male circumcision decreases penile sensitivity · as well as unusual sensations at the dorsal...
TRANSCRIPT
Male circumcision decreases penile sensitivity
Justine Schober MD University of Pittsburgh Medical Center – Hamot Hospital, Erie PA
Rockefeller University, New York, NY
“Anatomy is not destiny but a little neuroanatomy helps”
Don Pfaff
Foreskin Function
• Sensation
• Protection
The Foreskin
• The outer epithelium has the protective function of internalizing the glans (clitoris and penis), urethral meatus (in the male) and the inner preputial epithelium, thus decreasing external irritation or contamination
• The prepuce is a specialized, junctional mucocutaneous tissue which marks the boundary between mucosa and skin; it is similar to the eyelids, labia minora, anus and lips
• The male prepuce also provides adequate mucosa and skin to cover the entire penis during erection
• The unique innervation of the prepuce establishes its function as an erogenous tissue
Winkelmann Proc Mayo Clin 1959;
Silver Staining for Innervation
Penile Sensation
Attributes of SensationSome of these may be changed with circumcision
Quality-----
Meissner's corpuscles which record touch sensation
Krause end-bulbs respond to thermal stimuli
Pacinian corpuscles which respond to changes in tension and pressure
Genital corpuscles which respond to friction
Quantity----Intensity
Duration
Extensivity******
Quantity (Extensivity) is Changed in Circumcision
• The extensivity of sensation varies with the extensivity of its objects or the sense organ stimulated.
• As an example, a hand dipped into warm water up to the elbow produces a more extensive heat sensation than is done by the finger-tip dipped into it.
Foreskin Innervation
• Various receptor types sense changes in temperature, position, pressure, pain, light touch, itch, burning and pleasurable sexual sensations
• Free nerve endings were identified in the papillary dermis visualized as thin fibers, mostly varicose, with either branched or single processes, either straight or bent.
• Two types of sensory corpuscle were identified: capsulated and non-capsulated. Meissner-like corpuscles were located in the papillary dermis. Capsulated corpuscles resembled typical Pacinian corpuscles, comprising a single central axon surrounded by non-neural periaxonic cells and lamellae.
Epithelial-Neuronal Interactions
Quality and Quantity of the epithelium related to temperature, inflammation and hormonal status can change sensory capabilities for:
• Friction • Pressure stimulation • Stretching
*For both spinal cord and the vagal pathways
Innervation for Sexual Arousal
• A circuit or feedback loop
• As arousal increases, genital sensitivity to stimuli increases
• Multiple avenues to arousal through stimulation of different sites that overlap
• Convergence- cutaneous stimulation from receptive fields of corresponding areas of pressure sensitive interneurons come together onto spinal interneurons
• Overlap of dermatomesIncrease in responsiveness as a stimulus is moved from the periphery to the center of the field
• Summation effects-stimuli covering smaller areas might evoke only weak reflexes, whereas stimuli over a larger area could evoke a stronger reflex
Pfaff Estrogens and Brain Function
Springer -Verlag1980
Terminal Innervation for Sensation
Sensation is a bit like an electrical circuit
Sexual Arousal Begins at the Epithelium -
It is Dependent on the Epithelium (Quantity) and Terminal Innervation (Quality)
Influences on this tissue that change sexual sensation:
• Skin temperature
• Hormonal environment
• Mechanical compliance of the tissue
• Inflammation
• Transmitters, Neuropeptides
Martin Alguacil, J Urol 2006
Study of Belgian Men using SAGASFM
• The analysis sample consisted of 1059 uncircumcised and 310 circumcised men.
• For the glans penis, circumcised men reported decreased sexual pleasure and lower orgasm intensity. They also stated more effort was required to achieve orgasm, and a higher percentage of them experienced unusual sensations (burning, prickling, itching, or tingling and numbness of the glans penis).
• For the penile shaft a higher percentage of circumcised men described discomfort and pain, numbness and unusual sensations.
• In comparison to men circumcised before puberty, men circumcised during adolescence or later indicated less sexual pleasure at the glans penis, and a higher percentage of them reported discomfort or pain and unusual sensations at the penile shaft.
sexual pleasure response means orgasm intensity response means ease of orgasm response means
Comparison of Uncircumcised and Circumcised Men
Circumcised Men- Site Stimulation Glans Penis
Significantly less sexual pleasure from stimulation than men in uncircumcised group at:
• dorsal side of the glans (P ≤ 0.001)
• lateral side of the glans (P ≤ 0.001)
• ventral sides of the glans (P = 0.02)
Orgasm was less intense than men in uncircumcised group from stimulation:
• dorsal side (P = 0.006)
• lateral sides (P = 0.02)
More effort exerted in achieving orgasm at the lateral sides (P = 0.04).
• Furthermore, a larger percentage of men in this group reported numbness at the dorsal, lateral, and ventral sides (all P ≤ 0.001), as well as unusual sensations (burning, prickling, itching, or tingling) at the lateral sides (P = 0.02) and at the ventral side (P = 0.003) of the glans
Circumcised Men- Site Stimulation, Penile Shaft
A higher percentage of circumcised men reported discomfort or pain at the dorsal, lateral, and ventral sides (all P ≤ 0.001)
• Higher orgasm intensity was found in circumcised men at the ventral side (P = 0.009)
A higher percentage of circumcised men reported numbness at:
• the dorsal (P = 0.04)
• lateral (P ≤ 0.001)
• ventral sides (P = 0.003)
As well as unusual sensations at the dorsal (P = 0.04), lateral (P = 0.005), and ventral sides (P ≤ 0.001). The intensity of the unusual sensations at the dorsal side (P = 0.04) of the penile shaft was significantly higher for the circumcised men
Absolute Circumcision Outcomes for Sensation?
• The only reliable way to evaluate the influence of circumcision on genital sensitivity and sexual function is to address the same person before and after adult circumcision
Comparison of Men Circumcised Before Puberty to Men Circumcised During Adolescence or in Adulthood
Comparison of Men Circumcised Before Puberty to Men Circumcised During Adolescence or in Adulthood
Why Might This Be True?
• Sexual arousal is based on anatomical, neural, hormonal, and genetic elements, and is also influenced by effects of culture and of contexts that are specific to each individual.
• Penile sensory activation is similar in all male vertebrates and is based on somatosensory information from the foreskin, glans, and urethra.
• The strongest somatosensory contribution to male (penile) sensitivity is mediated through the dorsal penile nerve. The glans and foreskin are densely innervated by the terminal branches of the dorsal penile nerve, terminal innervation from these structures provides the primary source of sensory information to the CNS for the induction of sexual reflexes/arousal
• Research on both animals and humans support this theory. Animals show impaired erectile and ejaculatory function after desensitization of the glans.
• The area of the preputium ridged band is considered the most sensitive part of the human penis.
• Removal of the Foreskin changes the quality and quantity of sensory input to the CNS
Amputation of Terminal Nerves
• Reinnervation
• Nerve regeneration
• Axonal sprouting
• Cortical remapping
After Terminal Nerve Amputation
After Amputation of Terminal Nerves
• Axons distal to the lesion are disconnected from the neuronal body and degenerate, leading to denervation of the peripheral organs
• Wallerian degeneration creates a microenvironment distal to the injury site that supports axonal regrowth, while the neuron body changes in phenotype to promote axonal regeneration.
• The significance of axonal regeneration is to replace the degenerated distal nerve segment, and achieve reinnervation of target organs and restitution of their functions. However, axonal regeneration does not always allows for adequate functional recovery, so that after a peripheral nerve injury, patients do not recover normal motor control and fine sensibility.
• The lack of specificity of nerve regeneration, in terms of motor and sensory axons regrowth, pathfinding and target reinnervation, is one the main shortcomings for recovery
Allodi Prog Neurobiol. 2012
What Happens After The Foreskin Is Cut Off
Neuroplasticity!Cellular Mechanisms: Changes in synaptic strength
Structural changes like synaptogenesis and
axon sprouting
Cortical reorganization: Remapping after the injury
sexual pleasure response means orgasm intensity response means ease of orgasm response means
Conclusion
• Circumcision decreases penile sensitivity
• For the glans penis, circumcised men reported decreased sexual pleasure and lower orgasm intensity. They also stated more effort was required to achieve orgasm and a higher percentage of them experienced unusual sensations and numbness.
• For the penile shaft a higher percentage of circumcised men described discomfort, pain, numbness and unusual sensations.
• In comparison to men circumcised before puberty, men circumcised in adolescence or later indicated less sexual pleasure at the glans penis, and a higher percentage reported discomfort, pain and unusual sensations at the penile shaft.
“ More Fuss per Square Centimeter Than Anything ”
Chris Woodhouse