Involvement of the external anal sphincter in amyotrophic lateral sclerosis

Non-motor symptoms in patients with amyotrophic lateral sclerosis: current state and future directions

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive degeneration of both upper and lower motor neurons. A defining histopathological feature in approximately 97% of all ALS cases is the accumulation of phosphorylated trans-activation response (TAR) DNA-binding protein 43 protein (pTDP-43) aggregates in the cytoplasm of neurons and glial cells within the central nervous system. Traditionally, it was believed that the accumulation of TDP-43 aggregates and subsequent neurodegeneration primarily occurs in motor neurons. However, contemporary evidence suggests that as the disease progresses, other systems and brain regions are also affected. Despite this, there has been a limited number of clinical studies assessing the non-motor symptoms in ALS patients. These studies often employ various outcome measures, resulting in a wide range of reported frequencies of non-motor symptoms in ALS patients. The importance of assessing the non-motor symptoms reflects in a fact that they have a significant impact on patients' quality of life, yet they frequently go underdiagnosed and unreported during clinical evaluations. This review aims to provide an up-to-date overview of the current knowledge concerning non-motor symptoms in ALS. Furthermore, we address their diagnosis and treatment in everyday clinical practice.

Dysautonomia in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease, characterized in its typical presentation by a combination of lower and upper motor neuron symptoms, with a progressive course and fatal outcome. Due to increased recognition of the non-motor symptoms, it is currently considered a multisystem disorder with great heterogeneity, regarding genetical, clinical, and neuropathological features. Often underestimated, autonomic signs and symptoms have been described in patients with ALS, and various method analyses have been used to assess autonomic nervous system involvement. The aim of this paper is to offer a narrative literature review on autonomic disturbances in ALS, based on the scarce data available to date.

Sensory Involvement in Amyotrophic Lateral Sclerosis

Although amyotrophic lateral sclerosis (ALS) is pre-eminently a motor disease, the existence of non-motor manifestations, including sensory involvement, has been described in the last few years. Although from a clinical perspective, sensory symptoms are overshadowed by their motor manifestations, this does not mean that their pathological significance is not relevant. In this review, we have made an extensive description of the involvement of sensory and autonomic systems described to date in ALS, from clinical, neurophysiological, neuroimaging, neuropathological, functional, and molecular perspectives.

The Cell Autonomous and Non-Cell Autonomous Aspects of Neuronal Vulnerability and Resilience in Amyotrophic Lateral Sclerosis

Simple Summary

Amyotrophic lateral sclerosis (ALS) is a fatal disease characterized by a progressive paralysis due to the loss of particular neurons in our nervous system called motor neurons, that exert voluntary control of all our skeletal muscles. It is not entirely understood why motor neurons are particularly vulnerable in ALS, neither is it completely clear why certain groups of motor neurons, including those that regulate eye movement, are rather resilient to this disease. However, both vulnerability and resilience to ALS likely reflect cell intrinsic properties of different motor neuron subpopulations as well as non-cell autonomous events regulated by surrounding cell types. In this review we dissect the particular properties of different motor neuron types and their responses to disease that may underlie their respective vulnerabilities and resilience. Disease progression in ALS involves multiple cell types that are closely connected to motor neurons and we here also discuss their contributions to the differential vulnerability of motor neurons.

Abstract

Amyotrophic lateral sclerosis (ALS) is defined by the loss of upper motor neurons (MNs) that project from the cerebral cortex to the brain stem and spinal cord and of lower MNs in the brain stem and spinal cord which innervate skeletal muscles, leading to spasticity, muscle atrophy, and paralysis. ALS involves several disease stages, and multiple cell types show dysfunction and play important roles during distinct phases of disease initiation and progression, subsequently leading to selective MN loss. Why MNs are particularly vulnerable in this lethal disease is still not entirely clear. Neither is it fully understood why certain MNs are more resilient to degeneration in ALS than others. Brain stem MNs of cranial nerves III, IV, and VI, which innervate our eye muscles, are highly resistant and persist until the end-stage of the disease, enabling paralyzed patients to communicate through ocular tracking devices. MNs of the Onuf’s nucleus in the sacral spinal cord, that innervate sphincter muscles and control urogenital functions, are also spared throughout the disease. There is also a differential vulnerability among MNs that are intermingled throughout the spinal cord, that directly relate to their physiological properties. Here, fast-twitch fatigable (FF) MNs, which innervate type IIb muscle fibers, are affected early, before onset of clinical symptoms, while slow-twitch (S) MNs, that innervate type I muscle fibers, remain longer throughout the disease progression. The resilience of particular MN subpopulations has been attributed to intrinsic determinants and multiple studies have demonstrated their unique gene regulation and protein content in health and in response to disease. Identified factors within resilient MNs have been utilized to protect more vulnerable cells. Selective vulnerability may also, in part, be driven by non-cell autonomous processes and the unique surroundings and constantly changing environment close to particular MN groups. In this article, we review in detail the cell intrinsic properties of resilient and vulnerable MN groups, as well as multiple additional cell types involved in disease initiation and progression and explain how these may contribute to the selective MN resilience and vulnerability in ALS.

Prevalence of Gastrointestinal Symptoms, Severity of Dysphagia, and Their Correlation with Severity of Amyotrophic Lateral Sclerosis in a Mexican Cohort

OBJECTIVES

Our study aimed to identify the prevalence and severity of gastrointestinal (GI) symptoms and dysphagia in patients with amyotrophic lateral sclerosis (ALS) and to assess whether a correlation exists between these symptoms and the severity of ALS progression.

METHODS

The presence and severity of GI symptoms and dysphagia were identified by means of the Gastrointestinal Symptom Rating Scale (GSRS) and the Functional Outcome Swallowing Scale (FOSS). The Revised ALS Functional Rating Scale (ALSFRS-R) was utilized to determine the severity of ALS. Analysis of data was performed with Spearman correlations in semi-qualitative variables of clinical scales. ALSFRS-R scores were divided into 2 categories: those with mild to moderate ALS (≥40-30 points) and patients with moderate to advanced ALS (29-≤20 points).

RESULTS

We studied 43 patients with definite ALS. The most frequent GI symptoms were constipation (60.5%), rectal tenesmus (57.5%), hard stools (55.0%), and borborygmus (42.5%). The moderate to advanced ALS stage was correlated with constipation (r = 0.334; p = 0.028), acid regurgitation (r = 0.384; p = 0.013), eructation (r = 0.334; p = 0.032), rectal tenesmus (r = 0.498; p = 0.001), and functional dysphagia (r = 0.656; p = <0.001).

CONCLUSIONS

Early detection of these GI symptoms can guide timely therapeutic decisions to avoid weight loss, a predictor for worse prognosis. This study highlights the relevance of the detection of these symptoms in ALS patients who score ≤29 points in the ALSFRS-R scale to establish an appropriate treatment, prevent systemic complications, provide more comfort, and improve quality of life.

Bowel, bladder, and sudomotor symptoms in ALS patients

OBJECTIVES

To describe prevalence rates of bowel, bladder, and sudomotor symptoms in patients with amyotrophic lateral sclerosis (ALS) in relation to disease onset and progression. Treatment strategies and efficacies were also assessed.

METHODS

A pilot patient cohort revealed increased incidences of bowel/bladder and sudomotor symptoms. Questionnaires derived from formal bowel and bladder survey instruments were administered to a second cohort of patients during multidisciplinary ALS clinic visits.

RESULTS

The pilot cohort of 30 patients reported an increase in bowel symptoms from 17% prior to 70% after the diagnosis of ALS, and an increase in urinary symptoms from 24% to 76%. In the second cohort of 66 patients an increase in constipation from 33% prior to 64.7% after the diagnosis of ALS was reported. 25.4% of patients reported bowel urgency initially, which increased to 33.3% over time. Constipation was most commonly treated with docusate, dietary fiber supplementation, fluid/exercise, and polyethylene glycol. In the second cohort the prevalence of overactive bladder symptoms increased from 3.1% prior to 25.0% after the diagnosis of ALS. Urinary symptoms are most commonly treated with catheters and oxybutynin. A sudomotor survey found stinging eyes in 17.2% of patients, oily/greasy skin in 14.1% of patients, and flaking of the skin in 29.7% of patients.

CONCLUSIONS

Bowel and bladder symptoms are common in the ALS population and respond to treatment. Sudomotor symptoms are also common. Inquiring about these symptoms at clinic visits and initiating treatment can significantly improve the patients' quality of life.

Proteostatic imbalance and protein spreading in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder whose exact causative mechanisms are still under intense investigation. Several lines of evidence suggest that the anatomical and temporal propagation of pathological protein species along the neural axis could be among the main driving mechanisms for the fast and irreversible progression of ALS pathology. Many ALS-associated proteins form intracellular aggregates as a result of their intrinsic prion-like properties and/or following impairment of the protein quality control systems. During the disease course, these mutated proteins and aberrant peptides are released in the extracellular milieu as soluble or aggregated forms through a variety of mechanisms. Internalization by recipient cells may seed further aggregation and amplify existing proteostatic imbalances, thus triggering a vicious cycle that propagates pathology in vulnerable cells, such as motor neurons and other susceptible neuronal subtypes. Here, we provide an in-depth review of ALS pathology with a particular focus on the disease mechanisms of seeding and transmission of the most common ALS-associated proteins, including SOD1, FUS, TDP-43, and C9orf72-linked dipeptide repeats. For each of these proteins, we report historical, biochemical, and pathological evidence of their behaviors in ALS. We further discuss the possibility to harness pathological proteins as biomarkers and reflect on the implications of these findings for future research.

The Dying Forward Hypothesis of ALS: Tracing Its History

The site of origin of amyotrophic lateral sclerosis (ALS), although unsettled, is increasingly recognized as being cortico-fugal, which is a dying-forward process primarily starting in the corticomotoneuronal system. A variety of iterations of this concept date back to over 150 years. Recently, the hallmark TAR DNA-binding protein 43 (TDP-43) pathology, seen in >95% of patients with ALS, has been shown to be largely restricted to corticofugal projecting neurons (“dying forward”). Possibly, soluble but toxic cytoplasmic TDP-43 could enter the axoplasm of Betz cells, subsequently causing dysregulation of nuclear protein in the lower brainstem and spinal cord anterior horn cells. As the disease progresses, cortical involvement in ALS becomes widespread, including or starting with frontotemporal dementia, implying a broader view of ALS as a brain disease. The onset at the motor and premotor cortices should be considered a nidus at the edge of multiple cortical networks which eventually become disrupted, causing failure of a widespread cortical connectome.

Sleep disturbances in patients with amyotrophic lateral sclerosis: current perspectives

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease inevitably leading to generalized muscle weakness and premature death. Sleep disturbances are extremely common in patients with ALS and substantially add to the burden of disease for both patients and caregivers. Disruption of sleep can be caused by physical symptoms, such as muscle cramps, pain, reduced mobility, spasticity, mucus retention, and restless legs syndrome. In addition, depression and anxiety may lead to significant insomnia. In a small subset of patients, rapid eye movement (REM) sleep behavioral disorder may be present, reflecting neurodegeneration of central nervous system pathways which are involved in REM sleep regulation. With regard to overall prognosis, sleep-disordered breathing (SDB) and nocturnal hypoventilation (NH) are of utmost importance, particularly because NH precedes respiratory failure. Timely mechanical ventilation is one of the most significant therapeutic measures to prolong life span in ALS, and transcutaneous capnometry is superior to pulse oxymetry to detect NH early. In addition, it has been shown that in patients on home ventilatory support, survival time depends on whether normocapnia, normoxia, and elimination of apneic events during sleep can be reliably achieved. Several studies have investigated sleep patterns and clinical determinants of sleep disruption in ALS, but exact prevalence numbers are unknown. Thus, constant awareness for sleep-related symptoms is appropriate. Since no curative treatment can be offered to affected patients, sleep complaints should be thoroughly investigated in order to identify any treatable etiology and improve or stabilize quality of life as much as possible. The use of hypnotics should be confined to palliation during the terminal phase and refractory insomnia in earlier stages of the disease, taking into account that most compounds potentially aggravate SDB.

Gut microbiota in ALS: possible role in pathogenesis?

Introduction: The gut microbiota has important roles in maintaining human health. The microbiota and its metabolic byproducts could play a role in the pathogenesis of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Areas covered: The authors evaluate the methods of assessing the gut microbiota, and also review how the gut microbiota affects the various physiological functions of the gut. The authors then consider how gut dysbiosis could theoretically affect the pathogenesis of ALS. They present the current evidence regarding the composition of the gut microbiota in ALS and in rodent models of ALS. Finally, the authors review therapies that could improve gut dysbiosis in the context of ALS. Expert opinion: Currently reported studies suggest some instances of gut dysbiosis in ALS patients and mouse models; however, these studies are limited, and more information with well-controlled larger datasets is required to make a definitive judgment about the role of the gut microbiota in ALS pathogenesis. Overall this is an emerging field that is worthy of further investigation. The authors advocate for larger studies using modern metagenomic techniques to address the current knowledge gaps.

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.

Motor neuron vulnerability and resistance in amyotrophic lateral sclerosis

In the fatal disease-amyotrophic lateral sclerosis (ALS)-upper (corticospinal) motor neurons (MNs) and lower somatic MNs, which innervate voluntary muscles, degenerate. Importantly, certain lower MN subgroups are relatively resistant to degeneration, even though pathogenic proteins are typically ubiquitously expressed. Ocular MNs (OMNs), including the oculomotor, trochlear and abducens nuclei (CNIII, IV and VI), which regulate eye movement, persist throughout the disease. Consequently, eye-tracking devices are used to enable paralysed ALS patients (who can no longer speak) to communicate. Additionally, there is a gradient of vulnerability among spinal MNs. Those innervating fast-twitch muscle are most severely affected and degenerate first. MNs innervating slow-twitch muscle can compensate temporarily for the loss of their neighbours by re-innervating denervated muscle until later in disease these too degenerate. The resistant OMNs and the associated extraocular muscles (EOMs) are anatomically and functionally very different from other motor units. The EOMs have a unique set of myosin heavy chains, placing them outside the classical characterization spectrum of all skeletal muscle. Moreover, EOMs have multiple neuromuscular innervation sites per single myofibre. Spinal fast and slow motor units show differences in their dendritic arborisations and the number of myofibres they innervate. These motor units also differ in their functionality and excitability. Identifying the molecular basis of cell-intrinsic pathways that are differentially activated between resistant and vulnerable MNs could reveal mechanisms of selective neuronal resistance, degeneration and regeneration and lead to therapies preventing progressive MN loss in ALS. Illustrating this, overexpression of OMN-enriched genes in spinal MNs, as well as suppression of fast spinal MN-enriched genes can increase the lifespan of ALS mice. Here, we discuss the pattern of lower MN degeneration in ALS and review the current literature on OMN resistance in ALS and differential spinal MN vulnerability. We also reflect upon the non-cell autonomous components that are involved in lower MN degeneration in ALS.

Extra-motor abnormalities in amyotrophic lateral sclerosis: another layer of heterogeneity

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease defined by the presence of muscle weakness. The motor features of disease are heterogeneous in site of onset and progression. There are also extra-motor features in some patients. The genetic basis for extra-motor features is uncertain. The heterogeneity of ALS is an issue for clinical trials. Areas covered: This paper reviews the range and prevalence of extra-motor features associated with ALS, and highlights the current information about genetic associations with extra-motor features. Expert commentary: There are extra-motor features of ALS, but these are not found in all patients. The most common is cognitive abnormality. More data is required to ascertain whether extra-motor features arise with progression of disease. Extra-motor features are reported in patients with a range of causative genetic mutations, but are not found in all patients with these mutations. Further studies are required of the heterogeneity of ALS, and genotype/phenotype correlations are required, taking note of extra-motor features.

Gamma motor neurons survive and exacerbate alpha motor neuron degeneration in ALS

The molecular and cellular basis of selective motor neuron (MN) vulnerability in amyotrophic lateral sclerosis (ALS) is not known. In genetically distinct mouse models of familial ALS expressing mutant superoxide dismutase-1 (SOD1), TAR DNA-binding protein 43 (TDP-43), and fused in sarcoma (FUS), we demonstrate selective degeneration of alpha MNs (α-MNs) and complete sparing of gamma MNs (γ-MNs), which selectively innervate muscle spindles. Resistant γ-MNs are distinct from vulnerable α-MNs in that they lack synaptic contacts from primary afferent (I_A) fibers. Elimination of these synapses protects α-MNs in the SOD1 mutant, implicating this excitatory input in MN degeneration. Moreover, reduced I_A activation by targeted reduction of γ-MNs in SOD1^G93A mutants delays symptom onset and prolongs lifespan, demonstrating a pathogenic role of surviving γ-MNs in ALS. This study establishes the resistance of γ-MNs as a general feature of ALS mouse models and demonstrates that synaptic excitation of MNs within a complex circuit is an important determinant of relative vulnerability in ALS.

Motility disorders in the patient with neurologic disease

Gastrointestinal symptoms are common in the patient with chronic neurologic disease and may loom large in terms of impact on quality of life and on nutrition and mobility. A knowledge of the range of gastrointestinal disorders associated with a given neurologic disease, together with an understanding of the risks and benefits of various therapeutic options and approaches, should aid gastroenterologists in their efforts to contribute to the care of these patients. In most instances a multidisciplinary team (neurologist/neurosurgeon, gastroenterologist, nutritionist, therapist, specialist nurse) aware of the wishes and needs of the family and their carers and mindful of the nature and the natural history of the underlying disease process are best placed to assess and manage these problems.

Transition from the locked in to the completely locked-in state: a physiological analysis

OBJECTIVE

To clarify the physiological and behavioral boundaries between locked-in (LIS) and the completely locked-in state (CLIS) (no voluntary eye movements, no communication possible) through electrophysiological data and to secure brain-computer-interface (BCI) communication.

METHODS

Electromyography from facial muscles, external anal sphincter (EAS), electrooculography and electrocorticographic data during different psychophysiological tests were acquired to define electrophysiological differences in an amyotrophic lateral sclerosis (ALS) patient with an intracranially implanted grid of 112 electrodes for nine months while the patient passed from the LIS to the CLIS.

RESULTS

At the very end of the LIS there was no facial muscle activity, nor external anal sphincter but eye control. Eye movements were slow and lasted for short periods only. During CLIS event related brain potentials (ERP) to passive limb movements and auditory stimuli were recorded, vibrotactile stimulation of different body parts resulted in no ERP response.

CONCLUSIONS

The results presented contradict the commonly accepted assumption that the EAS is the last remaining muscle under voluntary control and demonstrate complete loss of eye movements in CLIS. The eye muscle was shown to be the last muscle group under voluntary control. The findings suggest ALS as a multisystem disorder, even affecting afferent sensory pathways.

SIGNIFICANCE

Auditory and proprioceptive brain-computer-interface (BCI) systems are the only remaining communication channels in CLIS.

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.

Autonomic impairment in amyotrophic lateral sclerosis

PURPOSE OF REVIEW

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive loss of motor neurones, but it is increasingly recognized to be a more disseminated disease. The autonomic nervous system may also be involved. Here we review the literature with specific emphasis on autonomic functions in ALS.

RECENT STUDIES

Ample evidence exists for subclinical dysfunction of cardiovascular, sudomotor, gastrointestinal, salivary and lacrimal regulation, even in early ALS cases. Autonomic disturbances may lead to circulatory collapse or sudden death in respirator dependent patients. Several studies suggest the existence of sympathetic hyperactivity in ALS. We discuss some possible pathophysiological mechanisms of the subtle abnormalities and some clinical and treatment implications.

SUMMARY

The wide range of autonomic involvement, together with results suggesting cognitive and extrapyramidal dysfunction, supports the view that ALS is a multisystem degenerative disease.

Descending pathways modulating the spinal circuitry for ejaculation: effects of chronic spinal cord injury

Sexual dysfunction is a common complication in men with chronic spinal cord injury. In particular, ejaculation is severely compromised or absent and the resulting infertility issues are important to this group of predominantly young men. To investigate the neural circuits and descending spinal pathways involved in ejaculation, animal models have been developed in normal and spinal cord-injured preparations. Primarily through studies in rats, spinal ejaculatory circuits have been described including (i) autonomic circuits at the thoracolumbar and lumbosacral levels mediating the emission phase of ejaculation, (ii) somatic circuits at the lumbosacral level controlling the expulsion phase of ejaculation through sequential and rhythmic contraction of perineal striated muscles (e.g. bulbospongiosus), and (iii) a proposed ejaculatory pattern generator in the lumbar cord. Midthoracic incomplete chronic spinal cord injury has revealed the dependency of spinal ejaculatory circuits on bilateral spinal pathways from the brainstem via modulation of pudendal motor neuron reflexes and pudendal nerve autonomic fibers. Accordingly, sensory input from the dorsal nerve of the penis, required to trigger the ejaculatory response in animals and humans, is no longer inhibited from the lateral paragigantocellularis nucleus in the ventrolateral medulla. This inhibitory effect, likely presynaptic through a serotonergic pathway, is thought to be necessary to provide the rhythmic, bursting, and sequential contractions of the perineal muscles during ejaculation. Chronic lateral hemisection injury, which severs half of the descending lateral funiculus-located pathways, results in new functional connections of the pudendal reflex inhibitory and pudendal sympathetic activation pathways across the midline, above and below the lesion, respectively. Clinical correlations in spinal cord-injured men have demonstrated the validity of the rodent animal for the study of ejaculatory dysfunction after chronic injury.

Constipation in neurological diseases

Hippocrates noted that "it is a general rule, that intestines become sluggish with age", though the precise mechanisms for this association remains uncertain even today.

Reference values of motor unit potentials (MUPs) of the external anal sphincter muscle

OBJECTIVE

To provide reference values for the isolated motor unit potentials (MUPs) in the external anal sphincter (EAS) muscle, as mean duration, mean amplitude, mean area, number of turns and number of phases, related to the age of the patient. These data are not available in worldwide literature in spite of the fact that the EAS muscle is being increasingly mentioned in relation to differential diagnosis.

METHODS

Study of 235 subjects aged 0-80 years using an automated analysis program.

RESULTS

The study performed shows a clear gradual progression of the mean duration with patient age. The variability of all other parameters tested is also analyzed.

CONCLUSIONS

Our study shows that the classical values of MUPs isolated in the EAS muscle are directly related to age, and that this method is fully reliable to study its pathological conditions.

Specific expression of the urotensin II gene in sacral motoneurons of developing rat spinal cord

The neuropeptide urotensin II (UII) is expressed in motoneurons of the brainstem and spinal cord in adults. Here, the expression pattern of the UII gene was studied in the developing rat spinal cord. UII mRNA was detected by reverse-transcription-polymerase chain reaction (RT-PCR) as early as E10. From E14 to E21, in situ hybridization revealed intense expression of the UII gene specifically in sacral motoneurons, while only faint expression was detected at cervical and thoracic levels. After birth (P0, P4), the expression of UII mRNA increased in motoneurons at all rostrocaudal levels. Thus, UII is the first gene reported to show expression limited to the sacral pool of motoneurons, which are known to have particular properties in terms of targets and programmed cell death.

Electrodiagnostic studies in amyotrophic lateral sclerosis and other motor neuron disorders

The clinical electrodiagnostic medicine (EDX) consultant asked to assess patients with suspected amyotrophic lateral sclerosis (ALS) has a number of responsibilities. Among the most important is to provide a clinical assessment in conjunction with the EDX study. The seriousness of the diagnoses and their enormous personal and economic impact require a high-quality EDX study based on a thorough knowledge of and experience with motor neuron diseases (MNDs) and related disorders. Clinical evaluation will help determine which of the EDX tools available to the EDX consultant should be applied in individual patients. Although electromyography (EMG) and nerve conduction study are the most valuable, each of the following may be helpful in the assessment of selected patients based on their clinical findings: repetitive nerve stimulation, motor unit number estimate, single-fiber EMG, somatosensory evoked potential, autonomic function test, and polysomnography. The pertinent literature on these is reviewed in this monograph. The selection and application of these EDX tools depend on a thorough knowledge of the MNDs and related disorders.