**4. Physiology and pathophysiology of the genital organ**

The genital organ primarily shares lumbosacral innervation with the lower urinary tract. Erection is a vascular event3; occurring secondarily after dilatation of the cavernous helical artery and compression of the cavernous vein to the tunica albuginea3. Helical artery dilatation is brought about by activation of cholinergic and nitrergic nerves; this activation facilitates nitric oxide secretion from the vascular endothelium. Ejaculation is brought about by contraction of the vas deferens and the bladder neck, in order to prevent retrograde ejaculation, by activation of adrenergic nerves **(Fig. 3)**. Sacral Onuf's nucleus innervates the bulbocavernosus muscle; and is thought to participate in erection and ejaculation. Sexual intercourse in healthy men can be divided into 3 phases65: a) desire (libido), b) excitement and erection, and c) orgasm, seminal emission from the vas deferens, and ejaculation from the penis. Erection can be further classified into 3 types by the relevant stimulation: 1) psychogenic erection (by audiovisual stimulation), 2) reflexive erection (by somatosensory stimulation), and 3) nocturnal penile tumescence (NPT) (associated with rapid eye movement [REM]-sleep). 'Morning erection' is considered the last NPT in the nighttime.

Computational Intelligence in Electromyography Analysis – 292 A Perspective on Current Applications and Future Challenges

Sphincter EMG for Diagnosing MSA and Related Disorders 293

and by projecting to the midbrain periaqueductal gray and the Barrington's nucleus

In experimental animals, dopamine is known to facilitate erection and mating behaviors13. The MPOA/PVN receives projections from the nigral dopaminergic neurons. Prolactinergic neurons are thought to be inhibitory in sexual function. Prolactin-producing pituitary tumors often cause gynecomastia and erectile dysfunction in male patients. Hyperprolactinemia occurs after the use of sulpiride, metoclopramide, and chlorpromazine (all dopamine receptor antagonists). Therefore, dopaminergic neurons seem to facilitate

In humans, the EUS and EAS share sacral pudendal innervation from Onuf's nucleus.12,20 The EAS lies around the anal canal and forms an 8-shaped sphincter system on the pelvic floor **(Fig. 4)**. Although injury to the peripheral nerves may lead to the dysfunction of the EUS alone, lesions of the sacral Onuf's nucleus affect both the EAS and EUS. For this reason, we use EAS-EMG to assess urinary incontinence, as it is easier to perform and less painful than EUS-EMG. For the same reason, few studies have utilized EUS-EMG.14,17 In women, the EUS muscle can be examined using a perineal approach. Examination of this muscle is more difficult in men; we can approach it with the fingers by feeling for the prostate within the rectum. However, EUS should be chosen in cases exhibiting a decelerating burst ('whale

The EAS can be divided into a deep part (thick; around the rectal neck to the anal canal) and a subcutaneous part (thin; around the anus). The deep EAS is a major constituent in the generation of anal pressure to hold feces in when the rectum is full. The normal range of static anal pressure is more than 40 cmH2O, and that of anal squeeze pressure is more than 50 cmH2O.22 The former is thought to reflect hypogastric adrenergic innervation, whereas the latter reflects somatic Onuf's nucleus innervation.22 The subcutaneous EAS is easy to examine. It is reached by inserting a needle about 1 cm from the anal orifice, to a

Although the EAS is a skeletal muscle, it usually fires continuously during both waking and sleeping states. To assess EAS, an EMG computer with quantitative, template-operated MUP analysis software is recommended. The commonly used amplifier filter setting is 5– 10 kHz. The tip of a concentric needle usually monitors an area approximately 500 micrometers in diameter, which includes approximately 20 MUPs. To assess acute denervation, insertion and spontaneous activities are checked as with the evaluation of other skeletal muscles. When the muscle is completely denervated, the EMG becomes silent. After an interval of 10–20 days, the insertion potentials become prolonged and abnormal spontaneous muscle activities, e.g., fibrillation potentials and positive sharp waves, appear. However, in the EAS, due to the continuous firing activities, it is not easy to see denervation potentials. In such cases, examination of the bulbocavernosus muscle

oxytocinergic neurons whereas they inhibit prolactinergic neurons.

**5. Methods and interpretations of sphincter EMG** 

noise') with complex repetitive discharge in Fowler's syndrome.24

(identical to the PMC).

depth of 3–6 mm.43

has been recommended44.

PAG, periaqueductal gray; LC, locus coeruleus; NBM, nucleus basalis Meynert; PVN, paraventricular nucleus; MPOA, medial preoptic area; A, adrenergic/noradrenergic; ZI, zona incerta; VTA, ventral tegmental area; SNC, substantia nigra pars compacta; DLTN, dorsolateral tegmental nucleus; PBN, parabrachial nucleus; IML, intermediolateral nucleus; GABA, γ-aminobutyric acid; T, thoracic; L, lumbar; S, sacral; NA, noradrenaline; Ach, acetylcholine; NO, nitric oxide. See text.

**Figure 3.** Neural circuitry relevant to erection.

Among the 3 types of erection, reflexive erection requires an intact sacral cord, particularly the intermediolateral (IML) cell columns. Pathology studies have shown that involvement of the IML nucleus is common in MSA, whereas it is uncommon in Parkinson's disease. Therefore, reflexive erection can be affected in patients with MSA. In patients with a suprasacral spinal cord lesion, reflexive erection might be preserved, whereas psychogenic erection is severely disturbed because of a lesion in the spinal pathways to the sacral cord. Libido and erection are thought to be regulated by the hypothalamus; particularly the medial preoptic area (MPOA) and the paraventricular nucleus (PVN).13,72 Recent neuroimaging studies have shown that penile stimulation or watching pornography activated these areas in humans70. NPT15 seems to be regulated by the hypothalamic lateral preoptic area,21 raphe nucleus, and locus ceruleus. Oxytocinergic neurons in the hypothalamic PVN are thought to facilitate erection by projecting directly to the sacral cord, and by projecting to the midbrain periaqueductal gray and the Barrington's nucleus (identical to the PMC).

In experimental animals, dopamine is known to facilitate erection and mating behaviors13. The MPOA/PVN receives projections from the nigral dopaminergic neurons. Prolactinergic neurons are thought to be inhibitory in sexual function. Prolactin-producing pituitary tumors often cause gynecomastia and erectile dysfunction in male patients. Hyperprolactinemia occurs after the use of sulpiride, metoclopramide, and chlorpromazine (all dopamine receptor antagonists). Therefore, dopaminergic neurons seem to facilitate oxytocinergic neurons whereas they inhibit prolactinergic neurons.
