ICSI is a process of direct injection of a single sperm into the cytoplasm of an oocyte. It has been performed extensively in multiple centers to treat patients with severe male factor infertility. Till date, the success of ICSI procedures has been related to several factors, like, the viability of the spermatozoon, the quality of the oocyte, effective activation of the oocyte, and the ability of the oocyte to tolerate intra-cytoplasmic manipulation. This technique is used in the situations where standard IVF is unlikely to succeed as in patients with less than 500,000 motile sperm present in the ejaculate or less than 4% normal forms with strict criteria evaluation. In addition, couples who have failed to fertilize any oocytes in a prior IVF cycle are considered appropriate candidates for IVF-ICSI.
The method of ICSI proceeds as follows-
i)Oocyte processing: the oocytes are prepared by removing the cumulus mass and corona radiata with hyaluronidase. The oocytes are then examined under the inverted microscope to assess the maturation stage by observing the presence of a germinal vesicle, germinal vesicle breakdown, and the extruded first polar body. Metaphase II oocytes are identified by the presence of the extruded first polar body. Intracytoplasmic sperm injection is performed on all metaphase II oocytes.
ii) Metaphase II oocytes have their diploid complement of chromosomes delicately arranged on the metaphase plate near the polar body. The mechanical disruption of the metaphase plate can occur by injury from the injection pipette or the presence of a motile sperm in the oocyte cytoplasm. Each oocyte is placed in a droplet of medium surrounding the central droplet which contains the spermatozoa.
iii) The droplets are covered with lightweight paraffin oil and the petri dish is placed on a heated stage of the microscope. The microscope is equipped with two hydraulic micromanipulators which are fitted to two tool holders for the micropipettes. During the injection procedure oocytes are stabilized with a holding micropipette, and injected with an injection pipette.
iv) The polar body is held at the 12 or 6 o'clock position and the injection micropipette containing the single sperm is pushed through the zona pellucida and oolemma into the cytoplasm of the oocyte at the 3 o'clock position. A single sperm is injected head first into the ooplasm with 1-2 pl of medium. The injection pipette is withdrawn gently and the oocyte is released from the holding pipette. Further handling of injected oocytes is similar to that for oocytes in standard IVF.
The key factors affecting the outcome of ICSI are as said:-
â€¢ Spermatozoal factors: the only criterion for successful ICSI is the presence of at least one viable spermatozoon to inject per oocyte in the prepared pellet of the washed semen sample.
â€¢ Female factors: the fertilization rates are unaffected by maternal age, but pregnancy rates were significantly lower with increased maternal age. Pregnancy rates are known to be 49, 23 and 6 percent for couples in whom maternal age was more than 34, between 35 and 39, and more than 40 years.
â€¢ Cytoplasmic Injection/oocyte injury: Disruption of the oocyte sufficient to cause oocyte demise may occur during ICSI. Results from some of the major centers performing ICSI show rates of oocyte loss after injection of 7 to 14 percent. Although the precise reasons for oocyte injury are not known, it is though to occur as a result of plasma membrane and ultrastructural disturbances associated with injection, damage to the meiotic spindle during injection, and/or extrusion of the oocyte cytoplasm following injection.
â€¢ The changes in temperature causes irreversible changes in the meiotic spindle of the human oocyte.
The risk factors associated with ICSI include general risks of IVF as well as the specific risks related to the micromanipulation procedure of ICSI. One of the most significant risks associated with stimulation of the ovaries is the ovarian hyperstimulation syndrome (OHSS). This can manifest as massive ovarian enlargement, peritoneal irritation due to follicular rupture or hemorrhage, ovarian torsion, ascites, pleural effusion, oliguria, electrolyte imbalance, hypercoagulability and sometimes death. The syndrome occurs in a moderate form for 3-4% percent of initiated cycles, and in a severe form for 0. 1-0.2 % of the population undergoing controlled ovarian hyperstimulation. Other reported complications of ovarian hyperstimulation are pituitary hemorrhage, endometriotic bloody ascites, and genital cancer. Complications of ovarian retrieval have been reported for transvaginal aspiration as well as laparoscopic aspiration. After achieving a clinical pregnancy, the chance of a spontaneous abortion occurring for IVF-ICSI cycles ranges from 10-16%. Ectopic pregnancies occur in up to 3-5.5 % of gestational cycles and can be life threatening. The etiology is usually pelvic adhesions and tubal damage from pelvic inflammatory disease or previous surgery. Multifetal pregnancies occur in 22 percent of cases of IVF with embryo transfer, and 44 to 46 percent of ICSI cases.
Every technology comes with some demerits. The line of control between natural and artificial thing can be lightened but not removed. The birth defects associated with these technologies have been observed lately. Of 877 children born after ICSI procedures, 23 (2.6 percent) had major congenital malformations compared to 2.0 to 2.8 percent in the general population and 1.9 to 2.9 percent of children resulting from assisted reproductive techniques. Sex chromosomal abnormalities have also been reported in ICSI cases.
Since the report of a successful delivery from in vitro fertilization in the year 1978, the advances in the field of assisted reproduction and micromanipulation have been truly dramatic. The phenomenon of ICSI has proved to be fruitful in the area of male infertility. Previously, couples were forced to depend on the techniques of donor insemination or adoption. But now the situations have changed. The couples can expect despite severe impairments in semen quality or low sperm count, even the presence of a single sperm in the ejaculate is no more a barrier. The older techniques of micromanipulation that was revolutionary less than five years ago are now obsolete and are replaced by even more successful methods. The non-obstructive azoospermia due to maturation arrest or other impairments in germ cell maturation have been added to the list of treatable factors in male infertility since sperm can frequently be extracted directly from testicular parenchyma that is surgically biopsied. ICSI is a boon for the patients without sperm in the testicular parenchyma, round spermatid or secondary spermatocyte.
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