Sexual Medicine FINE-TOUCH PRESSURE THRESHOLDS IN THE ADULT PENIS SORRELLS Fine-touch et al. pressure thresholds in the adult penis Morris L. Sorrells, James L. Snyder, Mark D. Reiss, Christopher Eden*, Marilyn F. Milos†, Norma Wilcox and Robert S. Van Howe‡ Retired, *HIV/AIDS researcher, San Francisco, CA, †National Organization of Circumcision Information Resource Centers, ‡Department of Paediatrics and Human Development, Michigan State University College of Human Medicine, MI, USA Accepted for publication 22 October 2006 OBJECTIVE last ejaculation, ethnicity, country of birth, circumcision had lower pressure thresholds and level of education. than the ventral scar of the circumcised penis. To map the fine-touch pressure thresholds of the adult penis in circumcised and CONCLUSIONS uncircumcised men, and to compare the two RESULTS populations. The glans of the circumcised penis is less The glans of the uncircumcised men had sensitive to fine touch than the glans of the significantly lower mean (SEM) pressure uncircumcised penis. The transitional region SUBJECTS AND METHODS thresholds than that of the circumcised men, from the external to the internal prepuce at 0.161 (0.078) g (P = 0.040) when controlled is the most sensitive region of the Adult male volunteers with no history of for age, location of measurement, type of uncircumcised penis and more sensitive than penile pathology or diabetes were evaluated underwear worn, and ethnicity. There were the most sensitive region of the circumcised with a Semmes-Weinstein monofilament significant differences in pressure thresholds penis. Circumcision ablates the most sensitive touch-test to map the fine-touch pressure by location on the penis (P < 0.001). The most parts of the penis. thresholds of the penis. Circumcised and sensitive location on the circumcised penis uncircumcised men were compared using was the circumcision scar on the ventral KEYWORDS mixed models for repeated data, controlling surface. Five locations on the uncircumcised for age, type of underwear worn, time since penis that are routinely removed at circumcision, pressure sensitivity, penis INTRODUCTION penile sensitivity, or a reduction in erectile difference between circumcised and function. uncircumcised men [9]. Likewise, in a London Infant male circumcision, the most common population, men from Islamic countries medical procedure in the USA, might also be Bleustein et al. [7], in a comparison study of were more likely to have premature the most divisive. The long-term health men with and with no erectile dysfunction ejaculation [10]. impact of neonatal circumcision has received (ED), using quantitative somatosensory little study, while the consequences of testing that included vibration, pressure, The type of nerve endings in the penis vary circumcision on sexual function in the adult spatial perception, and warm and cold with location. The glans penis primarily has male have received even less attention. thermal thresholds, found that uncircumcised free nerve endings that can sense deep men had worse vibratory sensation and better pressure and pain [11]. The transitional area A poorly documented study by Masters and fine-touch sensation. These differences from the external to the internal surface of Johnson, briefly mentioned only in their book disappeared when controlled for age, the prepuce, or ‘ridged band’, has a pleated [1] and never subjected to peer-review, hypertension and diabetes. appearance that is continuous with the claimed to find no difference in the fine- frenulum and has a high density of fine-touch touch perception of the glans of circumcised Whether the penis is circumcised or not might neuroreceptors, such as Meissner’s corpuscles and uncircumcised men. Several studies also affect coitus. For women, having a male [12–14]. Based on this histology, the assessed the impact of circumcision on sexual partner with a foreskin increased the duration transitional region and the ventral surface of function in adult men [2–6]. These studies had and comfort of coitus and increased the the prepuce would be expected to have lower few subjects, a relatively short follow-up and likelihood of achieving single and multiple thresholds for light touch. a reliance on subjective self-reporting orgasms [8]. A recent multinational obtained from men with a history of penile population survey using stopwatch Controversy over the sensory consequences and sexual dysfunction. Notable in these assessment of the intravaginal ejaculation of infant male circumcision on adult sexual studies is the high percentage (27.3% [4] to latency time (IELT) found that Turkish men, function has been fuelled by a lack of 64.2% [6]) of subjects who were circumcised the vast majority of whom are circumcised, objective data. By objectively measuring to correct a penile problem, and who reported had the shortest IELT. When Turkish men were penile sensitivity, the present study aimed to no improvement after surgery, a decrease in excluded from the analysis, there was no map the fine-touch pressure thresholds of the © 2007 THE AUTHORS 864 JOURNAL COMPILATION © 2007 BJU INTERNATIONAL | 99, 864–869 | doi:10.1111/j.1464-410X.2006.06685.x FINE-TOUCH PRESSURE THRESHOLDS IN THE ADULT PENIS FIG. 1. Locations on the dorsal penis evaluated for FIG. 2. Locations on the ventral penis evaluated for preputial orifice; (4) the muco-cutaneous fine-touch pressure thresholds. fine-touch pressure thresholds. junction; (5) the ridged band; (6) the preputial mucosa; (7) the coronal sulcus; (8) the coronal 1. 11. ridge; (9) the middle of dorsal aspect of the SHAFT PROXIMAL CORONAL glans; (10) the glans at the meatus; on the TO CORONAL RIDGE ventral surface of the penis, the locations RIDGE 12. 2. FRENULUM were (11) the coronal ridge; (12) the frenulum OUTER AT URETHRAL at the urethral slit; (13) the frenulum near the PREPUCE SLIT ridged band; (14) the frenulum at the muco- 3. 13. cutaneous junction; (15) the rim of the ORIFICE FRENULUM preputial orifice; (16) the outer prepuce; (17) RIM NEAR the shaft proximal to the coronal ridge; and 4. RIDGED BAND locations pertaining to circumcised men only MUCO- 14. (18) the circumcision scar on the dorsal CUTANEOUS FRENULUM AT surface and (19) the circumcision scar on the JUNCTION MUCO-CUTANEOUS ventral surface. Locations 2–5 and 13–16 5. JUNCTION were measured only in uncircumcised men RIDGED 15. BAND ORIFICE because these locations are ablated by 6. RIM circumcision. PREPUTIAL 16. MUCOSA OUTER Because of the method of data collection, it 7. PREPUCE was impossible for the physician measuring SULCUS 17. the fine-touch thresholds to be unaware of 8. SHAFT PROXIMAL the circumcision status of the subject. CORONAL TO CORONAL Likewise, because of the number of locations RIDGE RIDGE sampled, it was also impossible for the 9. 18. statistician to be unaware of the circumcision SCAR / MIDDLE status of the subject. OF GLANS DORSAL 10. SURFACE GLANS 19. Based on unpublished pilot data, it was AT MEATUS SCAR / determined that sampling 50 uncircumcised VENTRAL and 150 circumcised men would have 80% SURFACE power to show a difference of 0.046 g with a penis and quantify the differences in penile type I error of 5%. Demographic information sensitivity between men with and without genitals, e.g. hypospadias; a history of by circumcision status were compared using foreskins. diseases or conditions known to affect sexual Mantel-Haenszel, Fisher’s exact, chi-square sensitivity and function, e.g. diabetes mellitus; and t-tests. Fine-touch pressure thresholds by SUBJECTS AND METHODS a history of genital, prostate, or urinary tract location were compared using t-tests and disease of any kind, including but not limited linear regression. Mixed models for repeated Subjects were recruited by posting ‘fliers’ at to sexually transmitted diseases, open sores, data on single subjects stratified by location the San Francisco Bay Area medical school. or lesions at the time of screening; prostatitis; of measurement, which control for within- Also, announcements were made on a medical prostate cancer; BPH; spinal cord injury; subject variability, were developed using radio programme, and advertisements were peripheral nerve injury; peripheral locations present in both the circumcised and placed in local Bay Area general circulation neuropathy; sciatica; any penile piercing; the complete penis. Models were assessed newspapers. penile enlargement surgery; any form of using forward, backwards and stepwise psychiatric condition; or a history of alcohol selection. Similar models were developed Subjects were men aged >18 years in good or substance abuse. Informed consent was using only locations on the glans penis. This health, with no genital alterations, except for obtained before testing. study protocol was approved by the Western circumcision, as determined by health- Institutional Review Board. screening questions. A short questionnaire The fine-touch sensitivity of 19 locations on was completed to determine ethnicity, place the penis was measured using Semmes- of birth, highest education degree obtained, Weinstein monofilament touch-test sensory type of underwear worn, timing of last evaluators (North Coast Medical Supply, RESULTS ejaculation, referral source, and health status. Morgan Hill, CA, USA) [15–17] to create a Circumcision status was determined by a penile sensitivity map (Figs 1 and 2) In all, 163 subjects were enrolled; one physical examination. uncircumcised man was excluded for On the dorsum of the penis, these locations diabetes, two uncircumcised men and one Exclusion criteria were: transsexuals; intersex were: (1) the shaft proximal to coronal ridge; circumcised man were excluded for individuals; males born with abnormal (2) the outer prepuce; (3) the rim of the hypospadias. All of the men completed the © 2007 THE AUTHORS JOURNAL COMPILATION © 2007 BJU INTERNATIONAL 865 SORRELLS ET AL. testing once it started. A comparison of the TABLE 1 The demographics of the subjects by circumcision status demographic information by circumcision status is shown in Table 1. Men born outside Measure Not circumcised (68) Circumcised (91) Comparison the USA were eight times more likely to be Mean (SD) age, years 51.0 (12.9) 48.3 (12.5) 0.180* uncircumcised.