Erectile Dysfunction

Question 1

What events lead to the increase in pressure within the corpora cavernosa?

Answer 1

• dilation of arterioles
• trapping of blood in expanding sinusoids
• compression of subtunical veins
• stretching of tunica, occluding emissary veins
• contraction of ischiocaverousus muscles

(increase in oxygen tension and intracavernous pressure increase to cause erection)

Question 2

Describe the changing pressure of the corpus spongiosum and glands penis during erection.

Answer 2

pressure is ⅓ to ½ of the pressure in corpus cavernosa because of minimal venous occlusion

Question 3

Which peripheral neural systems are responsible for directing erection v. sensation and motor of the penis?

Answer 3

sympathetic (detumesence) and parasympathetic (tumescence) direct erection

somatic nerves S2-4 (pudendal nerve) are responsible for sensation and contraction of bulbocavernosus and ischiocavernosus muscles

Question 4

Which levels of autonomic pathways are involved in penile erection?

Answer 4

T10-12 sympathetic fibers (via hypogastric plexus)

S2-4 parasympathetic pathways (via pelvic plexus)

Question 5

Which supra spinal pathways are important for sexual function and penile erection?

Answer 5

medial pre optic area
paraventricular nucleus of the hypothalamus
hippocampus

Question 6

What substance is responsible for initiating smooth muscle cross bridge cycling?

Answer 6

cytosolic free calcium via primary messenger NO and secondary messenger cGMP

Question 7

How does calcium initiate smooth muscle contraction?

Answer 7

elevated levels of calcium cause binding to calmodulin, exposing sites of myosin light-change; phosphorylation of myosin light changes triggers cycling of myosin light chains to generate force

Question 8

What mechanism causes relaxation of smooth muscle of arterioles?

Answer 8

decrease in sarcoplasmic calcium stops cross-cycling mechanism along with cGMP and cAMP as secondary messengers

cavernous nerve stimulates NO production which increases cGMP, which decreases Ca2+ via cGMP specific protein kinase

Question 9

What is a critical way that erectile dysfunction can be distinguised as psychogenic in nature?

Answer 9

typically nocturnal erections are preserved in psychogenic ED, often the dysfunction begins suddenly and can be associated with specific situations or partners

Question 10

Describe the pathophysiology of psychogenic ED.

Answer 10

exaggerated normal supra-sacral inhibition and sympathetic outflow

Question 11

What conditions can include neurogenic erectile dysfunction?

Answer 11

any pathologic process of the pre optic area, paraventricular nucleus or hippocampus including:

Parkinson’s disease, Stroke, encephalitis, epilepsy, Alzheimer’s Disease, dementia, trauma, spinal cord injury, spina bifida, disc herniation, tumor, transverse myelitis, MS, surgery of the pelvic organs (radical prostatectomy, cystectomy, rectal cancer, IBD) or vascular insufficiency due to pelvic fracture

Question 12

What are possible endocrine causes of ED?

Answer 12

–hypogonadism (low testosterone

Question 13

How are CAD and atherogenic ED related?

Answer 13

atherogenic ED shares the same risk factors of CAD and can itself serve as a risk factor for CAD (HTN, hyperlipidemia, smoking, diabetes, trauma, irradiation)

note that atherosclerosis occurs diffusely along the internal pudendal, common penile cavernous arteries

Question 14

What is the pathophysiology of venogeic ED.

Answer 14

• -failure of adequate venous occlusion commonly presenting as inability to maintain an erection (before ejaculation)
• -structural alteration in the fibroelastic component may result in venous leak as well
• -insufficient trabecular SM relaxation can cause inadequate sinusoidal expansion and insufficient compression of subtunical venules
• -acquired venous shunts following surgery for priapism

Question 15

Which nerves are responsible for erection v. ejaculation?

Answer 15

Point an Shoot
erection= parasympathetic
ejaculation= ejaculation

Question 16

What medications are known to cause ED?

Answer 16

substance abuse
anti-hypertensives (thiazides, B-blockers)
sedatives, anti-depressants, analgesics
histamine receptor blockers (cimetidine)
LHRH-agonists or estrogen (leuprolide)

Question 17

What are lifestyle changes that can address risk factors for ED?

Answer 17

reduce fat and cholesterol in diet
decrease or limit alcohol consumption 
eliminate tobacco use and substance abuse
Weight loss if appropriate
regular exercise

Question 18

What is the mechanisms of action for Sidenafil, vardenafil and tadalafil?

Answer 18

they inhibit PDE5 and increase cGMP that promotes and sustains smooth muscle relaxation

Question 19

How does a vacuum constriction device work?

Answer 19

patient causes venous blood to flow into penis with applied vacuume chamber around the penis, a band at the base of the penis traps the blood, maintaining an erection

adverse effects of ecchymosis and petechiae, pain, numbness and blocked ejaculation

Question 20

Describe the 2 options for 2nd line intracavernosal therapy/

Answer 20

intracavernosal self-injection of E1 alprostadil (85% effective)

intraurethral alprostadil (30-45% effective)

Question 21

What is the indication for a penile prosthesis?

Answer 21

for patients that have severe damage or who have failed previous conservative therapies (pump in scrotal sack transfers water from reservoir to malleable implants)

Question 22

What are possible post-operative complications of a penile prosthesis?

Answer 22

mechanical malfunction of the reservoir 
infection
auto-inflation
aneurysmal dilation
erosion
glands bowing