Easily decapitated spermatozoa defect: a possible cause of unexplained infertility

We report the first 16 cases of a new sperm abnormality which we call 'easi ly decapitated spermatozoa defect'. This was discovered during intracytopla smic sperm injection (ICSI) in couples with unexplained infertility. Semen analysis was normal, but minimal micromanipulation for ICSI resulted in dec apitation of the spermatozoon during immobilization, For some oocytes the h ead and tail were injected separately, in others the intact sperm was injec ted after minimal immobilization, A fertilization rate of 47.5% was obtaine d using ICSI, Conventional in-vitro fertilization (IVF) on sibling oocytes (three cases) or in a previous cycle (three cases) resulted in total failur e of fertilization, All patients reached the embryo transfer stage and thre e pregnancies resulted, Findings on electron microscopy in four cases inclu ded spermatozoa with degeneration or absence of the basal plate, abnormalit ies of the proximal centriole and degeneration of the midpiece with a large cytoplasmic droplet. We conclude that an occult sperm abnormality presenti ng as easily decapitated spermatozoa during ICSI could be a cause of unexpl ained infertility, as it resulted in total failure of fertilization in conv entional IVF. Further research is necessary to investigate this sperm abnor mality.