Necrozoospermia: when sperm are dead rather than still
A sample where almost nothing is moving has two very different explanations: the sperm are alive but cannot swim, or they are dead. Necrozoospermia is the second. Only a vitality stain can tell them apart, and the answer changes what can be done.
Why vitality testing is the whole question
Motility and vitality are not the same measurement. A vitality test — usually eosin-nigrosin staining or a hypo-osmotic swelling test — works because dye penetrates the damaged membrane of a dead sperm but is excluded by a live one. WHO sets the reference limit at 54% vital.
This matters enormously for treatment. Live but immotile sperm can be used for ICSI, and specialised selection techniques can identify viable ones. Genuinely dead sperm cannot fertilise an egg at all. If your report shows very low motility, ask whether vitality was tested — without it, the two situations look identical on paper.
What causes it, and what to do
Infection and inflammation of the reproductive tract are among the most common and most treatable causes, and often appear alongside raised white blood cells. Long periods without ejaculation allow sperm to age and die in storage, so a very long abstinence before the test can produce a misleadingly poor result — repeating with 2 to 3 days of abstinence is a simple first step.
Other contributors include varicocele, oxidative stress, testicular heat exposure, spinal cord injury, and anti-sperm antibodies. Some cases follow no identifiable cause.
Where sperm are dying during storage or transit rather than being produced dead, retrieving sperm directly from the testicle can bypass the problem entirely — testicular sperm are often viable when ejaculated sperm are not.
FAQ
What is the difference between necrozoospermia and asthenozoospermia?
Asthenozoospermia means sperm are alive but not swimming well. Necrozoospermia means they are dead. Both look like "low motility" on a basic report, which is why a vitality stain is needed. Live-but-immotile sperm can still be used for ICSI; dead sperm cannot fertilise an egg.
Can necrozoospermia be treated?
Often, yes. Treating a reproductive tract infection, shortening a very long abstinence period, repairing a varicocele, and reducing oxidative stress all help. Where ejaculated sperm keep coming back dead, sperm retrieved directly from the testicle are frequently viable and can be used with ICSI.
Could a bad result just be how the sample was handled?
Yes. Sperm die quickly when a sample gets cold, sits too long before analysis, or contacts a standard lubricant. A single poor vitality result should be confirmed on a repeat sample produced on-site or delivered promptly, with 2 to 3 days of abstinence.