Background: Asthenozoospermia is a status of low or absent sperm motility in fresh ejaculate. Absolute
asthenozoospermia, i.e., 100% immotile sperms, is reported in one of 5000 men. Many factors are involved in impaired sperm motility and in turn male factor infertility. The ultrastructure defects of sperm tail are considered the most important factors that cause severe asthenozoospermia.
Aim: To evaluate the ultrastructure abnormalities of the sperm tail in infertile men with severe asthenozoospermia.
Patients and Methods: This study was conducted on 22 asthenozoospermic (total motility < 5%) infertile patients and 10
matched fertile controls. Sperm motility was evaluated by Computer-Aided Semen Analysis (CASA). Ultrastructural defects of the sperm tail were evaluated using transmission electron microscope (TEM).
Results: Sperm tail defects were evident in 100% of the examined cases in this order of frequency : microtubular disturbance (91%), mitochondrial anomalies (45%), and fibrous sheath dysplasia (9%). Most of the cases showed more than one anomaly.  Patients with mitochondria anomalies had the least total motility (1.93±1.73), while patients with microtubular disturbance had the highest total motility (3.02±0.53). Moreover, patients with complex anomalies revealed the least total motility (1.5%).
Conclusion: Transmission electron microscope is a vital step that should be performed in infertile men with severe
asthenozoospermia who are resistant to medical treatment.