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

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

nitric oxide. See text.

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

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,

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

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 depth of 3–6 mm.43

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 has been recommended44.

Sphincter EMG for Diagnosing MSA and Related Disorders 295

**6. Sphincter EMG in autonomic disorders** 

pathology in MSA is neuronal cell loss in the sacral Onuf nucleus.33,37

Cardiovascular autonomic failure in MSA is thought to derive from neuron loss in the thoracolumbar intermediolateral (IML) cell columns of the spinal cord and the medullary circulation center. In contrast, lower urinary tract disorder in MSA is thought to reflect multiple lesions in the basal ganglia and the pontine storage center (storage-facilitating areas), as well as in the pontine micturition center in or adjacent to the locus ceruleus and the sacral IML cell columns (voiding-facilitating areas).11 In addition, a distinguishing

The first reports on neurogenic changes of EAS-EMG in MSA are attributed to Sakuta et al. (1978).62 Since then, EAS-EMG results for over 500 MSA patients have been reported, with abnormality rates of more than 70% in many studies5,30,36,38,47,53,62,64,71. EAS-EMG is better tolerated and yields identical results to those from EUS investigation5. Abnormalities have also been recorded in the bulbocavernosus muscles in MSA.67 In a larger study, Beck et al. (1994) reported that all (100%) 62 MSA patients with urological symptoms had abnormalities in both EAS and EUS-EMG.5 Palace et al. (1997) reported abnormal EAS-EMG in 103 (82%) of 126 patients with MSA38. Chandiramani et al. (1997) found abnormal EAS-EMG in 49 (94%) of 52 patients with MSA10. Kirchhof et al. (1999) found abnormal EAS-EMG in 89 (91%) of 98 patients with MSA28. Sakakibara et al. (2000) found an abnormal EAS-EMG in 53 (74%) of 71 MSA patients52. These abnormalities correspond to selective loss of ventral horn cells and astrogliosis; the loss is particularly severe in the second and third sacral segments (Onuf's nucleus) in MSA11. Sphincter EMG has been proposed as a means of distinguishing between MSA and idiopathic Parkinson's disease (as described below), since the anterior horn cells of Onuf's nucleus are not affected in idiopathic Parkinson's disease.10 In contrast, there have been debates about whether or not sphincter EMG can be used to distinguish MSA from idiopathic Parkinson's disease. In a study of 13 patients with idiopathic Parkinson's disease and 10 patients with MSA, Giladi et al. (2000) found significant overlap in all EMG parameters (presence of fibrillation potentials, MUP duration, presence of satellite potentials, percentage of polyphasic potentials)19. However, the durations of MUPs in both the MSA and Parkinson's disease groups were longer than in

It is reported that EAS-MUP abnormalities can distinguish MSA from idiopathic Parkinson's disease in the first 5 years after disease onset.30,69,74 However, the prevalence of such abnormalities in the early stages of MSA has not been well known. In our recent study of 84 probable MSA cases, 62% exhibited neurogenic change.80 The prevalence was relatively low presumably because up to 25% of our patients had a disease duration of 1 year or less. In such early cases, the diagnosis of MSA should be made with extreme caution. In addition to the clinical diagnostic criteria, we usually add an imaging study and we perform gene analysis to the extent possible. The prevalence of neurogenic change was 52% in the first

**6.1. MSA** 

other studies.

This figure illustrates where to insert concentric needles to measure external sphincter EMG.

**Figure 4.** The external anal sphincter and the external urethral sphincter.

A normal MUP usually has a 50–500 microV amplitude, a 3–8 msec duration, and 2–4 phases. In order to assess reinnervation, usually 10–20 single MUPs are recorded, which are automatically provided by an EMG computer. To ascertain single MUP, we still check each wave manually and adjust the onset and offset of each wave. It is particularly important to include late components (satellite potentials) to measure the duration of each unit.42 When the muscle is chronically denervated, an intact nerve tends to innervate the adjacent denervated muscle fibers. As a result, MUPs become of high amplitude, of long duration, and polyphasic. Among various EMG parameters, the use of duration, MUP area, and number of turns is recommended for optimal diagnostic power (sensitivity and specificity) in the EAS muscle.45 In addition, the results are dependent on the methods used; e.g., including or excluding late components. Palace et al. proposed that either of two criteria is sufficient to diagnose neurogenic changes in the EAS-EMG: (*a*) more than 20% of MUPs have a duration > 10 msec, or (*b*) the average duration of MUPs > 10 msec, particularly including the late components.38 When satellite potentials were excluded, the duration of MUPs did not differ significantly between Parkinson's disease and MSA.48 When lower motor neuron-type abnormalities are not apparent, it is reported that abnormal MUP recruitment pattern suggests pyramidal tract involvement.18 In addition to MUP analysis in the external sphincter muscles, other neurophysiologic tests, e.g., pudendal nerve conduction, sacral reflexes, somatosensory evoked potentials and cranial magnetic stimulation, and urodynamic studies, can be of particular value in the study of autonomic patients.29,40,41
