Abnormal sensorimotor integration in writer's cramp: study of contingent negative variation

To investigate the pathophysiology of idiopathic focal dystonia, we recorded contingent negative variation (CNV) as a physiological index of sensorimotor integration in 14 right-handed patients with writer's cramp and compared it with normative data. CNV was recorded in the S2 choice reaction time paradigm: Two kinds of auditory S2 (Go or No-Go) were given 2 s after the auditory S1, and the subject reacted only to the Go signal by extending the wrist. In normal subjects, the late CNV amplitude had no difference at Cz between left- and right-hand tasks and was symmetric without significant amplitude laterality irrespective of the side of hand movement. In patients with writer's cramp, the late CNV amplitude at Cz was relatively larger for the left-hand task than the right-hand task (p < 0.03), and a significant amplitude laterality of the late CNV (larger on the right) was present especially at the central area for the right-hand task (p < 0.03). Since the late CNV is known to be generated, at least in part, from primary and supplementary motor cortices, the significant laterality of the late CNV seen with the right-hand task in patients with writer's cramp might represent functional abnormality of motor cortices possibly as the result of basal ganglia function.

Exercise-induced muscle cramp. Proposed mechanisms and management

Muscle cramp is a common, painful, physiological disturbance of skeletal muscle. Many athletes are regularly frustrated by exercise-induced muscle cramp yet the pathogenesis remains speculative with little scientific research on the subject. This has resulted in a perpetuation of myths as to the cause and treatment of it. There is a need for scientifically based protocols for the management of athletes who suffer exercise-related muscle cramp. This article reviews the literature and neurophysiology of muscle cramp occurring during exercise. Disturbances at various levels of the central and peripheral nervous system and skeletal muscle are likely to be involved in the mechanism of cramp and may explain the diverse range of conditions in which cramp occurs. The activity of the motor neuron is subject to a multitude of influences including peripheral receptor sensory input, spinal reflexes, inhibitory interneurons in the spinal cord, synaptic and neurotransmitter modulation and descending CNS input. The muscle spindle and golgi tendon organ proprioceptors are fundamental to the control of muscle length and tone and the maintenance of posture. Disturbance in the activity of these receptors may occur through faulty posture, shortened muscle length, intense exercise and exercise to fatigue, resulting in increased motor neuron activity and motor unit recruitment. The relaxation phase of muscle contraction is prolonged in a fatigued muscle, raising the likelihood of fused summation of action potentials if motor neuron activity delivers a sustained high firing frequency. Treatment of cramp is directed at reducing muscle spindle and motor neuron activity by reflex inhibition and afferent stimulation. There are no proven strategies for the prevention of exercise-induced muscle cramp but regular muscle stretching using post-isometric relaxation techniques, correction of muscle balance and posture, adequate conditioning for the activity, mental preparation for competition and avoiding provocative drugs may be beneficial. Other strategies such as incorporating plyometrics or eccentric muscle strengthening into training programmes, maintaining adequate carbohydrate reserves during competition or treating myofascial trigger points are speculative and require investigation.

McArdle's disease with non-insulin-dependent diabetes mellitus: the beneficial effects of hyperglycemia and hyperinsulinemia for exercise intolerance

A 64-year-old female with McArdle's disease and non-insulin-dependent diabetes mellitus (NIDDM) is reported. She had none of the characteristic symptoms of McArdle's disease such as muscle cramps but her serum creatine kinase level was elevated. Muscle biopsy with negative muscle phosphorylase staining showed McArdle's disease. Modified forearm ischemic exercise test was done at two conditions; fasting and two hours after a meal. When fasting, the level of lactic acid did not elevate after exercise. After a meal, however, the serum lactic acid level rose with the elevation of plasma glucose and IRI. Thus, we suggested that high plasma glucose and insulin due to NIDDM may induce blood-borne glucose uptake with exercise.

Impaired sensory-motor integration during grasping in writer's cramp

Six subjects with writer's cramp and six healthy control subjects were examined while lifting a small instrumented object with variable weight and friction using the precision grip. The isometric grip and load forces were sampled at 400 Hz and stored in a flexible laboratory computer system for later analysis. Quantitative measurement of vibration and temperature sensibility showed normal sensory perception in the writer's cramp subjects. They exhibited an impaired programming of the grip-lift force co-ordination, while the ability to generate unimodal force-rate trajectories and to characterize the pattern of the force output according to memory representations of weight and friction of the object were intact. The capacity to terminate quickly the programmed grip force in lifts erroneously programmed too high was impaired. Writer's cramp subjects also employed excessive grip force during the static phase of the lift, and some patients had a short grip force latency after sudden unpredicted load increases, indicating a disinhibited spinal reflex response. The results indicate an impaired capacity in writer's cramp subjects to integrate sensory information in the motor programming and force regulation during precision grip tasks, despite a normal sensibility.

Generator sites for spontaneous activity in neuromyotonia. An EMG study

A 16-year-old female patient with symptoms and signs compatible with neuromyotonia was studied with various neurophysiological tests and with muscle biopsy. Nerve conduction studies revealed signs of axonal motor neuropathy. EMG showed denervation in distal muscles, and moderate neurogenic changes in other muscles. Abundant spontaneous motor unit activity was recorded in all muscles. This activity did not disappear upon proximal nerve blockade with local anaesthetics. Based on the shape of spontaneous discharges and their behaviour on nerve stimulation and during voluntary effort, the site of generation was suggested. This varied for different discharges, from proximally in the nerve, to various sites along the intramuscular nerve tree. In some axons there were signs of conduction block proximal to the generation site for the spontaneous discharges. Different axons showed various degrees of abnormality; local hyperexcitability triggering new impulses only after the passage of a preceding impulse, increased hyperexcitability generating spontaneous activity, total impulse blocking, and finally axonal degeneration. Treatment with dihydantoin reduced the spontaneous activity with concomitant clinical improvement.

Cirrhosis and muscle cramps: evidence of a causal relationship

The aim of the study was to define the features, prevalence, and pathophysiology of therapy for muscle cramps in cirrhotic patients. The first protocol study included 294 cirrhotic patients and 194 age- and sex-matched controls. Controls were defined as inpatients or outpatients without any clinical and laboratory evidence of liver disease. Features and prevalence of muscle cramps were defined on the basis of a standard questionnaire. As far as the pathophysiological associations of muscle cramps were concerned, the following parameters were evaluated: mean arterial pressure (MAP), nutritional status, liver function tests, plasma volume (PV), plasma renin activity (PRA), and electrolyte, mineral, and acid-base status. The prevalence of cramps was higher in cirrhotic patients than in controls, and it was related to the duration of recognized cirrhosis and to the severity of liver function impairment. At a multiple regression analysis, the presence of ascites, low values of MAP, and high values of PRA were the independent predictive factors for the occurrence of cramps in cirrhosis. In the second protocol study, the effects of a sustained expansion of the effective circulating volume induced by intravenous infusion of human albumin were compared with those of a placebo in 12 cirrhotic patients with more than three cramp crises a week. Compared with the placebo, albumin reduced the cramp frequency (P < .01). In conclusion, an increased prevalence of true muscle cramps occurs in patients with cirrhosis. Our data indicate that the pathophysiological link between cirrhosis and cramps may be represented by the reduction of the effective circulating volume. They also indicate that weekly infusion of human albumin may be an effective treatment for cramps in cirrhosis.

Movement-related cortical potentials in writer's cramp

Movement-related cortical potentials in response to simple, self-paced, brisk index finger abduction movements were recorded in patients with simple and complex writer's cramp and compared with those of age-matched control subjects. Analysis of the movement-related cortical potential waveforms showed that the Bereitschaftspotential, the peak of the negative slope, and the frontal peak of the motor potential did not differ in the two groups, except for the average amplitude of the early part of the negative-slope peak, which was decreased in the patient group during the interval of 300 to 200 msec prior to electromyographic onset. This finding was restricted to the electrodes overlying the contralateral and midline central electrodes. Movement-related cortical potentials from patients and control subjects could be equally accounted for by a four-dipole source model with sources located in the contralateral and ipsilateral sensorimotor regions and the supplementary motor area. There was a trend for a reduction in the strength of the sensorimotor sources active during the premotor period in the patient group, but the difference did not reach a significant level for any individual source. No differences were found between the movement-related cortical potentials elicited by movements of the affected and unaffected hand, or between those of patients with simple or complex hand cramps. This result suggests a deficiency of contralateral motor cortex activation just prior to the initiation of voluntary movements in patients with focal dystonia.

Modulation of electromyographic activity of wrist flexor and extensor muscles in patients with writer's cramp

Patients with writer's cramp have two well-recognized neurophysiological abnormalities: reduced reciprocal inhibition of the wrist flexor motoneurons at rest, and increased cocontraction of antagonist muscles of the forearm during voluntary activity. In this article we present evidence for an impaired integration of sensory inputs into the voluntary motor activity during performance of a force-related task in patients with writer's cramp. Normal (control) subjects and patients activated wrist flexor and extensor muscles to maintain a predetermined level of force. Electrical stimuli were applied to median and radial nerve afferents and the modulatory effects induced in the electromyographic (EMG) activity were measured. For each muscle studied and nerve stimulated, we defined a characteristic sequence of excitatory (E) and inhibitory (I) phases of modulation of the averaged rectified EMG activity in control subjects. E and I phases were thought to represent excitation and inhibition, respectively, of the corresponding motoneuronal pool to homonymous or reciprocal afferent inputs. There were no differences between control subjects and patients regarding the level of background EMG activity in the agonist muscles during wrist flexion or wrist extension. In the agonist wrist flexors, patients had reduced homonymous and reciprocal inhibition. In the agonist wrist extensors, patients had reduced reciprocal excitation and reciprocal inhibition. These results are compatible with an abnormal CNS processing of the inputs generated by external stimuli during voluntary contraction of wrist flexor and extensor muscles. Defective integration of inputs from peripheral nerve afferents into the command for voluntary movement may partly underlie the pathophysiology of the motor dysfunction in patients with writer's cramp.

Reciprocal inhibition in writer's cramp

We studied the inhibition of median H-reflexes by conditioning stimuli on the radial nerve in 13 patients with writer's cramp, eight of the simple type and five of the dystonic type, and in 14 normal volunteers. The patients and controls were right-handed, and their right arms were studied. Asymptomatic left arms were also studied in nine of 13 patients. In the control group we identified three periods of inhibition, with maximum peaks at conditioning-test intervals of 0 ms (41 +/- 17%), 20 ms (40 +/- 13%), and 100 ms (36 +/- 20%). In the patient group, the amplitudes of inhibition of these three periods in both arms were significantly less than those in the control group. However, there were no significant differences in the amplitudes of inhibition of these three periods between symptomatic and asymptomatic arms. There were also no significant differences between simple and dystonic writer's cramps. Our results indicate that the attenuation of reciprocal inhibition was present not only in symptomatic arms but also in asymptomatic arms of patients with writer's cramp. The defect of reciprocal inhibition in the asymptomatic hand has never been documented. We suggest that the preexistent electrophysiological abnormality may provide an explanation for the development of hand cramp after shifted writing.

Human motor unit activity during induced muscle cramp

Muscle cramp was induced in the medial head of the gastrocnemius muscle in four of seven subjects using unloaded maximal voluntary contraction of the triceps surae in the shortened position. Surface electromyography over the medial and lateral heads of gastrocnemius and the soleus muscles demonstrated that the muscle activity during cramp was localized to part or all of the medial head of the gastrocnemii. In the same muscle, a tungsten electrode was used to record from 200 motor units during 16 episodes of cramp and 871 units during 26 voluntary contractions. For the first 30 s, significantly higher motor unit firing rates were recorded during cramp compared with unloaded voluntary contractions. Motor unit firing rates were also more variable during cramp. When the cramped muscle was stretched forcibly to break the cramp, motor unit activity increased in all the triceps surae muscles. In some experiments, the Achilles tendon of five subjects was vibrated for 50 s before and after voluntary contraction or cramp. The tonic vibration reflex (TVR) was depressed or absent after four episodes of cramp but it was unchanged after voluntary contraction. These data are interpreted to indicate that motor units are involved in ordinary muscle cramp. A positive feedback loop between peripheral afferents and alpha motor neurons, mediated by changes in presynaptic input, is a possible mechanism underlying muscle cramp.

Tonic vibration reflex and muscle afferent block in writer's cramp

Patients with focal dystonia take advantage of certain cutaneous or proprioceptive sensory inputs to alleviate their symptoms ("sensory trick"). We examined the effects of increasing muscle spindle activity by the tonic vibration reflex maneuver and decreasing it by intramuscular injection of lidocaine. The vibration was applied to the palm or the tendon of forearm muscles in 15 patients with writer's cramp and 15 age-matched normal subjects. In 11 patients, the vibration induced dystonic postures or movements typical of those seen during writing. Normal subjects showed either no response to the vibration or a gradually developing tonic vibration reflex only in the wrist and finger flexors, which produced visible movements with a significantly longer latency (12.5 +/- 6.7 seconds [mean +/- standard deviation]) than what was observed in the patients (2.7 +/- 2.5 seconds, p < 0.0001). Local injection of lidocaine (0.5%, 5-40 ml/muscle) attenuated the tendon reflex with relatively little effect on the M response. Injection into muscles with increased activity produced marked reduction of dystonic movements and significant clinical improvement in 13 patients, whereas injection into the other muscles had no effect. The clinical benefit lasted for 1 to 24 hours after injection. In 13 patients who had additional injections of 10% ethanol, which blocks sodium channels for a longer period than does lidocaine, the duration of action was prolonged to 5 to 21 days. These findings suggest that muscles causing dystonic movements have abnormal sensitivities to vibration at rest and that muscle afferents may play a pivotal role in producing dystonic movements.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind trial of botulinum toxin for treatment of focal hand dystonia

Ten patients with focal dystonia of the hand, all of whom had benefited in an open-label study of botulinum toxin, were treated with botulinum toxin-A in a double-blind study. Response was assessed by three measures: (a) subjective rating, provided by patients' reports of the effect of the injections on the dystonia; (b) objective testing, consisting of manual muscle testing (MRC scale) to measure muscle strength in all patients, timing of a writing sample and counting the number of errors of writing off-the-line in six patients with writer's cramp, counting the number of errors on a standard test of transcription in two patients with stenographer's cramp, and rating by professional musicians of the performances of two patients with musician's cramp; and (c) physicians' rating, provided by a review of the patients' videotaped performance by neurologists who were unaware of which treatment was administered. Eight of the 10 patients had greater subjective improvement with botulinum toxin than with placebo, and this impression was verified by at least one objective test in six patients. Two patients failed to have a better response to botulinum toxin than to placebo, and their reports were verified by the objective tests. This study confirms the efficacy of botulinum toxin in many patients with focal hand dystonia.

Painful unilateral epileptic seizure

Two rare cases with focal, paroxysmal pain as the initial manifestation of partial epilepsy have been reported. The pain attacks subsided after treatment with anti-epileptic drugs.

The origin of muscle fasciculations and cramps

The anatomic site of origin of muscle fasciculations and cramps has been debated for many years. Many authors have argued for a central origin of the abnormal discharges in the anterior horn cells. However, most of the evidence favors a very distal origin in the intramuscular motor nerve terminals. The factors giving rise to these discharges are not well understood. Fasciculations may be related to chemical excitation of motor nerve terminals, whereas cramps may result from mechanical excitation of motor nerve terminals during muscle shortening.

Motor neuron 'bistability'. A pathogenetic mechanism for cramps and myokymia

In three patients suffering from chronic muscle cramps, spasms and myokymia, these involuntary contractions were triggered in the triceps surae, quadriceps, flexor carpi radialis or flexor digitorum by means of single or short-train stimulation of homonymous Ia afferents, elicited by electrical means or tendon taps. In some cases cramp was induced by the first afferent volleys; more often, however, continued stimulation produced stepwise recruitment of motor units (whose rhythmic firing was visible as myokymia in the muscle) until cramp developed. Cramps and myokymic discharges could usually be terminated by a single maximal stimulus to the motor axons (producing antidromic invasion and Renshaw inhibition of the motor neurons), or by short trains of volleys in inhibitory pathways from the skin. The fact that it was possible to induce myokymia and cramps by brief synaptic excitation and terminate them by antidromic invasion or synaptic inhibition, suggests that the mechanism generating these disturbances is intrinsic to alpha-motor neuron somata. Similar on-off switching of self-sustained motor discharges has been observed in the decerebrate cat and is known to depend on 'bistability' of the motor neuron membrane. We propose that a similar mechanism is responsible for discharges that produce cramp.

Exercise-induced muscle pain, soreness, and cramps

The three types of pain related to exercise are 1) pain experienced during or immediately following exercise, 2) delayed onset muscle soreness, and 3) pain induced by muscle cramps. Each is characterized by a different time course and different etiology. Pain perceived during exercise is considered to result from a combination of factors including acids, ions, proteins, and hormones. Although it is commonly believed that lactic acid is responsible for this pain, evidence suggests that it is not the only factor. However, no single factor has ever been identified. Delayed onset muscle soreness develops 24-48 hours after strenuous exercise biased toward eccentric (muscle lengthening) muscle actions or strenuous endurance events like a marathon. Soreness is accompanied by a prolonged strength loss, a reduced range of motion, and elevated levels of creatine kinase in the blood. These are taken as indirect indicators of muscle damage, and biopsy analysis has documented damage to the contractile elements. The exact cause of the soreness response is not known but thought to involve an inflammatory reaction to the damage. Muscle cramps are sudden, intense, electrically active contractions elicited by motor neuron hyperexcitability. Although it is commonly assumed that cramps during exercise are the result of fluid electrolyte imbalance induced by sweating, two studies have not supported this. Moreover, participants in occupations that require chronic use of a muscle but do not elicit profuse sweating, such as musicians, often experience cramps. Fluid electrolyte imbalance may cause cramps if there is profuse prolonged sweating such as that found in working in a hot environment. Thus, despite the common occurrence of pain associated with exercise, the exact cause of these pains remains a mystery.

[Treatment of writer's cramp with botulinum toxin]

Writer's cramp is a focal dystonia that is resistant to most treatment regimens. This article describes two patients with writer's cramp who were successfully treated with botulinum toxin injections into the forearm muscles. Transient weakness due to the effect of botulinum toxin was registered in the injected muscles. No other side effects were observed. The beneficial effect of a single injection lasted from three to four months and could be reproduced by repeated injections over a three year follow-up period. We conclude that botulinum toxin injections may provide safe and effective treatment in selected patients with writer's cramp.

[Muscle cramps: mechanism , etiology and current treatment]

Spasms of skeletal muscles occur in healthy individuals or in the course of functional disorders of the peripheral motor neuron or its axons. Like fasciculations, they are a motor manifestation, but a painful one. Cramps evoke the notion of ephapsis and of immature terminal axons. There are, however, also other responsible regulatory systems, mostly the sensible and spinal ones. Three personal observations are used to illustrate the various triggering mechanisms. A review of the literature on this subject is added. Symptomatic treatment has not changed over past decades: Quinidine remains the treatment of choice. Other stabilizers of cell membranes are actually available, whose usefulness varies as a function of the cause of cramps.

[Three siblings of painful muscle cramps (generalized muscle cramp disease) with alopecia and endocrinological disorders]

Three siblings with generalized painful muscle cramps, generalized alopecia, and endocrinological abnormalities are presented. Their clinical features are very similar to those in sporadic cases reported as having generalized muscle cramp disease. Autosomal recessive inheritance was suggested in our patients. Abnormal laboratory tests include hypersecretion of insulin after glucose loading, elevated levels of luteinizing hormone (LH) and follicular stimulating hormone (FSH), and hypersecretion of LH in the LH-RH test. An elevation of IgG and IgG index in the cerebrospinal fluid (CSF) of two patients suggests IgG production in the CSF. Oral administration of 75 to 150 mg of dantrolene sodium decreased the frequency, intensity, and duration of cramps in all cases. Autoimmune mechanisms based upon hereditary abnormalities are suggested as a cause of their disease.

Isaac's syndrome: report of a case responding to valproic acid

Isaac's syndrome is an uncommon, but distressing, condition of spontaneous abnormal muscle activity caused by neuronal hyperexcitability possibly due to damage to slow potassium channels. The underlying aetiology may be peripheral nerve damage from a wide variety of causes, including autoimmune disease. We report a case that failed to respond to carbamazepine or phenytoin but responded dramatically to valproic acid. Thus, valproic acid may be an effective treatment for Isaac's syndrome where these other drugs have failed.

[Methods for detection of changes in muscle tonus]

Muscular spasm is a frequent symptom which is difficult to record precisely. On the basis of literature on the subject and of own studies, we undertook to describe various methods of examination which could be used to demonstrate such changes. Up to now, palpation is still the most important and most exact method for the experienced examiner. In this way local as well as extended muscular spasms can be made evident. The disadvantage however is the lack of objective proof. The easy-to-use Tissue-Compliance-Meter of Fischer, which measures the consistency of soft tissue, documents the intraindividual difference rather than the interindividual difference. This is due to the individually variable thickness of the subcutaneous fatty tissue. However, on the whole there is a good correlation to the findings of palpation. The pendulous-test and badismography allow especially the conclusion with regard to unilateral changes of tonus in the gluteal and upper leg muscles. This method also very well suits the intraindividual comparison, but less so the interindividual one. The continuous electromyogram is able to show the enhanced activity in spasmotic muscles also during sleep. The evaluation of enhanced muscle activity remains uncertain when using plain electromyogram. Recording of muscle tissue oxygen pressure is of little use to evaluate muscle spasm. Nonetheless, it provides interesting insights into pathogenetic questions. Thermography, measuring the blood circulation at the skin surface, is especially suited for perceiving intraindividual differences in case of muscle spasm. Nuclear magnetic resonance spectroscopy allows for noninvasive pH measurements in the muscle and therewith renders certain data concerning the degree of tension of this tissue. It is not yet suited for routine examination. The value of positron emission tomography for registering muscle spasm remains uncertain. Hopefully, this method, which documents the muscle energy metabolism, will enable us to more clearly evaluate muscle spasm than previous methods have done. Light and electron microscopic studies have provided contradictory results concerning histological changes in muscle biopsy in case of muscle spasm.

Long-term botulinum toxin treatment of focal hand dystonia

We treated focal hand dystonia in 53 patients with botulinum toxin injections for up to 6 years. Eighty-one percent of the patients improved with at least one injection session. Sixty-five percent of the injections produced transient weakness. We followed 37 of the patients for at least 2 years from the start of treatment, 24 of whom discontinued treatment because of inadequate response, loss of response, inaccessibility of a treatment provider, or the expense of the toxin. Women, who had a greater extent and longer duration of benefit than men, were more likely to continue treatment. The mean interval between injection sessions was 6 months. In most patients, we injected the toxin into the same combination of muscles at each session. The dose of toxin generally fluctuated within a range of 20 units. Side effects were mild and transient and unrelated to the long-term use of botulinum toxin. Botulinum toxin injection is safe and effective for the long-term management of focal hand dystonia.

Muscle cramp as the result of impaired GABA function--an electrophysiological and pharmacological observation

We investigated the mechanism of cramps in 2 patients: a 48-year-old man with bulbospinal neuronopathy, and a 46-year-old man with amyotrophic lateral sclerosis. Cramps were quite easily induced by volitional exertion and high-frequency stimulation of the peripheral nerves. When an ulnar nerve was blocked with lidocaine at the elbow, no cramp was induced despite the application of high-frequency stimulation at the wrist. Diazepam (GABAA agonist) was effective in the first patient and baclofen (GABAB agonist) in the second, with no cramps induced in spite of increasing stimulation intensity. Impairment of interneurons mediated by GABA as the neurotransmitter is thought to be involved in the mechanism of the cramps.

Abnormal cortical responses in patients with writer's cramp

We evaluated sensorimotor processing in patients with writer's cramp using PET and H2(15)O blood flow scans. The study included six right-handed patients with unilateral writer's cramp and eight right-handed normals. Subjects had blood flow scans at rest and during vibration of either the "affected" or "unaffected" hand. Vibration produced a consistent peak response in primary sensorimotor area (PSA) and supplementary motor area (SMA), both contralateral to the vibrated hand. Both responses were significantly reduced approximately 25% in patients with writer's cramp (PSA, p = 0.002; SMA, p = 0.02) whether vibrating the affected or unaffected hand. This indicates that patients with unilateral writer's cramp have bilateral brain dysfunction. These data provide objective evidence of abnormal central sensorimotor processing in writer's cramp.

Biomechanical abnormalities in musicians with occupational cramp/focal dystonia

Occupational factors and peripheral injuries are frequently implicated in the development of hand cramps and the syndrome of persistent manual incoordination among musicians and others most commonly given a diagnosis of focal limb dystonia. In an attempt to gain insight into the character and influence of risk factors in the evolution of this disorder, the authors conducted detailed evaluations of 33 individuals who responded to a questionnaire sent to university- and conservatory-level music schools in Germany in September 1989. Response was invited from any musician with complaints of impaired hand control. Of the 33 individuals accepted for evaluation, 18 were musicians who met clinical criteria for the diagnosis of occupational cramp/focal dystonia (OC/FD). Nineteen of the original 33 subjects underwent a quantitative biochemical assessment, comparing active and passive ranges of motion at all joints below the shoulder with those for cohorts of unimpaired musicians, matched for gender and musical instrument. Of the 19 tested biomechanically, 14 had OC/FD and the remaining five had either persistent pain or nonspecific movement idiosyncracies interfering with playing. Compared with the matched groups of normals, no consistent biomechanical abnormality was found in the non-OC/FD group; in the OC/FD group two thirds had marked limitation of passive and/or active abduction range between the central digits of both hands. Based on detailed training and performance histories in these subjects, the authors conclude that a specific biomechanical condition in the hand can interfere with certain high-speed digital movements required in musical instrument performance. Unintended muscle synergies, postures, and movement patterns can develop as attempts are made to increase the speed and fluency of such movements. As rehearsal is intensified, degraded movements are stabilized ("programmed"). In this situation, OC/FD appears to represent an aberrant outcome of normal motor learning whose physiologic correlates mimic neuropathologically based dystonia. The implications for prevention are discussed.

Writers' cramp

At least 4000 people suffer from writers' cramp in the UK. While diagnosis is straightforward, treatment is difficult and many therapies are unsatisfactory. This article reviews the various manifestations of writers' cramp, the physiological evidence indicating that it is a neurological disease and the therapeutic techniques available.

The influence of muscular lengthening on cramps

Muscle cramps induced by voluntary contraction and by electrical stimulation of the peripheral nerve were studied electrophysiologically in 10 healthy subjects. The aim was to verify that cramps can be evoked by electrical stimulation of peripheral nerve and to clarify the physiological mechanism responsible by analyzing the effect of muscular stretching on cramps. Our results showed: (1) Cramps can be induced even after peripheral nerve block by electrical stimulation distal to the block. (2) No cramps were recorded during or following maximal voluntary contraction without muscular shortening, while 7 of 10 subjects showed a true cramp following maximal effort with shortening of the muscle. (3) Muscle stretching caused a sudden interruption of cramps induced by either voluntary contraction or electrical stimulation of the peripheral nerve, even after the induction of nerve block. (4) The lengthening state of the muscle can strongly influence the possibility of evoking cramps by electrical stimulation of nerve. Our study verifies the experimental model proposed by Lambert in 1969, emphasizing the relevance of frequency of stimulation and confirming the hypothesis that cramps are of peripheral origin. The effects of muscle stretch and lengthening on cramp interruption and development also have a peripheral mechanism.

[The destabilization of the 1st carpo-metacarpal joint in musicians' cramp]

Destabilisation of the first carpometacarpal joint in musicians and in occupational cramps constitutes a functional dystonia. Joint laxity predisposes to these conditions as well as the musician's technique or the working position. This destabilisation can cause a lesion of the anterior oblique ligament of the trapezo-metacarpal joint progressing towards osteoarthritis in the long term. Rehabilitation attempts to act on the functional dystonia and on the hand by maintaining carpo-metacarpal structures and reinforcing the musculature of the hand.

[Clinical studies of writer's cramp in 30 patients]

30 patients with writer's cramp were examined by a neurologist and a psychiatrist. The syndrome was frequently associated with a postural tremor. We found no evidence for a peripheral causation. Electromyographical recordings showed co-contractions of agonists and antagonists as well as individual patterns of increased muscle activity during writing. CT and MRI scans were normal in most patients. The psychiatric examination revealed a history of situational stress at the onset of the disease and also some abnormalities in the biography and personality traits. Since the latter findings were not consistently present we have no evidence that the disease is a neurotic manifestation. We consider it likely that secondary psychoreactive processes may have some significance in the individual patient.

Clinical presentation and treatment of black widow spider envenomation: a review of 163 cases

STUDY OBJECTIVE

To review cases of black widow spider envenomation to describe the clinical presentation and evaluate the efficacy of treatment.

DESIGN

Retrospective chart review.

SETTING

An urban toxicology referral center.

TYPE OF PARTICIPANTS

All patients attended by the toxicology service and discharged from our hospital between January 1982 and December 1990 with a diagnosis of black widow spider envenomation.

INTERVENTIONS

Inclusion criteria were either a positive black widow spider identification or a visible envenomation site ("target lesion"). Depending on the clinical presentation, patients were categorized as grade 1, 2, or 3 in severity. The efficacy and side effects of treatment alternative were evaluated.

MEASUREMENTS AND MAIN RESULTS

One hundred sixty-three patients met the inclusion criteria. The most common sites of envenomation were the upper and lower extremities. The most common presenting complaint was generalized abdominal, back, and leg pain. One hundred eighteen patients initially presented to our institution, and 45 were transfers. Pain relief of grade 2 and 3 envenomations was achieved most effectively with either black widow spider-specific antivenin alone or a combination of IV opioids and muscle relaxants. Fifty-eight patients received antivenin with complete resolution of symptoms in a mean time of 31 +/- 26.7 minutes. Of the 118 patients initially seen at our institution, the mean total duration of symptoms was 9 +/- 22.7 hours in patients receiving antivenin and 22 +/- 24.9 hours in patients not receiving antivenin. Fifty-two percent of patients not receiving antivenin required hospitalization, whereas only 12% of those receiving antivenin were admitted. One patient died of severe bronchospasm after receiving antivenin. Calcium gluconate was not effective in providing symptomatic relief in this series, with 96% of the grade 2 and 3 envenomations treated initially with calcium gluconate requiring the addition of IV opioids or other analgesics for symptomatic relief. Fifty-five percent of patients initially receiving IV morphine and 70% of those initially receiving both IV morphine and benzodiazepines obtained symptomatic relief without additional medication.

CONCLUSION

One hundred sixty-three envenomations by black widow spiders were reviewed and graded according to severity with treatment modalities evaluated. Although calcium gluconate usually has been considered the first-line treatment of severe envenomations by black widow spiders, we found it ineffective for pain relief compared with a combination of IV opioids and benzodiazepines. The use of antivenin significantly shortened the duration of symptoms in severe envenomations.

Triphasic waves and spike wave stupor

Triphasic waves are usually thought of as indicating a metabolic encephalopathy. Recent investigations have added nonmetabolic etiologies to the differential diagnosis of triphasic waves. Seizures are not generally thought of as associated with triphasic waves. Similarities in the appearance of records with encephalopathies and continuous triphasic waves and those of some patients with the Lennox-Gastaut syndrome have been noted. We presented a case which suggests that the presence of TW in a patient with a metabolic encephalopathy might suggest petit mal status epilepticus.

Neuromuscular hyperexcitability features in patients suffering from musculoskeletal pain: a neuroepidemiologic survey

We studied the reported frequencies of clinical complaints of neuromuscular hyperexcitability (muscle cramps and fasciculations) in random samples of 527 Dutch adults, who were and 253 Dutch adults, who were not suffering from musculoskeletal pain and tenderness. Data were collected by telephone-interview and by self-administered questionnaire. Muscle cramps and fasciculations were recorded more frequently in the category that suffered from musculoskeletal pain (p less than 0.001). This association warrants further investigation into the possible intrinsic role of neuromuscular hyperexcitability in musculoskeletal pain and primary fibromyalgia.

Cramps: a sign of motoneurone 'bistability' in a human patient

In a patient suffering from severe long-lasting cramps, cramps were triggered in the triceps surae by volleys in homonymous Ia afferents (elicited by electrical stimulation or by tendon taps) and were interrupted by antidromic invasion and Renshaw inhibition of triceps surae motoneurones (evoked by a single maximal stimulation of motor axons). This result suggests that the mechanisms which generate the cramps are intrinsic to alpha-motoneurone somata. A similar on-off switching of a self-sustained motor discharge has been observed in the decerebrate cat and recognized to depend on 'bistability' of the motoneuronal membrane. We propose that the same mechanism may be at the origin of the cramp discharge.

[Pain in multiple sclerosis. Clinical aspects and therapy]

Although pain is not considered a typical symptom of multiple sclerosis, more than 50% of patients with MS present with pain syndromes. In the setting of an incurable disease, symptom control and particularly pain control is very important in achieving a better quality of life. For paroxysmal pain syndromes such as trigeminal neuralgia or painful tonic seizures, carbamazepine and other anticonvulsive drugs are the cornerstone of treatment. On the other hand, drugs are not always effective in treating the various chronic pain syndromes such as dysesthetic extremity pain or leg spasms. In these conditions, individualized regular physiotherapy may relieve pain.