Hard Flaccid Syndrome Proposed to Be Secondary to Pathological Activation of a Pelvic/Pudendal-Hypogastric Reflex
By: Irwin Goldstein, MD, Alvarado Hospital, San Diego, California, San Diego Sexual Medicine, California; Barry R. Komisaruk, PhD, Rutgers University, Newark, New Jersey; Alyssa Yee, MD, San Diego Sexual Medicine, California | Posted on: 04 May 2023
Hard flaccid syndrome, in which the penis is observed in an unwanted persistent semirigid flaccid state (Figure 1), is an acquired, persistent, painful, and bothersome sexual dysfunction that is poorly understood.1-3 During physical examination, the flaccid penis is shrunken, contracted, and noncompressible, and on palpation feels hard, described by the patient as tender. Most individuals with hard flaccid syndrome are in their 20s or 30s, with multiple biopsychosocial concerns.1-3 Biological complaints include penile morphometric changes such as wrinkles or indents; cold-feeling glans; decreased penile sensation, especially in the glans; urinary symptoms such as decreased force of stream; constipation; high-tone pelvic floor dysfunction; perineal and penile pain during ejaculation; and erectile dysfunction with loss of morning erections. These symptoms often worsen when standing. From a psychosocial perspective, symptoms of hard flaccid syndrome trigger significant emotional distress manifested by anxiety, depression, decreased libido, and insomnia, and inability to maintain romantic relationships.1-3
Patients with hard flaccid syndrome have presented to our sexual medicine practice with increasing frequency as patients read about this topic online. We propose that this syndrome, which presents at the level of the end organ (ie corpora cavernosa), results from excessive sympathetic activity in the hypogastric nerve leading to extreme, unrelenting erectile tissue smooth muscle contraction. This hypothesis is supported in part by the observation that intracavernosal injection of phentolamine (an α-adrenergic antagonist) temporarily resolves the hard flaccid state and induces penile erection.4-7 This implies that the hypogastric nerve plays a role in maintaining baseline sympathetic tone that results in the normal flaccid penile state. However, in patients with hard flaccid syndrome, the proposed excessive sympathetic activity in the hypogastric nerve can account for many of the symptoms resulting from intense pathological smooth muscle contraction of erectile tissue, bladder neck, and rectum (Figure 2).
We propose that the penile pain associated with hard flaccid syndrome is a form of genito-pelvic dysesthesia (GPD).8 An expert panel assembled by the International Society for the Study of Women’s Sexual Health defined the term GPD to represent an unpleasant, atypical sensation (eg, pain) in the genito-pelvic region (eg, genitals). The advantage of using this new classification is that GPD can originate in 1 or more of 5 regions: (1) end organ, (2) pelvis/perineum, (3) cauda equina, (4) spinal cord, (5) and brain.8
Thus, we propose that hard flaccid syndrome is a consequence of pathological activation of a somato-visceral and/or a viscero-visceral reflex that we term a “pelvic/pudendal-hypogastric” reflex. This reflex can be pathologically activated at multiple different anatomical sites via triggers located in regions 1-5 (Figure 3). The afferent limb of this proposed reflex is the dorsal branch of the pudendal (somatic) nerve (S2-4) that conveys penile skin sensation and/or the cavernosal branch of the pelvic (visceral) nerve (S2-4) that likely conveys intracavernosal distension pressure sensation of the rigid penile erection.9 The first synapse is at the sacral level of the spinal cord (S2-4) in the conus medullaris. The connection between the afferent and efferent limbs of the reflex is likely crossed and uncrossed, di- or poly-synaptic, rather than monosynaptic (W. C. De Groat, personal communication, December 16, 2022).10 The synapse with the efferent limb of the reflex (ie, the hypogastric preganglionics) is located at the lumbar level (L2-4) of the spinal cord. The hypogastric preganglionics synapse in the inferior mesenteric ganglia and the superior and inferior hypogastric plexus, while the hypogastric postganglionics pass to the corpora cavernosal erectile smooth muscle tissue, bladder neck, and rectum to release norepinephrine, thereby inducing smooth muscle contraction.
We propose that this “pelvic/pudendal-hypogastric” reflex can be pathologically activated in the following regions in the hard flaccid syndrome. For patients with region 1 (end organ) pathology, we hypothesize excess sympathetic activity occurs secondary to injury to the erect penis (during intercourse, masturbation, jelqing), and some symptom relief is obtained by downregulating sympathetic triggers using analgesics, anti-inflammatory agents, oral alpha-blocking agents (doxazosin, tamsulosin), and/or low-intensity shock wave therapy. For patients with region 2 (pelvic/perineum) pathology, excess sympathetic activity may occur secondary to pain from pudendal nerve neuropathy after blunt perineal trauma (bicycle riding, spinning, horseback riding) and/or high tone pelvic floor dysfunction. In such region 2 patients, neural inhibitory agents (pregabalin, gabapentin, amitriptyline), skeletal muscle relaxing agents (diazepam), pudendal nerve blocks, and/or pelvic floor physical therapy aid in reducing pelvic/perineal drives of increased sympathetic tone. For patients with region 3 (cauda equina) pathology, excess sympathetic activity is thought to occur secondary to sacral radiculopathy from a lumbosacral annular tear and/or sacral Tarlov cyst. In our experience, region 3 patients have a more treatment-resistant hard flaccid state. In this population, once regions 1 and 2 have been ruled out with neurogenital testing and administration of regional anesthetic agents and lumbosacral MRIs show evidence of cauda equina pathology, patients undergo region 3 anesthesia testing.8 Those patients with a positive response have undergone spine surgery to resolve the sacral radiculopathy and recovered from hard flaccid syndrome.11
We herein report management of an 18-year-old patient with hard flaccid syndrome. He presented to our sexual medicine facility in 2018 with a 4-month history of erectile dysfunction, depression, decreased penis/glans sensation, and hard flaccid syndrome that involved a smaller, firmer, painful flaccid penis. Conservative medical treatments, sex therapy, and pelvic floor physical therapy performed over a 4-year period yielded no improvement. When the patient revealed a history of low back pain with intermittent sciatica, sacral radiculopathy was suspected. Neurogenital testing performed in 2022 was abnormal, with a pattern consistent with cauda equina pathology.8 A subsequent lumbar MRI revealed an L5-S1 disc protrusion with annular tear (Figure 4). He underwent a left transforaminal epidural spinal injection and experienced a transient “much better” improvement in hard flaccid symptoms. At age 23, he underwent a left L5-S1 lumbar endoscopic interlaminar discectomy.11 At 1-year follow-up, he has significantly improved erectile function, penile/glans sensation, and reduction in hard flaccid syndrome symptoms. He is continuing both pelvic floor physical therapy and sex therapy.
- Gul M, Towe M, Yafi FA, Serefoglu EC. Hard flaccid syndrome: initial report of four cases. Int J Impot Res. 2020;32(2):176-179.
- Gul M, Huynh LM, El-Khatib FM, Yafi FA, Serefoglu EC. A qualitative analysis of Internet forum discussions on hard flaccid syndrome. Int J Impot Res. 2020;32(5):503-509.
- Abdessater M, Kanbar A, Akakpo W, Beley S. Hard flaccid syndrome: state of current knowledge. Basic Clin Androl. 2020;30:7.
- Glina S, Shindel A, Eardley I, Ghanem H. Cavernosal alpha-blockade: a new technique for investigating and treating erectile impotence by GS Brindley. J Sex Med. 2008;5(8):1791-1794.
- Stief CG, Wetterauer U. Erectile responses to intracavernous papaverine and phentolamine: comparison of single and combined delivery. J Urol. 1988;140(6):1415-1416.]
- Kaplan SA, Reis RB, Kohn IJ, Shabsigh R, Te AE. Combination therapy using oral alpha-blockers and intracavernosal injection in men with erectile dysfunction. Urology. 1998;52(5):739-743.
- Belew D, Klaassen Z, Lewis RW. Intracavernosal injection for the diagnosis, evaluation, and treatment of erectile dysfunction: a review. Sex Med Rev. 2015;3(1):11-23.
- Goldstein I, Komisaruk BR, Pukall CF, et al. International Society for the Study of Women’s Sexual Health (ISSWSH) review of epidemiology and pathophysiology, and a consensus nomenclature and process of care for the management of persistent genital arousal disorder/genito-pelvic dysesthesia (PGAD/GPD). J Sex Med. 2021;18(4):665-697.
- Allen K, Wise N, Frangos E, Komisaruk B. Male urogenital system mapped onto the sensory cortex: functional magnetic resonance imaging evidence. J Sex Med. 2020;17(4):603-613.
- De Groat WC, Lalley PM. Reflex firing in the lumbar sympathetic outflow to activation of vesical afferent fibres. J Physiol. 1972;226(2):289-309.
- Kim CW, Goldstein I, Komisaruk BR, et al. Lumbar endoscopic spine surgery for persistent genital arousal disorder/genitopelvic dysesthesia resulting from lumbosacral annular tear-induced sacral radiculopathy. J Sex Med. 2023;20(2):210-223.