PageSend to friend

Dr. Miles G. Johnston, BSc, PhD

Professor, Laboratory Medicine and Pathobiology, University of Toronto

Senior Scientist, Neuroscience Program, Sunnybrook Health Sciences Centre

Dr. Johnston received a B.Sc. (1974) in Physiology/Pharmacology at the University of Toronto and a Ph.D. in the Division of Experimental Pathology (Department of Pathology) at the same Institution in 1979. Following post-doctoral training at the A.R.C. Institute of Animal Physiology, Babraham, Cambridge, England from 1979-1981, he returned to Canada to take up a faculty position at the University of Toronto. Currently, he is a Professor in the Department of Laboratory Medicine and Pathobiology and is a Senior Scientist in the Neuroscience Program at Sunnybrook Health Science Centre.

Research Focus
Hydrocephalus is a chronic brain disorder characterized by expansion of the ventricles and in some cases, significant neurological damage. Current treatments are only partially effective and there is an urgent need to reassess the conceptual foundation on which our understanding of this disease is based. Perhaps the greatest paradox in the hydrocephalus field is the failure of researchers to consistently measure transmantle pressure gradients in humans and in animal models of the communicating form of the disorder. Without such a gradient it is difficult to conceptualize how ventricular distention occurs.

The overall objective of our work is to investigate the mechanisms responsible for ventricular expansion in hydrocephalus. We are examining two parallel, but hopefully intersecting concepts to address this issue. In one of these, we are investigating the possibility that trans-parenchymal pressure gradients caused by disruption of brain matrix components represents one of the pivotal events in causing ventriculomegaly. In a second approach, we are studying a 'lymphatic hypothesis'. It is increasingly evident that a major portion of cerebrospinal fluid absorption occurs via transport into lymphatic vessels located in the nasal area. We have observed a lymphatic CSF absorption deficit in a rat model of hydrocephalus and current studies are examining the relationship between this defect and ventricular expansion. The matrix and lymphatic based concepts are quite possibly linked since lymphatic dysfunction is known to elevate intracranial pressure and this likely exacerbates the trans-parenchymal pressure gradients elicited by matrix disruption in the brain.