Photo via Flickr user J Brew

Last month, Brian (who asked we not use his last name) woke up in the middle of the night to the feeling of his dick hardening in his boxers. He could vaguely feel its outline as it tightened, becoming more erect, as his wife lay sleeping next to him. Could this be a dream? he thought. But, almost instantly, the optimism of that latter possibility came crashing down.

"I sort of pushed my hips forward against my boxers and looked for the bulge," he said, "and obviously it was still gone."

A year ago, Brian, a 38-year-old who lives in the Midwest, had a penectomy—the surgical removal of a penis. He'd gone to his doctor, complaining of what he thought might be a genital wart, but after meetings with few specialists, he learned it was late-stage squamous cell carcinoma, a form of skin cancer. Doctors recommended the penectomy.

"That was a bad day," he told me over the phone.

Oddly, since the surgery, he's been struck by an occasional sensation that the penis is still there, like a phantom limb.

For years, patients with phantom limbs were told the phenomenon was "all in their head," but now, research suggests up to 80 percent of people who have had an arm or leg amputated report a feeling of a body part that isn't there. For men who have had their penises amputated, the same holds true.

The phenomenon was first reported by Scottish physicians in the late 1700s, who mentioned phantom penises off-handedly in larger work about phantom limbs, according to a journal article. In 1815, Scottish surgeon Andrew Marshal described a man who'd lost his entire penis: "In the case of W. Scott, whose penis was carried off by a gun-shot, the stump of it, which was even with the skin of the pubis, resumed the peculiar sensibility of the glans penis," he wrote in his notes, which were published in 1815, two years after his death. Another Scottish surgeon, John Hunter, described several instances of the ghost dick in his 1786 book, Observations on Certain Parts of the Animal Oeconomy, including one man who received so much pleasure from his phantom penis that he was able to ejaculate through his "stump."

Unlike phantom limbs, which are known to cause pain, phantom penises seem more often associated with pleasure.

But Wayne Earle, a 48-year-old Australian, finds nothing pleasurable about his phantom penis. Earle, the founder of CheckYourTackle, a website dedicated to raising awareness about male cancers and providing support for cancer victims, had a complete penectomy in 2014 to stop the spread of squamous cell carcinoma.

"I still wake up occasionally with it, and it does get aroused when [my wife] Tracy and I kiss, cuddle, or get close," he told me via Facebook messenger. "This is a big part of my depression, as you still get the sexual urges just like any other man. You still produce testosterone, and the body does self-adjust, but you still get urges and a phantom erection. There is no way that it is pleasurable."

In 1950, in the the journal Transactions of the American Neurological Association, Boston surgeon A. Price Heusner described an elderly man whose penis was "accidentally traumatized and amputated" and had an occasional "painless but always erect penile ghost whose appearances were neither provoked nor provokable by sexual phantasies." The man had to check regularly to make sure it wasn't still there.

A year later, Alfred Crone-Münzebrock published his study of 12 men, cancer survivors who opted for amputation and had remaining stumps. Seven of them reported phantom penises, with two of those men associating the phenomenon with pain.

In 1999, Dr. C. Miller Fisher, a Boston neurologist who died in 2012, published a case study of a 44-year-old businessman whose penile skin cancer, manifested as a painful sore on the penis, necessitated a full penectomy. After the surgery, he reported phantom boners, often resulting from erotic stimulation like "seeing a pretty young woman." The phantom penis was essentially a replica of the one he'd actually had, and he reported feeling phantom pain emanating from the cancerous sore.

It only really happens if I start to think about it. Otherwise, it's more just the general shape and idea of a penis. — Matt

Earle experienced the phantom penis everyday in the six months following his surgery. "It is one of the things that is not really discussed with you and the doctors at the time of diagnosis," he told me. He described the ghost of his penis as mentally, emotionally, and physically painful, saying it was one of the worst experiences of his cancer journey.

"As time went on, it gradually reduced" he wrote, "and [now] I just don't feel it anymore, or in my mind, I have somewhat blocked it out, as most of the muscle that help control erections are still in place."

Theories about the causes of phantom limbs are ever-changing. Most researchers seem to believe that it's the result of maladaptive changes to the brain after surgery. Others think it's related to the nervous system and the spine.

Even less is known about the cause and tendencies of the phantom penis. The lack of penile cancer support groups, compared to other types of cancer, mean less internet discussion of the phenomenon.

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A 2008 study by V.S. Ramachandran, a neuroscientist at UC San Diego who did not respond to multiple requests for comment, revealed completely new angles to the phantom penis phenomenon: In his research, Ramachandran found that trans women who had their penises removed reported experiencing phantom penises at a far lower rate (about 30 percent) than men who've lost penises to penectomies (about 60 percent).

Additionally, he interviewed 29 trans men and found that 18 of them experienced phantom penises, despite never having had an actual penis.

Ramachandran acknowledges that it's possible that these phantom experiences are confabulation, or distorted memories, but he lists seven reasons why he believes they're not. (Among them: Patients could describe their phantoms penises in great detail, could not will them to go away, and many of the phantom penises were different from the patient's "ideal penis" in size, shape, or length.)

Matt, an 18-year-old trans college student in North Carolina who didn't want us to use his last name, said he first felt a phantom penis before he went through puberty.

"At that age, I didn't really understand what it was—just that I could feel something that obviously wasn't there," he wrote to me in an email. "About the time I learned about sex and all of that fun stuff and started going through puberty (13ish) I started to mess around with the whole phantom penis thing. This probably sounds really weird, but I figured out that if I pretended to masturbate like a cis guy, I could feel it. Along with that, thinking about sex gave me what I guess you'd call the 'phantom erection.'"

He's never been able to reach orgasm through this style of masturbation, but he's come close. His "phantom penis" is there about half the time. The shape, he said, is not very defined, but it does stay consistent for the most part.

"I'd say there's like roughly five inches of space where I can tell it's there," he wrote. "I haven't been able to really identify whether or not I can differentiate between the different parts of it. Oddly enough, the phantom testicle thing is rarely apparent. It only really happens if I start to think about it and try to feel it. Otherwise, it's more just the general shape and idea of a penis."

For Matt, who started taking testosterone a few weeks ago (which has boosted the prevalence of the phantom), the phenomenon is bittersweet.

"The presence of it both affirms my self image as a guy and frustrates me, actually," he said. "It's affirming in the sense that I know that I'm a guy, and my body knows as well. On the other hand, it's kind of frustrating to feel the penis and then look in the mirror and have there be nothing—much less something that can be used for sex or using the bathroom, like a cis male."