Quantitative anal sphincter EMG in multisystem atrophy and 100 controls

Diagnostic and Prognostic Value of External Anal Sphincter EMG Patterns in Multiple System Atrophy

Background

It is debated whether external anal sphincter (EAS) electromyography can distinguish between multiple system atrophy (MSA) and Parkinson's disease (PD), whereas its usefulness for MSA prognosis is unknown.

Objectives

We explored the diagnostic and prognostic value and clinical correlations of EAS electromyography patterns in MSA.

Methods

We collected clinical data and EAS electromyography findings in 72 patients with MSA and 21 with PD.

Results

We identified four EAS patterns. The normal pattern was frequently observed in PD and associated with prolonged survival when identified in MSA. Abnormal patterns were predominant in MSA. The most severe pattern was associated with the highest likelihood of MSA diagnosis and with the worst prognosis in the MSA cohort. MSA patients with EAS abnormalities often showed urogenital symptoms and fecal incontinence.

Conclusions

The increasing severity of EAS electromyography patterns paralleled diagnostic accuracy and survival in MSA, and correlated with prevalence of bladder and bowel symptoms. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Ultrasound-Guided Needle Electromyography of the External Anal Sphincter

BACKGROUND

Anal sphincter needle electromyography (EMG) is a useful tool to evaluate various neurologic lesions. However, landmark-based needle placement has risks of missing the intended target including risk of bowel penetration. Ultrasound guidance has been widely used to enhance needle placement for various interventional procedures, but it has not been previously reported for use in anal sphincter EMG.

OBJECTIVE

To demonstrate the accuracy of ultrasound-guided needle insertion into the external anal sphincter (EAS).

DESIGN

Observational study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

A single live male participant and six fresh cadavers.

METHODS

A preliminary study was conducted in a single live male participant to investigate the utility of ultrasonography imaging for the EAS and proper transducer location. After this preliminary study, 12 sides of the EAS in six fresh cadavers were assessed. A hooked fine wire was inserted into the EAS under ultrasound guidance.

MAIN OUTCOME MEASURES

Accuracy of needle placement was assessed after cadaver dissection.

RESULTS

The EAS was easily identified with ultrasound in preliminary and cadaver studies. The needle tips were located in the EAS in 11 of 12 cadavers.

CONCLUSIONS

Ultrasound-guided needle EMG of the EAS is convenient and accurate in cadavers and may be useful in clinical practice. Further studies comparing ultrasound-guided and landmark-guided needle EMG of the EAS in live patients will be needed.

Neurophysiology of the pelvic floor in clinical practice: a systematic literature review

Neurophysiological testing of the pelvic floor is recognized as an essential tool to identify pathophysiological mechanisms of pelvic floor disorders, support clinical diagnosis, and aid in therapeutic decisions. Nevertheless, the diagnostic value of these tests in specific neurological diseases of the pelvic floor is not completely clarified. Seeking to fill this gap, the members of the Neurophysiology of the Pelvic Floor Study Group of the Italian Clinical Neurophysiology Society performed a systematic review of the literature to gather available evidence for and against the utility of neurophysiological tests. Our findings confirm the utility of some tests in specific clinical conditions [e.g. concentric needle electromyography, evaluation of sacral reflexes and of pudendal somatosensory evoked potentials (pSEPs) in cauda equina and conus medullaris lesions, and evaluation of pSEPs and perineal sympathetic skin response in spinal cord lesions], and support their use in clinical practice. Other tests, particularly those not currently supported by high-level evidence, when employed in individual patients, should be evaluated in the overall clinical context, or otherwise used for research purposes.

Gastrointestinal dysfunction in idiopathic Parkinsonism: A narrative review

Currently, gastrointestinal (GI) dysfunctions in Parkinson's disease (PD) are well-recognized problems and are known to be the initial symptoms in the pathological process that eventually results in PD. Many types of PD-associated GI dysfunctions have been identified, including weight loss, nausea, hypersalivation, dysphagia, dyspepsia, abdominal pain, intestinal pseudo-obstruction, constipation, defecatory dysfunction, and small intestinal bacterial overgrowth. These symptoms can influence on other PD symptoms and are the second most significant predictor of the quality of life of these patients. Recognition of GI symptoms requires vigilance on the part of clinicians. Health-care providers should routinely ask direct questions about GI symptoms during office visits so that efforts can be directed at appropriate management of these distressing manifestations. Multiple system atrophy (MSA) and progressive supranuclear palsy are two forms of neurodegenerative Parkinsonism. Symptoms of autonomic dysfunctions such as GI dysfunction are common in patients with parkinsonian disorders. Despite recent progress in the recognition of GI dysfunctions, there are a few reviews on the management of GI dysfunction and GI symptoms in idiopathic Parkinsonism. In this review, the clinical presentation, pathophysiology, and treatment of each GI symptom in PD, MSA, and prostate-specific antigen will be discussed.

Sphincter electromyography in diabetes mellitus and multiple system atrophy

AIMS

Abnormalities of external anal sphincter electromyography (EAS-EMG) characterize multiple system atrophy (MSA) and focal cauda equina or conus medullaris lesions. This study is designed to determine whether and how diabetic polyneuropathy (DPN) affects EAS as compared to the abnormalities seen in MSA.

METHODS

We conducted multi-motor unit potential (MUP) analysis of EAS in 22 healthy controls, 32 diabetes mellitus (DM) patients without neuropathy, 38 DPN patients, and 68 MSA patients.

RESULTS

DPN patients had a significant (P < 0.01) increase in MUP mean duration, mean amplitude, percentage of long duration MUPs, and satellite rate, but to a lesser extent than MSA. Mean duration and satellite rate showed the least overlap among different groups in individual value distributions.

CONCLUSIONS

Compared with MSA, DPN affects EAS to a lesser degree as judged by neurogenic MUP abnormalities in EMG. Mean duration and satellite rate may serve as the most discriminating aspects in MUP analysis of EAS.

Electrophysiological features of lower motor neuron involvement in progressive supranuclear palsy

BACKGROUND

Abnormalities of the spinal cord were considered uncommon in progressive supranuclear palsy (PSP), and therefore spinal symptoms were not included among PSP characteristic features. However there have been some neuropathological reports of spinal cord lesions in patients with PSP. The aim of our study was to find out if the possible lower motor neuron involvement in PSP is reflected by electromyographic (EMG) and/or electroneurographic (ENG) abnormalities.

MATERIAL

24 patients with clinically probable PSP (mean age 67.5 yrs; 66% males) were included in the study. The control group for ENG studies consisted 25 age matched healthy volunteers.

METHODS

Nerve conduction studies in the ulnar, peroneal and sural nerves and EMG of the first interosseus dorsal and tibial anterior muscles were performed.

RESULTS

The only ENG abnormality observed was decreased compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes in the ulnar nerve. Such decrease was registered in 8.3% and 20% of PSP patients respectively. There was no significant difference between the values of ENG parameters between PSP patients and the control group. In EMG abnormalities suggesting chronic reinnervation were recorded in the first interosseous dorsal (FID) muscle in 45.8%, and in the tibialis anterior (TA) muscle in 37.5% of PSP patients. A significant correlation was found between the age of PSP patients and their mean motor unit potential (MUP) amplitude in TA muscle (p=0.04) and also between the age of onset and MUP amplitude in both, the TA and FID muscles (p=0.026 and p=0.03 respectively).

CONCLUSIONS

In PSP, neurogenic EMG abnormalities in skeletal muscles are present in nearly half the patients suggesting a loss of motor neurons in the anterior horns of the spinal cord which is in line with our histopathological findings. In contrast, electrophysiological signs of neuropathy in peripheral nerves in PSP are very rare. Concluding, although PSP is characterized by the pathological process in specific basal ganglia and brainstem areas, our electromyographic study suggests the need for broadening the spectrum of PSP for lower motor neurons degeneration.

Anal sphincter electromyography in patients with newly diagnosed idiopathic parkinsonism

OBJECTIVES

The differential diagnosis of patients with idiopathic parkinsonism is difficult, especially early in the course of the disease. External anal sphincter electromyography (EAS-EMG) has been reported to be of value in the differential diagnosis between Parkinson's disease (PD) and multiple system atrophy (MSA). Patients with MSA are reported to have pathological EAS-EMG and patients with PD are reported to have significantly less pathological EAS-EMG results. Comparisons between patients with parkinsonian disorders have usually been made many years into the disease, and thus it is largely unknown if the results of EAS-EMG can be used to distinguish the different diagnoses in the early phase of the disease.

MATERIALS AND METHODS

We investigated 148 newly diagnosed patients with idiopathic parkinsonism from a population-based incidence cohort (100 definite PD, 21 probable PD, 16 MSA, 11 progressive supranuclear palsy, and 40 controls) with EAS-EMG within 3 months of their first visit and, in the majority of patients, before start of treatment with dopaminergic drugs. The clinical diagnoses were made using established clinical diagnostic criteria after a median follow-up of 3 years.

RESULTS

All patient groups had more pathological EAS-EMG results than controls. No EAS-EMG differences were found between the patient groups, especially not between PD and MSA.

CONCLUSIONS

External anal sphincter electromyography examination cannot separate the different parkinsonian subgroups from each other in early course of the diseases.

Advances in diagnostic assessment of fecal incontinence and dyssynergic defecation

Disorders of the anorectum and pelvic floor affect approximately 25% of the population. Their evaluation and treatment have been hindered by a lack of understanding of underlying mechanism(s) and a working knowledge of the diagnostic advances in this field. A meticulous evaluation of anorectal structure and its function can provide invaluable insights to the practicing gastroenterologist regarding the pathogenic mechanism(s) of these disorders. Also, significant new knowledge has emerged over the past decade that includes the development of newer diagnostic tools such as high-resolution manometry and magnetic resonance defecography as well as a better delineation of the clinical and pathophysiologic subtypes of constipation and incontinence. This article provides an up-to-date review on the role of diagnostic tests in the evaluation of fecal incontinence and constipation with dyssynergic defecation.

Anal sphincter motor unit potential (MUP) differences between sides, between rest and voluntary contraction, and between MUP analysis programs in normal subjects

Trauma to the external anal sphincter resulting in incontinence is a relatively common disorder. Methods to detect damage include pudendal nerve conduction studies and needle EMG. We have applied a quantitative EMG technique using decomposition-enhanced software to isolate motor unit potentials (MUPs) and their surface representation from an anal probe electrode in healthy nulliparous women. MUPs were readily isolated and metric values compared favorably with those recorded with different software.

Anal sphincter EMG in the diagnosis of parkinsonian syndromes

BACKGROUND

The role of electromyography (EMG) recorded from the external anal sphincter (EAS) in the diagnosis of atypical parkinsonian syndromes is a matter for continuous debate. Most studies addressing this issue are retrospective.

METHODS

In this study, we prospectively investigated six patients with Parkinson's Disease (IPD), 14 patients with multiple system atrophy (MSA) and eight with progressive supranuclear palsy (PSP) using EMG of the EAS, motor-evoked potential (MEP) to the EAS and EMG of m. gastrocnemius and nerve conduction velocity measured at the sural nerve. Patients were followed up for 2 years to secure correct diagnosis.

RESULTS

The mean duration of motor unit potentials (MUPs) recorded from the EAS was significantly longer in patients with MSA and PSP compared with MUPs recorded from patients with PD (P < 0.005 for both). There were no signs of diffuse loss of motor neurons or peripheral neuropathy. MEP revealed signs of supranuclear affection in patients with MSA, whereas in patients with PSP the mechanism is a focal loss of motor neurons in Onuf's nucleus.

CONCLUSION

Abnormal EMG of the EAS is strongly suggestive of atypical parkinsonism and the pathophysiology may be different in patients with MSA and PSP.

Neurophysiology in neurourology

The bladder has only two essential functions. It stores and periodically empties liquid waste. Yet it is unique as a visceral organ, allowing integrated volitional and autonomous control of continence and voiding. Normal function tests the integrity of the nervous system at all levels, extending from the neuroepithelium of the bladder wall to the frontal cortex of the brain. Thus, dysfunction is common with impairment of either the central or peripheral nervous system. This monograph presents an overview of the neural control of the bladder as it is currently understood. A description of pertinent peripheral anatomy and neuroanatomy is provided, followed by an explanation of common neurophysiological tests of the lower urinary tract and associated structures, including both urodynamic and electrodiagnostic approaches. Clinical applications are included to illustrate the impact of nervous system dysfunction on the bladder and to provide indications for testing.

Neurophysiological testing in anorectal disorders

Neurophysiological tests of anorectal function can provide useful information regarding the integrity of neuronal innervation, as well as neuromuscular function. This information can give insights regarding the pathophysiological mechanisms that lead to several disorders of anorectal function, particularly fecal incontinence, pelvic floor disorders and dyssynergic defecation. Currently, several tests are available for the neurophysiological evaluation of anorectal function. These tests are mostly performed on patients referred to tertiary care centers, either following negative evaluations or when there is lack of response to conventional therapy. Judicious use of these tests can reveal significant and new understanding of the underlying mechanism(s) that could pave the way for better management of these disorders. In addition, these techniques are complementary to other modalities of investigation, such as pelvic floor imaging. The most commonly performed neurophysiological tests, along with their indications and clinical utility are discussed. Several novel techniques are evolving that may reveal new information on brain-gut interactions.

Neurophysiology of the neurogenic lower urinary tract disorders

The nervous system structures involved in the control of the lower urinary tract (LUT) are usually divided using a neuroanatomical classification system into suprapontine, pontine, spinal and sacral. In all patients with LUT symptoms, after exclusion of local causes, a nervous system disorder needs to be considered. For the diagnosis of neurogenic LUT disorders, in addition to clinical assessment, neurophysiologic testing might be useful. Imaging and other laboratory studies (e.g., cystometry) often provide relevant additional information. Neurophysiologic tests are more useful in patients with sacral compared with suprasacral disorders. Although in patients with LUT disorders external urethral sphincter (EUS) electromyography (EMG) would seem the most appropriate, anal sphincter EMG is the single most useful diagnostic test, particularly for focal sacral lesions, and atypical parkinsonism. Another clinically useful method that tests the sacral segments, and complements EMG, is the sacral (penilo/clitoro-cavernosus) reflex. Kinesiologic EMG is useful to demonstrate detrusor sphincter dyssynergia (i.e., increased EUS activity during bladder contraction), which is particularly common in spinal cord disease. Somatosensory evoked potential (SEP) and motor evoked potential (MEP) studies (cortical and lumbar) may be useful to diagnose clinically silent central lesions. MEP, in addition, seems to be very promising in research into cortical excitability. Theoretically, cortical SEP on bladder/urethra stimulation would be much more useful than pudendal SEP because it tests thin nerve afferents from the pelvic viscera. However, the utility of this technique is limited by technical difficulties, which can be partially overcome by the concomitant recording of a palmar sympathetic skin response (SSR). SSR recorded from the saddle region is also useful for testing the lumbosacral sympathetic system. Although the technique of detrusor EMG has been recently described in humans, a clinically useful test for evaluating the sacral parasympathetic system, which is crucial for LUT functioning, is still lacking.

Neurophysiological testing in anorectal disorders

The neurophysiological techniques currently available to evaluate anorectal disorders include concentric needle electromyography (EMG) of the external anal sphincter, anal nerve terminal motor latency (TML) measurement in response to transrectal electrical stimulation or sacral magnetic stimulation, motor evoked potentials (MEPs) of the anal sphincter to transcranial magnetic cortical stimulation, cortical recording of somatosensory evoked potentials (SEPs) to anal nerve stimulation, quantification of electrical or thermal sensory thresholds (QSTs) within the anal canal, sacral anal reflex (SAR) latency measurement in response to pudendal nerve or perianal stimulation, and perianal recording of sympathetic skin responses (SSRs). In most cases, a comprehensive approach using several tests is helpful for diagnosis: needle EMG signs of sphincter denervation or prolonged TML give evidence for anal motor nerve lesion; SEP/QST or SSR abnormalities can suggest sensory or autonomic neuropathy; and in the absence of peripheral nerve disorder, MEPs, SEPs, SSRs, and SARs can assist in demonstrating and localizing spinal or supraspinal disease. Such techniques are complementary to other methods of investigation, such as pelvic floor imaging and anorectal manometry, to establish the diagnosis and guide therapeutic management of neurogenic anorectal disorders.

Is sphincter electromyography a helpful investigation in the diagnosis of multiple system atrophy? A retrospective study with pathological diagnosis

Sphincter electromyography (spEMG) is often used as an ancillary test when multiple system atrophy (MSA) is suspected. Our aim was to determine the clinical features associated with spEMG being performed, the influence of the result on the final clinical diagnosis, and its utility as a clinical investigation. A retrospective audit of all cases in the Queen Square Brain Bank between 1989 and 2002 was performed. The clinical features and diagnostic accuracy were compared between patients in whom spEMG was performed and those in whom it was not. From 845 sets of complete clinical records, we identified 37 (4.4%) cases that had been investigated with spEMG. Thirty of these cases had a pathological diagnosis of MSA. Of these 30, 24 had abnormal spEMGs, 5 had a borderline result, and only 1 had a normal spEMG. Sixty-six cases had pathologically proven MSA but no spEMG. Those investigated with spEMG were younger at disease onset (P < 0.001), more frequently male (P = 0.03), and more likely to have had other investigations performed. They had a greater incidence of pyramidal tract signs at final clinical diagnosis, and the final clinical diagnostic accuracy was higher (P = 0.04). Due to the retrospective nature of the study, balanced populations for calculation of sensitivity and specificity were not available. In this selected series of pathologically confirmed cases, investigation with spEMG was one of several factors associated with improved clinical diagnostic accuracy. A normal spEMG is unlikely in pathologically proven MSA, at least in cases with a mean symptom duration of more than 5 years when the test is performed.

Sonographic assessment of urinary retention in multiple system atrophy and idiopathic Parkinson's disease

Sonography of the bladder was performed before and after voluntary voiding in 20 subjects with possible/probable multiple system atrophy (MSA), 20 patients with idiopathic Parkinson's disease (PD), and 20 healthy controls. Mean residual volume was 173 ml (SD, 194) in MSA and significantly increased compared to both PD (21 ml; SD, 49) and controls (13 ml; SD, 12). Incomplete voiding (>100 ml of residual volume) was found in 11 subjects with MSA but only in 1 patient with PD. Positive predictive value of increased residual volume for MSA was 91.6% in this study, whereas negative predictive value was only 67.8. Bladder sonography is an objective, simple, and safe tool that allows one to screen for urinary retention, which is highly suggestive but incompletely sensitive for MSA. Because sonography is easily accessible and rapidly performed, it is feasible for routine assessment of atypical Parkinsonism.

Clinical differentiation of parkinsonian syndromes: prognostic and therapeutic relevance

Parkinson disease is the most common cause of parkinsonism, but other causes should always be excluded because they have a different prognosis, respond differently to medical treatment, and should not be managed by surgical means. However, diagnosis, even by experts, is challenging; one autopsy series showed an error rate of 24%. Distinction between various diagnostic possibilities depends on the history and examination findings. The use of certain medications, the rapid rate of disease progression, early onset of falling, the presence of certain dysautonomic symptoms, cognitive or behavioral changes, or a history of poor response to dopaminergic therapy may suggest an atypical form of parkinsonism. Postural hypotension, dementia, supranuclear ophthalmoparesis, or early postural instability should alert the examiner to consider an atypical cause of parkinsonism. Tests of autonomic function and brain imaging are often helpful in distinguishing these diseases.

Sphincter electromyography and multiple system atrophy

Electromyographic studies of the sphincter in patients with multiple system atrophy have shown increased duration and polyphasia of motor unit potentials. These electrophysiological markers have been used to argue for the selective degeneration of sacral motor neurons in Onuf's nucleus in patients with multiple system atrophy. Studies comparing sphincter electromyographic changes in patients with multiple system atrophy and Parkinson's disease have shown significant differences between these two patient populations. Despite the controversy surrounding this claim, recent studies using quantitative electromyographic techniques support the view that reinnervation of the anal sphincter muscles may be a useful diagnostic marker for distinguishing multiple system atrophy from Parkinson's disease. A critical review of these data is needed to assess the validity and reliability of electromyographic changes in multiple system atrophy.

Standardization of anal sphincter electromyography: quantification of continuous activity during relaxation

AIM

Sphincter motor units (MUs) are continuously firing during relaxation. The quantification of this activity is a potentially useful electromyographic (EMG) parameter related to the number of MUs innervating the muscle and the level of motor neuron excitation. The aim of the present study was to develop a reliable, quantitative measure of continuous sphincter muscle activity during relaxation.

METHODS

EMG activity was analyzed during relaxation, 1 minute after insertion of the concentric needle electrode into four sites in the external anal sphincter (EAS) muscle. In 10 control subjects, 8 interference pattern samples were obtained by "turn/amplitude" analysis. In 35 control subjects, a multi-MUP count of continuously firing motor unit potentials (MUPs) was used, quadruplets with scores of 0-6 obtained, and the lower reference limits (95th percentile) calculated. This approach was then evaluated in 57 patients (182 muscles) with cauda equina or conus medullaris lesion (CECML) and 7 patients (13 muscles) with "idiopathic fecal incontinence."

RESULTS

The lower reference ("outlier") limits for MUP count were 0 0 6 6 and 0 1 2 2 for the subcutaneous, and 0 0 0 6 and 0 0 1 1 for the deeper EAS muscles. Both patient groups had a significantly diminished number of continuously firing MUPs, which was below the reference range in 43% of the EAS muscles from CECM patients and in 85% of muscles from patients with idiopathic fecal incontinence. In patients with CECML, the decrease in MUP count correlated with the severity of the lesion, as defined by the sensory deficit.

CONCLUSIONS

MUP count in sphincter muscles during relaxation is technically feasible, and it is a promising tool, particularly in patients with idiopathic fecal incontinence.

Sphincter electromyography in diagnosis of multiple system atrophy: technical issues

Possible technical reasons for the controversy over the role of sphincter electromyography (EMG) in the diagnosis of multiple system atrophy (MSA) were analyzed. In a review of the literature, a high sensitivity (>60%) was found reported in 11 studies that included late components, and no value of the test was found in 4 studies that excluded them. This was also corroborated in a pilot study of 5 patients with probable MSA. With late components included, the mean motor unit potential (MUP) duration was prolonged in all 4 patients with an adequate single-MUP analysis sample and, with late components excluded, in 2 of 5 patients on multi-MUP analysis. At least in diagnostic EMG of MSA patients, late components should be included in the measurement of MUP duration.

The role of electrophysiology in the evaluation of incontinence and prolapse

PURPOSE OF REVIEW

Apart from histopathology, electrophysiological methods are the only tests to reveal neuromuscular involvement in the absence of gross anatomical lesions. They have played a major role in establishing the neuromuscular lesion due to vaginal delivery as a risk factor for incontinence and pelvic organ prolapse, but there is no consensus on the usefulness of different methods. It is timely to reevaluate their validity, and their role in urogynecology.

RECENT FINDINGS

The most important development is the move towards standardization of the diagnostic approach, based on computer assisted quantified techniques of concentric needle electromyography. Studies using less operator biased techniques have confirmed subtle pelvic floor muscle changes in parous women. Reports on usefulness of different tests as predictors of treatment outcome are controversial.

SUMMARY

Standardization of concentric needle electromyography strengthened the position of this test as practical and informative. Neuromuscular changes following vaginal delivery have been reconfirmed, but the usefulness of particular electrophysiological tests in the individual patient needs to be further researched. Valid clinical neurophysiological methods remain valuable as research tools for incontinence and prolapse pathophysiology.

Parkinsonian syndromes and differential diagnosis

PURPOSE OF REVIEW

Physicians are becoming more astute at diagnosing the various parkinsonian syndromes but in clinical practice it is still often difficult to make the correct diagnosis. This review discusses new evidence that may aid physicians in correctly identifying parkinsonian syndromes.

RECENT FINDINGS

We will review the newest developments in the areas of clinical features, electrophysiologic tests, autonomic tests, neuropsychologic tests, imaging, and biochemical markers which may be of value in differentiating these syndromes.

SUMMARY

Accurate diagnosis of the parkinsonian syndromes has important implications for patients, in terms of both prognosis and management. Investigations reported during the last year provide new insight into the distinguishing features of these syndromes and may help clinicians and researchers define these disorders more precisely.