SPINAL CORD EJACULATION MECHANISM REVEALED

Researchers have identified a specialized area of neurons in the spinal cord that coordinate ejaculation, raising the possibility that electrical or pharmacologic interventions to stimulate this area could be used to help the process occur.

The French scientists pioneering the research are working with spinal cord injury patients, who, they say, would be the first target population for any interventional approaches.

But they also suggest that their findings might lead to treatments for the broader male population who experience problems with ejaculation. These could include interventions to stimulate or inhibit this area to accelerate or delay ejaculation, depending on the individual's needs.

Their research was published online on December 5 in the Annals of Neurology.

"This study describes SEG [spinal ejaculation generator] in humans and opens up new research avenues for the treatment of ejaculatory disorders including anejaculation, which can be reported as an 'inability to climax,'" the researchers conclude. "The SEG may be targeted by pharmacological and/or epidural electrical or magnetic stimulation."

They add, however, that the priority for future research should be the restoration of ejaculation in patients with spinal cord injury, thus alleviating the need for assisted reproductive techniques.

Senior author, François Giuliano, MD, Hôpital Raymond Poincaré, Garches, France, explained to Medscape Medical News that a major issue for many male patients with spinal cord injury is that they cannot ejaculate and provide sperm for procreation.

"Spinal cord injury patients are often young — having had sports or motor accidents — and many of the males have not yet fathered a child, but procreation is still important for them. I deal with these patients every day and most express the wish to be able to have a child."

He noted that 9 of 10 male patients with spinal cord injury cannot ejaculate normally. "Although some patients can manage sexual intercourse — often with the help of erectile dysfunction drugs — most will still not be able to ejaculate. For the purposes of retrieval of sperm for procreation, ejaculation is possible for some of these patients with intense stimulation of the penis with medical intervention, but for others this is still insufficient. Our discovery of the area of the spinal cord involved could lead to treatments to make this possible."

The current research involved two parts:

1. A retrospective clinical analysis of 384 patients with spinal cord injury to investigate whether the ability to ejaculate in response to intense penile vibratory stimulation (PVS) was connected to site of injury; and
2. A neuroanatomic analysis of spinal cord tissue from postmortem samples from six men and six women without spinal cord injury, in which the researchers looked for different markers known to characterize neurons that control ejaculation in male rats.

Dr Giuliano explained that previous research has established that rats have a specialized area of neurons in the spinal cord that coordinates ejaculation. This has been termed "spinal ejaculation generator."

This is a small group of neurons which controls every single physiological event that leads to ejaculation. This is a complex sexual response involving many different processes from the transport of sperm from the testes to the expulsion of semen from the urethra, which all appears to be coordinated at a spinal cord level."

"We have found that human males — but not females — have the same such organization of neurons."

The results of the clinical investigation concurred with those of the anatomic study in that injury of L3–L5 segments of the spinal cord was the sole independent predictor for failure of PVS to induce ejaculation, and the L3–L5 segments are where the spinal ejaculation generator neurons were found.

Dr Giuliano commented: "There is perfect corroboration between the neuroanatomical study and the clinical data."

He added: "We believe this area of specialized neurons coordinates stimuli from the periphery and from the brain to produce ejaculation, but when there is an injury to the L3–L5 segment of spinal cord there is a disconnect from the brain and spinal cord and peripheral stimulation alone is not enough."

"The hope is that now we have identified this specialized area of the spinal cord, we can use other ways of stimulating these neurons — maybe with electrical, magnetic, or pharmacologic methods — to enable ejaculation to occur."

He explained that the concept is similar to spinal generators for walking or breathing. "A mix of electrical and pharmacological stimulations are being developed to help restore ability to walk. The same principle could be applied for the ability to ejaculate."

Dr Giuliano noted, however, that even if patients with spinal cord injury regain the ability to ejaculate, it is very unlikely that they will experience sexual climax. "Most spinal cord injury patients have a complete loss of sensation within the pelvis. Even if we are able to restore ejaculation, I would doubt that this would enable climax to be experienced for these patients."

But he pointed out that there are other benefits of ejaculation for such patients. "For example, many spinal cord patients have spasticity — a strong and undesired contraction of striated muscles in their limbs — and for some unknown reason this is relieved for many hours after ejaculation, which induces a sense of relaxation. This in itself is pleasurable. This is something that is not well understood but is well documented."

Dr Giuliano added, however, that for men without spinal cord injury, assistance with ejaculation would be expected to also facilitate climax.