commissurotomy
/ˌkɒmɪsjəˈrɒtəmi/ /ˌkɒmɪʃəˈrɒtəmi/Surgery and Medicine
noun
1The procedure of widening the orifice of a valve of the heart, especially the mitral valve, originally by incisions made at the commissures of the orifice and later also by other techniques; an instance of this.
2The procedure of incising or dividing a commissure of the nervous system; an instance of this.
Origin
1940s. From commissure + -o- + -tomy.