Assess sexual development,  height and weight, pigmentation, distribution of body hair and, in women, galactorrhea. Evaluate the external genitalia for any local pathology, including testicular size (normal 15-25 ml), the clitoris and the prostatic gland. Palpate the peripheral pulses (arms, legs, penis), auscultate the heart, and take the blood pressure.

Neurological examination

A standard neurological examination, including assessment of the mental state, is important to exclude any underlying neurological disease. Inspect the lower back for naevi, hypertrichosis, and a sacral sinus and the feet for deformity and muscle atrophy. The sacral segments are especially important. The bulbocavernosus muscles can be palpated in the male, and tested for voluntary ("move the penis"), and reflex contraction. Anal sphincter and levator ani tone (pubococcygeus muscle) and their voluntary and reflex contraction can be palpated in both sexes. In addition to standard reflexes the cremasteric reflex (testing the L1 segment), and the bulbocavernosus and external anal reflex (testing the S2-S4/5 segments) should be evaluated. The bulbocavernosus reflex can be elicited by squeezing the glans and assessing contraction of the anal sphincter (in both sexes), or the bulbocavernosus muscle (in males), by palpation. The superficial external anal reflex is an objective response. Touch and pain perception in the perineum, perianal and genital skin, in addition to testing over other dermatomes, is essential. The neurological examination can be extended by neurophysiological tests. Thus, reflex responses can be recorded with greater sensitivity electromyographically; and perineal sensation can be quantified using special devices and algorithms (see below).

Investigation of erectile function

Although essential data will be obtained by history, objective evaluation of erection is the "gold standard" to determine its quality. Spontaneous and physiologically induced erection can be studied with a variety of techniques. Spontaneous nocturnal penile tumescence and rigidity can be measured in the sleep laboratory using strain gauges (measuring penile expansion), visual inspection and measuring the buckling force (for assessment of rigidity), with polygraphic confirmation of sleep phases (Karacan and Ilaria 1978, Wasserman et al 1980). Various low-cost screening tests for nocturnal penile expansion have been proposed, but their validity is questionable (Condra et al 1987). Continuous monitoring of nocturnal penile tumescence and rigidity can be obtained by a rigidometer during normal sleeping conditions at home (Kaneko & Bradley 1986), and also during daytime napping (Morales 1994) or in the awake sexually stimulated examinee (Thase et al 1988). A comprehensive discussion of the utility and limitations of the noturnal penile tumescence test has been given by Morales et al (1990).

Investigation of erectile capacity

Given that no major vascular problem is present (particularly no significant venous incompetence) an intracorporeal injection of a vasoactive substance (papaverine; combination of papaverine + phentolamine; prostaglandin E1) will lead to an erection, thus strengthening the suspicion of a neurogenic or psychogenic etiology for erectile dysfunction (Mueller & Lue 1988, Haldeman et al 1995). Additional self-stimulation increases this test’s sensitivity (Lue 1990).

Investigation of nervous system function

In patients with erectile and ejaculatory dysfunction suspected due to a neurologic disorder neurophysiologic tests are useful (Mauroy et al 2003, Lundberg 2001), including sensory (somatosensory and viscerosensory) and motor (somatic and autonomic), tests (Table 3).

Special devices and algorithms can be used for quantifying genital sensation. Vibratory perception thresholds (biothesiometry/vibrametry) on the penis correlate with electrodiagnostic testing (Padma-Nathan 1988). The vibration perception threshold (VPT) in the penis (glans and shaft) in a neurologically healthy man is similar to that of the feet. In females VPT is best measured on the clitoris, labia majora and perineum (Helström & Lundberg 1992, Hulter et al 1998, Hulter & Lundberg 2005). The vibratory threshold at the clitoris in neurologically healthy women is the same as in the hands. VPT is of particular importance in women with suspected lesions of peripheral sensory nerves in the pelvic floor (Haldeman et al 1995). Tests evaluating small fiber function may be informative, i.e. testing penile (Yarnitsky et al 1996) or vaginal and clitoral warm and cold sensory thresholds (Vardi et al 2000).

Electromyography (EMG) has been used to demonstrate activation patterns of striated muscles in the sexual response (Gerstenberg et al 1990) but it is mainly used to differentiate normal from denervated (reinnervated) muscle. Concentric needle EMG is the method of choice to diagnose lower motor neuron involvement in the lower sacral segments (Vodusek & Fowler 2004). Different tests involving stimulation and recording of somatosensory and motor evoked responses, and sacral reflexes reflect the function of defined parts of the motor and sensory nervous system. These tests measure conduction through nervous pathways and are sensitive to demyelination, but less sensitive to axonal lesions - which predominate in clinical practice. Tests have been proposed to assess the lumbosacral sympathetic system (the sympathetic skin responses) and penile smooth muscle (Vodusek 1998, Vodusek et al 2005). These tests cannot in themselves define erectile dysfunction as neurogenic (Haldeman et al 1995) since the relationship of neurophysiologic test abnormalities to sexual dysfunction itself has proven elusive. However, measurements of dorsal penile nerve conduction, the bulbocavernosus reflex, and pudendal SEP are valuable in evaluating patients with suspected neurogenic erectile dysfunction (Haldeman et al 1995). Unfortunately, tests assessing penile autonomic innervation and smooth muscle function are unreliable. Cystometry, other urodynamic tests, and anorectal function tests may strengthen a diagnosis of sacral autonomic dysfunction. Useful guidelines have been set out by the Therapeutics and Technology Assessment Subcommittee of the AmericanAcademy of Neurology (1995).

Laboratory investigation of blood and urine

Basic laboratory data (including sedimentation rate, blood cell count, fasting blood sugar, serum lipids, urinanalysis) as well as serum parameters screening for hepatic, kidney and thyroid function rarely add information. Hormone analyses, especially prolactin and testosterone levels have been proposed as screening tests for both sexes. In women with menstrual irregularities or signs of masculinisation, endocrinological opinion may be helpful.

Investigation of vascular function

If intracorporeal injection testing of penile tumescence has strengthened a suspicion of vascular etiology in the male patient with erectile dysfunction, further investigations may be contemplated, as a rule performed by urologists. Penile blood pressure can be measured using a simple Doppler method and then related to the arm blood pressure. Vascular competence can be measured by angiography, MRI, colour ultra-sonography and dynamic cavernosography. It has been stressed that the purpose of testing should always be defined: pharmacotesting may be sufficient for the majority of patients, and the invasive tests reserved for those in whom surgery is contemplated (Meuleman & Diemont 1995).

In females there are also a number of vascular tests available. A new technique for quantitative assessment of female sexual arousal using noncontrast dynamic MR imaging has been developed (Maravilla et al 2005). However, the sensitivity of these tests in clinical diagnosis has not been reported.