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.

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.

Simulation studies on the motor unit potentials with satellite components in amyotrophic lateral sclerosis and spinal muscle atrophy.

INTRODUCTION: We compared motor unit potentials (MUPs) with satellite components recorded in two anterior horn disorders: amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA, types II and III). METHODS: We analyzed MUPs recorded from biceps brachii muscle, including 209 associated with ALS (12 patients) and 127 with SMA (5 patients). Simulations were applied to determine the origin of satellites in these processes. RESULTS: MUP parameters differ in ALS and SMA. Simulations indicate that the satellite potential in ALS often originated from a single fiber, whereas in SMA it originated from a group of fibers of smaller diameters than the surrounding ones. CONCLUSIONS: These results suggest that, except for neurogenic factors, the variability of muscle fiber diameters also leads to the formation of MUPs with satellites. This variability seems to be responsible for the differences in the shape of the main and satellite MUP components in ALS and SMA.

The auditory system involvement in Parkinson disease: electrophysiological and neuropsychological correlations.

In the course of Parkinson disease (PD), apart from motor symptoms, presence of mental disturbances such as dementia and depression is common. The aims of this study were to assess the auditory system involvement in patients with PD using electrophysiological and neuropsychological tests and to correlate the cognitive impairment and the auditory evoked potentials tests results. The auditory and cognitive functions were studied in 53 patients with idiopathic PD, mean age 65.8 +/- 9.1 years; mean disease duration 7.8 +/- 5.0 years; mean motor disability score 2.5 +/- 0.8 points in Hoehn-Yahr scale compared with a control group matched for age and sex. In patients and controls, cognitive functions were analyzed electrophysiologically using middle latency auditory evoked potentials (MLAEP) and long latency (event-related potentials, P300) auditory evoked potentials. Neuropsychological testing consisted of Wisconsin Card Sorting Test (WCST). According to WCST results, patients with PD were divided into 2 subgroups: patients with normal and abnormal WCST performance (WCST(-) and WCST(+) subgroups, respectively). Sixteen of 46 patients (34.8%) showed cognitive impairment when evaluated with WCST. Statistically significant differences in middle latency auditory evoked potentials and P300 results between WCST(-) and WCST(+) groups were found consisting of P300 abnormalities in 93.8% patients in WCST(+) and 57.7% in WCST(-) group. Middle latency auditory evoked potentials were abnormal in 71.4% and 63% patients in WCST(+) and WCST(-) group, respectively. P300 was absent significantly more often (P < 0.01) in the subgroup with cognitive impairment. The difference in middle latency auditory evoked potentials results between these subgroups was statistically insignificant. The auditory evoked potentials changes were more common among patients with abnormal WCST performance. According to our results, the auditory evoked potentials of different latencies are helpful in the assessment of cognitive changes accompanying PD.

Accessory deep peroneal nerve - a clinically significant anomaly?

BACKGROUND AND PURPOSE: The accessory deep peroneal nerve (ADPN), a variant of the peroneal nerve, may give motor branches to the extensor digitorum brevis muscle (EDB) in 19-28% of the general population and in up to 78% of subjects in familial cases. The aim of our study was to evaluate its significance in the examination of the peroneal nerve. MATERIAL AND METHODS: Three groups of patients were analyzed. Group I consisted of 310 patients whose neurography recordings were analyzed retrospectively. Group II consisted of 24 healthy controls and group III consisted of 8 relatives of a healthy control having the ADPN detected. All patients underwent routine neurography of the peroneal nerve with muscular response recorded from the EDB. Groups II and III had additional stimulation behind the lateral malleolus. RESULTS: On routine neurography, ADPN was found in 7.7% of patients in group I and 12.5% in group II. Stimulation behind the lateral malleolus detected it in 25% of group II and in 50% of group III. The highest CMAP amplitude obtained by stimulation of the ADPN equalled 3.71 mV and was over half of the total EDB response. The presence of the ADPN significantly influences routine neurography of the peroneal nerve in 7.7-12.5% of patients. Stimulation behind the lateral malleolus detected it in 25% of group II and in 50% of the maternal line of the family in group III. In the familial case ADPN was present in 50% of maternally related subjects, reflecting autosomal dominant transmission. CONCLUSIONS: ADPN may innervate the greater part of the EDB and in cases of peroneal neuropathy may be important for preserving function of the muscle.

A novel Met116Thr mutation in the GDAP1 gene in a Polish family with the axonal recessive Charcot-Marie-Tooth type 4 disease.

Mutations in the gene coding for ganglioside-induced differentiation-associated protein-1 (GDAP1), which maps to chromosome 8q21, have been described in families with autosomal recessive Charcot-Marie-Tooth disease (CMT4A). Interestingly, some mutations in the GDAP1 gene have been reported in the demyelinating form of CMT1 disease, whereas others were found in patients with the axonal type of CMT disease. So far, 23 mutations in the GDAP1 gene have been reported in patients of different ethnic origins. In this study we report a novel mutation Met116Thr in the GDAP1 gene identified in a three generation Polish family with axonal CMT4.

Early onset Charcot-Marie-Tooth type 1B disease caused by a novel Leu190fs mutation in the myelin protein zero gene.

The spectrum of Charcot-Marie-Tooth (CMT) phenotypes segregating with mutations in the Myelin Protein Zero (MPZ) gene is wide and ranges from congenital hypomyelinating neuropathy (CHN) through demyelinating form of CMT to the axonal type of CMT disease. Within 94 MPZ gene mutations reported up to now, only a few were identified in the exon 4 of the MPZ gene. In this study we have identified a novel Leu190fs mutation in the MPZ gene. The Leu190fs mutation was found in a 14-year-old girl suffering from Charcot-Marie-Tooth type 1 disease (CMT1) with onset in early infancy. Similarly to the other MPZ gene frame-shift mutations reported as far the Leu190fs seems to have a dominant negative effect.

[F-wave amplitude in peripheral nervous system lesions]. / Amplituda fali F w uszkodzeniach obwodowego ukladu nerwowego.

BACKGROUND AND PURPOSE: F-wave is a late response recorded from muscle elicited by electric impulse conveyed antidromically to alpha-motor neurons of the spinal cord. F-wave latency and frequency are assessed in routine electroneurography providing information of conduction in the proximal segment of the nerves. F-wave amplitude is rarely analyzed, while it could add valuable information on excitability of motor neurons in different disease states. This study was conducted to determine whether F-wave amplitude is indicative of the level of the peripheral nervous system lesion. MATERIAL AND METHODS: EMG recordings of 204 consecutive patients suspected of peripheral nerves system lesion were retrospectively analyzed. Based on the clinical diagnosis three groups were defined: neuropathy (N=100), myopathy (N=33), ALS (N=18), reference (musculoskeletal pain syndromes: N=53). F-wave amplitude and F/CMAP-ratio (CMAP-compound motor action potential) and their relation to parameters of impulse conduction in motor nerve fibers was analyzed. RESULTS: Mean F/CMAP ratio was 11.1% in ALS, 5% in myopathy (p=0.008), 7.1% in neuropathies and 5.6% in the reference group. Giant F-wave (more than 10% of CMAP) was observed in 30% of nerves in ALS, 15% in neuropathy and 10% in myopathy (p=0.036). F-wave amplitude correlated significantly with CMAP amplitude in all groups, while F/CMAP ratio was inversely related to CMAP amplitude in ALS (r=-0.43, p<0.01) and neuropathy (r=-0.37, p<0.0001). F-wave frequency was similar in all groups and correlated with CMAP amplitude. CONCLUSIONS: F-wave amplitude is not indicative of the level of peripheral nervous system lesions. Giant F-wave is observed in neurogenic processes. It reflects an increase of motor unit size in the reinnervation process, but possibly also a change of excitability of motor neuron and its axon.

[Neurophysiological testing in myasthenia syndromes]. / Obraz elektrofizjologiczny zespolów miastenicznych.

Myasthenic syndromes are a heterogeneous group of congenital or acquired disorders of neuromuscular junction. Despite major advance in genetics and molecular biology of disorders of neuromuscular junction, clinical diagnosis and choice of treatment largely depends on results of neurophysiological tests. Different protocols of repetitive nerve stimulation and single fibre EMG are indispensable in confirming neuromuscular junction defect, they can also give additional information on the level of abnormality and differentiate myasthenia gravis from Lambert-Eaton syndrome (pre- or postsynaptic defect). Characteristic features of repetitive nerve stimulation test e.g. repetitive response allow diagnosing congenital myasthenic syndromes such as slow channel syndrome or acetylcholine deficiency. Patophysiological basis of neurophysiological tests of neuromuscular transmission is presented. Different neurophysiological findings in cases of Lambert-Eaton myasthenic syndrome and congenital myasthenic syndromes are presented.