Normal
Genital organs
- Male
- Genital organs: penis (corpora cavernosa, corpus spongiosum, tunica albuginea), glans, urethra, testes, epididymis, vas deferens, seminal vesicles, prostate.
- Male sexual response
- Libido (desire) → excitement/erection → orgasm (seminal emission from vas deferens and ejaculation from penis).
- Genital stimuli + central drive (libido-desire) → spinal ejaculation generators (lumbosacral cord) → sympathetic hypogastric efferents to vas deferens and bladder neck + pudendal efferents to bulbocavernosus/perineal muscles → emission + rhythmic contractions → ejaculation.
- Erection types (male):
- Psychogenic erection
- Audiovisual stimuli
- Visual/erotic stimuli → cortex/limbic system → hypothalamus (MPOA, PVN) → brainstem (PAG, pontine erection‑related centres) → descending pathways in spinal cord → pelvic parasympathetic efferents → penile/clitoral vasodilation.
- Reflexive erection / genital engorgement
- Somatosensory genital stimulation
- Genital touch → pudendal/pelvic/hypogastric afferents → lumbosacral spinal cord (S2–S4) → pelvic parasympathetic efferents → cavernous/clitoral vessels → erection/engorgement.
- Nocturnal erection:
- Nocturnal penile tumescence
- Hypothalamic lateral preoptic area → raphe and locus coeruleus → spinal erection centres → spontaneous erections during sleep.
- Male sexual dysfunctions
- Loss of libido (reduced sexual desire).
- Erectile dysfunction (difficulty achieving or maintaining penile erection).
- Ejaculatory dysfunction (e.g. reduced, absent or abnormal ejaculation, including retrograde when bladder neck control is impaired).
- Orgasmic dysfunction (diminished or absent orgasm despite stimulation).
- Female
- Genital organs:
- Clitoris, vagina, labia, uterus and associated vascular erectile tissue.
- Female sexual response:
- Genital and psychogenic stimuli [Libido (corticolimbic–hypothalamic)]→ spinal cord and thalamus → hypothalamus and limbic/cortical areas → descending activation of pelvic parasympathetic and pudendal pathways → vaginal/clitoral engorgement and lubrication (S2–S4) + rhythmic pelvic floor/vaginal contractions during orgasm (pudendal somatic output).
- Female sexual dysfunction
- Loss of libido
- Reduced clitoral engorgement
- Reduced vaginal secretion are the main dysfunctions;
Peripheral efferent innervation of genital organs
- Parasympathetic pelvic pathway for erection/engorgement (men and women):
- Sacral intermediolateral cell columns (S2–S4 “sacral erection centre”) → pelvic nerves (cholinergic and nitrergic) → cavernous/helical arteries in penis or clitoral/vaginal erectile tissue → vasodilation, increased blood flow, venous compression → erection or clitoral/vaginal engorgement.
- Nitric oxide synthase in cavernous nerves/endothelium → nitric oxide → cGMP signalling (degraded by phosphodiesterase‑5 in penis and clitoris).
- Sympathetic hypogastric pathway for emission/ejaculation:
- Thoracolumbar intermediolateral cell columns (T12–L2) → hypogastric nerves →
- Vas deferens and seminal vesicles → contraction → seminal emission.
- Bladder neck and proximal urethra → contraction → prevention of retrograde ejaculation into bladder.
- Somatic pudendal pathway:
- Anterior horn/Onuf’s nucleus (S2–S3) → pudendal nerve →
- Bulbocavernosus and perineal muscles (male) → rhythmic contractions contributing to ejaculation and orgasm.
- Perineal and pelvic floor muscles (female) → rhythmic contractions in orgasm.
Peripheral afferent innervation
- Genital somatosensory afferents:
- Glans penis, penile shaft, clitoris, labia, vagina mechanoreceptors → pudendal, pelvic and hypogastric nerves → dorsal roots (lumbosacral and thoracolumbar cord).
- Ascending conduction:
- Genital afferents in anterior and dorsal spinal cord pathways → thalamic nuclei → medial preoptic area and paraventricular nucleus in hypothalamus and higher cortical areas (for perception of sexual sensation and arousal).
Spinal cord centres and reflexes
- Sacral erection/engorgement centre:
- Genital somatosensory inputs → sacral spinal cord (S2–S4 intermediolateral columns) → pelvic parasympathetic efferents → reflexive erection or clitoral/vaginal engorgement; preserved in supra‑sacral lesions.
- Spinal ejaculation/organism circuitry:
- Genital/pelvic afferents → lumbosacral spinal cord (including Onuf’s nucleus and associated interneurons) → patterned activation of sympathetic (hypogastric) and somatic (pudendal) outputs → emission + rhythmic perineal/penile contractions (ejaculation) or vaginal contractions (orgasm).
Hypothalamic control and limbic integration
- Libido and psychogenic erection/engorgement:
- Genital somatosensory afferents → spinal cord → thalamic nuclei → medial preoptic area (MPOA) and paraventricular nucleus (PVN) of hypothalamus.
- Erotic visual inputs: retina → visual pathways → mamillary body → MPOA.
- Hypothalamic erection/engorgement pathways:
- PVN oxytocinergic neurons → direct descending projections to sacral spinal cord (parasympathetic erection centre) → facilitation of penile erection and likely vaginal/clitoral engorgement.
- PVN oxytocinergic neurons → projections to midbrain periaqueductal grey (PAG) and pontine centres → additional facilitation/modulation of erection and genital responses.
- Nocturnal penile tumescence:
- Hypothalamic lateral preoptic area → brainstem structures (raphe, locus coeruleus) and spinal centres → regulation of REM‑associated nocturnal erections.
Dopamine, oxytocin and prolactin in sexual function
- Dopaminergic facilitation:
- Substantia nigra pars compacta and ventral tegmental area → dopaminergic projections → medial preoptic area and paraventricular nucleus → activation of hypothalamic circuits facilitating erection and mating behaviours.
- Increased dopamine concentration in medial preoptic area during sexual stimulation (men and animals) supports a facilitatory role.
- Receptor‑specific roles:
- Hypothalamic dopamine D1 and D2 receptors → participate in erection; D2 receptors → also participate in ejaculation.
- Oxytocin:
- PVN oxytocinergic neurons → spinal cord and brainstem → promote erection and likely vaginal engorgement; serum oxytocin rises during human masturbation.
- Prolactin (inhibitory):
- Prolactinergic neurons → inhibit sexual function; dopaminergic neurons → inhibit prolactin secretion → removal of inhibition on sexual function.
Cortical and limbic contributions
- Emotional and cognitive aspects:
- Limbic and paralimbic structures (including hippocampus and related areas) → hypothalamus (MPOA, PVN) → brainstem and spinal sexual circuits.
- Sexual functions (libido, erection, orgasm) are closely associated with brain areas involved in emotion and reward, integrating sensory stimuli, memory, mood and context.
- Frontal control and awareness:
- Medial frontal and prefrontal cortices → connections with limbic system and basal ganglia → modulation of sexual drive, initiation, inhibition and behavioural expression of sexual acts.
Disease
General
- Key neurological patterns to remember
- Suprapontine/brain (frontal, basal ganglia, hypothalamus, limbic): mainly loss of libido and psychogenic erection/arousal, often with OAB.
- Spinal cord (especially supra‑sacral): loss of psychogenic but preservation of reflex erection; impaired ejaculation and female genital engorgement.
- Sacral cord and peripheral (e.g. spina bifida, MSA sacral involvement): disruption of reflex erection/engorgement and ejaculation, with severe bladder dysfunction.
Brain diseases
Stroke
- Frontal, basal ganglia and internal capsule lesions disrupt cortico–basal ganglia–hypothalamic control, leading to loss of libido and erectile/ejaculatory problems, often alongside bladder dysfunction.
Alzheimer disease
- Temporoparietal and frontal involvement plus loss of central cholinergic neurons can reduce libido and contribute to sexual apathy or disinhibition; sexual issues often coexist with overactive bladder.
White matter disease (WMD)
- Diffuse subcortical white matter damage, especially affecting frontal connections, is associated with gait disorder, OAB and changes in sexual drive or behaviour in older adults.
Normal‑pressure hydrocephalus
- Frontal hypoperfusion and subcortical fibre disruption cause the triad of gait disturbance, cognitive decline and urinary incontinence, with frontal behavioural changes that can include altered sexual drive.
Parkinson disease
- Loss of nigrostriatal dopamine and hypothalamic involvement lead to loss of libido and erectile dysfunction in a large proportion of patients
- Dopaminergic therapy can improve erection but may provoke hypersexuality in some.
Dementia with Lewy bodies (DLB)
- More widespread cortical and subcortical Lewy body pathology than Parkinson disease, with prominent cognitive and psychiatric features; sexual dysfunction (libido and erection) is common and often more severe, on top of marked bladder symptoms.
Multiple system atrophy (MSA)
- Degeneration in basal ganglia, cerebellum, pons and lumbosacral spinal cord;
- Sexual dysfunction (especially in men) can be an early or initial symptom, reflecting involvement of hypothalamus and sacral intermediolateral nucleus.
Spinal cord diseases
Traumatic spinal cord injury (SCI)
- Complete transverse SCI:
- Loss of genital sensation, loss of psychogenic erection, relative preservation of reflex erection;
- Ejaculation usually impaired, female genital engorgement and lubrication are reduced.
- Incomplete SCI:
- Mixed patterns with preserved sensation and mixed storage/voiding and sexual dysfunction (e.g. some erection but impaired ejaculation).
Multiple sclerosis (MS)
- Incomplete spinal lesions and sometimes supraspinal plaques cause detrusor overactivity, DSD and/or detrusor underactivity
- Sexual dysfunction is common, mainly from spinal cord lesions and sometimes insular involvement.
Neuromyelitis optica spectrum disorder (NMOSD)
- Severe myelopathy produces more pronounced bladder dysfunction than typical MS and is associated with sexual dysfunction related to motor disability and depression.
Spina bifida (cystic and occult)
- Malformation of lumbar/sacral cord and roots leads to mixed upper and lower motor neuron signs, impaired bladder sensation and mDO‑DU;
- Sexual function can be impaired through pelvic nerve and pudendal involvement, particularly in cystic forms.
Management
General approach
- Take a focused sexual history: libido, arousal (erection/engorgement, lubrication), ejaculation and orgasm.
- Relate symptoms to neurological diagnosis and lesion level (suprapontine, spinal, sacral/peripheral).
- Consider motor, autonomic, cognitive and mood factors that limit sexual activity in neurological disease.
Address reversible and comorbid factors
- Review and adjust medications that worsen sexual function (for example, some antidepressants, dopamine antagonists, prolactin‑raising drugs).
- Screen for and treat depression, anxiety and pain, which commonly coexist and impair libido and performance.
- Manage LUT dysfunction in parallel (OAB, incontinence, retention), as fear of leakage and catheter issues can secondarily reduce sexual activity.
Disease‑specific considerations mentioned
- Parkinson disease
- Recognise high rates of loss of libido and erectile dysfunction.
- Understand that dopaminergic drugs can improve erection but may provoke hypersexuality and impulse control disorders; dosing needs individual adjustment and monitoring.
- Deep brain stimulation of the subthalamic nucleus may improve sexual well‑being but can also trigger mania with hypersexuality in some patients.
- Multiple system atrophy
- Sexual dysfunction (especially in men) can be an early or even initial symptom; take it seriously as a diagnostic clue.
- Recognise that hypothalamic and sacral intermediolateral involvement underlies combined sexual and bladder dysfunction.
- Spinal cord injury
- In complete supra‑sacral injury, expect loss of genital sensation and psychogenic erection with preservation of reflex erection; ejaculation often impaired.
- Use focused penile vibration and/or electrostimulation techniques to assist ejaculation for fertility and sexual function.
- In women, expect impaired genital engorgement and lubrication; counsel and use mechanical and lubricating aids.
- Multiple sclerosis and NMOSD
- Assume a high prevalence of sexual dysfunction in both men and women; spinal cord lesions are the main driver.
- Recognise that sexual dysfunction can occur independently of motor disability, so ask proactively even if walking is relatively preserved.
- In NMOSD, expect sexual dysfunction to parallel severity of myelopathy and depression.
Mechanism‑based counselling and support
- Explain to patients and partners which components are affected (desire vs arousal vs orgasm) and which pathways (psychogenic vs reflex vs spinal) are intact.
- Encourage adaptation: focusing on preserved reflex mechanisms (e.g. local stimulation where spinal reflexes remain), use of assistive devices, and timing around medication effect (e.g. dopaminergic “on” periods).
- Involve multidisciplinary teams where available (neuro‑urology, sexual medicine, psychology, rehabilitation) to optimise both function and quality of life.