Intracytoplasmic Sperm Injection (ICSI) is a procedure where a sperm cell is injected directly into an ovum in vitro. ICSI is recommended for couples faced with male infertility, such as low sperm count, poor sperm motility, poor sperm quality, sperm unable to penetrate an egg; or azoospermia, the absence of sperm in semen.
Sperm may be retrieved from the male partner through normal ejaculation, however there are indications for alternative methods of retrieval, especially in cases where the patient has azoospermia due to obstruction. Needle aspiration allows for sperm retrieval to be done quickly and easily. This procedure is usually done under sedation, with minimal discomfort. If the man had previously undergone a vasectomy, microsurgical vasectomy reversal can be performed, thereby allowing sperm to be released during ejaculation as per normal.
ICSI is performed according to the following steps:
- Under high-power magnification, a specialized pipette is used to hold the mature ovum in place.
- Using a delicate, sharp hollow needle, a single sperm cell is aspirated for injection.
- The needle is carefully inserted through the oolemma (i.e. outer shell) and into the cytoplasm of the ovum.
- The sperm is injected into the ovum’s cytoplasm to achieve fertilization, and the needle is withdrawn.
- The ovum is examined for evidence of successful fertilization.
Intracytoplasmic sperm injection differs from natural fertilization in several important ways. Under normal circumstances, sperm compete for fertilization and only the most mature, viable sperm cell penetrates the ovum and is allowed to fertilize the egg. In place of this feature, a selection device is used to harvest the most mature sperm cells for ICSI. Mature sperm cells are of high quality, showing fewer DNA strand breaks and lower levels of aneuploidy (i.e. abnormal number of genes or chromosomal regions). Thus, the sperm cell that is injected into the ovum would have had a good chance of fertilizing it naturally.
After repeated unsuccessful traditional IVF trials, intracytoplasmic sperm injection can be implemented to enhance the fertilization phase of in vitro fertilization, and in some countries, ICSI technology is implemented right away. Using healthy ova of good quality, ICSI is successful in treating men with impaired sperm or azoospermia. It is also useful for couples interested in testing for genetic disorders. Since only one sperm cell is used for fertilization, false positive genetic testing results due to contamination of the sample by other sperm cells can be ruled out.