A needle in a haystack? Best to use a microscope.
Background: For men who have no sperm in the ejaculate (non-obstructive azoospermia), there are several sperm retrieval techniques that can be used all of which involve obtaining sperm either with a small scrotal and testicular incision (testicular sperm extraction, TESE) or needle placed into the testicle (testicular sperm aspiration, TESA; Fine Needle Aspiration, FNA mapping). The optimal technique which results in the least scarring to the testicle is microdissection testicular sperm extraction (microTESE). MicroTESE is the technique utilized to search through the seminiferous tubules of each testis to identify and obtain sperm (if present) from the testes of men with non-obstructive azoospermia. If sperm are identified (as few as just several sperm could be adequate), these may be used for fertilization using in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).
Predictive factors for microTESE: Men who are older or have smaller testes, higher FSH, or higher BMI levels are do not have worse sperm retrieval rates with microTESE. MicroTESE is successful post-chemotherapy as well with varying rates depending on the type of chemotherapy regimen. However, male BMI is a predictor of successful pregnancy.
You only need one sperm: With the use of IVF and ICSI since the 1990’s, millions of motile sperm are no longer required to fertilize an egg. The procedure can be performed with the best sperm available, but can be completed successfully with a single non-motile sperm. The embryologist selects a specific sperm and the sperm is placed in a small hollow needle. This needle is used to pierce the outer layer of the egg, and the sperm is injected into the egg cytoplasm (center). Following this, the egg (now with sperm inside) is placed in the incubator and then checked for signs of fertilization.
What is ICSI? you may ask: ICSI is an in vitro fertilization procedure during which a single sperm is directly injected into the eggs which have been obtained from the female partner. Prior to the use of ICSI in the 1990’s, the only option for men with poor semen parameters and male factor infertility was donor sperm or adoption.
Following ICSI, successful fertilization is required for embryos to form. Fertilization is a complicated process during which one sperm unites with an activated egg (oocyte). The most important steps for successful fertilization include sperm capacitation, sperm binding to the egg’s outer coating (zone pellucida), and fusion with the egg. After the sperm enters the egg’s cytoplasm, a reaction occurs (the cortical reaction), preventing more sperm from fertilizing the same egg. The oocyte then completes its second (meiotic) division producing the final egg (haploid ovum) and releasing a polar body. The sperm nucleus then fuses with the ovum with fusion of the sperm and egg’s genetic material. There are many possible reasons for fertilization to be unsuccessful which will be considered in the management by your physicians.
For additional information about the initial workup for non-obstructive azoospermia and considerations before microTESE, please visit the Center for Male Health and Reproduction site. You may also contact us with any additional questions and our physician team will respond.