Due to the development of ICSI, the need for fewer and fewer number of sperm to accomplish fertilization has led to novel ways of obtaining sperm.
Prior to ICSI, many more sperm were needed and procedures such as microepidymal sperm aspiration (MESA), which required general anesthesia and took several hours to perform, were employed to obtain sperm from men with congenital absence of the vas or in place of vasectomy reversal. Men with severe oligospermia , azoospermia by semen analysis, and Sertoli cell only syndrome were unable to be treated with this approach.
Since the advent of ICSI, the number of sperm necessary for fertilization theoretically equals the number of eggs (oocytes) available, thus allowing sperm recovery methods that produce a much smaller but adequate number of sperm. PESA can be used for men with congenital absence of the vas and in lieu of vasectomy reversal. This procedure involves insertion of a small needle, under local anesthesia, directly into the epididymis for aspiration of a fewer number of sperm than would be necessary for fertilization by conventional IVF. However, in most cases there are more than enough sperm to fertilize all female eggs by ICSI. With newer cryopreservation techniques, there may even be sufficient numbers of sperm for freezing so that additional ICSI procedures could be performed in the future without the need to obtain more fresh sperm.
Testicular Sperm Extraction – TESE
TESE is a procedure which is rapidly becoming the procedure of choice for many men with severe male factor problems in relation to male infertility. A testicular biopsy is performed under local anesthesia or light sedation and the sperm are extracted from the biopsy specimen by the embryologist. These sperm sometimes lack motility, and fertilization rates are less than with ejaculated or epididymal sperm, yet fertilization is possible even for some men with complete azoospermia by semen analysis, those with Sertoli cell only syndrome if islands of active spermatogenesis can be located, and by some reports even when immature forms of sperm are used.
From these scenarios, what is becoming apparent is that fertilization is possible as long as the genetic material from the sperm is transferable into the female egg. Whereas we once believed that the shape of the sperm, their number and ability to progressively move were the major factors determining the fertility potential of an individual, it is likely from our experience with ICSI, that the normalcy of the genetic material is all that is important in this regard. The sperm itself is simply the messenger for delivering the genetic package. Therefore, as technological advances allow ways of obtaining at least the genetic material from the sperm, we will continue to increase the types of male infertility problems that ART can successfully treat.