Erectile dysfunction (ED) is broadly classified into: (a) organic ED
(caused by organic changes in the nervous and vascular systems and penile tissues involved
in erection); (b) functional/psychogenic ED which is mainly caused by psycho- logical
factors; and (c) mixed ED which is a combination of organic and func- tional/psychogenic
ED.
It is important to differentiate precisely between organic and
functional/psycho- genic etiologies, but it should not be assumed that treatment measures
can be directed solely to either one cause without considering therapy for the other type.
Diagnosis should begin with a clinical interview and assessment via
standard questionnaires such as the International Index of Erectile Function (IIEF). The
diagnosis then enters the examination and testing phase, which initially involves erectile
function tests to differentiate between organic and functional/psychogenic ED.
Erectile function tests could start with administration of
sildenafil, with further tests such as the audiovisual sexual stimulation (AVSS) loading
test and measure- ment of nocturnal penile tumescence (NPT) only being conducted in
patients who do not have a complete erection with sildenafil.
If the condition is found to be organic, investigations are then
conducted to determine whether the cause is injury to the penile vascular system (arterial
or venous), or the penile nervous system.
Diagnosis of vascular ED is by: (a) screening tests for injury to the
penile arterial and venous systems and corpus cavernosum, including intracavernosal
injection of vasoactive drugs [e.g. alprostadil (prostaglandin E1) or
papaverine] and measurement of the penogram index (PI) by penography; (b) imaging
techniques such as the color Doppler test, internal pudendal arteriography,
dynamic infusion cavernosometry and cavernosography (DICC); or (c) cavernosal biopsy.
Endocrine disorders account for only a relatively
small proportion of men with ED. However, it is important to recognize and diagnose
endocrine diseases as they are treatable and have wider and sometimes serious implications
beyond ED. A thorough search for endocrine disease is therefore important in the evalua-
tion of patients presenting with ED.
Where financial constraints permit and pathology
services are easily accessible, it is helpful to undertake basic tests such as measurement
of total testosterone, prolactin and thyroid-stimulating hormone (TSH) levels in all
patients presenting with ED, even if they are merely to set the baseline for future
reference. Further laboratory investigations should be conducted if any of these
parameters are abnormal.
Neurogenic ED can be caused by injury or disease of
the brain, spinal cord or peripheral nerves serving the penis. Cortical disease processes
that lead to neu-rogenic ED include strokes, tumors, epilepsy, Parkinson’s disease
and Alzheimer’s disease.
Spinal cord lesions that can result in ED include
spinal cord injury, multiple sclerosis, spina bifida, tabes dorsalis, syringomyelia,
herniated disk and tumors. Peripheral neuropathy leading to ED may be due to surgical
injury, or trauma to the pelvic plexus, pudendal nerves or cavernosal nerves.
Neurologic testing should assess peripheral, spinal
and supraspinal centers, and both somatic and autonomic pathways associated with erection.
Tests of the somatic nervous system include penile
biothesiometry, the bulbo-cavernous reflex latency (BCRL) test, the dorsal nerve
conduction velocity (DNCV) test, and the dorsal nerve somatosensory evoked potential
(DNSEP) test.
Tests of the autonomic nervous system include
cardiovascular reflex tests, sym- pathetic skin response (SSR) studies, cystometrographic
(CMG) studies, nocturnal penile tumescence (NPT) recordings, corpus cavernosum
electromyography (CCEMG), single potential analysis of cavernous electrical activity, and
cavernosal biopsy.
- Psychological causes of ED may be immediate (e.g. due to
‘spectatoring’, disruption of erotic emotions, unfamiliarity with sexual
techniques, anatomical ignorance, and various myths and misconceptions), or they
may be earlier/deeper and more remote. The latter causes include a suppressive sexual
environment during adole- scence, marital problems and depressive illness.
Sex counselling cannot improve erectile dysfunction due to organic
causes, but it helps to remove anxiety about the sexual act in men with psychogenic ED.
The primary objective of `brief sex therapy' is to remove immediate
causes, and this alone is sometimes adequate to provide considerable relief of symptoms.
Key strategies in sex therapy include sensate focus exercises,
techniques for removing the fear of failure and dealing with obsessive thoughts,
encouragement of egoism, and advice on intercourse techniques.
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