Rigi10™ Malleable Penile Prosthesis
Also Known As
Teratospermia, Abnormal sperm morphology, Sperm morphological abnormalities, Morphologically abnormal spermatozoa, Sperm shape abnormalities
Definition
Teratozoospermia, also referred to as teratospermia, is a medical condition characterized by the presence of a high percentage of abnormally shaped (morphologically abnormal) sperm in a man’s ejaculate.1 This condition is a significant consideration in the evaluation of male infertility, as the precise structure of a spermatozoon is critical for its journey through the female reproductive tract and its ultimate ability to successfully fertilize an oocyte. The term ‘terato-‘ originates from Greek, meaning monster, reflecting the abnormal forms of the sperm. Sperm morphology is assessed during a semen analysis, where the shape and size of the sperm head, midpiece, and tail are examined under a microscope. According to the stringent criteria, such as Kruger’s strict criteria which are often incorporated into World Health Organization (WHO) guidelines, teratozoospermia is typically diagnosed when the percentage of sperm with normal morphology is below 4%.1 This means that over 96% of the observed sperm exhibit some form of structural defect. These defects can be highly varied, including heads that are too large (macrocephaly), too small (microcephaly), tapered, pyriform (pear-shaped), or amorphous (lacking a defined shape), as well as abnormalities in the acrosome (the cap-like structure on the sperm head essential for egg penetration). Midpiece defects might include being bent, asymmetric, or too thick/thin, while tail abnormalities can involve being coiled, short, multiple, or absent. The presence of these morphological defects can impair sperm motility, making it difficult for sperm to swim effectively towards the egg. Furthermore, abnormal morphology can interfere with the sperm’s capacity to penetrate the cervical mucus, bind to the zona pellucida (the outer layer of the egg), and undergo the acrosome reaction, which is necessary for fertilization.1 Isolated teratozoospermia is a specific diagnosis where abnormal sperm morphology is the only significant finding in the semen analysis, with other parameters such as sperm concentration (count) and motility falling within normal reference ranges.1 Understanding the nuances of teratozoospermia is crucial for diagnosing male infertility and guiding appropriate clinical management and treatment strategies.1
Clinical Context
Teratozoospermia is clinically relevant in the context of male infertility investigations. When a couple experiences difficulty conceiving, a semen analysis is a fundamental component of the male partner’s evaluation, and sperm morphology is a key parameter assessed.1 Isolated teratozoospermia, where abnormal sperm shape is the primary or sole abnormality in the semen analysis (with normal sperm count and motility), presents a particular clinical challenge due to conflicting data on its precise impact on natural fertility and the outcomes of assisted reproductive technologies (ART).1
Clinically, teratozoospermia is considered when the percentage of morphologically normal spermatozoa falls below established lower reference limits, often 4% according to Kruger’s strict criteria.1 The presence of a high number of abnormally shaped sperm can indicate underlying issues with spermatogenesis (sperm production) or sperm maturation. Various factors can contribute to teratozoospermia, including genetic predispositions, hormonal imbalances, varicocele (enlargement of veins within the scrotum), infections of the reproductive tract, exposure to gonadotoxins (e.g., certain medications, radiation, chemotherapy, environmental toxins), oxidative stress, and lifestyle factors such as smoking, excessive alcohol consumption, and obesity.1
Patient selection for further investigation or specific treatments often depends on the severity of teratozoospermia, the presence of other male infertility factors, the female partner’s fertility status, and the couple’s reproductive goals. For instance, in cases of severe teratozoospermia, particularly when associated with other sperm abnormalities (oligoasthenoteratozoospermia – OAT), or when specific genetic defects affecting sperm morphology are identified (e.g., globozoospermia, macrocephalic sperm syndrome), more advanced ART procedures like Intracytoplasmic Sperm Injection (ICSI) are often recommended.1 ICSI involves the direct injection of a single selected sperm into an egg, bypassing many of the natural barriers to fertilization that morphologically abnormal sperm may struggle to overcome.
Surgical procedures may be considered if an underlying correctable cause is identified, such as varicocelectomy for a clinically significant varicocele, although the impact of varicocele repair on isolated teratozoospermia specifically is a subject of ongoing research and debate.1
Expected outcomes for couples where the male partner has teratozoospermia are variable. Some studies suggest that even with isolated teratozoospermia, natural conception is possible, albeit potentially at a lower rate.1 For those undergoing ART, the data is mixed. While severe teratozoospermia was historically considered a strong indication for ICSI, some recent meta-analyses suggest that isolated teratozoospermia may not be strongly associated with poor fertility outcomes from standard In Vitro Fertilization (IVF) or even Intrauterine Insemination (IUI) in certain cases.1 However, the presence of specific sperm head defects, which can correlate with sperm DNA damage, elevated oxidative stress, and apoptotic alterations, may negatively impact embryo development and pregnancy rates even with ART.1 Therefore, a comprehensive clinical evaluation, including potential advanced sperm function tests, is crucial to guide treatment decisions and counsel patients appropriately regarding their chances of achieving a successful pregnancy.1