Sphincter electromyography in diagnosis of multiple system atrophy: technical issues

Laboratory-Supported Multiple System Atrophy beyond Autonomic Function Testing and Imaging: A Systematic Review by the MoDiMSA Study Group

Background

Neuroimaging has been used to support a diagnosis of possible multiple system atrophy (MSA). Only blood pressure changes upon standing are included in the second consensus criteria but other autonomic function tests (AFT) are also useful to diagnose widespread and progressive autonomic failure typical of MSA. Additional diagnostic tools are of interest to improve accuracy of MSA diagnosis.

Objectives

To assess the utility of diagnostic tools beyond brain imaging and AFT in enhancing a laboratory-supported diagnosis of MSA to support the upcoming revision of the consensus criteria.

Methods

The International Parkinson and Movement Disorders Society MSA Study Group (MoDiMSA) performed a systematic review of original papers on biomarkers, sleep studies, genetic, neuroendocrine, neurophysiological, neuropsychological and other tests including olfactory testing and acute levodopa challenge test published before August 2019.

Results

Evaluation of history of levodopa responsiveness and olfaction is useful in patients in whom MSA-parkinsonian subtype is suspected. Neuropsychological testing is useful to exclude dementia at time of diagnosis. Applicability of sphincter EMG is limited. When MSA-cerebellar subtype is suspected, a screening for the common causes of adult-onset progressive ataxia is useful, including spinocerebellar ataxias in selected patients. Diagnosing stridor and REM sleep behavior disorder is useful in both MSA subtypes. However, none of these tools are validated in large longitudinal cohorts of postmortem confirmed MSA cases.

Conclusions

Despite limited evidence, additional laboratory work-up of patients with possible MSA beyond imaging and AFT should be considered to optimize the clinical diagnostic accuracy.

Application of bulbocavernosus reflex combined with anal sphincter electromyography in the diagnosis of MSA and PD

BACKGROUND

Multiple system atrophy (MSA) and Parkinson's disease (PD) are characterized by abnormal changes in the extrapyramidal system and autonomic nervous system. The two diseases are consistent in some clinical manifestations and few objective indicators for preclinical prediction.

METHOD

The value of anal sphincter electromyography (EAS-EMG) in the diagnosis of MSA has been recognized by researchers, while the bulbocavernosus reflex (BCR) has been found to be of great significance in the diagnosis of PD and MSA. In this study, the diagnostic value of BCR combined with EAS-EMG in patients with MSA and PD was further discussed.

RESULTS

Forty-three patients with MSA, 120 patients with PD and 40 normal controls were recruited, and the BCR and EAS-EMG were evaluated. The average duration, average amplitude, percentage of polyphasic waves, satellite potential, phase pattern and amplitude of strong contraction were observed. The results showed that the abnormal rate of BCR in the control group was 0%, and the abnormal rate of EAS-EMG was 2.5%; these differences were statistically significant compared with the MSA group (BCR 90.9%, EAS-EMG 93.9%). For patients with PD, there were some significant differences in BCR and EAS-EMG between the control group and the PD group.

CONCLUSION

Our study revealed that BCR combined with EAS-EMG detection can provide an objective electrophysiological basis for the diagnosis of MSA and PD, which is beneficial for the early treatment of disease.

Differential Diagnosis of Multiple System Atrophy-Parkinsonism and Parkinson's Disease Using α-Synuclein and External Anal Sphincter Electromyography

Background and aim: Discriminating multiple system atrophy-parkinsonism (MSA-P) from Parkinson's disease (PD) is challenging. We aimed to provide a new method to make an identification between MSA-P and PD by combining biofluid marker with electrophysiology marker.

Methods: The XYCQ EV Enrichment KIT was applied to extract extracellular vesicles (EVs) from saliva. The levels of α-syn which included total α-syn (α- syn_Total), phosphorylated-ser129 α-syn (α-syn_PS129) and oligomeric α-syn (α-syn_Olig) in EVs of saliva were tested by new developed Electrochemiluminescence (ECL) assays. We collected multi-motor unit potential (MUP) of all participants who conducted external anal sphincter electromyography (EAS-EMG). The duration, phase, amplitude and satellite potential of EAS-EMG were analyzed. The Receiver operator characteristic (ROC) curve was adopted to analyze the diagnostic utility of α-syn in EVs of saliva, EAS-EMG for MSA-P.

Results: In EVs of saliva, the α-syn_Total concentrations were lower in MSA-P than PD (P = 0.003). No significant difference was shown in α-syn_Olig and α-syn_PS129. α-syn_Total 4.46 pg/ng distinguished MSA-P from PD with area under the curve (AUC) 0.804. Compared with PD, the duration, phase and satellite potential of EAS-EMG in MSA-P were increased (P = 0.002, 0.008, 0.001). There was no significant difference in amplitude. ROC curve showed that the duration (AUC: 0.780), phase (AUC: 0.751), and satellite potential (AUC: 0.809) had both diagnostic value for MSA-P. The combination of α-syn_Total in salivary EVs and EAS-EMG (including duration, phase and satellite potential) could efficiently make a differentiation between MSA-P and PD with sensitivity of 100% and specificity of 86%. The AUC value was 0.901.

Conclusion: The study suggested the combination of α-syn_Total in salivary EVs and EAS-EMG could help efficiently distinguish MSA-P from PD.

Early presentation of urinary retention in multiple system atrophy: can the disease begin in the sacral spinal cord?

Lower urinary tract (LUT) dysfunction presents early in multiple system atrophy (MSA), usually initially as urinary urgency, frequency and incontinence, and voiding difficulties/urinary retention becomes apparent over time. We have observed a subset of patients who instead presented initially with urinary retention requiring catheterisation. At presentation, these patients had only subtle neurological signs that would not fulfil the diagnostic criteria of MSA; however, the anal sphincter electromyography (EMG) was abnormal and they reported bowel and sexual dysfunction, suggesting localisation at the level of the sacral spinal cord. They subsequently developed classical neurological signs, meeting the diagnostic criteria for probable MSA. One patient was confirmed to have MSA at autopsy. We postulate that in a subset of patients with MSA, the disease begins in the sacral spinal cord and then spreads to other regions resulting in the classical signs of MSA. The transmissibility of alpha-synuclein has been demonstrated in animal models and the spread of pathology from sacral cord to other regions of the central nervous system is therefore plausible. Patients presenting with urinary retention and mild neurological features would be an ideal group for experimental trials evaluating neuroprotection in MSA

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.

The Utility of Post-Void Residual Volume versus Sphincter Electromyography to Distinguish between Multiple System Atrophy and Parkinson's Disease

OBJECTIVE

To determine the ability of sphincter electromyography (EMG) and post-void residual urine volume (PVR) during a free-flow study and a pressure-flow study (PFS) for distinguishing multiple system atrophy (MSA) from Parkinson's disease (PD).

METHODS

We retrospectively reviewed 241 case records; both urodynamic study and sphincter EMG were performed in patients with MSA (n = 147) and PD (n = 94).

RESULTS

There was a statistically significant difference (p < 0.01) in the mean PVR during the free-flow study (113.1 ± 7.5 mL in MSA and 40.4 ± 3.8 mL in PD), mean PVR during PFS (230.1 ± 12.6 mL in MSA and 71.7 ± 6.6 mL in PD), and mean duration of MUP for sphincter EMG (9.3 ± 0.1 ms in MSA and 7.7 ± 0.1 ms in PD). The area under the curve used for differentiating MSA from PD was 0.79 and 0.73 for PVR during PFS and the free-flow study, respectively. There was a mean duration of 0.69 ms for the sphincter EMG.

CONCLUSIONS

The present results suggested that PVR was more appropriate than sphincter EMG for differentiating MSA from PD.

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.

Motor unit potentials with satellites in dystrophinopathies

INTRODUCTION

The objective of this study was to analyze the motor unit potentials (MUPs) with satellite components i.e., delayed by at least 2ms baseline from the main component, in the dystrophinopathies.

METHODS

The parameters of the MUPs recorded from the biceps brachii muscle in the Duchenne and Becker Muscle Dystrophy (DMD, BMD) were analyzed. The origin of the MUP satellite components was studied using a computer simulation.

RESULTS

As compared with normal potentials, both the main and the satellite MUP components are smaller in size, while the main components are more irregular. The computer simulation allows the range of muscle fiber diameters to be determined, and suggests that the variability characterizing diameters within the motor unit is responsible for generating the delayed, satellite components, via the linear relationship between the fiber diameter and the conduction velocity of the action potential.

DISCUSSION

The enhanced understanding of the origin of the MUP satellite components augments the knowledge about the relationship between muscle morphology and bioelectrical activity. The indirect evaluation of the range of muscle fiber diameters by means of a computer simulation may provide a new quantitative morphological data available from the EMG.

Do Sacral/Peripheral Lesions Contribute to Detrusor-Sphincter Dyssynergia?

OBJECTIVES

While detrusor-sphincter dyssynergia (DSD) occurs in conjunction with lesions between the brainstem and the sacral cord, it is not well known whether sacral/peripheral lesions contribute to DSD. We studied the relationship between DSD and sacral/peripheral lesions.

METHODS

One hundred and forty-four patients with diverse neurologic etiologies underwent urodynamic study and analysis of motor unit potentials in the external sphincter muscles, 117 of whom were able to void during a urodynamic test. Sacral/peripheral lesion (SPL) is defined as neurogenic change in motor unit potentials. Detrusor overactivity (DO) is defined as involuntary detrusor contractions during the filling phase, which commonly occurs in lesions above the sacral cord. We considered DO as a putative indicator of supra-sacral lesion.

RESULTS

DSD was found in 44 (30.6%), SPL in 71 (49.3%), and DO in 83 (57.6%) of 144 patients, respectively. The incidence of DSD was the same in the SPL positive group (31%) and the SPL negative group (30.1%). By contrast, within the subgroup of patients without DO, the incidence of DSD was significantly more common in the SPL positive group (41.4%) than in the SPL negative group (25.0%) (P < 0.05). In 53 of the SPL positive group who were able to void, postvoid residual >100 mL was more common in patients with DSD (not statistically significant).

CONCLUSION

The results of the present study suggest that not only suprasacral pathology, but also sacral/peripheral lesions can produce DSD. In light of the previous reports, DSD might also result from partial lesions in peripheral branches of the sphincter circuit.

Lower Urinary Tract Function in Spinocerebellar Ataxia 6

OBJECTIVE

To investigate lower urinary tract function in spinocerebellar ataxia type 6 (SCA6).

METHODS

We recruited, without bias, nine SCA6 patients with a mean cytosine-adenine-guanine repeat length of 24.3 (21-26, normal <18). They were four men, five women; mean age 58.6 years; mean disease duration 8.2 years. We performed a urinary symptom questionnaire and a urodynamics.

RESULTS

Urinary symptoms were observed in five of nine patients (56%) and urinary frequency in three of nine patients (33%), and none had urinary retention. Urodynamic abnormalities included detrusor overactivity in one (11%) and weak detrusor on voiding in two, but none had postvoid residual urine. Sphincter electromyography revealed, while mild in degree, neurogenic change in five of the eight patients (63%) on whom the test was performed.

CONCLUSION

We observed urinary frequency in 33%; detrusor overactivity in only 11%; and neurogenic change in the sphincter electromyography in 63% of our nine SCA6 patients. These findings might be relevant to the cerebellar and spinal cord pathologies of this disease.

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.

Overactive bladder in diabetes: a peripheral or central mechanism?

AIMS

To study diabetic cystopathy with reference to overactive bladder (OAB).

METHODS

We retrospectively analyzed diabetic cystopathy in our digitized database that comprised 2300 case records, including data from a lower urinary tract symptoms questionnaire, data from a urodynamic study, and data from neurological examinations.

RESULTS

Diabetic cystopathy was seen in 4% of cases (84 cases): 58 males, 26 females; mean age, 60.8 years; duration of diabetes, 143.5 months; HbA1C, 7.7 %. In addition to large post-void residual and decreased sensation, OAB, detrusor overactivity (DO), and increased bladder sensation were seen in 55%, 42%, and 14%, respectively. The frequency of DO in patients with increased bladder sensation was 58%. DO increased with age, but not with the duration of diabetes. A brain MRI was performed in 32 cases. The frequency of multiple cerebral infarction (MCI) in patients with DO was 76.5%. The remaining 23.5% of patients with DO had no MCI, and the remaining 42% with increased bladder sensation had no DO.

CONCLUSIONS

OAB commonly occurs in diabetic cystopathy. Both central and peripheral mechanisms are involved, e.g., MCI due to diabetic cerebral vasculopathy for the DO, and, to a lesser extent, peripheral nerve irritation for the DO and increased bladder sensation.

Psychogenic urinary dysfunction: a uro-neurological assessment

AIMS

The diagnosis of psychogenic urinary dysfunction (PUD) is one of exclusion, particularly from urologic and neurologic causes, and is usually accompanied by more obvious psychologic/ psychiatric features. We here describe patients with PUD who were diagnosed in our uro- neurological laboratory.

MATERIALS AND METHODS

We reviewed the digitized records of 2,300 urodynamic cases treated in the past 6 years to identify patients who fulfilled the diagnostic criteria of PUD. All 2,300 patients had completed a urinary questionnaire and undergone both electromyography (EMG)-cystometry and a detailed neurological examination. In addition, pressure-flow analysis, neurophysiology tests including sphincter EMG analysis, and MRI of the brain and spinal cord were performed as applicable.

RESULTS

PUD was seen in 16 cases (0.7%): 6 men, 10 women, mean age 37 years. Lower urinary tract symptoms (LUTS) included overactive bladder (OAB) alone in 5, difficult urination alone in one, and both in 10. LUTS commonly occurred in particular situations, for example, OAB only while riding the train. Some patients showed extremely infrequent toileting. The urodynamic findings were normal except for increased bladder sensation (50%) for OAB and acontractile detrusor (31%) for difficulty. The final diagnosis was conversion reaction in six followed by anxiety in four.

CONCLUSIONS

PUD patients experienced the situational occurrence of OAB and/or difficult urination and, in some patients, extremely infrequent toileting. The main urodynamic abnormalities were increased bladder sensation and acontractile detrusor. However, even in cases suggestive of PUD, a non-PUD pathology behind the symptoms should be explored.

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.

Urinary retention due to an isolated sacral root injury caused by sacral fracture

STUDY DESIGN

A case report.

SETTING

Urodynamic laboratory in a university hospital, Chiba, Japan.

CASE REPORT

A young woman who suffered from urinary retention following a skiing accident. A sacral X-ray (lateral view) revealed an S2-3 sacral fracture. The patient gradually regained the ability to urinate. At 3 months after the accident, she still suffered difficult urination, although her neurological findings were normal. A urodynamic study showed an acontractile detrusor and a neurogenic sphincter electromyogram (EMG), together indicative of isolated sacral nerve injury.

CONCLUSIONS

It was postulated that the S2-3 sacral fracture had led to bilateral traction of the S2-3 nerve roots, producing transient bladder paralysis (parasympathetic fibers) and incomplete sphincter paresis (somatic fibers). Sacral fracture is also of high clinical suspicion for urinary retention in frail elderly people, because it can result from simple falls.

Pyridostigmine in autonomic failure: can we treat postural hypotension and bladder dysfunction with one drug?

In a 66-year-old man with autonomic failure, pyridostigmine (180 mg/day orally) improved both postural hypotension and underactive detrusor bladder dysfunction. Acetylcholinesterase inhibition may be useful in the management of orthostatic hypotension and bladder dysfunction in autonomic failure patients.

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.

Urinary dysfunction and autonomic control in amyloid neuropathy

Uro-neurological assessment was performed in four patients with small-fiber neuropathy due to amyloidosis (2 transthyretin-type/2 immunoglobulin light-chain-type). Voiding difficulties were due to detrusor weakness and impaired bladder sensation. In two patients cholinesterase inhibition treatment caused urge incontinence, indicating detrusor denervation supersensitivity. The underlying mechanisms of urinary dysfunction seem to involve postganglionic cholinergic and afferent somatic nerves.

When is Onuf's nucleus involved in multiple system atrophy? A sphincter electromyography study

BACKGROUND

External anal sphincter (EAS) electromyography (EMG) abnormalities can distinguish multiple system atrophy (MSA) from Parkinson's disease in the first five years after disease onset. However, the prevalence of the abnormalities in the early stages of MSA is unknown.

OBJECTIVES

To present EAS-EMG data in the various stages of MSA.

METHODS

84 patients with "probable" MSA were recruited (42 men, 42 women; mean age 62 years (range 47 to 78); mean disease duration 3.2 years (0.5 to 8.0; <1 year in 25%); 50 cerebellar form (MSA-C), 34 parkinsonian form (MSA-P)). EAS motor unit potential (MUP) analysis and EMG cystometry were carried out in all patients.

RESULTS

The overall prevalence of neurogenic change of the EAS MUP was 62%-52% in the first year after disease onset, increasing to 83% by the fifth year (p<0.05); it also increased with severity of gait disturbance (p<0.05), storage and voiding disorders, and detrusor sphincter dyssynergy (NS). The neurogenic change was not correlated with sex, age, MSA-P/C, postural hypotension, constipation, erectile dysfunction in men, underactive or acontractile detrusor, or detrusor overactivity. In 17 incontinent patients without detrusor overactivity or low compliance, urinary incontinence was more severe in those with neurogenic change than in those without (p<0.05).

CONCLUSIONS

Involvement of Onuf's nucleus in MSA is time dependent. Before the fifth year of illness, the prevalence of neurogenic change does not seem to be high, so a negative result cannot exclude the diagnosis of MSA.

How to diagnose MSA early: the role of sphincter EMG

Multiple system atrophy (MSA) is a degenerative disease manifesting a combination of parkinsonism, cerebellar, pyramidal, and autonomic (including urinary, sexual and anorectal) dysfunction. It is pathomorphologically defined, but lacks a definitive clinical diagnostic test. In patients with probable MSA, abnormal sphincter EMG, as compared to control subjects, has been found in the majority of patients in all the different forms of the disease in most studies, including patients who, as yet, have no urological or anorectal problems. Patients with Parkinson's disease (PD) as a rule do not show marked sphincter EMG abnormalities in the first five years of the disease. Thus, abnormal spontaneous activity or marked motor unit potential changes in sphincter muscles are helpful in distinguishing MSA from PD in the first five years after the onset of symptoms and signs, and from pure autonomic failure, as well as from cerebellar ataxias, if other causes for sphincter denervation have been ruled out. EMG does not distinguish MSA from progressive supranuclear palsy. How early in the course of MSA these abnormalities become significant enough to support diagnosis remains to be established by prospective studies.

Usefulness of an increase in size of motor unit potential sample

OBJECTIVE

It is known that the sensitivity of quantitative electromyographic (EMG) analysis of motor unit potentials (MUPs) improves with an increase in MUP sample size to more than 20. However, no normative data and estimate of sensitivity have been published.

METHODS

In the present study sample sizes of 5, 10, 15, 20, 30 and 40 MUPs were obtained from the external anal sphincter (EAS) muscles of 81 controls and 70 patients with cauda equina lesions. For each sample size normative limits and sensitivities for mean values and 'outliers' were calculated for 8 MUP parameters.

RESULTS

As the size of the MUP samples increased, normative limits narrowed and sensitivities increased for both statistics of all MUP parameters (sensitivities were 26% at 10, 44% at 20, and 67% at 40 MUPs with mean values and outliers of MUP area, duration and number of turns).

CONCLUSIONS

Our results confirmed a substantial increase in the sensitivity of MUP analysis by enlargement of the MUP sample size to more than 20 MUPs. The gain in sensitivity seem to be greater than the increase obtained by examination of contralateral EAS muscle.

SIGNIFICANCE

Findings might be useful to clinical neurophysiologists planning strategies for electrodiagnostic evaluation of lower sacral segments.