Migraine and Its Association with Hyperactivity of Cell Membranes in the Course of Latent Magnesium Deficiency-Preliminary Study of the Importance of the Latent Tetany Presence in the Migraine Pathogenesis.

So far, there is no consistent and convincing theory explaining the pathogenesis of migraines. Vascular disorders, the effect of oxidative stress on neurons, and the contribution of magnesium-calcium deficiencies in triggering cortical depression and abnormal glutaminergic neurotransmission are taken into account. However, there are no reliable publications confirming the role of dietary deficits of magnesium and latent tetany as factors triggering migraine attacks. The aim of the study was to evaluate the influence of latent magnesium deficiency assessed with the electrophysiological tetany test on the course of migraine. The study included: a group of 35 patients (29 women and six men; in mean age 41 years) with migraine and a control group of 24 (17 women and seven men; in mean age 39 years) healthy volunteers. Migraine diagnosis was based on the International Headache Society criteria, 3rd edition. All patients and controls after full general and neurological examination were subjected to a standard electrophysiological ischemic tetany test. Moreover, the level of magnesium in blood serum was tested and was in the normal range in all patients. Then, the incidence of a positive tetany EMG test results in the migraine group and the results in the subgroups with and without aura were compared to the results in the control group. Moreover, the relationship between clinical markers of spasmophilia and the results of the tetany test was investigated in the migraine group. As well as the relationship between migraine frequency and tetany test results. There was no statistically significant difference in the occurrence of the electrophysiological exponent of spasmophilia between the migraine and control group. Neither correlation between the occurrence of clinical symptoms nor the frequency of migraine attacks and the results of the tetany test was stated (p > 0.05). However, there was an apparent statistical difference between the subgroup of migraine patients with aura in relation to the control group (p < 0.05). The result raises hope to find a trigger for migraine attacks of this clinical form, the more that this factor may turn out to be easy to supplement with dietary supplementation.

Motor Unit Number Index (MUNIX) as a biomarker of motor unit loss in post-polio syndrome versus needle EMG.

MUNIX method (Motor Unit Number Index) had been not used to assess number of motor neurons in post-polio syndrome in contrary to needle electromyography. OBJECTIVES: To confirm if MUNIX reflects motor unit loss and clinical stage and to assess difference in MUNIX and EMG results between muscles in different stage. METHODS: 132 Muscles (MUNIX) and 96 (EMG) in 12 patients were studied and divided into groups: with normal strength(N), stable weakness and atrophy(S), new weakness and atrophy(W). RESULTS: In PPS group MUNIX global was 561.36 ±â€¯282.6 (right 6 muscles) and 561.27 ±â€¯281.1 (left) significantly lower than in control group (six muscles 1139.6 ±â€¯164.5) (p < 0.05). MUNIX global correlated with MRC global. MUNIX was greater in muscles with normal strength (95-100% of normal values) than in those with stable weakness (48%-0% of normal values) and new weakness (65%-0% of normal values). Respectively to clinical stage of muscle MUP (motor unit potential) amplitude increased to 350% of normal value, from 250% to 110%, and from 300% to 700%. No correlation was found between MUP parameters and MRC values. CONCLUSIONS: MUNIX reflects motor dysfunction and could be a good biomarker for loss of motor neurons in PPS.

Comprehensive evaluation of EMG and biopsy findings supported by computer simulations - A preliminary study.

OBJECTIVE: The aim was to compare muscle fiber diameters obtained from standard muscle biopsy and from computer simulations based on recorded motor unit potentials (MUPs). METHODS: Electromyography (EMG) and muscle biopsy were performed in 14 patients with a suspicion of a neuromuscular disorder. Histograms of the simulated muscle fiber diameters (SMFDs) were compared with those from the biopsy RESULTS: The values of the SMFDs were similar to those in the muscle biopsy for the same patient (p = 0.05) in all 14 cases. CONCLUSIONS: Comprehensive evaluation of EMG and biopsy findings supported by computer simulations may help resolve the discrepancy between the assessment of muscle by EMG and biopsy by explaining different results obtained with these two methods. SIGNIFICANCE: Evaluation of the SMFDs that are comparable to biopsy findings extends the amount of information available from EMG.

Electromyographic findings in sporadic inclusion body myositis.

INTRODUCTION: Clinically oriented diagnostic criteria can be as specific for diagnosis of sporadic inclusion body myositis (sIBM) as pathological criteria, especially at the time of presentation. EMG may provide an convincing proof that a muscle biopsy should be performed. AIMS: To compare the EMG results in patients with sIBM divided into subgroups based on the newest ENMC criteria for sIBM and to obtain the utility of EMG in the diagnostic process at the time of presentation. METHODS: We retrospectively analysed 16 patients with sIBM for motor unit action potential (MUAP) morphology as well as occurrence and distribution of abnormal spontaneous activity (SA) in muscles. RESULTS: Abnormal SA was recorded in 62.5% of sIBM patients. We found statistically significant differences between subgroups in the incidence of polyphasic MUAPs and high amplitude outliers which were more commonly seen in the "clinico-pathologically defined sIBM". Duration of MUAP in the tibialis anterior was significantly shorter in "probable sIBM". DISCUSSION: "Pseudo-neurogenic" MUAPs, mainly in lower limb muscles, are more commonly seen in "clinico-pathologically defined sIBM" while myopathic MUAPs with prominent abnormal SA are recorded in patients diagnosed with "probable sIBM". Both EMG patterns may be suggestive of sIBM and be an indication for further diagnosis.

Abnormal spontaneous activity in primary myopathic disorders.

INTRODUCTION: Reproducible non-insertional spontaneous activity (SA), with the exception of endplate activity, is an unequivocal sign of abnormality and is one of the most useful findings obtained on electromyography. METHODS: In this retrospective study we analyzed occurrence and distribution of abnormal SA in 151 patients with genetically confirmed myopathies. RESULTS: Complex repetitive discharges (CRDs) occurred more frequently than fibrillation potentials (fibs) and positive sharp waves (PSWs) in centronuclear myopathy (CNM) and limb-girdle muscular dystrophy type 2A (LGMD-2A), whereas fibs/PSWs were observed more often in desminopathy and facioscapulohumeral dystrophy (FSHD). Abnormal SA was commonly found in CNM (66.7%) and desminopathy (61.5%), occasionally in Duchenne (DMD) and Becker muscular dystrophy (BMD) (45.2% and 27.6%, respectively), but rarely in FSHD (14.9%) and LGMD-2A (12.0%). CONCLUSIONS: Abnormal SA probably occurs more frequently in disorders associated with structural changes in muscle fibers. Screening for SA may be a valuable tool for diagnosis of non-myotonic myopathies. Muscle Nerve 56: 427-432, 2017.

Diagnostic value of blink reflex in multisystem atrophy, progressive supranuclear palsy and Parkinson disease.

UNLABELLED: Abnormal blink reflex (BR) is a result of reticular brainstem pathways dysfunction and seems to be one of the features of brain degenerative disorders. The aim of the study was to estimate the diagnostic value of blink reflex in neurodegenerative diseases such as: multisystem atrophy (MSA), progressive supranuclear palsy (PSP) and Parkinson disease (PD). Material consisted of 99 patients with clinically probable MSA (51), PSP (28) and PD (20). MSA patients were divided into two subgroups, with dominant cerebellar (MSA-C) and parkinsonian signs (MSA-P). The mean age of patients was 64.9 years (47-79 years); males - 55.3%. Blink reflex was obtained in a typical way. RESULTS: The significant differences in mean values of blink reflex latencies between PD and other subgroups (MSA-P, MSA-C, PSP) were found, but all of them were in normal range. In individual patients with PD and PSP (50% and 18%, respectively) delayed R2 latencies were recorded. CONCLUSIONS: The most frequently abnormal blink reflexes, comparing the MSA, PSP and PD groups, were present in PD patients. We postulate that this may be explained by pathological influence of nigrostriatal pathway on the circuit linking the basal ganglia, cerebellum and brainstem.

Motor unit number estimation as a complementary test to routine electromyography in the diagnosis of amyotrophic lateral sclerosis.

Electromyographic (EMG) abnormalities that reveal denervation and reinnervation caused by lower motor neuron degeneration do not reflect the number of motor units that determines muscle strength. Consequently, motor unit activity potential (MUAP) parameters do not reflect muscle dysfunction. The aim of the study was to compare the value of motor unit number estimation (MUNE) and MUAP parameters as indicators of clinical muscle dysfunction in patients with amyotrophic lateral sclerosis (ALS), and to analyze the role of MUNE as a supplement to the EMG criteria for the diagnosis of ALS. In 25 patients with ALS, MUNE by the multipoint incremental method in the abductor digiti minimi (ADM) and quantitative EMG in the first dorsal interosseous (FDI) were obtained. The Medical Research Council (MRC) scale was used to evaluate clinical muscle dysfunction. A strong correlation between the number of motor units evaluated by MUNE and ADM clinical function by the MRC scale was found (P<0.001). An increased value of surface-detected single motor action potential was associated with a decreased MRC score for ADM (P<0.1). No relation was found between MUAP parameters in FDI and MRC scores. Our data support the value of the MUNE method for the detection of motor unit loss in ALS, and it could be postulated that MUNE studies may be considered complementary tests for ALS in a future revision of ALS criteria.

Motor unit reorganization in progressive muscular dystrophies and congenital myopathies.

The aim of this study was to analyze motor unit reorganization in different types of progressive muscular dystrophies and congenital myopathies. The study population consisted of patients with genetically verified progressive muscular dystrophies: Duchenne (DMD) (n=54), Becker (BMD) (n=30), facio-scapulo-humeral (FSHD) (n=37), and Emery-Dreifuss (E-DD) (n=26). Patients with probable limb-girdle dystrophy (L-GD) (n=58) and congenital myopathies (n=35) were also included in the study. Quantitative EMG recordings were obtained from 469 muscles. Muscle activity at rest and during slight voluntary and maximal muscle contraction was analyzed. The motor unit activity potential (MUAP) duration, amplitude, area, size index (SI), polyphasicity, and the presence of "outliers" were evaluated. Diminished values of MUAP parameters and decreased maximal amplitude of maximal muscle contraction were recorded most frequently in DMD and mainly in the biceps brachii muscles. SI was the most frequently changed EMG parameter. "Outliers" with amplitude below the normal range were recorded more frequently then a decreased mean MUAP amplitude (what could indicate a very high sensitivity of this EMG parameter). Pathological interference pattern was recorded in 34.7% of biceps brachii and in 21.2% of rectus femoris muscles. In FSHD, decreased MUAP duration and SI and pathological interference pattern with low amplitude were recorded most frequently in the tibial anterior and deltoid muscles. The presence of potentials with reduced parameters is a result of decreasing motor unit area (reduced number and size of muscle fibers), while high amplitude potentials recorded in BMD and E-DD could indicate a slow and mild course of disease and muscle regeneration.

Peripheral nerve involvement in myotonic dystrophy type 2 - similar or different than in myotonic dystrophy type 1?

INTRODUCTION: Multisystem manifestations of myotonic dystrophies type 1 (DM1) and 2 (DM2) are well known. Peripheral nerve involvement has been reported in DM1 but not in genetically confirmed DM2. The aim of our study was to assess peripheral nerve involvement in DM2 using nerve conduction studies and to compare these results with findings in DM1. METHODS: We prospectively studied patients with genetically confirmed DM2 (n=30) and DM1 (n=32). All patients underwent detailed neurological examination and nerve conduction studies. RESULTS: Abnormalities in electrophysiological studies were found in 26.67% of patients with DM2 and in 28.13% of patients with DM1 but the criteria of polyneuropathy were fulfilled in only 13.33% of patients with DM2 and 12.5% of patients with DM1. The polyneuropathy was subclinical, and no correlation was found between its presence and patient age or disease duration. CONCLUSIONS: Peripheral nerves are quite frequently involved in DM2, but abnormalities meeting the criteria of polyneuropathy are rarely found. The incidence of peripheral nerve involvement is similar in both types of myotonic dystrophy.

Impairment of neuromuscular transmission in transient global amnesia - does it really exist?

BACKGROUND: The main hypotheses regarding mechanisms of transient global amnesia (TGA) are ischemia in hippocampal structures, epileptic genesis, and migraine. In accordance with the hypothesis of a shared, common pathophysiological mechanism in both TGA and migraine, neuromuscular transmission (NMT) abnormalities previously found in migraine were also suspected in TGA. OBJECTIVE: The aim of our study was to analyze NMT in TGA patients to reveal a subclinical impairment of neuromuscular transmission as a possible indicator of underlying channelopathy, which would point to a shared etiology with migraine. MATERIALS AND METHODS: The study group consisted of 15 patients (6 males) with TGA (mean age 69.5±7.4yrs). The duration of amnesia ranged from 1 to 6h (mean 4.4h). Single fiber electromyography (SFEMG), the most sensitive tool for NMT assessment, of the voluntarily activated frontal muscle was performed 1-5 days after a TGA incident. RESULTS: Abnormal SFEMG was found in 1 patient (6.6%). In all other patients, SFEMG was in the normal range. CONCLUSION: Our neurophysiological study does not confirm NMT defects in TGA. The role of channelopathy with NMT dysfunction in the pathogenesis of TGA is rather unlikely, whereas subclinical NMT abnormalities were certainly proven in migraine.

Does quantitative EMG differ myotonic dystrophy type 2 and type 1?

Genetic testing is considered the only reliable diagnostic approach in myotonic dystrophy. However it has recently been reported that a considerable number of patients with genetically proven types of the disease have unusual phenotypic presentation. The aim of our study was to evaluate motor unit reorganization reflected by various electrophysiological abnormalities in myotonic dystrophies and to compare findings between type 1 (DM 1) and type 2 myotonic dystrophy (DM2). Quantitative electromyography (EMG) recordings in 63 patients (33 with DM1 and 30 with DM2) from the biceps brachii (BB), rectus femoris (RF), first dorsal interosseus (FDI), and tibialis anterior (TA) muscles were analyzed. Mean amplitude and size index (SI) of motor unit potentials recorded in TA and RF muscles, mean potential duration in TA, and mean SI and the number of outliers with amplitude above the normal range in BB were significantly increased in DM2 as compared to DM1. Myotonic discharges were recorded more frequently in DM1 than in DM2. EMG findings significantly differ between DM1 and DM2. The presence of high amplitude potentials in lower limb muscles in DM2 patients, atypical for myogenic muscle lesions, could be explained by muscle fiber hypertrophy observed in muscle biopsies.

Are we really closer to improving the diagnostic sensitivity in ALS patients with Awaji criteria?

The Awaji criteria, recently introduced to increase diagnosis sensitivity in amyotrophic lateral sclerosis (ALS), equate the diagnostic significance of neurogenic electrophysiological changes to clinical signs of lower motor neuron dysfunction. They also increase the electrophysiological significance of fasciculation potentials (FPs). The aim of our study was to analyse whether the new parameters improve diagnostic sensitivity in ALS patients primarily diagnosed with the El Escorial criteria. Medical and electrophysiological records of 135 consecutive patients with ALS and 25 patients with progressive muscular atrophy (PMA) who underwent electrophysiological examination of at least three anatomical regions were analysed retrospectively. Results showed that implementation of the Awaji criteria increased the level of ALS diagnosis sensitivity in 5.9% of cases - 1.5% due to the new role of FPs potentials and 4.4% because of equalization of clinical and EMG findings. In 4% of patients the ALS diagnosis was, however, changed from laboratory-supported probable ALS to possible ALS. In conclusion, our study confirms that Awaji modifications are able to improve the diagnostic certainty in a few ALS cases. Although the new approach to FPs markedly increases the number of involved muscles, it only slightly raises the number of involved regions.

Value of short exercise and short exercise with cooling tests in the diagnosis of myotonic dystrophies (DM1 and DM2).

INTRODUCTION: Standard electromyography (EMG) is useful in the diagnosis of myotonic dystrophy type 1 (DM1) and type 2 (DM2), but it does not differentiate between them. The aim of this study was to estimate the utility of the short exercise test (SET) and short exercise test with cooling (SETC) in differentiating between DM1 and DM2. METHODS: SET and SETC were performed in 32 patients with DM1 (mean age 35.8 ± 12.7 years) and 28 patients with DM2 (mean age 44.5 ± 12.5 years). RESULTS: We observed a significant decline in compound motor action potential (CMAP) amplitude in DM1 with both SET and SETC immediately after effort. In DM2, there was no marked change in CMAP amplitude with either SET or SETC. CONCLUSIONS: SET and SETC may serve as useful tools for clinical differentiation between DM1 and DM2, and they may be used as a guide for molecular testing.

Long lasting dysautonomia due to botulinum toxin B poisoning: clinical-laboratory follow up and difficulties in initial diagnosis.

BACKGROUND: Botulism is an acute form of poisoning caused by one of four types (A, B, E, F) toxins produced by Clostridium botulinum, ananaerobic, spore forming bacillus. Usually diagnosis of botulism is considered in patients with predominant motor symptoms: muscle weakness with intact sensation and preserved mental function. CASE PRESENTATION: We report a case of 56-year-old Caucasian female with a history of arterial hypertension, who presented with acute respiratory failure and bilateral ptosis misdiagnosed as brainstem ischemia. She had severe external and internal ophtalmoplegia, and autonomic dysfunction with neither motor nor sensory symptoms from upper and lower limbs. Diagnosis of botulinum toxin poisoning was made and confirmed by serum antibody testing in the mouse inoculation test. CONCLUSIONS: Ophtalmoplegia, autonomic dysfunction and respiratory failure can be caused by botulism. Early treatment and intensive care is essential for survival and recovery. The electrophysiological tests are crucial to correct and rapid diagnosis. Botulism (especially type B) should be considered in any case of acute or predominant isolated autonomic dysfunction.

Relationships between clinical data and quantitative EMG findings in facioscapulohumeral muscular dystrophy.

BACKGROUND AND PURPOSE: In recently published reports, electrophysiological findings were analysed, in some facioscapulo-humeral muscular dystrophy (FSHD) cases without genetic disease confirmation. In several reports, some electrophysiological findings were described, not specific for myopathy. The aim of study was to analyse electrophysiological findings in a genetically homogeneous FSHD group to find possible relationships between electromyography (EMG) abnormalities and clinical symptoms. MATERIAL AND METHODS: 37 patients with genetically proven FSHD (23 men and 14 women) aged 7-58 years (mean 28.8 years) were studied. Electromyographic examinations were done according to a uniform scheme for FSHD. Quantitative EMG examination was performed in vastus lateralis, tibialis anterior, deltoid and biceps brachii muscles. RESULTS: There was no correlation between clinical features and electrophysiological findings. EMG confirmed myopathic changes in all patients with most advanced changes in tibialis anterior and deltoid muscles. Some of these changes were unspecific for myopathy and the degree of their intensity differed in particular muscles. The most advanced changes were observed in the tibialis anterior and deltoid muscles. The usefulness of the size index for myopathic processes assessment was confirmed. Analysis of so-called outliers for motor unit activity potential parameters did not show any new data for evaluation of the myopathic process. Myopathic changes in our material were not as advanced as those described in classical dystrophies. Histopathological examinations of skeletal muscle were normal in about 1/3 of patients. CONCLUSIONS: We established that myopathic changes are clearly present in FSHD, with different degrees of intensity, most pronounced in tibialis anterior and deltoid muscles. There was no correlation between electrophysiological findings and clinical features. The size index provided the highest motor unit potential diagnostic sensitivity in FSHD.

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.

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.

Clinical and functional assessment of dysautonomia and its correlation in Alzheimer's disease.

The aims were to assess dysautonomia in Alzheimer's Disease (AD), clinically and electrophysiologically, using sympathetic skin response (SSR) test and R-R interval variation (RRIV) test and to analyze the relationship between symptoms of dysautonomia and SSR/RRIV results. A tota of 54 patients with AD and 37 controls were evaluated using Autonomic Symptoms Questionnaire and SSR/RRIV test. Clinical dysautonomia was observed in 66% of patients (eg, orthostatic hypotension in 34.5%, constipation in 17.2%, urinary incontinence in 13.8%). The SSR test was abnormal in 26%, but the RRIV test was abnormal in 97.7% of cases; there was significant difference in RRIV test results between AD and controls (R mean 8.05% and 14.6%, respectively). In AD, clinical dysautonomia occurs at a various degree, and the abnormal SSR and RRIV test results were not always related to the presence of clinical dysautonomia; this observation points that the tests could be used as a useful tool in the assessment of subclinical dysautonomia.

Is peripheral neuron degeneration involved in multiple system atrophy? A clinical and electrophysiological study.

UNLABELLED: Lower motor neuron lesions are not among the characteristic features of multiple system atrophy (MSA), although electromyography (EMG) and autopsy studies revealed peripheral neuron abnormalities in some cases of MSA. The aim of the study was to evaluate subclinical involvement of the peripheral neuron in MSA using EMG and electroneurography (ENG). MATERIAL: 48 patients with clinically probable MSA (mean age 60.6 years; 67% males) were included in the study and divided into subgroups, with predominant cerebellar (MSA-C) and parkinsonian signs (MSA-P). METHODS: ENG in ulnar, peroneal and sural nerves and EMG of the first interosseus dorsal and tibial anterior muscles were performed. RESULTS: Abnormal ENG in one nerve was recorded in 20.8% of patients, and in two nerves in another 20.8% of patients. The most frequent and significant findings were decreased compound motor action potential amplitudes in the ulnar nerve in the overall MSA group as well as in the MSA-P type as compared to controls. Abnormalities suggesting reinnervation was observed in 43 of 96 examined muscles (44.7%). In individual cases, neurogenic features were recorded in one muscle in 31.2% of patients and in two muscles in 29.1% of patients. CONCLUSIONS: Subclinical axonopathy in MSA is not frequent and is more pronounced in MSA with predominant parkinsonian signs. In MSA, neurogenic EMG abnormalities in muscles are more frequent than peripheral nerve lesions and as evidenced by increased motor unit potential amplitudes, could be considered a sign of anterior horn cell involvement and a hallmark of the "continuum" of neurodegeneration in MSA.