The newest of the aspiration techniques is testicular sperm retrieval (TESA - TESE). In this procedure, a small amount of testis tissue is taken by biopsy under local anesthesia. It is a breakthrough in that it demonstrates that sperm do not have to "mature" and pass through the epididymis in order to fertilize an egg. Because of their immaturity, however, testicular sperm need ICSI.
Testicular sperm extraction is indicated for patients in whom there is a blockage in the epididymis very near the testis (either from prior surgery, infection or from birth), or a blockage within the ducts of the testes (efferent ductules).
It is also used for men with extremely poor sperm production, in which so few sperm are produced that they cannot reach the ejaculate. Pregnancies are now routine in cases of poor sperm production, but there is some concern with the use of this sperm because in most cases the underlying condition causing the poor sperm production is still unknown.
Therefore, in these cases, it must be realized that the condition which may have caused the infertility, may be transmitted to the progeny. Recently, even spermatids (round cells that eventually become a sperm with a tail) have been used to achieve pregnancies with ICSI.
However, this has raised much speculation and concern about the use of genetic material from a still-evolving germ cell for clinical purposes before the system has been appropriately investigated and its genetic stability examined in animal models.
Spermatid injections are currently considered experimental procedures. One drawback of testis sperm is that is does not freeze as readily as epididymal or vasal sperm and thus it is more likely that the male partner will need to undergo repeated procedures for each IVF attempt.