Intracytoplasmic Sperm Injection (ICSI)
Intracytoplasmic Sperm Injection (ICSI) is a form of gamete (sperm and egg) micromanipulation that involves the direct injection of a single sperm into the cytoplasm (inside portion) of an oocyte (egg). ICSI is used for several reasons:
Previous IVF cycles with poor fertilization results. When someone has poor fertilization in a previous cycle the ICSI procedure can improve the chances of fertilization. If normal fertilization will occur through standard IVF then ICSI may not be useful.
Poor semen parameters. If the semen analysis and semen profile indicate there is a significant problem for fertilization to occur you may be advised to choose ICSI. Using motility, morphology, and sperm concentration, clinics make recommendation of ICSI in the interest of maximizing fertilization. When any of these parameters are below what is considered normal, ICSI may be of benefit. The goal of performing ICSI is to minimize the risk of fertilization failure. It is very important to understand that it is not just sperm numbers that matter here. When sperm are in reduced numbers or have abnormal morphology and motility, the function of the sperm can be significantly impaired. While there may be plenty of sperm for fertilization, their ability to penetrate the outer layer of the oocyte, the zona, may be impaired. ICSI overcomes this by placing a single sperm within the egg.
Oligospermia and Azoospermia. Male patients that do not produce sperm may have to undergo procedures involving aspiration of sperm from the epididymis of the testicle or from a testicular biopsy. Some men have a congenital absence of the duct that transports sperm known as the vas deferens while others may have acquired obstructions of the genital tract from things such as scar tissue, infections, and vasectomies. Other causes for azoospermia include deficiencies in sperm production that may be due to physical or hormonal defects. For more information about sperm extraction procedures, including MESA and PESA, click here.
After the eggs are harvested and identified by the embryologist, the outer layer of cells around each egg, known as the cumulus oophorus, is removed. The cumulus oophorus is made up of hormone secreting cells known as granulosa cells. Removing the granulosa cells reveals the outer shell around the egg known as the zona pellucida. By using a powerful microscope we are able to isolate a single sperm, aspirate it into an extremely thin glass pipette and inject it through the zona pellucida into a single egg. In the image below, the pipelle on the left is used to hold the oocyte in position while the glass pipette on the right is injecting a sperm into the cytoplasm. A single sperm is injected into each egg. The procedure is repeated until all eggs are fertilized.
Risks associated with ICSI
ICSI has been performed for many years with multiple studies being done to look for problems associated with the use of ICSI. There have been several research papers suggesting there may be an increased risk associated with ICSI though this increase in risk has been challenged by many other papers. It is fairly well accepted that there is an increased risk of Y-chromosome microdeletions occurring in the population of males who need ICSI. The Y-chromosome microdeletion or YCD is a genetic abnormality occurring on the Y chromosome. The Y chromosome contains the genetic information that tells the body how to make sperm. Approximately 2% of men with an abnormal semen analysis will have a microdeletion of the Y chromosome. If a male offspring results from the procedure, the child will inherit the fathers Y chromosome and therefore will inherit the deletion on the Y chromosome. This would likely lead to the child having problems with sperm production in the future. A Y-chromosome microdeletion can also be associated with an increased risk of hypospadeus, a condition where the opening of the penis is on the bottom side of the shaft instead at the tip of the penis. In the setting of a YCD, hypospadeus is thought to occur in 1 in 100 births instead of the normal incidence of 1 in 350 births. Donor sperm could be used as an alternative to ICSI but this is not usually necessary as the risks are considered relatively low.