Rowińska-Marcińska K

Chronic acquired demyelinating motor neuropathy

ABSTRACT A patient with chronic, acquired, demyelinating, pure or predominantly motor asymmetric neuropathy is described. Electrophysiological tests showed multifocal conduction block in motor nerves. The sensory system was intact and the first signs of slight trival involvement appeared after 4 years of disease duration. The antiganglioside antibodies were present in serum and the patient responded to immunosuppressive therapy (azathioprine). Distinction of such cases from motor neuron disease is critical since motor demyelinating neuropathy is treatable in most cases.

Atypical motor unit potentials in Emery-Dreifuss muscular dystrophy (EDMD)

OBJECTIVE The aim of the study was to analyse electromyographic changes in Emery-Dreifuss muscular dystrophy (EDMD) that are atypical for myopathy. Our special interest was focused on high amplitude polyphasic motor unit potentials (MUPs), also termed irregular MUPs. METHODS We studied 21 EDMD patients with the diagnosis based on clinical data, DNA analysis and immunohistochemical muscle studies. Rectus femoris muscle biopsies were investigated in all affected patients. Electrophysiological investigations involved quantitative concentric needle electromyography (CNEMG) of biceps brachii (BB) and rectus femoris (RF) muscles. Simulation studies were performed to approximate the number, diameter and distribution of muscle fibers, which contribute to irregular MUPs. RESULTS The EMG data in EDMD were compatible with myopathy. Irregular MUPs showed longer duration, larger area, size index and higher amplitude then simple ones (P < 0.05). The approximation of features of muscle fibers contributing to irregular MUP also indicated smaller (<45 microm) and larger (>55 microm) diameters than normal (50 +/- 5 microm). Muscle biopsy specimens revealed the variable muscle fiber size due to atrophy, hypertrophy, and muscle fiber splitting. CONCLUSIONS Irregular MUPs recorded in EDMD are due to hypertrophied and atrophied fibers as well as increased fiber density. They reflect reorganization of the motor unit in a slow progression myopathic process (muscle fiber hypertrophy and splitting). SIGNIFICANCE Irregular MUPs in EDMD most probably reflect increased variability of the muscle fiber size.

Shape irregularity of motor unit potentials in some neuromuscular disorders

The aim of this study was to test whether analysis of the irregularity of the motor unit potential waveform may supplement conventional evaluation. We have found that the irregularity is not a characteristic feature of potentials either in neurogenic disorders or in myopathy. We have found, however, that within myo‐ and neuropathic disorders, the irregularities differ between slow (such as Becker muscle dystrophy and chronic spinal muscle atrophy) and fast progressing processes (such as amyotrophic lateral sclerosis and Duchenne muscle dystrophy). These differences depend on the different number of phases and turns contributing to wave formation. In slowly progressing processes, very irregular potentials are more often polyphasic, whereas in acute processes they may be polyturn or polyphasic. The results suggest that it is the irregularity of the potential that provides new information, not available so far, on the activity of the pathological process.

Double discharges of motor units in neuromuscular disorders.

Repetitive discharges (RDs) are observed in electromyograms recorded from healthy as well as diseased muscles. We have evaluated the prevalence of RDs in some neuromuscular diseases and analysed the time parameters of recordings displaying RDs as well as shapes of the potentials. In our clinical material, RDs have been observed exclusively in lower motor neuron lesions, never in healthy or in myopathic muscles. The prevalence index of RDs in amyotrophic lateral sclerosis (0.06) was found to be different from that in chronic spinal muscle atrophy (0.004). The types of double potential shape have been categorised. The relationships between the amplitude of the second component and the interspike duration and that between the interspike duration and the jitter were calculated. The amplitude of the second component diminished and jitter of the components increased with the shortening of the interval between components. The authors suggest that in lower motor neuron lesions, the RDs of the motorunit (MU) may be one of the first signs of the MUs dysfunction.

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.

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. Muscle Nerve, 2012

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.

Carpal tunnel syndrome or congenital hand anomaly: a clinical and electromyographic study

Dear Editor, Pediatric carpal tunnel syndrome (CTS) is a rare disorder (Deymeer and Jones, 1994). Most children with CTS do not have typical symptoms, and progressive clumsiness of the hand and thenar atrophy may be a presenting feature (Van Meir and De Smet, 2003). The prominent thenar wasting in a child can also represent a developmental anomaly of the hand (Cavanagh et al., 1979); hence, a careful diagnostic workup is necessary before a decision of surgical treatment of CTS in children. We present the cases of two children with Cavanagh syndrome, with bilateral thenar hypoplasia and congenital scaphoid bone hypoplasia. In one of them, a superimposed CTS was diagnosed. Case 1: A 10-year-old girl was referred to diagnosis of bilateral wasting of her thenars, noted 2 years previously. There was no associated trauma. She had no sensory complaints, associated symptoms, or relevant family history. Examination revealed marked flattening of the thenar eminence bilaterally and weakness of both the thenar muscles. Sensation was preserved, and deep tendon reflexes were normal. X-ray revealed scaphoid bone hypoplasia on the left side. Motor nerve conduction studies of the median nerve evoked lowamplitude compound muscle action potential (CMAP) from the thenar muscles bilaterally, with a normal distal latency. The sensory responses were preserved, with normal amplitude, but there was slowing of conduction velocity (44.2 m/s on the left and 48 m/s on the right) and significant focal prolongation of the sensory ‘itching’ latency in the distal part of the median nerve (0.7 ms on the right and 1 ms on the left). Bilateral abnormalities were also demonstrated by comparing latency to II lumbrical/II interosseus muscles (latency difference 1.1 ms). There was no denervation in thenar muscles in concentric needle electromyogram (EMG). Magnetic resonance imaging (MRI) of the wrist demonstrated compression of the median nerve at the carpal tunnel. Case 2: A 17-year-old boy was referred to our Department for reevaluation of ‘failed’ carpal tunnel release. Because of recurrent pain of his wrists, a presumptive diagnosis of CTS was made 3 years previously, and carpal tunnel release on the left side was performed, with no improvement. He had only a history of nephrolithiasis. On examination, there was wasting and weakness of his thenar eminence bilaterally, shortening and limitation of supination of the left forearm. There were no sensory abnormalities. His general pediatric examination was normal. X-ray revealed bilateral scaphoid bone hypoplasia and shortening of the ulnar bone on the left side. Nerve-conduction studies of the motor median nerve did not evoke any response from the thenar muscles bilaterally. Median nerve sensory conduction studies were normal, and there was no significant difference between latency to II lumbrical and II interosseus muscles or inching of the sensory median nerve across carpal tunnel. No denervation was observed in the thenar muscles in concentric needle EMG. In both the patients, thenar wasting was accompanied by congenital scaphoid bone hypoplasia, indicating a developmental abnormality. Electromyography study in Case 1 demonstrated associated mild lesion of the median nerve at the level of carpal tunnel. Congenital thenar hypoplasia accompanying anomalies of the metacarpal bones is known as Cavanagh syndrome (Cavanagh et al., 1979). The electrophysiological studies in Cavanagh syndrome patients reveal absent or low-amplitude CMAPs recorded from the thenar muscles and normal median sensory responses, excluding the diagnosis of CTS. In the majority of children with CTS, the median nerve lesion can be attributed to skeletal anomalies (Van Meir and De Smet, 2003). In both of our patients, the clinical findings and scaphoid bone hypoplasia demonstrated by x-ray of the wrist suggested the diagnosis of the Cavanagh syndrome. In our experience, low-amplitude CMAP recorded from the median nerve in the presence of well-preserved sensory responses in a patient with carpal bone hypoplasia does not preclude the diagnosis of CTS as in our Case 1. The sensory ‘inching’ of the median nerve and comparison of Address correspondence to: Anna Kostera-Pruszczyk, Department of Neurology, Medical University of Warsaw, Banacha 1 a, 02 097 Warsaw, Poland. Tel: þ48-22-599-29-86; Fax: þ48-22-599-18-57; E-mail: akostera@amwaw.edu.pl Journal of the Peripheral Nervous System 10:338–339 (2005)

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.