It has been known for many years that in certain cases of central facial palsy, the muscles on one side of the face which fail to contract to voluntary innervation may do so in laughing. Monrad-Krohn has shown that the contraction of the facial muscles in laughing may be even greater on the side paralyzed for voluntary innervation than on the normal side. At the meeting of the American Neurological Association in May, 1927, he reported cases of this type but did not give any explanation. It seems to me that the condition of the deep sensation of the facial muscles may have some influence over the degree of contraction of these muscles, and that when this sensation is lost, contraction of these muscles may be affected. I made reference to this fact in discussing Monrad-Krohn's paper.
In April 1906, I reported1 two cases before the Philadelphia Neurological Society