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MIAMI -- The oft-cited claim that there are more than 8,000 nerve endings in the clitoris comes from a 1976 by Thomas Lowry and Thea Lowry, in reference to a study of cows. No one had fact-checked that claim in humans -- until now.

There are, in fact, an average of 10,280 nerve fibers according to a histomorphometric evaluation of the dorsal nerve of the clitoris presented by Blair Peters, MD, of Oregon Health & Science University in Portland, at the Sexual Medicine Society of North America annual meeting.

"This information is already directly informing techniques I use to optimize sensation in gender-affirming surgeries, and should inform future work" related to restoring sensation for patients with dorsal nerve or clitoris injuries, said Peters.

The researchers found a mean number of 5,140 nerve fibers (range 4,926 to 5,543) in individual clitoral dorsal nerve samples from consenting transmasculine patients undergoing phalloplasty. Because there are two dorsal nerves in the clitoris, doubling the mean nerve fibers count brought the number to 10,280 (range 9,852 to 11,086).

"Compare that to the median nerve that we're all familiar with for carpal tunnel syndrome that innervates most of the human hand -- that is 18,000 nerve fibers," said Peters. "So compare the size of a hand to the size of the glans of the clitoris, and it gives you context of how densely innervated the structure actually is."

While medical study of the penis, including its sensory anatomy, is extensive, the clitoris has long been overlooked in medical literature, and its nerves poorly represented in medical textbooks. The "8,000" figure was originally questioned in 2018 by activist Jessica Pin, who came from livestock studies. Pin has subsequently pushed for including information about clitoral nerves in medical textbooks.

Quantifying the nerve fibers in the human clitoris has a range of practical applications, from improving reconstruction following clitoral injuries, restoration following genital mutilation, and improving sensory outcomes in gender-affirming surgery.

"There are people who have entire fellowships that are devoted to preserving erectile function, making erections straight, and they spend years and years doing this really specialized technical training, becoming really familiar with the innervation of not only the skin, but the corporal bodies that fill with blood," said Rainey Horwitz, MS, a medical student at St. Louis University School of Medicine, who was not involved in the study. "Not a single specialty has done that for the clitoris, or really feels any urgency or need to do that."

Kimberly Lovie, MD, director of medical imaging and AI at New H Medical in New York City and the director of research and development at the sexual wellness company Cerē, said that this research is a basis for preventing damage to the clitoris during surgery for endometriosis or labiaplasty, for example.

For many other parts of the body, "you do after-imaging to see if your surgery helped, if it caused harm by accident, and to see if there were any complications," said Lovie, who was not involved in the study. "And that's really not done for the vulva at all. It's not done for the clitoris."

Researchers used dorsal clitoral nerve samples from seven transmasculine patients prior to phalloplasty. To count the nerves, the 5 mm samples were sectioned into thin 1 μm cross-sections, stained, and then magnified 1,000 times using a microscope and imaging software. The researchers assumed anatomic symmetry of the two dorsal nerves to get their total nerve count. Peters noted that the study did not account for unmyelinated nerves, so the count is likely higher.

Neither Horwitz nor Lovie said they had ever learned about the anatomy of the clitoris in medical school, a fact that bothered them when patients asked questions.

"The significance is," Horwitz said of the new study, "we're not cows."

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