Constitutional predisposition to central nervous system (CNS) disease determined by tests of lateral asymmetry. A...

Three factors in combination cause diseases of the central nervous system (CNS): specific etiological agent, physical stress and a general constitutional predisposition to CNS diseases. Research has tended to focus on the first to the disregard of the second and third factors. A newly developed test of functional body asymmetry, however, may have application to the elucidation of the role of physical stress and the constitutional predisposition to CNS diseases. In the present study, neurophysioligcal tests of lateral asymmetry in hand preference and thumb opposition rotation divide the normal population equally into a pure dominant group and a cross-dominant group. Neurological interviews with each group show cross-dominant normal subjects to be more vulnerable to physical stress factors such as overexertion and sleep disturbance. In a previous sutdy applying the same tests, patients with manifest primary diseases of the CNS such as parkinsonism showed cross-dominance in more than 90% of cases. These results with cross-dominant normals and CNS disease patients suggest that cross-dominance indicates a constitutional predisposition to CNS diseases. They also suggest that cross-dominant normal individuals are vulnerable to pysical over-exertion and the specific etiological agent responsible for a distinct CNS syndrome. As far as temporal order is concerned, since it is present in 50% of the normal population, cross-dominant laterality would appear to be a condition prior to any disease process rather than a consequence of CNS disease.