Spermatozoa are normally produced in the testes, however they may not be present in the sperm sample of some men. This may be due to:
- Sterilization
- blockage of the vas deferens
- incomplete spermatozoa development.
These are treated with puncture using a fine needle of either the epididymis (Microepididymal sperm aspiration – MESA) or the testes (testicular sperm aspiration – TESA). This procedure is performed under anaesthesia and is very effective if combined with micromanipulation (ICSI).