Micromanipulation: Assisted Fertilization
Micromanipulation has been used for animal research for decades. This technology was not applied to human oocytes until the mid-1980s. Micromanipulation is used in cases of severe male factor with IVF in an attempt to improve fertilization rates. The first micromanipulation procedure involved a zona-drilling technique described by Gordon and Talansky, where small holes were drilled in the zona pellucida with the used of acidified Tyrodes media released through micropipettes. Although fertilization rates of 25 percent were achieved, half of the fertilized oocytes were polyspermic (fertilized by two or more sperm).
Partial Zona Dissection (PZD)
Malter and Cohen first described a technique involving partial dissection of the zona by placing a small slit into the zona instead of a drilling procedure. This method relied on mechanical tearing of the zona, which was achieved, by placement of a micropipette through the zona pellucida and impaling the zona against a stationary holding pipette. Although polyspermic embryo production approached that of zona-drilling; the overall monospermic rate was higher (24 percent) when compared to zona drilling (13 percent). Although fertilization rates were higher, the ultimate pregnancy rates from PZD and zona-drilled embryos were disappointing.
Subzonal Insertion (SUZI)
The technique of microinjection of sperm underneath the zona into the perivitelline space of the oocyte was reported by Metka and colleagues in 1985 and the first human pregnancy was reported by Ng and colleagues in 1988. The monospermic fertilization rates were comparable or slightly better than PZD, however, polyspermic rates were high compared to routine IVF.
Intracytoplasmic Sperm Injection (ICSI)
In 1992, Palermo and colleagues reported the use of ICSI for the treatment of severe male factor. This technique injects a single sperm into the cytoplasm of the oocyte. Monospermic fertilization rates approach 65 percent. In 1996, 30 percent of ART cycles utilized ICSI replacing PZD and SUZI for treatment of male factor infertility.
Micro-epididymal Sperm Aspiration (MESA)
This is a technique used to aspirate sperm from the epididymis of men who have congenital absence of the vas deferens. The MESA technique can be combined with in vitro fertilization with ICSI for couples afflicted with this condition.
Sperm obtained from testicular tissue has been combined with ICSI to treat male factor in men with poor quality sperm when no sperm are retrieved by MESA.Physician Resources