bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypertrophic mononeuritis clinically presenting with painful legs and moving toes
Authors: Mitsumoto Hiroshi , Levin Kerry H. , Wilbourn Asa J. , Chou Samuel M.
Published: January 2005

A 40‐year‐old woman presented with progressive lower leg pain and spontaneous toe movement. The EMG showed a posterior tibial nerve mononeuropathy and continuous myokymic discharges in posterior tibial‐innervated muscles. The MRI revealed a markedly enlarged posterior tibial nerve. Toe movements and myokymia were unaffected by the proximal transection of the lesion but ceased abruptly when the distal end of the fusiform “tumor” was resected, suggesting that spontaneous electrical foci may have been located along the nerve lesion. The markedly enlarged nerve segment contained edematous, swollen fascicles with marked Schwann cell onion‐bulb lesions and angiocentric, lymphocytic, and lymphofollicular infiltration. This nerve lesion is an example of a newly recognized entity called hypertrophic mononeuritis.
The correlation between electrical after‐activity and slowed relaxation in myotonia
Authors: Iaizzo Paul A. , Lehmann‐Horn Frank
Published: January 2005

The correlation between electrical and mechanical after‐activity was studied in resealed fiber segments from patients with recessive generalized myotonia (Becker) and in intact fibers from normal muscles which were bathed in 9‐anthracene carboxylic acid. The tests were performed in vitro on small bundles of 100 fibers or less. Electromyographic activity and contractile force were measured simultaneously. The relaxation of rested‐state twitches and tetani was slowed and accompanied by after‐activity in both types of preparations. Often random activity was recorded. In all cases, the contractile force was highly correlated with the electromyographic signs of myotonia. These observations support the hypothesis that electrical afteractivity is fully responsible for the slowed relaxation in recessive generalized myotonia.
Temperature dependence of the electrical and mechanical responses of the adductor pollicis muscle in humans
Authors: Hopf Hanns Christian , Maurer Konrad
Published: January 2005

Changes at low temperatures of the electrical and mechanical activity of the adductor pollicis muscle were studied in 10 volunteers. Decreasing temperatures resulted in increased amplitude and duration of the negative phase and peak‐to‐peak amplitude of the evoked muscle action potential. Distal latency, electromechanical latency, contraction time, and half‐relaxation time were also increased while isometric force, contraction velocity, and relaxation velocity were decreased. The increase of contraction time is greater over the temperature range below 28°C than above 29°C. Skin temperature differs significantly from muscle temperature, showing about 3°C lower values during cooling and up to 4°C higher values during rewarming with radiant heat.
Differential expression of nuclear genes for cytochrome c oxidase during myogenesis
Authors: Lomax Magaret I. , Coucouvanis Electra , Schon Eric A. , Barald Kate F.
Published: January 2005

Recent studies of patients with mitochondrial myopathies suggest the existence of both muscle‐specific and developmentally regulated isoforms of cytochrome c oxidase (COX), the terminal enzyme complex of the electron transport chain. To investigate the temporal pattern of gene expression of nuclear genes for COX in developing muscle, the steady‐state levels of COX mRNA in total RNA from a satellite cell‐derived mouse muscle cell line, C2C12, were analyzed and compared with COX mRNA levels in mature rat skeletal muscle. Undifferentiated myoblasts, myotubes just after fusion (early myotubes), and fully differentiated, contractile, striated myotubes (late myotubes) were analyzed for mRNA levels for four of the 10 different nuclear‐encoded COX subunits: IV, Vb, VIc and VIII‐liver. Of these, IV, Vb and VIc are identical in both bovine heart and liver, whereas subunit VIII has heart and liver isoforms. In C2C12 myoblasts, the level of mRNA for subunits IV, Vb, and VIII‐liver is equal to or greater than the level in tissues such as brain, skeletal muscle, and liver. As myoblasts fuse and differentiate into myotubes, the levels of mRNA for these subunits undergo radically different changes. Transcripts for subunits IV and Vb accumulate to higher levels during myogenesis. The level of subunit VIII transcripts decreases during myogenesis, providing additional evidence that subunit VIII has tissue‐specific isoforms in the rat. Little mRNA for COX VIc was detected in either the C2C12 cell line or in primary embryonic rat myoblasts or myotubes in culture in spite of high levels in adult skeletal muscles, suggesting that subunit VIc may have both fetal and adult isoforms in rodents.
Calcium channel blocker influences the density of alpha‐actinin labeling at the rat neuromuscular junction
Authors: Meshul Charles K. , Kriho Virginia , Kriho Nicholas , Hopkins William F. , Matsumura Fumio , Pappas George D.
Published: January 2005

Alpha‐actinin is a muscle protein located along the Z‐disc. Incubation of frog muscle with the calcium ionophore, A23187, can decrease the immunogold labelling of alpha‐actinin.14 Pyridostigmine (PYR) is an inhibitor of acetylcholinesterase, which causes disruption of Z‐discs only in the region of the motor endplate. This is probably due to excess influx of calcium ions, leading to activation of proteases. Pretreating animals with the calcium channel blocker diltiazem can significantly reduce damage to the Z‐discs at the motor endplate caused by PYR. It was of interest to determine whether the distribution of alpha‐actinin had been altered following PYR administration and whether diltiazem could prevent those changes. There was less alpha‐actinin labelling at the motor endplate compared to away from this region for all treatment groups. Animals administered diltiazem showed less labelling compared to PYR, but with no disruption of Z‐discs at the motor endplate following diltiazem. Pretreatment with diltiazem reduced the incidence of Z‐disc damage, but the degree of alpha‐actinin labeling at the endplate was less than that seen with diltiazem alone. The greater effect seen at the endplate implies that neuromuscular activity is an important factor. The drugs may be causing a reduction in alpha‐actinin labelling by different mechanisms.
Fasciitis, perimyositis, myositis, polymyositis, and eosinophilia
Authors: Serratrice G. , Pellissier J. F. , Roux H. , Quilichini P.
Published: January 2005

Several groups of cases of fasciitis and myositis with eosinophilia are reported. The common features are inflammation into fascia and/or perimysium, and/or muscle fibers; eosinophilia in blood and/or in muscle biopsy. The following classification of 24 cases is suggested: at one end of the spectrum are fasciitis with eosinophilia: diffuse fasciitis (Shulman syndrome): 10 cases (3 with hematological complications); 2 cases of diffuse fasciitis with muscle atrophy; 3 cases of restricted fasciitis. Relapsing perimyositis with eosinophilia belong to the same spectrum, either diffuse (5 cases) with myalgias, or localized (2 cases). Other cases are focal myositis or multiple myositis, polymyositis with eosinophilia. The relationship among these cases is discussed. There is a continuum among the different groups. The pathophysiology remains unknown.
Growth and denervation response of skeletal muscle fibers of newborn rats
Authors: Schmalbruch Henning
Published: January 2005

The cross‐sectional area of the fibers of hindlimb muscles of rats increased 10–40 times during the first 6 weeks after birth. Denervation at birth stopped the growth of the muscle fibers. The number of satellite cells decreased, and eventually all fibers vanished. Reinnervation, if any, was poor. Partial denervation did not induce collateral reinnervation. Some denervated gastrocnemius muscles were reinnervated and after 8–12 months contained hypertrophic fibers and signs of necrosis and regeneration. When soleus muscles were completely denervated and cross‐reinnervated after 4 weeks by the peroneal nerve, only half as many fibers became reinnervated after neonatal denervation as compared to muscles denervated at the age of 4 weeks. The experiments suggest that immature muscle fibers are less apt to become reinnervated than mature fibers. The few reinnervated fibers may be overloaded and therefore hypertrophy and eventually necrotize. Regeneration is abortive because satellite cells are scarce. These results may be relevant for the understanding of neuromuscular disorders with early (fetal) onset.
Schwartz–Jampel syndrome: I. Clinical, electromyographic, and histologic studies
Authors: Spaans Frank , Theunissen Pierre , Reekers Ad , Smit Leo , Veldman Henk
Published: January 2005

In a new, typical case of Schwartz–Jampel syndrome (SJS) the origin of the disorder was found to be purely myogenic. Concentric needle EMG showed abundant and persistent spontaneous activity, maximal at insertion, and uninfluenced by local curarization. Single‐fiber EMG showed rather stable, sometimes intermittent, discharge series with occasional amplitude and/or frequency fluctuations. It could be demonstrated that this activity did not consist of complex repetitive discharges, but of independent activity of individual muscle fibers. This contrasts with findings by other investigators that have been published in this journal. 8, 17 Light microscopic studies of quadriceps and intercostal muscles showed no abnormalities, whereas electron‐microscopic findings were in accordance with earlier studies in SJS. Endplate analysis revealed no specific changes; the postsynaptic stectures gave the impression of an accelerated‐maturation.
AAEM minimonograph #34: Polyneuropathy: Classification by nerve conduction studies and electromyography
Authors: Donofrio Peter D. , Albers James W.
Published: January 2005

Electrodiagnostic evaluation of patiets with suspected polyneuropathy is useful for detecting and documenting peripheral abnormalities, identifying the predominant pathophysiology, and determining the prognosis for certain disorders. The electrodiagnostic classification of polyneuropathy is associated with morphologic correlates and is based upon determining involvement of sensory and motor fibers and distinguishing between predominantly axon loss and demyelinating lesions. Accurate electrodiagnostic classification leads to a more focused and expedient identification of the etiology of polyneuropathy in clinical situations.
Isometric features of orthostatic tremor: An electromyographic analysis
Authors: Walker Francis O. , McCormick George M. , Hunt Vicki P.
Published: January 2005

A patient is described with “orthostatic” tremor. Electromyography revealed tremor bursts of 15 Hz in the lower extremities while standing and with isometric activation of the muscles, but the bursts disappeared with isotonic activation of muscles. Similar tremor was recorded in the arms with isometric, but not isotonic activation. Review of previously reported cases confirms these findings. The clinical and electrophysiologic features of this tremor distinguish it from other recognized forms of tremor.
A tetrodotoxin‐ and Mn2+‐insensitive Na+ current in Duchenne muscular dystrophy
Authors: Bkaily Ghassan , Jasmin Gaétan , Tautu Constantin , Prochek Libuse , Yamamoto Tatsuo , Sculptoreanu Adrian , Peyrow Mehrzad , Jacques Danielle
Published: January 2005

Muscle myotube cultures were obtained from normal and Duchenne muscular dystrophy (DMD) biopsies by using an explant technique. The currentvoltage (I/V) curve of the whole sodium (Na+) current (INa) in normal myotubes was similar to that obtained from DMD myotubes. However, the inactivation curve of the whole INa was different in normal myotubes when compared to that obtained from DMD myotubes. Addition of 10−4 tetrodotoxin (TTX, a fast INa blocker) decreased the whole INa in both preparations. The inorganic calcium (Ca2+) blocker manganese (Mn2+) completely blocked the remaining TTX‐resistant INa of normal myotubes and decreased this current in DMD myotubes leaving behind a TTX‐ and Mn2+ ‐insensitive INa that was insensitive to the Ca2+ blocker desmetoxyverapamil ((–)D888). The slow inward barium current (IBa) of both normal and DMD myotubes was blocked by Mn2+ and (–)D888. However the kinetics of the slow channel in normal myotubes was different from that of DMD myotubes. This study demonstrates the presence of a TTX‐ and Mn2+ ‐insensitive INa in DMD myotubes. This channel may contribute to the increase of intracellular Na+ ([Na]i) in DMD and allow Ca2+ to enter the cells through the Na+Ca2+ exchanger, thus contributing to calcium loading.
Quantitative electromyography in polymyositis: A reappraisal
Authors: Trojaborg Werner
Published: January 2005

Manual analysis of motor unit action potentials (MUAPs) was performed in 33 patients with polymyositis of whom 16 were studied in the acute stage and 17 in the chronic stage. Contrary to common description of “myopathic potentials” as being of low amplitude, short duration, and polyphasic shape, the quantitated study revealed no difference as to amplitude of short duration MUAPs in patients and normal subjects though short‐duration MUAP and short duration polyphasic potentials were 4 and 3 times, respectively, more common in patients than in controls. Although the mean duration of MUAPs usually was significantly shorter in polymyositis than in controls, the average scatter of MUAPs duration was the same in the 2 groups. The average incidence of polyphasic MUAPs was 4 times higher in patients than in controls, as was the incidence of those of long duration. To avoid misinterpretation of EMG findings due to an excess of polyphasic MUAPs, a greater number of individual potentials than usually recommended should be collected allowing a valid estimate of the mean duration of MUAPs of simple configuration.
A comparison of thermography and electromyography in the diagnosis of cervical radiculopathy
Authors: So Yuen T. , Olney Richard K. , Aminoff Michael J.
Published: January 2005

We studied 20 asymptomatic control subjects and 14 patients with clinically unequivocal cervical radiculopathy to compare the diagnostic value of thermography with that of electromyography. We measured the average skin temperature of designated regions over the neck, shoulder, and upper extremities. We then compared the temperature between corresponding regions of the two limbs, and between fingers innervated by different roots in the same hand. Thermography was abnormal in 6 patients (43%), whereas electromyography was abnormal in 10 (71%). Thermographic abnormalities were seen only in the hands and fingers, and the pattern did not follow the dermatome of the clinically involved cervical root. When compared to electromyography, thermography provided no additional diagnostic information. Thus, thermography does not have an established role in the evaluation of patients with cervical radiculopathy.
Twitch relaxation of the cat soleus muscle at different lengths and temperatures
Authors: Iaizzo Paul A. , Poppele Richard E.
Published: January 2005

We recorded isometric and isotonic twitches, in situ, from the cat soleus at various muscle lengths and temperatures. At a given temperature the duration of isometric twitches increased approximately 60% for each 10% increase in muscle length, which was primarily owing to decreases in the rate of relaxation. For the relaxation of isometric twitches recorded at different muscle lengths, the equivalent activation energies determined were the same (13.2 ± 0.3 kcal/M). The duration of isotonic twitch contractions increased only 20% for each 10% increase in muscle length. Even a small amount of shortening (3%) diminished the dependence of twitch duration on muscle length. In this case, twitch duration increased approximately 30% for every 10% increase in muscle length. Hence, even small changes in internal and/or external compliance (eg, changes in the tendon‐fiber continuity) can greatly influence twitch duration. Our findings are consistent with the hypotheses that in the cat soleus, Ca2+ sequestration is primarily governed by a single energy dependent process and that the Ca2+ sensitivity of the contractile apparatus increases with increasing sarcomere length.
Motor unit spike counts before and after maximal voluntary contraction
Authors: Gooch Judith L. , Newton Bruce Y. , Petajan Jack H.
Published: January 2005

Motor unit spike counts in the biceps brachii muscle were evaluated using a monopolar needle electrode during maintenance of antigravity posture with the elbow flexed to 45° before and after maximal voluntary contraction (MVC). After MVC, the number of motor unit spikes/second needed to maintain this posture was about 50% less than prior to MVC. Surface rectified integrated EMG activity declined in parallel to the decline in spike counts. To determine whether different muscles were compensating for the reduction in spike counts, synergistic muscles were examined simultaneously. Similar reductions were noted. In one deafferented subject, EMG activity increased rather than decreased after MVC. Fatigue decreases the contraction–relaxation rate of muscle fibers, which lowers fusion frequency. Thus, lower rates of motor unit activiation can result in the maintenance of constant force. A feedback system from muscle to CNS likely senses this slowing and leads to the spike count reduction.
Randomized, double‐blind trial of mazindol in Duchenne dystrophy
Authors: Griggs Robert C. , Moxley Richard T. , Mendell Jerry R. , Fenichel Gerald M. , Brooke Michael H. , Miller Phillip J. , Mandel Stephen , Florence Juliane , Schierbecker Janine , Kaiser Kenneth K. , King Wendy , Pandya Shree , Robison Jenny , Signore Linda
Published: January 2005

There is evidence that growth hormone may be related to the progression of weakness in Duchenne dystrophy. We conducted a 12‐month controlled trial of mazindol, a putative growth hormone secretion inhibitor, in 83 boys with Duchenne dystrophy. Muscle strength, contractures, functional ability and pulmonary function were tested at baseline, and 6 and 12 months after treatment with mazindol (3 mg/d) or placebo. The study was designed to have a power of >0.90 to detect a slowing to 25% of the expected rate of progression of weakness at P < 0.05. Mazindol did not benefit strength at any point in the study. Side effects attributable to mazindol included decreased appetite (36%), dry mouth (10%), behavioral change (22%), and gastrointestinal symptoms (18%); mazindol dosage was reduced in 43% of patients. The effect of mazindol on GH secretion was estimated indirectly by comparing the postabsorptive IGF‐I levels obtained following 3, 6, 9, and 12 months in the mazindol treated to those in the placebo groups. Although mazindol‐treated patients gained less weight and height than placebotreated patients, no significant effect on IGF‐I levels was observed. Mazindol does not slow the progression of weakness in Duchenne dystrophy.
Vector short‐latency somatosensory‐evoked potentials after median nerve stimulation
Authors: Kaji Ryuji , Sumner Austin J.
Published: January 2005

A new method has been developed for recording short‐latency somatosensory‐evoked potentials after median nerve stimulation. Negative electrical forces recorded with three orthodiagonal bipolar electrodes in the neck had a direction opposite to that of impulse conduction in the proximal peripheral and cervical somatosensory pathway. Sequential tracings of vectors opposite the electrical forces were made in three‐dimensional display, thus reproducing the actual time sequence of electrical events in those structures. Fixed generators such as the subcortical nuclei were also analyzed with this technique, and multiple generators of N13 potential (N13a and N13b) were visualized. This technique may be useful in the functional evaluation of the somatosensory pathway in the cervical cord.
Effects of short spaceflights on mechanical characteristics of rat muscles
Authors: Holy Xavier , Mounier Yvonne
Published: January 2005

The aim of this study was to investigate the contractile protein characteristics after 5‐day (Cosmos 1514) and 7‐day (Cosmos 1667) spaceflights. The experiments were performed on skinned fibers from the soleus, gastrocnemius lateralis, and plantaris muscles isolated from Wistar rats. A reduction in fiber diameter might explain the decrease in the maximal tension in the soleus, whereas this tension was unaltered in the gastrocnemius and the plantaris. Moreover the calcium sensitivity of the myofilament appeared modified in the soleus and in the gastrocnemius: The tension/pCa relationships were shifted toward higher calcium concentrations, indicating a decrease in the appearent calcium binding constant of the tropinin C. The tension/pCa relationship appeared unaltered in the plantaris after spaceflight. Finally, the studies of the time to reach a steady tension indicated an increase in the rate of force development in the soleus and, on the contrary, a slowing down in the plantaris. No change in the gastrocnemius was found. The results were analyzed with references to the different muscle functions in disuse atrophy.
Abnormal M‐wave responses during exercise in myotonic muscular dystrophy: A Na+‐K+ pump defect?
Authors: Fenton John , Garner Scott , McComas Alan J.
Published: January 2005

Maximum M‐waves (muscle compound action potentials) were studied in the abductor pollicis brevis (APB), extensor digitorum brevis (EDB), and tibialis anterior (TA) muscles of 12 patients with myotonic muscular dystrophy (MMD) and in the same number of control subjects, matched for age and sex. The peak‐to‐peak amplitudes and voltage‐time areas of the responses were measured at rest, between 40 maximum voluntary contractions (each lasting 3 s) and also during a 2‐min recovery period. In 34 of the 36 control muscles the M‐waves potentiated during the period of intermittent voluntary contractions. In the MMD patients, however, the M waves exhibited initial declines in 25 of 30 muscles. In the APB and EDB muscles the normalized mean values for the smallest M‐waves, recorded during the 350 s total observation periods, differed significantly between the 2 groups of subjects. It is suggested that the sarcolemmal Na+‐K+ pump has a raised threshold for activation in MMD patients.
Quantitation of axon loss and conduction block in peroneal nerve palsies
Authors: Brown William F. , Watson Brad V.
Published: January 2005

We compared conduction in motor fibers supplying the extensor digitorum brevis (EDB) and anterior lateral compartment (AL) muscles. The object was to determine whether there were any differences in the relative proportions of degenerated and blocked nerve fibers between the longer EDB and shorter AL fibers. In almost every case the percentage of motor fibers undergoing axonal degeneration was greatest in EDB fibers. Conversely, the percentage of conduction block was greatest in the AL motor fibers. As clinical recovery is dependent on AL muscles rather than EDB, electrophysiological study of the relative proportions of degenerated and blocked fibers in the former should provide a more reliable measure of outcome than similar studies of EDB. Conduction velocity distal to the fibular head was not slowed despite the large loss of EDB motor fibers. Evidence for selective involvement of the larger myelinated fibers is, therefore, lacking. The location of the major conduction abnormalities was in almost every case between the mid‐fibular head and popliteal fossa.
AAEM minimonograph #3: Motor unit recruitment
Authors: Petajan Jack H.
Published: January 2005

Motor unit recruitment is the process by which different motor units are activated to produce a given level and type of muscle contraction. At minimal levels of muscle contraction (innervation), muscle force is graded by changes in firing rate (rate coding) of individual motoneurons (MNs). At higher levels of innervation, recruitment is accomplished by the addition of different motor units firing at or above physiologic tremor rate. During slowly graded and ballistic increases in force, motor units are recruited in rank order of their size. In addition to MN soma diameter, other factors contribute to the selectivity of MN activation. For la afferent MN activation in the cat, synaptic density and efficacy as well as specific membrane resistance are also rank ordered for slow, fatigue resistant, and fast fatigue motor units with slow motor units recruited first. The central drive for motor unit activation is distributed to all the MNs of the pool serving a given muscle. Size‐structure organization of the MN pool determines the order of recruitment and how MNs interact with each other. Disorders of the motor unit affect recruitment. A method for the clinical electromyographic assessment of recruitment is suggested. Assessment is made at three levels of innervation: minimal contraction for onset and recruitment firing rates; moderate contraction required to maintain the limb against gravity for the maximum number of motor units, their firing rates, and motor unit spikes/s; maximal voluntary contraction (MVC) for detection of high threshold enlarged motor units characteristic of reinnervation and completeness of the interference pattern (IP). Loss of muscle fibers results in early and excessive recruitment at minimal and moderate levels of innervation. Loss of motor units can result in both an increased rate and range of single motor unit firing at all levels of innervation. With reinnervation and enlargement of motor units, firing rates increase significantly and the interference pattern during MVC is incomplete.
Tea‐sensitive potassium channels and inward rectification in regenerated rat sciatic nerve
Authors: Gardon Thomas R. , Kocsis Jeffery D. , Waxman Stephen G.
Published: January 2005

Sucrose gap and intra‐axonal recording technques were used to identify the types of ion channels and inward rectification that are present in regenerated axons of adult (>8 weeks) rat sciatic nerve after crush injury. In sucrose gap recordings, 4‐aminopyridine (4‐AP) led to slight broadening of the compound action potential (CAP) in normal nerve, and a greater broadening in regenerated nerves. By 12 days after sciatic nerve crush, regenerated nerves manifested an afterhyperpolarization (AHP) lasting up to 250 ms that was sensitive to tetraethylammonium (TEA). A similar TEA‐sensitive AHP could be elicited with repetitive stimulation. Hyperpolarizing constant current steps (0.1 to 0.5 mA; 600–900 ms duration) applied across the sucrose gap through regenerated axons evoked membrane hyperpolarizations with a depolarizing, Cs+‐sensitive relazation in the response to hyperpolarization, which is characteristic of inward rectification, occuring after about 70 ms. The relaxation was present as early as 21 days after nerve crush. Intra‐axonal recordings showed burst firing in 4‐AP that was terminated by an AHP that temporally correlated with the TEA‐sensitive AHP, and a relaxation in the respones to hyperpolazing current, similar to that of whole nerve recordings. The results demonstrate that in addition to voltagesensitive sodium channels and 4‐AP‐sensitive potassium channels, there are TEA‐sensitive and inwardly rectifying channels on mammalian regenerated peripheral nerve axons.
Normal maximal and minimal motor nerve conduction velocities in adults determined by a collision method
Authors: Arasaki Keisuke , Iijima Masakazu , Nakanishi Tokao
Published: January 2005

Using a new collision method, we measured motor nerve conduction velocities of the ulnar nerve in the forearm and the action potential amplitude of the abductor digit minimi muscle on 60 adults, ages 20 to 82 years and apparently free from diseases of the peripheral nervous system. Both maximal and minimal motor nerve conduction velocities were linear functions of age; 64.42 – 0.05 age and 60.45 – 0.12 age, respectively. The percentage of the minimal to the maximal motor nerve conduction velocities was expressed as 94.45 – 0.13 age. The maximum amplitude of evoked muscle action potentials was also correlated with age. This novel method may be useful in detecting pathology of motor nerve fibers which results in a decrease in submaximal conduction velocities.
Somatosensory evoked potentials of the medial and lateral plantar and calcaneal nerves
Authors: Dumitru Daniel , Kalantri Ananthlal , Dierschke Brenda
Published: January 2005

The ideal electrodiagnostic procedure to assess possible plantar neuropathies continues to elude investigators. Motor studies are rarely abnormal, pure sensory studies may be difficult to obtain, needle electromyography can demonstrate membrane instability in normal feet. Mixed nerve plantar studies may be more diagnostically valuable than the other techniques but they also have shortcomings. In this report, a technique utilizing somatosensory evoked potentials to assess the medial and lateral plantar and calcaneal nerves is demonstrated. Normative data with respect to latencies, amplitudes, and side‐to‐side differences are presented. Two illustrative cases are also discussed in which the more standard techniques to evaluate plantar neuropathies fail to do so, but the SEP methodology suggests compromise of the intrinsic foot nerves.
Magnetic stimulation of muscle evokes cerebral potentials
Authors: Zhu Yu , Starr Arnold
Published: January 2005

Somatosensory evoked potentials (SEPs) were recorded from the scalp in man to magnetic stimulation of various skeletal muscles. The potentials consisted of several components, the earliest of which decreased in latency as the stimulated site moved rostrally, ranging from 46 msec for stimulation of the gastrocnemius, to 14 msec for stimulation of the deltoid. Experiments were performed to distinguish the mechanisms by which magnetic stimulation of the muscle was effective in evoking these cerebral potentials. For the gastrocnemius, the intensity of the magnetic stimulus needed for evoking cerebral potentials was less than that required for activating mixed or sensory nerves in proximity to the muscle belly (eg, posterior tibial nerve in the popliteal fossa, sural nerve at the ankle). Vibration of the muscle or passive lengthening of the muscle, procedures which activate muscle spindles, were accompanied by a significant attenuation of the potentials evoked by magnetic stimulation of the muscle. Anesthesia of the skin underlying the stimulating coil had no effect on the latency or amplitude of the early components of the magnetically evoked potentials, whereas electrically evoked potentials from skin electrodes were abolished. Thus, the cerebral potentials accompanying magnetic stimulation of the muscle appear to be due to activation of muscle afferents. We suggest that magnetic stimulation of muscle can provide a relatively simple method for quantifying the function of muscle afferents originating from a wide variety of skeletal musculature.
Altered Na+ channel activity and reduced Cl− conductance cause hyperexcitability in recessive generalized myotonia (becker)
Authors: Franke Christian , Iaizzo Paul A. , Hatt Hanns , Spittelmeister Wolfgang , Ricker Kenneth , Lehmann‐Horn Franke
Published: January 2005

Intact muscle fibers or resealed fiber segments from 7 patients with recessive generalized myotonia were studied in vitro. All fibers had normal resting membrane potentials and normal resting [Ca2+]i several hours after removal. Contractions were characterized by slowed relaxation which was due to electrical after‐activity. Often spontaneous depolarizations were recorded intracellularly. In all fibers, the steady state voltage‐current relationship was abnormal, due to a reduced Cl2+ conductance. However, this conductance ranged from 0% to 66% of the total membrane conductance, whereas, in normal muscle, it was 80%. Theoretically, myotonic after‐discharges would not appear until the Cl− conductance is below 20%. Thus, the membrane hyperexcitability must be due to another defect, at least in the preparations in which the Cl− conductance was only slightly reduced. In all patches from all patients investigated with the patch clamp technique, we observed reopenings of the Na+ channels throughout depolarizing pulses (such behavior was absent in normal muscle). If a patch was polarized to potentials less negative than the resting potential, the duration of the reopenings increased. We conclude that a combination of reduced Cl− conductance and the reopenings of Na+ channels underlie the electrical afteractivity in recessive generalized myotonia.
Myotonia and neuromuscular transmission in the mouse
Authors: Költgen Dirk , Brinkmeier Heinrich , Jockusch Harald
Published: January 2005

The role of neuromuscular transmission and acetylcholine receptors in the phenotypic expression of hereditary myotonia was reinvestigated in two mutants of the mouse, ADR (adr/adr) and MTO (adrmto/adrmto). Three neuromuscular blockers, curare, flaxedil, and α‐bungarotoxin, did not prevent mechanical myotonia of EDL and soleus muscles from the two mutants. Furthermore, electrical myotonia was demonstrated in isolated ADR muscle fibers devoid of nerve endings. We conclude that neither release nor reception of acetylcholine are important for the mechanism of myotonia in mouse mutants. The previously described suppression of myotonic aftercontractions by high concentrations of curare (Muscle & Nerve 1987;10:293–298) could not be reproduced; rather, a prolongation of aftercontractions was found. The other drugs had no significant effect on myotonic aftercontractions. Because neuromuscular transmission is not involved in human myotonias, this result supports the use of myotonic mice as a model, at least for recessive generalized myotonia (Becker).
Chronic multifocal demyelinating neuropathy associated with central nervous system demyelination
Authors: Naganuma Mutsuo , Shima Kohji , Matsumoto Akihisa , Tashiro Kunio
Published: January 2005

We have carried out a long‐term study of lesions found in a man who had a demyelinating disease of both central and peripheral nervous systems. During the 10 years of his clinical course, he suffered from optic neuritis, multifocal myelitis, and chronic multifocal demyelinating neuropathy, with persistent conduction block. Our study revealed that both central and peripheral nervous system demyelination occurred repeatedly and simultaneously.
The silent period produced by electrical stimulation of mixed peripheral nerves
Authors: Leis A. Arturo , Ross Mark A. , Emori Takumi , Matsue Yoshihiko , Saito Takanori
Published: January 2005

The electromyographic silent period (SP) produced by electrical stimulation of the median and ulnar nerve, before and after lidocaine block of the ulnar nerve at the elbow, was recorded in the voluntarily contracting abductor pollicis brevis (APB) muscle of 4 normal subjects. Prior to block, stimulation of the corresponding segment in either nerve (e.g., wrist and elbow) elicited SPs with similar end points. With more proximal stimulation, the SPs consistently ended earlier. Following the block, ulnar nerve stimulation below the elbow failed to elicit a SP in any subject, despite a mechanical twitch caused by the antagonistic contraction of adductor pollicis muscle. Ulnar nerve stimulation above the block elicited a SP in all subjects similar to the preblock SP. In all 4 subjects, submaximal median nerve stimulation at the wrist produced an H‐reflex, followed by a SP in the absence of the direct M‐response. This SP, due to selective activation of sensory fibers, lacked a collision component, but, was otherwise similar to the SP elicited by supramaximal wrist stimulation. These findings indicate that the ascending volley following electrical stimulation of a mixed peripheral nerve produces the SP without apparent contribution from the descending motor volley.
Ca‐, Sr‐tension relationships and contraction velocities of human muscle fibers
Authors: Ruff Robert L. , Whittlesey Diana
Published: January 2005

Muscle fibers from the lateral gastrocnemius or intercostal muscles of 7 normal adult males were chemically skinned (sarcolemma disrupted) and isolated fibers were divided into two parts for histochemical determination of fiber type and physiologic studies. The Ca‐ and Sr‐induced tension relationships and maximum contraction velocities were measured. Slow twitch fibers developed tension at lower concentrations of Ca or Sr than fast twitch fibers. The difference between fast and slow twitch fibers was greatest when Sr was the activating cation. Fast and slow twitch fibers generated similar maximum tensions. The contraction velocities of fast twitch fibers were more than two‐fold greater than slow twitch fibers. Fast‐oxidative‐glycolytic (FOG, type IIA) and fast‐glycolytic (FG, type IIB) fibers had similar Ca‐ and Sr‐tension relationships and contraction velocities.
Electrophysiologic studies in the Guillain–Barré syndrome: Effects of plasma exchange and antibody rebound
Authors: Rudnicki S. , Vriesendorp F. , Koski C. L. , Mayer R. F.
Published: January 2005

Nerve conduction studies (NCS) and antiperipheral nerve myelin antibody (A‐PNM Ab) titers were measured serially in 29 patients with Guillain‐Barré syndrome (GBS), of whom 21 were treated with plasmapheresis. Data were obtained from 3 to 6 days until 1 to 2 years after onset of symptoms. Within 3 to 6 days, mean NCS were abnormal. They improved some by 1 week and became maximally abnormal by 4 to 8 weeks, during which time A‐PNM Ab fell to low levels. In 5 patients plasmapheresed, A‐PNM Ab fell and then increased at 4 to 8 weeks, followed by significant deterioration of NCS (P = 0.01) compared with those without antibody rebound at 18 weeks. These results suggest that, in monophasic GBS, there may be two mechanisms of conduction dysfunction such as early paranodal retraction and later demyelination. In some patients plasmapheresed, A‐PNM Ab may rebound associated with further conduction dysfunction. These patients may benefit from further plasmapheresis.
The neuromuscular basis of hereditary kyphoscoliosis in the mouse
Authors: Bridges Leslie R. , Coulton Gary R. , Howard Gillian , Moss Jill , Mason Roger M.
Published: January 2005

We describe a new neuromuscular disorder in the kyphoscoliotic mouse mutant (ky). Mice were killed at ages from birth to 210 days, and tissues were taken for standard light microscopy, histochemistry, nerve ending studies, and electron microscopy. At birth a few myofibers showed phagocytosis ultrastructurally. Between 6 and 25 days there was prominent necrosis and regeneration in soleus, gracilis, paraspinal, and back muscles. At 47 days, these muscles were atrophic and necrosis and regeneration were rare. At 136 days, all muscle groups, including head muscles, showed some degree of myofiber atrophy and gracilis was fibrotic. Prominent intramuscular axonal sprouting was present from 31 days. Peripheral nerves and anterior horn cells were normal. The findings indicate a neuromuscular basis of hereditary kyphoscoliosis in the mouse. The animal may be useful as a model of human muscle disease and scoliosis.
Myosin isoforms in hindlimb muscles of normal and dystrophic (ReJ129 dy/sol;dy) mice
Authors: Reggiani Carlo , Brocks Lenny , Wirtz Peter , Loermans Helene , te Kronnie Geertruy
Published: January 2005

Myosin isoform expression was studied in hindlimb muscles of control (Dy/Dy) and dystrophic (dy/dy) mice of the ReJ129 strain during postnatal development. Three myosin heavy chain isoforms (fast II‐B MHC, neonatal MHC, and slow or I MHC) were identified using monoclonal antibodies. Only original fibers, i.e., fibers formed during fetal life, were studied. Necrotic and regenerating fibers were excluded. The disappearance of neonatal MHC was found to be delayed in all muscles of dystrophic mice, except the soleus. The fraction of fibers containing I MHC was similar in control and dystrophic animals at all ages, except during the third postnatal week. The developmental increase in the fraction of fibers expressing II‐B MHC was interrupted in dystrophic mice by two marked declines. The first occurred during the second postnatal week at the beginning of the main wave of fiber necrosis, and the second occurred at between 30 and 90 postnatal days.
Conduction velocities of α‐motor fibers innervating human thenar muscles and order of recruitment upon voluntary contraction
Authors: Kakuda Naoyuki , Nagaoka Masanori , Tanaka Reisaku
Published: January 2005

Conduction velocity (CV) of single α‐motor fibers was measured using a combination of microneurogrphic and spike‐triggered averaging techniques on 7 healthy subjects (aged 25 to 42). Two tungsten microelectrodes were inserted percutaneously into the median nerve at the wrist and 4 to 6 cm more proximally. Motor unit activities recorded from thenar muscles during voluntary isometric contraction with a third microelectrode, were isolated with a window discriminator, and used to trigger an averager. CVs were calculated by dividing the interelectrode distance by the conduction time between unitary activities in the proximally and distally averaged neurograms. The CVs of 100 units ranged between 34 and 66 m/s, with the peak at around 50 m/s. The relationship between CVs and recruitment orders was compared within sets of 2 or 3 units recorded simultaneously. Statistical analysis using a χ2 test revealed that slower motor units tended to be recruited earlier than faster units (P < 0.001).
Conduction studies of the normal sural nerve
Authors: Horowitz Steven H. , Krarup Christian
Published: January 2005

The sural nerve was studied orthodromically using the near‐nerve technique in 273 normal subjects (155 females, 118 males) aged 5 to 90 years. The sensory action potential (SAP), evoked at the dorsum of the foot, was recorded at the lateral malleolus and midcalf, and at the midcalf when evoked at the lateral malleolus. In addition, the SAP was recorded at intermediate distal sites and at proximal sites at the popliteal fossa, the gluteal fold, and the S‐1 root. The amplitude of the SAP recorded at midcalf was 32% higher in females than in males. This was probably due to volumeconduction properties, as differences between genders were less noticeable at more distal recording sites. The amplitude decreased steeply and exponentially with age. Conduction distance had a strong influence on the amplitude of the SAP, which decreased with increasing distance following a power relationship with an exponent of 1.4 to 1.7. This decrease was due to temporal dispersion with decreased summation and increased phase cancellation. The conduction velocity was slightly lower along the very distal course of the nerve than along more proximal segments.
Technical artifact simulating “Motor Axonopathy”
Authors: Gilchrist James M. , Dosremedios Edmund , Johnson Gary , Tornabene Joseph
Published: January 2005

We describe 3 patients, referred for other problems, whose nerve conduction studies revealed low compound motor amplitudes, normal motor conduction velocities and normal sensory nerve studies, consistent with a motor axonopathy. EMG was normal. The unexpected nature of these findings precipitated a search for technical artifact. A partial transection of the active electrode was found. After replacement, repetition of the motor studies was normal. Our explanation was of a normal “reference” signal being subtracted from a present but diminished “active” signal.
Cyclosporin a therapy in paraprotein‐associated neuropathy
Authors: Waterston John A. , Brown Martin M. , Ingram David A. , Swash Michael
Published: January 2005

A case of IgG paraprotein‐associated demyelinating neuropathy complicated by respiratory failure, which was unresponsive to standard immunosuppressive drug therapy, is reported. Cyclosporin A therapy resulted in a marked clinical recovery with objective improvement in nerve conduction and vital capacity. The beneficial response suggests that cell‐mediated immunity is an important pathogenetic mechanism, and that cyclosporin A may be useful in the treatment of other refractory cases of paraprotein‐associated neuropathy.
Fatal familial infantile glycogen storage disease: Multisystem phosphofructokinase deficiency
Authors: Amit Rami , Bashan Nava , Abarbanel Jacob M. , Shapira Yehuda , Sofer Shaul , Moses Shimon
Published: January 2005

An infant girl of consanguinous Bedouin parents suffered from fatal early onset of progressive generalized muscle weakness. Her older brother suffered from similar weakness and cardiomyopathy, which led to his death at the age of 21 months. A muscle biopsy performed on the propositus at the age of 9 months was PAS‐negative, and showed nonspecific myopathic changes. A second muscle biopsy, performed at 21 months of age, a few days before her death, and postmortem study of heart and liver, disclosed excessive extralysosomal glycogen storage and reduced phosphofructokinase‐1 (PFK‐1) activity. Because the genes encoded for PFK‐1 in liver and muscle are located on separate chromosomes, the reduced enzyme activity in both tissues could not be related to a single mutation for this enzyme. Activity of 6‐phosphofructose‐2‐kinase (PFK‐2), a recently discovered physiological activator to all PFK‐1 isozymes, was normal in the liver. The possibility that this multisystem PFK‐1 deficiency may be related to the absence of a yet unknown activator, common to all PFK‐1 isozymes, is discussed.
AAEM minimonograph #38: Neuropathies in connective tissue disease
Authors: Olney Richard K.
Published: January 2005

Neuropathies are common in patients with known or suspected connective tissue disease. A vasculitic mononeuropathy multiplex is often seen in patients initially presenting with polyarteritis nodosa or developing arteritis as a complication of rheumatoid arthritis. However, vasulitic neuropathy may become confluent and present as as distal symmetrical polyneuropathy or occur without systemic necrotizing vasculitis. Distal symmetrical polyneuropathies without associated vasculitis are also common in many connective tissue diseases. Compression neuropathies, especially carpal tunnel syndrome, occur with increased frequency in rheumatoid arthritis. Finally, certain neurpathies may be the major presenting feature of particular connective tissue diseases. For example, trigeminal neuropathy often heralds the onset of systemic sclerosis or mixed connective tissue disease, and sensory neuronopathy may be the initial presenting feature of Sjögren's syndrome.
The heart in becker muscular dystrophy, facioscapulohumeral dystrophy, and bethlem myopathy
Authors: de Visser Marianne , de Voogt Willem G. , la Rivière Guusje V.
Published: January 2005

We report a study, assessing involvement of the heart in 33 familial cases of Becker muscular dystrophy (BMD), 31 familiar cases of facioscapulohumeral (FSH) dystrophy, and 27 familial cases of Bethlem myopathy. In the patients with BMD, correlations of myocardial involvement with age and extent of musculoskeletal involvement were made. We performed physical examination, chest X‐ray, electrocardiographic (EKG), and echocardiographic extients with FSH dystrophy. Thirteen patients with BMD (45%) showed EKG changes similar to those found in Duchenne muscular dystrophy. Only 1 of the 13 individuals with cardiac invovement was wheelchairbound. We found no evidence of cardiac changes in the patients with FSH dystrophy. In Bethlem myopathy, only 1 patient had a form of hypertrophic cardiomyopathy (asymmetrical septal hypertrophy).