IMSI (Intracytoplasmic Morphologically Selected Sperm Injection)
Up to now, testing and selecting ejaculated sperm or sperm from the testicles for its later use in ICSI was based in the observation of the head, tail and the intermediate segment of the gamete. However, the observation criteria and the selection of the spermatozoa to be microinjected is chosen by the specialist which gives certain subjectivity to the technique. For this reason some modification have been introduced in the ICSI procedure that led to IMSI (Intracytoplasmic Morphologically Selected Sperm Injection).
Advantages of IMSI
This new technique offers many advantages, among them selection of the gamete in real time, without damaging staining stands out. Besides, it is possible to observe them with a 6,300 magnifications facing the 400 magnifications of common ICSI. This detailed display allows biologists to dismiss those gametes with a bad morphology, i.e., those spermatozoa with defects in their head, intermediate segment or in the tail.
According to the WHO, and ideal spermatozoon should have an oval head, straight tail and a fixed, transparent core. Any deformed spermatozoon would not be chosen to
fertilise the egg because it may lead to a failure in the fertilisation and increase the risk of miscarriages.
Indications for IMSI
This technique is recommended in cases of:
- Several unsuccessful transfer attempts, either for the inability to fertilise an egg or because the fertilised eggs or embryos have stopped their development
- Patients with severe teratozoospermia
- Patients with altered results in the study of sperm DNA fragmentation
- Cases of long-term infertility with unkown origin
Disadvantages of IMSI
Some of the most obvious disadvantages that impede the spread of this technique are clearly evident. Furthermore, they are making it difficult for IMSI to widespread.
Firstly, the long duration of the procedure that may vary between 1.5 hours and 5 hours.
Secondly, its high cost makes it difficult for every laboratory to practice this technique. And in those laboratories that do practice this technique use it in cases where the low sperm and repeated cases of unsuccessful IVF or ICSI.
Despite of these existing evidences, more research with larger sample sizes should be carried out to demonstrate its clinic effectiveness and to better define its indications.