SINCE Kernig's description1 in 1907 of a localized sign pointing to meningeal disease, there has been a constantly increasing body of knowledge concerning such phenomena. It was evidently Kernig's early belief that the "leg sign" which he first described was a specific finding for epidemic cerebrospinal meningitis. This early belief was, of course, unfounded, and Kernig later corrected his statement, since the reaction is present in many other varieties of meningeal irritation. Many different, but related, signs of meningeal irritation have since been described, although none is of greater clinical importance than the Kernig leg sign. The purpose of this presentation is to point out the modification of the meningeal sign which frequently occurs when hemiparesis and meningeal irritation are present concomitantly. The recognition of this modification is of clinical importance, as will be shown. In addition, a study of the modification sheds further light on the poorly understood neurophysiologic mechanisms on which the occurrence of the meningeal signs depends.The Kernig leg sign was often described for a patient in the sitting position with his legs dangling over the side of the bed. If one leg is then passively extended on the thigh, a certain amount of reflex contraction of the hamstring muscles will prevent full extension in the patient with meningeal irritation. Since many patients with meningeal irritation are too ill to sit comfortably on the side of the bed, a modified version of the test is more commonly used to elicit the sign. The patient lies supine in bed while one leg is lifted passively so that the thigh is at right angles to the trunk and the leg is at right angles to the thigh. With the thigh in this position, passive extension of the leg on the thigh is attempted. In the patient with meningeal irritation the extension will be halted by contraction of the hamstring muscles. In addition to the limitation of passive extension of the leg, other phenomena occur with regularity.
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