Aetna considers the diagnosis and treatment of erectile dysfunction (impotence) medically necessary according to the criteria outlined below.

1. Diagnosis

   Aetna considers the following diagnostic workup of erectile dysfunction medically necessary:

   • Comprehensive history and physical examination (including medical and sexual history and psychosocial evaluation)
   • Duplexscan (Doppler and ultrasound) in conjunction with intracorporeal papaverine
   • Dynamic infusion cavernosometry and cavernosography only for members who are to undergo re-vascularization procedures and meet medical necessity criteria for penile re-vascularization (see below)
   • Pharmacological response test for erectile dysfunction (using vasoactive drugs, e.g., papaverine HCl, phentolamine mesylate, prostaglandin E1)
   • Pudendal arteriography (angiography) only for members who are to undergo penile re-vascularization and meet the medical necessity criteria for penile revascularization (see below).

   Aetna considers the following laboratory tests medically necessary for the diagnosis of erectile dysfunction:

   • Biothesiometry (Note: biothesiometry is considered an integral part of the comprehensive history and physical examination)
   • Blood glucose
   • Complete blood count
   • Creatinine
   • Hepatic panel
   • Lipid profile
   • Prostate specific antigen

   • Serum testosterone

     • Tests for evaluation of pituitary dysfunction (e.g., measurement of luteinizing hormone, follicle-stimulating hormone, and prolactin levels) if serum testosterone level is below normal

   • Thyroid function studies
   • Urinalysis.

   Note: Routine nocturnal penile tumescence (NPT) and/or rigidity testing has no proven value.  Nocturnal penile tumescence testing using the postage stamp test or the snap gauge test is rarely medically necessary; it is considered medically necessary where clinical evaluation, including history and physical examination, is unable to distinguish psychogenic from organic impotence and any identified medical factors have been corrected.  Nocturnal penile tumescence testing using the RigiScan is considered medically necessary only where NPT testing is indicated, and the results of postage stamp or snap gauge testing are equivocal or inconclusive.

   Aetna considers the following workup/laboratory tests for the diagnosis of erectile dysfunction experimental and investigational because their effectiveness has not been established:

   • Cavermap cavernous nerves electrical stimulation with penile plethysmography (also referred to as cavernosal nerve mapping).  This policy is based upon an assessment by the Centers for Medicare and Medicaid Services (CMS, 2006)
   • Corpora cavernosal electromyography
   • Dorsal nerve conduction latencies
   • Evoked potential measurements (including stimulus evoked response for measurement of bulbocavernosus reflex latency)
   • Iron binding capacity
   • Penile plethysmography
   • Prostatic acid phosphatase
      

2. Treatments

   Aetna considers the following therapies for the treatment of erectile dysfunction medically necessary:

   1. Injectable Medications

      Aetna considers self-administered injectable medications for the treatment of erectile dysfunction medically necessary.*  Medically necessary self-administered medications for erectile dysfunction include:

      1. Injections into the corpus cavernosa to cause an erection (papaverine, alprostadil, phentolamine) and,

      2. Medicated Urethral System for Erection (MUSE) method of treatment for erectile dysfunction that involves inserting medication through a small catheter into the urethra.

      Titrating doses of injectable impotence medications that are administered in a physician's office and the accompanying office visits are considered medically necessary.  This includes in office titrating doses of papaverine, alprostadil (prostaglandin E1 or Caverject) and phentolamine.  Except for phentolamine, which is not generally used alone, these drugs can be used alone or in combination.  The drug MUSE, a pellet from of alprostadil, is also used as an alternative to alprostadil injections.

      Diagnostic injections of impotence medications by the treating physician are also considered medically necessary.

      *Note: Coverage of injectable medications is subject to the terms of the member’s benefit plan.  Please check benefit plan descriptions for details.

   2. Oral and Transdermal Medications

      Aetna considers exogenous testosterone replacement therapy, including transdermal preparations, experimental and investigational for the treatment of non-hypogonadal impotence because its effectiveness in non-hypogonadal impotence has not been established.  (See CPB 0345 - Implantable Hormone Pellets.)

      Aetna considers topical cream or gel containing vasodilators, such as verapamil cream, experimental and investigational for the treatment of erectile dysfunction because their effectiveness for this indication has not been established.

      Note: Many Aetna pharmacy benefit plans exclude coverage of drugs for lifestyle enhancement or performance.  Please check benefit plan descriptions for details.  Under these plans, sildenafil citrate (Viagra), vardenafil hydrochloride (Levitra) and tadalafil (Cialis) are covered only when required by state regulation or when a plan sponsor has elected an optional rider under the pharmacy plan, or, for indemnity or PPO plans without a separate pharmacy benefit, when the plan sponsor has added optional coverage under the medical plan. 

   3. External Devices

      Aetna considers the external penile vacuum pump device medically necessary durable medical equipment (DME) when it is prescribed by a physician as an alternative to other therapies for erectile dysfunction.  External penile pumps are considered experimental and investigational for other indications including for the prevention of erectile dysfunction following prostatectomy because their effectiveness for these indications has not been estalbished.

   4. Implantable Devices

      Aetna considers implantation of semi-rigid penile prostheses or inflatable penile prostheses (implantable penile pumps) medically necessary for members with documented physiologic erectile dysfunction who have failed medical therapy or for whom medical therapy is contraindicated.  Implantable penile prostheses are considered experimental and investigational for other indications because their effectiveness for indications other than the one listed above has not been estalbished.

   5. Surgical Re-Vascularization

      Aetna considers penile re-vascularization for vasculogenic erectile dysfunction medically necessary only in men less than 55 years old who meet all of the following criteria:

      1. A focal blockage of arterial inflow is demonstrated by duplex Doppler ultrasonography or arteriography; and 
      2. Diagnostic work-up reveals normal corporeal venous function; and 
      3. Member is not actively smoking; and 
      4. Member is not diabetic and has no evidence of systemic vascular occlusive disease; and 

      5. The erectile dysfunction is the direct result of an arterial injury caused by blunt trauma to the pelvis and/or perineum. 

      Penile re-vascularization is considered experimental and investigational for other indications because its effectiveness for indications other than the one listed above has not been established.  Consistent with clinical guidelines of the American Urological Association, Aetna considers arterial reconstructive procedures, dorsal vein arterialization procedures, or penile venous occlusive surgery (e.g., venous ligation, dorsal vein ligation) in men with erectile dysfunction secondary to arteriosclerotic occlusive disease experimental and investigational because such procedures have not been proven to be effective.

   6. Experimental and Investigational Treatments

      Aetna considers the following treatments experimental and investigational for erectile dysfunction because their effectiveness has not been established:

      1. Acupuncture
      2. Extracorporeal shock wave therapy (ESWT)
      3. Percutaneous electrostimulation of the perineum

      4. Stem cell therapy (including adipose-derived stem cells).

   7. Peyronie's Disease

      1. Plaque Excisions and Venous Graft Patching

         Aetna considers surgical correction of Peyronie’s disease (e.g., plaque excisions and venous graft patching, tunica plication, Nesbit tuck procedure) medically necessary for the treatment of members with Peyronie's disease for 12 or more months with significant morbidity who have failed conservative medical treatment.  Surgical correction of Peyronie's disease is considered experimental and investigational when criteria are not met.

      2. Extracorporeal Shock Wave Therapy

         Aetna considers ESWT experimental and investigational for Peyronie’s disease because of a lack of evidence from prospective randomized controlled clinical studies of the effectiveness of ESWT for this indication. 

      3. Interferon Alpha

         For interferon alpha for Peyronie’s disease, see CPB 0404 - Interferons.

      4. Verapamil Iontophoresis or Verapamil Intra-Lesional Injection

         Aetna considers iontophoresis or intralesional injection of verapamil experimental and investigational for Peyronie’s disease because of a lack of evidence from prospective randomized controlled clinical studies of the effectiveness of this approach for this indication.

      5. Testosterone Injection

         Aetna considers testosterone injection experimental and investigational for Peyronie’s disease because of a lack of evidence from prospective randomized controlled clinical studies of the effectiveness of this approach for this indication.

This policy is supported by guidelines from the American Urological Association (Monatague et al, 2005; Monatague et al, 2006).

Researchers have been examining less invasive alternatives to surgery for Peyronie's disease.  A number of studies have examined the effectiveness of transdermal administration of verapamil as a treatment for Peyronie's disease.  One study found a non-significant improvement in penile curvature with transdermal administration of verapamil (Greenfield et al, 2007).  Greenfield et al (2007) stated that while surgery remains the gold standard of therapy to correct the acquired curvature of Peyronie's disease, the search for a less invasive therapy continues.  Transdermal drug delivery was proposed to be superior to oral or injection therapy because it bypasses hepatic metabolism and minimizes the pain of injection.  After electromotive drug administration with verapamil tunica albuginea specimens were demonstrated to contain detectable levels of the drug.  Due to varying success with verapamil as injectable therapy for Peyronie's disease, these researchers performed a double-blind, placebo controlled trial to determine the effectiveness of verapamil delivered through electromotive drug administration.  A total of 42 men with Peyronie's disease volunteered to participate in this study, which was approved by the authors' institutional review board.  A genito-urinary examination was performed on all patients, including plaque location, stretched penile length, objective measurement of curvature after papaverine injection and duplex ultrasound.  Each subject was randomized to receive 10 mg verapamil in 4 cc saline or 4 cc saline via electromotive drug administration.  A Mini-Physionizer (Physion, Mirandola, Italy) device was used at a power of 2.4 mA for 20 minutes.  Treatments were performed 2 times weekly for 3 months.  After 3 months each patient was re-evaluated with physical examination and duplex ultrasound by a technician blinded to the treatment received.  A modified erectile dysfunction index of treatment satisfaction questionnaire was also completed by each patient.  A total of 23 patients were randomized to the verapamil treatment group (group 1) and 19 were randomized to the saline group (group 2).  There were no significant differences between patient groups with respect to patient age, disease duration or pretreatment curvature.  In group 1, 15 patients (65 %) had measured improvement (mean 9.1 degrees, range 5 to 30), 5 (22 %) had no change and in 3 (13 %) the condition worsened.  In group 2, 11 patients (58 %) had measured improvement (mean 7.6 degrees, range 5 to 30), 7 (37 %) showed no change and in 1 (5 %) the condition worsened.  To better evaluate effectiveness the total number of patients experiencing significant improvement (20 degrees or greater) was calculated and compared.  Seven patients (30 %) in group 1 and 4 (21 %) in group 2 achieved this criterion.  The authors found that, although a greater percent of patients treated with verapamil in the electromotive drug administration protocol had a measured decrease in curvature, the results were not statistically significant.  The authors stated that further research is needed to determine whether electric current may have a role in the treatment of Peyronie's disease as well as if verapamil delivered via electromotive drug administration may have a role as effective treatment.

Cabello Benavente et al (2005) reported on a small, uncontrolled study of the effects of transdermal iontophoresis with verapamil and dexamethasone in patients with early Peyronie's disease, finding effects on pain, but limited effects on curvature.  These researchers treated 10 patients with Peyronie's disease of less than 1 year of evolution twice-weekly during 6 consecutive weeks using iontophoresis with a Miniphysionizer dispositive.  This device generates a 2-mA electric current during 20 mins that triggers the transdermal penetration of medication.  In every session dexamethasone 8 mg and verapamil 5 mg were administered inside a small self-adhesive receptacle on the penile skin overlying the fibrosis plaque.  To evaluate the efficacy, penile curvature was measured by Kelami's test, while the plaque size was assessed by penile ultrasound.  Other parameters like pain, erectile function and ability for vaginal intercourse were recorded using questionnaires.  Safety parameters were also assessed during treatment.  No improvement or progression in penile curvature was evidenced in any of the patients.  The hardness of the plaque was reduced in 5 patients, becoming impalpable in 2 of them.  Decrease in plaque volume was observed by penile ultrasound in 6.  Pain improved in 8 patients, disappearing in 6 of them.  One patient recovered his erectile function at the end of the treatment; whereas 3 referred that their ability for intercourse enhanced while 2 reported that treatment improved their sexual life in general.  These researchers didn't record any significantly side effects, except for a transitory and slight dermal redness on the site of electrode placement.  The authors concluded that transdermal iontophoresis had an effect on pain control in early stages of Peyronie's disease, but efficacy in reducing penile curvature seems to be limited.  They stated that controlled clinical trials are needed, and perhaps reviewing indications in order to obtain more relevant clinical effects.

Shirazi et al (2009) assessed the effect of intra-lesional verapamil on the treatment of Peyronie's disease.  This randomized study involved 80 patients.  First, they were divided into 2 groups -- the 1st group (case: 40 patients) received intra-lesional verapamil and the 2nd group (control: 40 patients) local saline injection.  They were followed about 24 weeks and evaluated for the size of plaques, plaque softening, reduction of pain and amelioration of penile deformity and erectile dysfunction (ED) (estimated by the International Index of Erectile Function) before and after treatment.  Reduction of plaque size was seen in 17.5 % of the case group and 12.8 % of the control group (p = 0.755).  Pain was reduced in 30 % of the case group and 28.2 % of the control group (p = 0.99).  Curvature was decreased in 17.5 % of the case group and 23.1 % the control group (p = 0.586).  Plaque softening was seen in 30 % of the case group compared with 25.6 % improvement in the control group (p = 0.803).  Also these investigators found 5 % and 2.6 % improvement in sexual dysfunction in the case and control groups, respectively (p = 0.985).  The authors concluded that although in some studies verapamil has been found to be effective in the treatment of Peyronie's disease, these researchers did not find any improvement in comparison with the control group.  They stated that larger scale studies are warranted to assess the effect of this drug on the treatment of Peyronie's disease.

Heidari et al (2010) evaluated the effect of intra-lesional injection of verapamil in Peyronie's plaque with confirmed lesion.  This randomized clinical trial was performed between March 2005 and March 2006 on 16 patients with Peyronie's disease.  Performing a comprehensive physical examination, the genitalia of the patients were checked to confirm the diagnosis and reject other sexual disorders.  Besides, parameters such as penis curving, lesion size were measured.  Then, based on the 10-point visual analog scale, sexual satisfaction of patients and their wives were recorded in a questionnaire.  Patients got intra-lesional verapamil every 14 days and were treated for 6 months.  After that, the parameters were assessed and data collected was analyzed using paired t-test.  P-value < 0.05 was considered statistically significant.  On average, lesion size and penis curving decreased 30 %.  Almost 20 % of patients and their wives were satisfied with the outcome of the treatment.  No significant side effect was seen during the treatment.  The authors concluded that injection of calcium channel blockers are effective for treatment of the Peyronie's disease; however, more studies with more patients are needed.

Early studies suggested a potential benefit on neurogenic ED (NED) from percutaneous electrostimulation of the perineum, although additional studies are needed.  Shafik et al (2008) examined the hypothesis that percutaneous perineal stimulation evokes erection in patients with NED.  Percutaneous electro-stimulation of the perineum (PESP) with synchronous intra-corporeal pressure (ICP) recording was performed in 28 healthy volunteers (age of 36.3 +/- 7.4 years) and 18 patients (age of 36.6 +/- 6.8 years) with complete NED.  Current was delivered in a sine wave summation fashion.  Average maximal voltages and number of stimulations delivered per session were 15 to 18 volts and 15 to 25 stimulations, respectively.  Percutaneous perineal electro-stimulation of healthy volunteers resulted in an increase in ICP (p < 0.0001), which returned to the basal value upon cessation of stimulation.  The latent period recorded was 2.5 +/- 0.2 seconds.  Results were reproducible on repeated PESP in the same subject but with an increase of the latent period.  Patients with NED recorded an ICP increase that was lower (p < 0.05) and a latent period that was longer (p < 0.0001) than those of healthy volunteers.  The authors concluded that PESP resulted in ICP increase in the healthy volunteers and patients with NED.  The ICP was significantly higher and latent period shorter in the healthy volunteers than in patients with NED.  They noted that PESP may be of value in the treatment of patients with NED, provided that further studies are carried out to reproduce these results.

There is reliable evidence that oral phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil, vardenafil, tadalafil, mirodenafil, and udenafil) improve erectile functioning in men with ED.  However, there is a lack of reliable evidence of the efficacy of hormonal treatments and the value of hormone testing for ED.

The American College of Physicians (ACP) developed guidelines on hormonal testing and pharmacological treatments of ED (Qaseem et al, 2009).  Current drug therapies include PDE-5 inhibitors as well as hormonal treatment.  The ACP recommended (i) clinicians initiate therapy with a PDE-5 inhibitor in men who seek treatment for erectile dysfunction and who do not have a contra-indication to PDE-5 inhibitor use, and (ii) clinicians base the choice of a specific PDE-5 inhibitor on the individual preferences of men with erectile dysfunction, including ease of use, cost of medication, and adverse effects profile.  The ACP did not recommend for or against routine use of hormonal blood tests or hormonal treatment in the management of patients with ED.

In a systematic review and meta-analysis, Tsertsvadze and colleagues (2009) evaluated the efficacy and harms of oral PDE-5 inhibitors and hormonal treatments for ED and assessed the effect of measuring serum hormone levels on treatment outcomes for ED.  The authors concluded that oral PDE-5 inhibitors improved erectile functioning and had similar safety and efficacy profiles.  However, results on the efficacy of hormonal treatments and the value of hormone testing in men with ED were inconclusive.  The authors selected randomized, controlled trials (RCTs) of oral PDE-5 inhibitors and hormonal treatment for ED, and observational studies reporting measurement of serum hormone levels, prevalence of hormonal abnormalities, or both in men with ED.  Two independent reviewers abstracted data on study, participant, and treatment characteristics; efficacy and harms outcomes; and prevalence of hormonal abnormalities.  Data, primarily from short-term trials (less than or equal to 12 weeks), indicate that PDE-5 inhibitors were more effective than placebo in improving sexual intercourse success (69.0 % versus 35.0 %).  The proportion of men with improved erections was significantly greater among those treated with PDE-5 inhibitors (range of 67.0 % to 89.0 %) than with placebo (range of 27.0 % to 35.0 %).  The PDE-5 inhibitors were associated with increased risk for any adverse events compared with placebo (e.g., relative risk with sildenafil, 1.72 [95 % confidence interval (CI): 1.53 to 1.93]).  In 4 head-to-head RCTs comparing sildenafil, vardenafil, and tadalafil, improvement of ED and adverse events did not differ among treatments.  Results from 15 RCTs evaluating hormonal treatment of ED were inconsistent on whether treatment improved outcomes.  Evidence was insufficient regarding whether men with ED had a higher prevalence of hypo-gonadism than men without ED. 

There is insufficient evidence of the effectiveness of acupuncture for the treatment of ED.  In a systematic review, Lee et al (2009) found insufficient evidence for the use of acupuncture in the treatment of ED.  Systematic searches were conducted in 15 electronic databases, with no language restrictions.  Hand-searches included conference proceedings and the authors' files.  All clinical studies of acupuncture as a treatment for ED were considered for inclusion, and their methodological quality was assessed using the Jadad score.  Of the 4 studies included, 1 RCT showed beneficial effects of acupuncture compared with sham acupuncture in terms of response rate, while another RCT found no effects of acupuncture.  The remaining 2 studies were uncontrolled clinical trials.  Collectively, these data showed that RCTs of acupuncture for ED are feasible but scarce.  Most investigations had methodological flaws (e.g., inadequate study design, poor reporting of results, small sample size, and publication without appropriate peer review process).  The authors concluded that the evidence is insufficient to suggest that acupuncture is an effective intervention for treating ED.  They stated that further research is needed to examine if there are specific benefits of acupuncture for men with ED.

There is emerging interest in the use of adipose-derived stem cells for treatment of Peyronie's disease.  Adipose-derived stem cells (ADSCs) are a somatic stem cell population contained in fat tissue that possess the ability for self-renewal, differentiation into one or more phenotypes, and functional regeneration of damaged tissue, which may benefit the recovery of erectile function.  Lin et al (2009) reviewed available evidence concerning ADSCs availability, differentiation into functional cells, and the potential of these cells for the treatment of ED.  These researchers examined data from 1964 to 2008 that were associated with the definition, characterization, differentiation, and application of ADSCs, as well as other kinds of stem cells for stem cell-based therapies of erectile dysfunction.  They noted that ADSCs are para-vascularly localized in the adipose tissue.  Under specific induction medium conditions, these cells differentiated into neuron-like cells, smooth muscle cells, and endothelium in vitro.  The insulin-like growth factor/insulin-like growth factor receptor pathway participates in neuronal differentiation while the fibroblast growth factor 2 pathway is involved in endothelium differentiation.  In a preliminary in vivo experiment, the ADSCs functionally recovered the damaged erectile function.  However, the underlying mechanism needs to be further examined.  The authors concluded that ADSCs are a potential source for stem cell-based therapies, which imply the possibility of an effective clinical therapy for ED in the near future.

Other treatments for ED include inflatable penile prostheses, and vacuum erectile devices, and vascular surgery.  Hellstrom and colleagues (2010) provided state-of-the-art knowledge regarding the treatment of ED by implant, mechanical device, and vascular surgery, representing the opinions of 7 experts from 5 countries developed in a consensus process over a 2-year period.  The inflatable penile prosthesis (IPP) is indicated for the treatment of patients with organic ED after failure or rejection of other treatment options.  Comparisons between the IPP and other forms of ED therapy generally reveal a higher satisfaction rate in men with ED who chose the prosthesis.  Organic ED responds well to vacuum erection device (VED) therapy, especially among men with a sub-optimal response to intra-cavernosal pharmacotherapy.  After radical prostatectomy, VED therapy combined with PDE-5 therapy improved sexual satisfaction in patients dissatisfied with VED alone.  Penile re-vascularization surgery seems most successful in young men with absence of venous leakage and isolated stenosis of the internal pudendal artery following perineal or pelvic trauma.  Currently, surgery to limit venous leakage is not recommended.  The authors stated that more research is needed in the area of re-vascularization surgery, in particular, venous outflow surgery.

Hilz and Marthol (2003) stated that neurogenic, particularly autonomic disorders, frequently contribute to the etiology and pathophysiology of ED.  Parasympathetic and sympathetic outflow mediates erection.  Non-cholinergic, non-adrenergic neurotransmitters induce activation of cyclic monophosphates, leading to relaxation of smooth muscles of the corpora cavernosa and by this to tumescence and rigidity, i.e., erection.  The diagnosis of neurologic causes of ED requires a detailed history and neurologic examination.  Conventional neurophysiological procedures evaluate the function of rapidly conducting, thickly myelinated nerve fibers only.  Therefore, techniques such as sphincter ani externus electromyography, latency measurements of the pudendal nerve or bulbocavernosus reflex studies frequently do not contribute to the diagnostic process.  The evaluation of small nerve fibers that are essential for erection, for example by means of psychophysical quantitative thermo-testing, might improve the diagnosis of neurogenic causes of ED.  In addition, the assessment of heart rate variability at rest, during metronomic breathing, Valsalva maneuver, and active standing might be helpful to identify an autonomic neuropathy as the cause of ED.

Hamdan and Al-Matubsi (2009) noted that ED etiology is multi-factorial, including endocrine, neurological, vascular, systemic disease, local penile disorders, nutrition, psychogenic factors, and drug-related.  This study was performed to compare the relevant comprehensive biochemical parameters as well as the clinical characteristics in diabetic ED and healthy control subjects and to assess the occurrence of penile neuropathy in diabetic patients and thus the relationship between ED and diabetes.  A total of 56 patients accepted to undergo assessment for penile vasculature using intracavernosal injection and color Doppler ultrasonography.  Of the 56 diabetic patients, 38 patients were found with normal blood flow and thus they were considered as the diabetic-ED group, whereas, ED diabetic patients with an arteriogenic component were excluded.  These patients with an age range between 17 and 58 years, complaining of ED, with duration of diabetic illness ranging from 2 to 15 years.  The control group comprised of 30 healthy subject aged between 19 and 55 years.  Peripheral venous levels of testosterone, prolactin, follicle stimulating hormone (FSH), luteinizing hormone (LH), thyroid stimulating hormone (TSH), malondialdehyde and glycosylated hemoglobin (HbA(1)c) were obtained in all subjects.  Valsalva maneuver and neurophysiological tests were also determined.  Testosterone, prolactin, FSH, LH, and TSH hormones of the diabetic patients were not significantly different from those of the control group.  Diabetic patients with ED have higher HbA(1)c and oxidative stress levels while the R-R ratio was significantly decreased.  Bulbocavernosus reflex latency was significantly prolonged, whereas its amplitude, the conduction velocity and amplitude of dorsal nerve of penis were significantly reduced in the diabetic patients.  The authors concluded that although ED is a multi-factorial disorder, yet, the present study revealed that in ED patients without arteriogenic ED a neurogenic component is present.  Furthermore, the complex effect of the Valsalva maneuver on cardiovascular function is the basis of its usefulness as a measure of autonomic function.  Thus, it can be of value in the diagnosis of ED although these hypotheses require follow-up in a large study cohort.

Lin et al (2012) noted that current therapeutic options for ED are less effective for patients having cavernous nerve (CN) injury or diabetes mellitus-related ED.  These 2 types of ED are thus the main focus of past and current stem cell (SC) therapy studies.  In a total of 16 studies so far, rats were exclusively used as disease models and SCs were mostly derived from bone marrow, adipose tissue, or skeletal muscle.  For tracking, SCs were labeled with LacZ, green fluorescent protein, 4',6-diamidino-2-phenylindole, DiI, bromodeoxyuridine, or 5-ethynyl-2-deoxyuridine, some of which might have led to data misinterpretation.  Stem cell transplantation was done exclusively by intra-cavernous (IC) injection, which has been recently shown to have systemic effects.  Functional assessment was done exclusively by measuring increases of IC pressure during electro-stimulation of CN.  Histological assessment usually focused on endothelial, smooth muscle, and CN contents in the penis.  In general, favorable outcomes have been obtained in all trials so far, although whether SCs had differentiated into specific cell lineages remains controversial.  Recent studies have shown that intra-cavernously injected SCs rapidly escaped the penis and homed into bone marrow.  This could perhaps explain why intra-cavernously injected SCs had systemic anti-diabetic effects and prolonged anti-ED effects.  The authors stated that these hypotheses and the differentiation-versus-paracrine debate require further investigation.

In an open-label, single-arm, prospective study, Gruenwald and colleagues (2012) noted that low-intensity extracorporeal shock wave therapy (LI-ESWT) has been reported as an effective treatment in men with mild and moderate ED.  These investigators determined the effectiveness of LI-ESWT in severe ED patients who were poor responders to PDE-5 inhibitor (PDE5i) therapy.  Patients with an erection hardness score (EHS) less than or equal to 2 at baseline were included in this study.  The protocol comprised 2 treatment sessions per week for 3 weeks, which were repeated after a 3-week no-treatment interval.  Patients were followed at 1 month (FU1), and only then an active PDE5i medication was provided for an additional month until final follow-up visit (FU2).  At each treatment session, LI-ESWT was applied on the penile shaft and crus at 5 different anatomical sites (300 shocks, 0.09 mJ/mm(2) intensity at 120 shocks/min).  Each subject underwent a full baseline assessment of erectile function using validated questionnaires and objective penile hemodynamic testing before and after LI-ESWT.  Outcome measures used were changes in the International Index of Erectile Function-erectile function domain (IIEF-ED) scores, the EHS measurement, and the 3 parameters of penile hemodynamics and endothelial function.  A total of 29 men (mean age of 61.3 years) completed the study.  Their mean IIEF-ED scores increased from 8.8 +/- 1 (baseline) to 12.3 +/- 1 at FU1 (p = 0.035).  At FU2 (on active PDE5i treatment), their IIEF-ED further increased to 18.8 +/- 1 (p < 0.0001), and 72.4 % (p < 0.0001) reached an EHS of greater than or equal to 3 (allowing full sexual intercourse).  A significant improvement (p = 0.0001) in penile hemodynamics was detected after treatment and this improvement significantly correlated with increases in the IIEF-ED (p < 0.05).  No noteworthy adverse events were reported.  The authors concluded that penile LI-ESWT is a new modality that has the potential to treat a subgroup of severe ED patients.  Moreover, they stated that these preliminary data need to be confirmed by multi-center sham control studies in a larger group of ED patients with long-term follow-up.