Erectile dysfunction

DIAGNOSIS
History
- To differentiate organic from psychogenic: Onset, Coarse, Duration
Morning or night erections, erections on masturbation or at any other situations.
- To determine the etiology:
Risk factors for atherosclerosis (DM, smoking, hypertension, hyperlipidemias), spinal cord injury, radical pelvic surgery, drug addiction, medications, systemic diseases, marital conflicts & other etiological factors mentioned above.
Examination
- General:
Male secondary sex characters
Pulses & sensations
Scars from previous surgery or trauma
- Local:
Penis: Size, scars, fibrosis, pulses meatus
Scrotum: Testicular size, and consistency
Rectal: Prostate & Seminal vesicles
Bulbocavernosus reflex (squeezing the glans penis results in contraction of the bulbocavernosus muscle felt by a finger in the anus. This test demonstrates integrity of the spinal sacral segments but can be elicited in only 70% of normal men.
Investigations
- Nocturnal penile tumescence (NPT) monitoring
Men go through several phases of sleep among which are the rapid eye movement phases that are associated with spontaneous penile erections. These phases occur 4 -5 times per night and last 15 to 20 minutes each thus occupying about 15% - 20% of total sleep time. If one wakes up during one of these phases he notices a night or morning erection. NPT are very important to differentiate organic from psychogenic impotence.
These erections can detected by wearing a SNAP GAUGE around the penis during sleep. This is a simple device with three strings each cutting at a certain amount of penile rigidity. The strength of erection is estimated by the number of strings that cut.
The Regiscan is another device that monitors the nocturnal erections precisely and gives a computer printout of the degree of rigidity, duration & number of erectile episodes for both the tip & base of the penis.
- Endocrine evaluation
Most important are blood sugar, s, Testosterone, s, Prolactin.
- Vascular evaluation
1- Papaverine or Prostaglandin (PGE1) Test:
Injection of a vasoactive vasodilating substance like papaverine, phentolamine or PG E1 into the corpora cavernosa leads to dilatation of the cavernosal arteries, sinusoidal relaxation resulting in passive venous occlusion and a full erection in most normal subjects. This test is used to exclude abnormalities in penile hemodynamics. It is a good positive test. Intracavernosal injections can also be used therapeutically by teaching the patient to inject himself at home 10 - 15 minutes before intercourse.
The main complication of intracavernosal injections is the possible occurrence of priapism (prolonged painful purposeless erection, not related to sexual stimulation & involving only the corpora cavernosa, sparing the corpus spongiosum and glans penis). This complication can be resolved by early intervention, aspiration of blood and injection of sympathomimetics.

2- Tests to evaluate penile arteries:
If the papaverine test is negative (no erection occurs) the penile arteries are evaluated. If the arteries were normal but no erection occurs with papaverine the veins should be evaluated for excessive drainage (corporal veno-occlusive dysfunction).

A- Doppler evaluation:
A doppler ultrasound machine is used to obtain:
- Penile brachial index: Penile systolic blood pressure divided by brachial systolic pressure. Normally > 0.8
- Penile mean brachial index: Penile systolic divided by mean brachial blood pressure. Normally > 1
- Penile brachial gradient: Penile systolic pressure minus brachial systolic. Normally < 20 mm Hg.
- Penile pulse waveform analysis: A normal penile pulse waveform shows a rapid upstroke, sharp peak, slower down-stroke which sometimes shows a diacritic notch.

B- Duplex ultrasonography:
Duplex ultrasonography with pulsed doppler analysis after papaverine injection is currently the method of choice for evaluating the penile cavernosal arteries. It provides an ultrasound image that allows the operator to set the cursor at the cavernosal artery at an exact angle thus obtaining precise measurements of its diameter and blood velocity. Normally:
- Maximum mean peak flow velocity in the cavernosal artery after papaverine injection: > 25 cm / sec.
- Diameter increase: > 75%
A normal duplex arterial response to papaverine in the absence of a rigid erection is suggestive of venous leak.
C- Selective internal pudendal angiography:
This is a very invasive procedure and should be performed only if the patient is being prepared for arterial surgery.

3- Tests to evaluate penile veins & corpora cavernosa:
These are moderately invasive. Cavernosometry should be performed if a corporal veno-occlusive dysfunction is suspected by a normal arterial response on duplex evaluation in the absence of a rigid erection with papaverine injection.
A- Cavernosometry:
After papaverine injection (60 mg) saline is injected at a rate sufficient to induce and maintain a rigid erection. Normally:
- Induction rate: < 40 ml/min.
- Maintenance rate: < 15 ml/min.
- An alternative method is to raise the IC pressure to 150 mm Hg then stop infusion. The rate of drop should be < 40 mm Hg in the first half minute.
B- Cavernosography:
If cavernosometry demonstrates corporal veno-occlusive dysfunction, a radio-opaque dye is injected IC (intracavernosal) instead of the saline infusion. A X-ray picture is then taken to demonstrate the site of venous leakage, any abnormal veins or any other pathology within the corpora cavernosa e.g. fibrous plaques.
- Neurologic evaluation

Afferent Pathways
1- Biothesiometry:
A biothesiometer is a vibration apparatus having a fixed frequency & a variable amplitude. It is used to measure the vibration sense at the sides of the penile shaft & glans. It is a good screening procedure for sensory deficit impotence.
2- Dorsal nerve somatosensory evoked potential:
This is a neurophysiologic test involving electrical stimulation of the dorsal nerve of the penis. Evoked EEG waveforms are recorded over the sacral cord & cerebral cortex, and analyzed using computer signal averaging and complex electronic equipment.
Obtaining the peripheral conduction time to the sacral cord & the central conduction time to the brain from one or more points on the penis aids in diagnosing sacral or suprasacral sensory lesions as well as calculating the dorsal nerve conduction velocity.

- Efferent Pathways
1- Cystometry with betanechol supersensitivity testing:
A rise in intravesical pressure of < 20 cm water after S.C. injection of 5 mg betanechol indicates a normal vesical parasympathetic outflow but is not specific regarding the cavernosal parasympathetic nerves.
2- Supersensitivity with a rigid erection, to a small dose of papaverine has been suggested but not widely accepted as a test for the integrity of the autonomic supply to the penis.
3- Normal NPT testing signifies integrity of the efferent pathways to the penis during sleep. However an abnormal NPT test could be due to a variety of neurologic and vascular conditions
Both afferent & efferent pathways:
Bulbocavernosus (sacral) evoked response:
- Stimulating electrode: On the penile shaft
- Recording electrode: In the bulbocavernous muscle to record reflex EMG responses.
- Reflex latency: Time from the stimulus to the first reflex EMG response. Normally < 40 msec.
This test is the neurophysiologic representation of the bulbocavernosus reflex (S2,3,4).

جميع حقوق الطبع والنشر محفوظة للدكتور حسين غانم لعام 1999