A rare form of painful nondystrophic myotonia

OBJECTIVE

In this paper we report a painful nondystrophic myotonia which has not been previously described. Pain is a rare symptom in myotonia. We report a myotonic disorder in a 34-year-old woman and her 14-year-old daughter. Painful cramps occur during and after exercise in the mother, and both patients can demonstrate unusual contractions in the tongue. In the present study we try to evaluate the mechanisms behind the unique finding of trains of high amplitude of positive waves, not seen in the earlier known myotonic conditions.

METHODS

Clinical investigations and electromyography with single and dual channel recordings and muscle morphometry were performed.

RESULTS

The electromyographic recordings reveal positive waves, fibrillation potentials and myotonic discharges. In addition, extraordinary findings were made of trains of high frequency positive potentials with very high amplitudes and with conduction block along the muscle fibres.

CONCLUSIONS

In this new form of myotonia with likely dominant heredity, the specific finding of trains of high amplitude positive waves indicates ephaptic transmission within bundles of neighbouring muscle fibres.

[Eccentric muscle work--the unknown side of our movements]

Eccentric muscle work is an important part of our everyday activity, i.e. in breaking and preventing falls. Eccentric phases of movements improve the efficiency of cyclic repetitive activities. The molecular function in eccentric work is not understood, however its characteristics are a low metabolic demand and a high power output. Compared to concentric work there are only small differences in the hemodynamics of eccentric work. The muscle capacity for mechanical load is the limiting factor in eccentric work. Unaccustomed eccentric activity leads to damage of the cytoskeleton, which is the reason for delayed onset of muscle soreness. In sports and rehabilitation eccentric training can result in significant strength gain. Its use is today established to improve structures, which are exposed to eccentric loads in everyday activity. The high mechanical power may be promising in the musculoskeletal rehabilitation of patients with cardiopulmonary limitations.

The role of flexibility in injury prevention and athletic performance: have we stretched the truth?

The use of stretching to prevent injury, off-set muscle soreness, and improve performance has been widely accepted and promoted in sports. However, little or no scientific evidence supports the practice, and recent research suggests that stretching, which increases flexibility beyond that needed for sport-specific movements, may cause injury. This article presents studies that have looked at the effects of stretching on injury and performance. Many earlier studies that showed benefits of stretching did not look at the effects of stretching alone; they also involved general cardiovascular workouts in the experimental but not control groups. More recent research shows that general fitness, rather than stretching, is a more important risk factor in injury prevention. This article also discusses studies of the relationship between joint laxity and injury and the role that stiffness may play in enhancing performance and preventing injury. Overall, the evidence suggests that increasing range of motion beyond function through stretching is not beneficial and can actually cause injury and decrease performance. These findings should be used to challenge common warm-up practices in athletics.

Muscle cramp in Machado-Joseph disease: altered motor axonal excitability properties and mexiletine treatment

Machado-Joseph disease is one of the most common hereditary spinocerebellar degenerative disorders with a wide range of clinical manifestations. Pathology studies have shown mild to moderate loss of anterior horn cells and, in terms of spinal pathology, Machado-Joseph disease is regarded as a type of lower motoneuron disease. Muscle cramps are often associated with lower motoneuron disorders, but features of cramps in Machado-Joseph disease patients have never been studied. We investigated the incidence and nature of muscle cramps in Machado-Joseph disease patients, the excitability properties of motor axons [strength-duration time constant (tau(SD)), threshold electrotonus, refractoriness and supernormality] using threshold tracking and the effects of mexiletine hydrochloride on those cramps. Of 20 consecutive patients, 16 (80%) had frequent, severe muscle cramps in the legs, trunk or arms that disturbed their daily activities. The frequency of pathological muscle cramps was similar to that for patients with amyotrophic lateral sclerosis (68%) and higher than those for patients with spinal muscular atrophy (33%) or peripheral axonal neuropathy (24%). Threshold-tracking studies showed that tau(SD), which in part reflects Na(+) conductance at the resting membrane potential, was significantly greater in the Machado-Joseph disease patients than in normal subjects; severe muscle cramps were associated with a longer tau(SD). Threshold electrotonus, refractoriness and supernormality were not significantly different between Machado-Joseph disease patients and normal subjects. Eight Machado-Joseph disease patients with severe cramps, who received mexiletine treatment, experienced nearly complete relief with a partial normalization of tau(SD) (P = 0.08). Muscle cramps are a very frequent and disabling factor in Machado-Joseph disease. Pathological muscle cramps responded well to mexiletine treatment, and this is consistent with the hypothesis that they are caused by an increase in persistent Na(+) conductance, possibly associated with axonal regeneration or collateral sprouting.

Repetitive nerve stimulation and muscle membrane excitability: case report and review

Few muscle disorders can be diagnosed by repetitive nerve stimulation (RNS). Decreasing compound muscle action potentials (CMAP) on high frequency RNS is recorded in muscle channelopathies, and particularly in sporadic and recessive congenital myotonia. In this myopathy, decreasing CMAP after exercise test and RNS are the most sensitive electrophysiological in detecting muscle membrane dysfunction and are considered highly informative even in mildly symptomatic patients. We report on a patient with excercise-induced diffuse muscle cramps and myalgia; muscle biopsy and laboratory investigations were normal. Decreasing CMAP on high frequency RNS suggested muscle membrane conduction anomalies and, though clinical and electrical myotonia was not detected, the neurophysiological finding raised the suspicion of congenital myotonia and addressed to molecular investigation.

Basal ganglia as a sensory gating devise for motor control

Basal ganglia lie between the cerebral cortex and the thalamus, and have dense fiber connections between them. These connections form 4-5 distinct loops or circuits to allow parallel processing of information. Among them, the most intensively studied is the motor loop, which comprises 2 distinct direct and indirect pathways. The direct pathway disinhibits the powerful inhibition of the internal segment of the globus pallidus/substantia nigra pars reticulata upon thalamic ventrolateral nuclei with a net result of facilitatory influence upon the motor cortex. By contrast, the indirect pathway exerts an inhibitory effect. Overall this dual system provides a center (excitatory)-surround (inhibitory) mechanism to focus its effect on selected cortical neurons. Although putative transmitters, inhibitory or excitatory nature of these projections and their receptors are mostly known, the functional role of the loop in motor control is not precisely understood. Several lines of evidence have recently been presented to support the view that this center-surround mechanism is used to focus the output to a specific group of muscles required for performing a specific task. This operation is made possible through opening the sensory channel for the expected sensory feed-back afferents during movement. Thus one of the important functions of basal ganglia seems to be the gating of sensory input for motor control.

A randomized, double-blind, placebo-controlled trial of supplementary vitamins E, C and their combination for treatment of haemodialysis cramps

BACKGROUND

Muscle cramps that improve after carnitine or vitamin E therapies are common in haemodialysis (HD) patients. Because vitamin C participates in carnitine biosynthesis, and its levels are reduced in uraemia, subclinical vitamin C depletion may contribute to HD cramps. Our aim was to determine the effects of vitamins C, E and their combination on the frequency and intensity of HD cramps.

METHODS

In this placebo-controlled, double-blind study, 60 HD-patients were randomized into four therapeutic groups. Each group (n=15) received six identical capsules daily for 8 weeks, containing one of the following: vitamin E (400 mg), vitamin C (250 mg), their combination, or placebo.

RESULTS

The frequency and intensity of HD cramps decreased significantly in all three vitamin groups compared with the placebo group at the end of the trial, and compared with the pre-treatment values. At the end of the trial, vitamins E, C, their combination, and placebo produced cramp reductions of 54, 61, 97 and 7%, respectively. The percentage cramp reduction had no significant correlation with age, sex, aetiology of end-stage renal disease, serum electrolytes or HD duration, but showed a positive correlation (r=0.33, P=0.01) with the type of therapy. No vitamin-related adverse effects were encountered during the trial.

CONCLUSION

Short-term treatment with the combination of vitamins E and C is safe and effective in reducing HD cramps; however, its safety for prolonged therapy has yet to be evaluated in HD patients.

Cerebral activation patterns in patients with writer's cramp: a functional magnetic resonance imaging study

Functional MRI (fMRI), visualizing changes in cerebral blood oxygenation, has to date not been performed either in patients with writer's cramp or in healthy subjects during writing. We compared the cerebral and cerebellar activation pattern of 12 patients with writer's cramp during writing with a group of 10 healthy subjects performing the same tasks over 30-s periods of rest or writing. Sixty echo planar imaging multislice datasets were analysed using SPM96 software. Data were analysed for each subject individually and groupwise for patients vs. controls. Healthy subjects showed a significant activation of the ipsilateral dentate nucleus, contralateral cerebellar hemisphere, contralateral primary sensorimotor cortex, and contralateral precentral gyrus during writing. Patients with writer's cramp showed significantly greater activation of the ipsilateral cerebellar hemisphere than controls. Also the activation in the primary sensorimotor cortex extended further caudally and anteriorly towards the premotor association area. Activation was observed in the thalamus during writing only among the patients. Our results indicate an increased basal ganglia output via the thalamus to the motor and premotor cortical areas in dystonia patients and support the notion of disinhibition of the motor cortex leading to cocontractions and dystonic postures.

Abnormal postexcitatory and interhemispheric motor cortex inhibition in writer's cramp

Focal transcranial magnetic stimulation (TMS) of the motor cortex was used to study excitatory and inhibitory stimulation effects in 25 patients with writer's cramp and 25 healthy volunteers. We investigated excitatory and inhibitory corticospinally mediated motor effects in muscles contralateral to the stimulation side as well as interhemispheric inhibition of tonic motor activity in muscles ipsilateral to stimulation. Motor evoked potentials (MEPs) were recorded from both first dorsal interosseus muscles. Motor thresholds at rest and amplitudes and latencies of MEPs obtained during maximal contraction were always bilaterally normal. The duration of postexcitatory inhibition was significantly shortened (168+/-55 vs. 198+/-39 ms in normal subjects, P=0.001) and the duration of interhemispheric inhibition prolonged (30.3+/-6.6 vs. 26+/-3.9 ms in normal subjects, P < 0.001). Both observations would be compatible with a decreased inhibition of corticospinal and transcallosal outputs of the motor cortex. The results were not influenced by fatigue effects. Abnormal motor cortex inhibition seems to be a generalized phenomenon in writer's cramp since it was detected in both hemispheres and during a simple isometric motor task which did not evoke dystonic symptoms.

Excitability properties of motor axons in patients with spontaneous motor unit activity

OBJECTIVES

Measures of nerve excitability provide information about biophysical properties of peripheral axons in disease states. One measure, the strength duration time constant (tau(SD)), was previously reported to be prolonged in motor axons of patients with acquired neuromyotonia. The present study used a new protocol that applies a more comprehensive and sensitive panel of measures of axonal excitability, to determine firstly whether changes in tau(SD) were present in a group of patients with evidence of spontaneous motor unit activity; and secondly, if such changes in tau(SD) were present, whether other parameters of axonal excitability were affected, to clarify the mechanism of the change in tau(SD).

METHODS

Eleven patients with both symptoms and EMG evidence of spontaneous motor unit activity were studied. Eight patients had autoimmune associated acquired neuromyotonia (aNMT) and three had the cramp fasciculation syndrome. The protocol first measured stimulus-response behaviour using two stimulus durations (from which the distribution of strength-duration time constants was estimated), and then threshold tracking was used to determine threshold electrotonus to 100 ms polarising currents, a current-threshold relation (indicating inward and outward rectification), and the recovery of excitability after supramaximal activation.

RESULTS

The results were compared with previously published normal data. The value for tau(SD) of motor axons in the patient group was 0.43 (0. 02) ms (mean (SEM)), identical with the control value. Most other indices of axonal excitability, including those dependent on fast potassium channels, were also found to be normal. When compared with age matched controls however, the patients with acquired neuromyotonia had significantly greater late subexcitability after an impulse, greater excitability overshoots after depolarisation or hyperpolarisation, and more accommodation.

CONCLUSIONS

No clear evidence for the mechanism of ectopic discharge in these patients was obtained, probably because the activity was generated focally, and most often at the motor nerve terminals. The unexpected finding of increased excitability overshoots and accommodation compared with age matched controls, suggests a relative up regulation of slow potassium conductance, possibly as a consequence of the continuous motor unit activity.

Afterdischarge activity in neuropathic patients with frequent muscle cramps

OBJECTIVES

To evaluate the presence of the afterdischarge activity following M- and F-waves in patients with peripheral neuropathies with or without muscle cramps.

MATERIAL AND METHODS

Ten patients with peripheral neuropathies complaining of frequent muscle leg cramps (Group 1) and 14 patients with peripheral neuropathies without muscle cramps (Group 2) participated in our study. The afterdischarge was evaluated through a repetitive stimulation of the peroneal and tibial nerves.

RESULTS

An abnormal afterdischarge activity following F-wave was identified below 5 Hz only in Group 1. On high frequency of stimulation (> 5 Hz), this activity was present in every patient in Group 1. Moreover, it was particularly present in the muscle affected by cramps.

CONCLUSION

Since the afterdischarges following F-waves have been considered to be the result of a hyperactive "bistable" state of alfa-motor neurons, our findings are indicative of an impairment of motor neuron excitability. Thus, it is hypothesizable that either peripheral and central mechanisms may together contribute in producing muscle cramps.

Muscle cramps: a 'complication' of cirrhosis

Muscle cramps are a common complaint in clinical practice. They are associated with various metabolic, endocrine, neurological and electrolyte abnormalities. A variety of hypotheses have been generated to explain the cause of muscle cramping, yet none has been able to support a consistent pathophysiological mechanism. Muscle cramps are painful, involuntary contractions of skeletal muscle. They occur frequently in individuals with cirrhosis, regardless of the etiology, and are thought to be a symptom of cirrhotic-stage liver disease. The pathophysiology of these cramps remains elusive; hence, a specific therapy has not been identified. Many therapeutic approaches have been offered, yet their efficacy, safety and mechanism of action remain poorly defined. This review defines muscle cramps and illuminates its prevalence in the cirrhotic individual. Current theories relating to the pathogenesis of muscle cramps are reviewed, and an overview of the various pharmacological agents that have had therapeutic success for this distressing and frustrating symptom is provided.

Alteration of sensorimotor integration in musician's cramp: impaired focusing of proprioception

OBJECTIVE

The influence of muscle vibration (MV) as a strong proprioceptive input on motorcortical excitability was studied in 5 patients with musician's cramp, 5 musician controls and 5 non-musician controls.

METHODS

The relaxed flexor carpi radialis (FCR), involved in the dystonic movement in all patients, was vibrated using low frequency (80 Hz) and low amplitude (0.5 mm). Transcranial magnetic stimulation (TMS; intensity, 120% of motor threshold) was applied without MV, 3 and 9 s after the onset of MV. Motor-evoked potentials (MEPs) in the FCR and in the antagonistic extensor carpi radialis (ECR) were recorded.

RESULTS

With MV, musician and non-musician controls showed a facilitation of MEPs in the FCR and a decrease of MEPs in the ECR. In musician's cramp, both phenomena were significantly less pronounced.

CONCLUSIONS

The reduced facilitation of MEPs in musician's cramp indicates a reduced MV-induced activation of motorcortical areas representing the FCR. The less pronounced inhibition by MV reflects a reduced inhibitory control of the antagonistic ECR. As there were no differences between musician and non-musician controls, the observed changes in musician's cramp refer to this special form of focal dystonia. An impairment of focused motorcortical activation by proprioceptive input from a muscle involved in the dystonic movement is suggested.

Delayed onset muscle soreness: effect of an ischaemic block upon mechanical allodynia in humans

The current study, for which ethical approval was obtained, was designed to assess the extent to which the tenderness or mechanical allodynia observed in delayed onset muscle soreness (DOMS) might be mediated by large diameter myelinated nerve fibres. Healthy human volunteers were recruited and randomly allocated to one of three groups: Normal-Control, Ischaemic-Control, and Test-DOMS (total n=21; n=7 in each group). In the Normal-Control group, subjects attended on a single occasion for assessment of mechanical pain threshold (MPT) at standardized sites over the biceps brachii using a pressure algometer for a period of 20 min. In both remaining groups, ischaemia was induced in subjects' non-dominant upper limbs by elevation of the limb, followed by application of a sphygmomanometer cuff at a pressure of 250 mmHg. Throughout the period of the block (20-40 min), sharp/blunt sensation was assessed at regular intervals. MPT was assessed upon inflation of the cuff and reassessed at 10 min intervals until deflation. In the two ischaemic block groups, current level of pain was also monitored using a computerized visual analogue scale (VAS) at the beginning and end of the procedure. Subjects in the Test-DOMS group attended 48 h prior to ischaemic block for induction of DOMS using a standardized regime of eccentric exercise, but thereafter were treated in exactly the same manner as the Ischaemic-Control group. Results showed a significant (P<0.05; ANOVA) increase in MPT in the Test-DOMS group by the 20 min point, corresponding to a 'normalization' of MPT; loss of the ability to distinguish between sharp/blunt sensation accompanied such changes. Parallel increases in reported pain were seen in both groups undergoing ischaemic block, indicating that the procedure did not alter nociception. While not definitive, these results suggest that altered processing of activity in large diameter (myelinated) afferents might underlie the mechanical allodynia observed in DOMS; thus, this is an area which warrants further investigation.

Possible mechanisms of muscle cramp from temporal and spatial surface EMG characteristics

In this study, the initiation and development of muscle cramp are investigated. For this, we used a 64-channel surface electromyogram (EMG) to study the triceps surae muscle during both cramp and maximal voluntary contraction (MVC) in four cramp-prone subjects and during cramp only in another four cramp-prone subjects. The results show that cramp presents itself as a contraction of a slowly moving fraction of muscle fibers, indicating that either the spatial arrangement of the motoneurons and muscle fibers is highly related or that cramp spreads at a level close to the muscle. Spectral analyses of the EMG and peak-triggered average potentials show the presence of extremely short potentials during cramp compared with during MVC. These results can also be interpreted in two ways. Either the motoneurons fire with enlarged synchronization during MVC compared with cramp, or smaller units than motor units are active, indicating that cramp is initiated close to or even at the muscle fiber level. Further research is needed to draw final conclusions.

Movement-related electroencephalographic desynchronization in patients with hand cramps: evidence for motor cortical involvement in focal dystonia

We studied the dynamic changes in the amplitude of scalp electroencephalographic (EEG) oscillations to self-paced simple index finger abduction movements in patients with writer's cramp and compared them with those of normal aged-matched controls. The changes in EEG oscillations were measured in predefined frequency bands (8-10, 10-12, 12-20, and 20-30 Hz) by using the event-related desynchronization technique. Movements of the affected and unaffected hand in patients with writer's cramp showed significantly less reduction in 20- to 30-Hz power compared with controls. The differences in movement-related EEG power decline were apparent over the contralateral central and midline regions before and after electromyographic onset. Because EEG beta rhythm in the sensorimotor region likely emanates from the motor cortex and is related to ongoing muscle activity, this abnormality could be a manifestation of the abnormal motor command at the cortical level.

Characteristics and etiology of exercise-related transient abdominal pain

PURPOSE AND METHODS

In order to investigate the characteristics of the exercise-related transient abdominal pain (ETAP) commonly referred to as "stitch," a questionnaire was administered to a total of 965 regular sporting participants involved in six sports.

RESULTS

The percentage of respondents claiming to have experienced ETAP within the past year for the respective sports were: running (69%, N = 439), swimming (75%, N = 103), cycling (32%, N = 76), aerobics (52%, N = 126), basketball (47%, N = 121), and horse riding (62%, N = 100). ETAP appears to be most prevalent in activities that involve repetitive torso movement, either vertical translation or longitudinal rotation. ETAP appears to be a single condition, common in its manifestation to most sufferers, and was described by respondents as a well-localized pain (79%), mostly experienced in the right or left lumbar regions of the abdomen (78%). The sensation of ETAP may be related to the severity of pain with less intense ETAP being described as cramping, aching, or pulling, and greater severity ETAP as sharp or stabbing in nature. Fourteen percent of respondents indicated that they experience shoulder tip pain (STP), which being the diaphragmatic-referred site could suggest irritation of the diaphragm. Respondents claiming to have experienced ETAP were more likely to report STP (r = 0.14, P < 0.01).

CONCLUSIONS

The findings of the present study provide perspective on previously suggested etiologies of ETAP, which include diaphragmatic ischemia and stress on the visceral "ligaments," and form the basis for examining alternative etiologies such as cramp of the musculature and irritation of the parietal peritoneum.

Gabapentin treatment for muscle cramps: an open-label trial

To evaluate the efficacy and safety of gabapentin in the treatment of muscle cramps, we engaged an open-label trial with a group of 30 patients with frequent (> 5 cramps/week), stable, long-lasting cramps, associated with different diseases. Gabapentin was effective in reducing the frequency and severity of muscle cramps and associated sleep disturbances (clinical outcome measures) within the first 2 weeks of medication at 600 mg/d. At the 1 month control (mean dosage, 825 +/- 35 mg), almost every patient had responded to treatment and two thirds experienced a total remission of symptoms. After 3 months of therapy (mean dosage, 892 +/- 180 mg), cramps disappeared in 100% of patients and this benefit persisted as long as 6 months. Additionally, we evaluated in 10 patients the Cramps Threshold Frequency (CTF) (neurophysiological outcome measure) before and during gabapentin treatment. Gabapentin significantly increased the CTF, returning it to normal values. With the limitation of an open-label methodology, our clinical and neurophysiologic experience suggests that a gabapentin dose of 600-1200 mg/d would be helpful in the treatment of muscular cramps.

RELIEF study: first consolidated European data. Reflux assEssment and quaLity of lIfe improvement with micronized Flavonoids

The RELIEF study (Reflux assEssment and quality of life improvement with micronized Flavonoids in chronic venous insufficiency [CVI]) is a prospective, controlled, multicenter, international study performed in patients with or without venous reflux. This study was conducted between March 1997 and December 1998 in 23 countries worldwide with the participation of more than 10,000 patients suffering from CVI. The European countries, the subject of this report, were represented by the Czech and Slovak Republics, Hungary, Poland, Russia, and Spain. The principal aims of the study were: 1. To validate the first quality-of-life scale specific to chronic venous insufficiency (CMVIQ) in different languages and to assess the evolution of quality of life in patients suffering from CVI, with or without venous reflux, treated with micronized purified flavonoid fraction (MPFF*) (1,000 mg/day). 2. To collect international epidemiologic data on venous reflux assessed with pocket Doppler and photoplethysmography. 3. To assess the evolution of symptoms and signs with a specific emphasis on edema through validated Leg-O-Meter measurement (heaviness, pain, cramps, sensation of swelling, edema) in patients suffering from CVI and treated with MPFF, 1,000 mg/day, during 6 months. The first country-by-country statistical analysis and the European consolidated analysis are now available. The CIVIQ questionnaires adapted to each participating country have been validated with highly significant validity and reproducibility (p<0.0001). All dimensions have demonstrated a highly significant and evolving improvement during the study. The results show several interesting findings concerning the epidemiologic data and, of these, two were particularly interesting: - More than 50% of patients suffering from CVI (class 0 to 4 of the CEAP classification) were reflux-free, which means that they were suffering from functional CVI. Patient distribution between the different classes of the CEAP classification changed in a statistically significant manner after 6 months' treatment with MPFF; the number of patients in the more severe classes decreased to the benefit of the less severe classes. Symptoms such as pain, leg heaviness, sensation of swelling, and cramps were significantly improved (p=0.0001). This was associated with a significant decrease in edema, when present, measured by leg circumferences with the Leg-O-Meter (p=0.0001). In conclusion, the European results of the RELIEF study showed the perfect validity and reproducibility of CIVIQ questionnaire adaptations, and the positive progression of quality-of-life scores on MPFF treatment. This progression was paralleled by clinical improvement of patients reflected not only by assessment of CVI symptoms and signs but also by evolution of the CEAP classification.

A novel method of inducing muscle cramps using repetitive magnetic stimulation

The lack of a practical model has hampered attempts to study the pathophysiology of muscle cramps. We investigated the feasibility, efficacy, and reproducibility of repetitive magnetic stimulation in producing experimental cramps. In 14 healthy subjects, the tibial nerve at the ankle was stimulated with a magnetic stimulator at rates beginning at 4 Hz to a maximum of 20 Hz. The frequency was gradually increased until a cramp was produced. Ten of 14 subjects demonstrated a muscle cramp. All subjects rated the discomfort of the procedure to be mild or moderate. Repeat testing yielded values that were highly reproducible. This technique holds promise for clinical studies and therapeutic trials.

Specific muscle EMG biofeedback for hand dystonia

Currently available therapies have only limited success in patients having hand dystonia (writer's cramp). We employed specific muscle EMG biofeedback (audio feedback of the EMG from proximal large muscles of the limb that show abnormally high activity during writing) in 10 of 13 consecutive patients (age, 19-62 years; all males) with a duration of illness from 6 months to 8 years. In three patients, biofeedback was not applicable due to lack of abnormal EMG values. Nine patients showed dystonic posture during writing and had hypertrophy of one or more large muscles of the dominant hand. The remaining four patients showed either involvement of small muscles or muscle wasting. Ten patients were given four or more sessions of EMG audio biofeedback from the proximal large limb muscles, which showed maximum EMG activity. They also practiced writing daily with the relaxed limb for 5 to 10 min. Nine patients showed improvement from 37 to 93% in handwriting, alleviation of discomfort, and pain (assessed on a visual analogue scale). One patient did not show any improvement. Thus EMG biofeedback improved the clinical and electromyographic picture in those patients with hand dystonia who showed EMG overactivity of proximal limb muscles during writing. This specific type of EMG biofeedback appears to be a promising tool for hand dystonia and might also be applied to other types of dystonias.

Deficient activation of the motor cortical network in patients with writer's cramp

OBJECTIVE

To study regional cerebral blood flow (rCBF) in patients with simple writer's cramp using PET to identify regions that malfunction.

BACKGROUND

Several lines of evidence indicate impaired cortical function in patients with focal dystonia, but the precise pathophysiology is still unknown.

METHODS

Seven patients with writer's cramp were compared with seven age- and sex-matched control subjects. Control subjects and patients were scanned during sustained contraction, tapping, and writing with the right hand. After realignment and stereotactic normalization of the scans, all tasks were compared with a rest condition. For each task, an intra- and intergroup comparison was performed using statistical parametric mapping. For each condition and within groups, rCBF correlation analysis was performed between some selected regions that were activated during movement.

RESULTS

In control subjects and patients, significant increases of rCBF were observed for each task in areas already known to be activated in motor paradigms. The intergroup comparison disclosed less activation in writer's cramp patients for several areas for all three tasks. This decrease reached significance for the sensorimotor cortex during the sustained contraction task and for the premotor cortex during writing. rCBF correlation analysis showed different patterns between control subjects and patients. At rest and during writing, the correlations between the putamen and premotor cortical regions and between the premotor cortical regions themselves were stronger in control subjects.

CONCLUSIONS

Deficient activation of premotor cortex and decreased correlation between premotor cortical regions and putamen suggest a dysfunction of the premotor cortical network in patients with writer's cramp possibly arising in the basal ganglia. The dysfunction is compatible with a loss of inhibition during the generation of motor commands, which in turn could be responsible for the dystonic movements.

Abnormal cortical processing of voluntary muscle relaxation in patients with focal hand dystonia studied by movement-related potentials

In order to clarify the abnormality in cortical motor preparation for voluntary muscle relaxation of the hand in patients with focal hand dystonia, Bereitschaftspotentials (BPs) preceding voluntary muscle contraction and relaxation were recorded in eight patients (three with simple writer's cramp and five with dystonic writer's cramp), and were compared with those from 10 normal subjects. Voluntary muscle relaxation: after keeping the right wrist in an extended position for > 5 s, the subject let the hand drop by voluntarily terminating muscle contraction of the wrist extensor without any associated muscle contraction. Voluntary muscle contraction: the right wrist was flexed by voluntarily contracting the wrist flexor muscle. Scalp EEGs were recorded from 11 electrodes placed over the frontal, central and parietal areas. In the control group, the BP measured at the movement onset was maximal at the left central area (C1), and distributed predominantly over the left hemisphere equally in both the contraction and relaxation tasks. In the focal hand dystonia group, BP was maximal at C1 in the contraction task, whereas, in the relaxation task, it was maximal at the midline central area (Cz) and symmetrically distributed. At the left central area, the BP amplitude in the focal hand dystonia group was diminished significantly in the relaxation task compared with the contraction task (P < 0.05). The present results demonstrate for the first time that the cortical preparatory process for voluntary muscle relaxation, or motor inhibition, is abnormal in focal hand dystonia.

Autosomal dominant muscle cramp syndrome in a Japanese family

OBJECTIVES

To identify the clinical, electrophysiological, histological, and genetic characteristics of a Japanese family with a muscle cramp syndrome.

METHODS

Fourteen patients (eight men, six women) were studied in four generations of a single family. Electrophysiological examinations were performed in four cases and muscle and nerve biopsies were performed on the propositus.

RESULTS

The mode of inheritance seemed to be autosomal dominant. The cramps occurred during both exertion and at rest, and during sleep. Electromyographic examination indicated a neurogenic aetiology. There was a decreased number of large myelinated fibres in the sural nerve, and fibre type grouping in the quadriceps femoris muscle biopsy.

CONCLUSIONS

The autosomal dominant muscle cramp syndrome in this family is probably caused by a polyneuropathy.

Past and current understanding of the pathophysiology of muscle cramps: why treatment of varicose veins does not relieve leg cramps

Historically relevant hypotheses on the pathophysiology of muscle cramps are reviewed. Psychosomatic, static, vascular, myogenic and neural theories are highlighted from a clinician's point of view. Modern neurophysiologic research leaves little doubt that muscle cramp is caused by excitation of spinal motor neurones mediated by changes in presynaptic input. Nevertheless, obsolete theories and relative treatments stubbornly persist in clinical practice.

Abnormal increase in the corticomotor output to the affected hand during repetitive transcranial magnetic stimulation of the primary motor cortex in patients with writer's cramp

In fourteen right-handed patients with writer's cramp and 10 right-handed controls, 10 trains of suprathreshold 1 Hz repetitive transcranial magnetic stimulation (rTMS) were applied over the left primary motor hand area. Each rTMS train lasted for a minute with an intertrain interval of 10 s. The motor evoked potentials (MEPs) were recorded from the relaxed contralateral first dorsal interosseus muscle. The mean MEP area of each rTMS train was taken as a measure of the corticospinal motor output to the affected hand. While the mean MEP area decreased significantly in controls, patients showed a significant increase in mean MEP area during rTMS. The differential effect on MEP size was highly significant. The abnormal rTMS-associated facilitation of the corticomotor output to the affected hand demonstrates an increased excitability of the corticospinal motor system in writer's cramp.

Abnormal contingent negative variation in writer's cramp

OBJECTIVE

To investigate the physiological abnormality in writer's cramp, a focal dystonia which specifically affects writing.

METHODS

We recorded brain potentials that precede hand and neck movements (contingent negative variation or CNV) in 11 patients and 11 age-matched normal subjects. A 1000 Hz tone burst (S1) was delivered to the right or left ear in random sequence, and 2 s after, a 2000 Hz tone burst (S2) was delivered to both ears simultaneously. For the response task to S2, the subjects were instructed to extend their fingers ipsilateral to the ear to which S1 was given in one experiment or to rotate the head to the side of the S1 presentation in another. All the patients had symptoms in the right hand only, and performed both tasks normally. CNV amplitudes were compared between normals and patients using unpaired t test.

RESULTS

They showed normal CNV for neck movement but significantly decreased CNV amplitudes for movements both in the affected and unaffected hands.

CONCLUSIONS

Our findings suggest that motor programming is specifically abnormal for the affected body part, including the asymptomatic contralateral limb, and that the clinical symptom may result from a deficient compensatory mechanism for abnormal motor programs or subroutines.

Low-frequency repetitive transcranial magnetic stimulation of the motor cortex in writer's cramp

OBJECTIVE

To study the short-term effects of slow repetitive transcranial magnetic stimulation (rTMS) of the motor cortex on cortical excitability and handwriting in patients with writer's cramp.

BACKGROUND

Cortical excitability of the primary motor cortex is abnormally enhanced in patients with writer's cramp. Therefore, reducing cortical excitability by low-frequency rTMS of the motor cortex might result in beneficial effects on handwriting in writer's cramp.

DESIGN/METHODS

We studied the effects of subthreshold 1-Hz rTMS on motor threshold and cortico-cortical excitability using the paired-pulse technique in seven patients and seven controls. In another 16 patients and 11 age-matched controls we evaluated changes in cortical excitability by measuring the stimulus-response curve and the postexcitatory silent period before and after subthreshold 1-Hz rTMS. In addition, we analyzed the handwriting before and 20 minutes after 1-Hz rTMS.

RESULTS

In the first experiment, low-frequency rTMS resulted in a normalization of the deficient cortico-cortical inhibition in the patients without affecting motor threshold. In the second experiment, 1-Hz rTMS resulted in a significant prolongation of the postexcitatory silent period without affecting the stimulus-response curve in the patient group. Moreover, the dystonic patients showed a significant reduction of mean writing pressure after subthreshold 1-Hz rTMS that was associated with clear but transient improvement in six patients.

CONCLUSIONS

In some patients 1-Hz rTMS can reinforce deficient intracortical inhibition and may improve handwriting temporarily. Our data support the notion that reduced intracortical inhibition plays a part in the pathophysiology of focal dystonia.

Quinine-induced hepatotoxicity

OBJECTIVE

To report a case of quinine-induced hepatotoxicity presenting within 24 hours following the ingestion of the first dose.

DATA SOURCES

Case report information was obtained from the medical record, the patient, and the physicians involved in this patient's case. MEDLINE and Index Medicus were searched to obtain relevant published literature from January 1942 to May 1997 using the terms quinine, muscle cramps, liver disease, and hepatotoxicity.

CASE SUMMARY

A 57-year-old Native American woman presented with symptoms of nausea, vomiting, generalized myalgia, headache, fever, chills, and rigor. The alkaline phosphatase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyltranspeptidase concentrations were dramatically elevated. Quinine was suspected as the cause after several days of hospitalization and continued therapy. With discontinuation of the quinine, the patient's symptoms resolved within 48 hours and the liver enzyme concentrations declined within 72 hours.

CONCLUSIONS

Documented hepatotoxicity has occurred with quinidine, the optical isomer of quinine. Limited awareness of quinine-induced hepatotoxicity may result in an unrecognized adverse effect.

Postexercise increase in nitric oxide in football players with muscle cramps

Nitric oxide, a free radical inter- and intracellular messenger molecule, is important in exercise physiology. This study tested the hypothesis that serum nitric oxide concentrations change after strenuous exercise with severe generalized muscle cramps. The study group consisted of 77 professional football players in preseason training. All players' concentrations of serum nitrite and of other serum chemicals were determined during their preseason evaluations and compared with the concentrations in 40 serum samples taken from 25 of those same players who required intravenous rehydration for severe generalized muscle cramps after a training session. Player weight and percentage of body fat were significantly higher in players who received intravenous fluids than in players who did not. The serum of players requiring intravenous hydration showed evidence of skeletal muscle breakdown (increases in lactate dehydrogenase, creatinine phosphokinase, aspartate aminotransferase, and alanine aminotransferase) and of dehydration (elevations in protein, blood urea nitrogen, and cholesterol). The major finding, however, was a nearly 300% increase in serum nitrite concentrations in players requiring rehydration. There were no correlations between concentrations of nitrate and of any of the other serum chemicals. These data support the hypothesis that large amounts of nitric oxide are synthesized in professional football players after strenuous exercise with severe muscle cramps. The study design did not allow us to determine whether this increase in nitric oxide was due to exercise or muscle cramps or both, but it does provide a basis for evaluating these relationships.

[Treatment of writer's cramp and other forms of limb dystonias with botulinum toxin]

All forms of limb dystonia can be treated with botulin toxin injection. The selection of dystonic muscles and performing the injections in writer's cramp are discussed in detail. Treatment strategy and outcome in other forms of limb dystonia are presented.

Fluid and electrolyte disturbances in heat illness

Three exercise-related heat illnesses are described in the literature -- heat cramps, heat exhaustion or heat syncope, and heat stroke. Of these, only exercise-induced heat stroke, which occurs infrequently, is definitely a heat illness caused by an increased rate of heat production unmatched by adequate heat loss causing progressive heat retention with the body temperature rising to dangerously high levels (> 41 degrees C). The terms heat cramps and heat exhaustion are misleading as neither is caused by an elevated body temperature; nor is there evidence that either is caused by specific fluid or electrolyte abnormalities. Cramps occur during or after exercise regardless of whether the exercise is performed in the heat or the cold, or in water. Current evidence suggests that a spinal neural mechanism may induce cramping that is unrelated to biochemical changes in either blood or in the affected skeletal muscles. Historically, heat exhaustion has been described as a condition of postural hypotension that develops immediately on termination of exercise especially when performed in the heat by unacclimatised persons. No modern evidence conflicts with this historical interpretation. Nor have more modern studies shown that exercise-related heat exhaustion is necessarily caused by specific fluid or electrolyte abnormalities. Similarly, there is no published evidence that fluid and electrolyte abnormalities are critical determinants of exercise-related heat stroke. This does not negate firm evidence that dehydration has important physiological effects that impair heat loss and exercise performance especially in the heat. Rather, it shows that exercise-induced heat stroke requires powerful initiating factors, in addition to dehydration which occurs commonly during prolonged exercise, whereas heat stroke is an extremely rare event. The purpose of this review is to provide an alternate, more critical review of the conditions that are considered to be exercise-related heat disorders and to evaluate the aetiological role of fluid and electrolyte disturbances. There is a need to better understand these conditions so that their clinical management can be based on modern information rather than on dated ideas, many of which have survived unchallenged for more than 50 years.

Cerebral and cerebellar activation in correlation to the action-induced dystonia in writer's cramp

The pattern of brain perfusion of four patients with writer's cramp and four control subjects were examined using positron emission tomography scans after [(15)O] butanol injections. Each subject was scanned 12 times to cover three repetitions of four different motor tasks with the right hand. Drawing of horizontal lines and variable durations of the writing of a prelearned text were performed in a pseudorandom order, the latter task commencing either simultaneously with or 30 sec or 120 sec before the tracer injection. The perceived difficulty and signs of dystonia progressed in correlation to the duration of writing. Statistical parametric maps were calculated to test hypotheses of regional specific effects dependent on the performed motor tasks. The patients with writer's cramp had progressively increased activity in the left primary sensorimotor and premotor cortices, the left thalamus, and the cerebellum with a right-side predominance in correlation to the duration of writing. The regions with activity increases thus corresponded to a cerebrocerebellar motor circuit. The duration of writing correlated to a progressive reduction of activity in the patients' left supramarginal and angular gyri (Brodmann areas 40 and 39) and an inferior part of the left temporal lobe (area 20). The control subjects had neither a significant increase or decrease of activity in correlation to the duration of writing. Group-specific differences were confirmed statistically in split-plot interaction analyses.

Abnormal motor unit synchronization of antagonist muscles underlies pathological co-contraction in upper limb dystonia

The aim of this study was to examine the pathophysiological mechanisms underlying co-contraction in patients with dystonia (n = 6) and writer's cramp (n = 5). Multi-unit needle and surface EMGs were recorded from extensor carpi radialis (ECR) and flexor carpi radialis (FCR) muscles during motor tasks that elicited dystonia or writer's cramp. The EMGs from ECR and FCR were recorded simultaneously and analysed using cross-correlation analysis. Similar recordings were obtained from healthy age- and sex-matched control subjects (n = 8). Despite co-contraction of the muscles, cross-correlograms from the healthy subjects did not reveal evidence of motor unit synchronization. Cross-correlograms from the dystonic subjects revealed a central peak with a median duration of 37 ms, indicating broad-peak motor unit synchronization. Cross-correlograms from patients with writer's cramp were either flat or modulated by a 11-12-Hz tremor. Frequency-domain analysis of ECR and FCR EMGs demonstrated significant coherence in the patients with dystonia and writer's cramp. These results indicate that co-contraction in dystonia is neurophysiologically distinct from voluntary co-contraction and is produced by abnormal synchronization of presynaptic inputs to antagonist motor neuron pools. ECR and FCR co-contraction in writer's cramp may be a compensatory process under voluntary control.

Effect of vitamin B6 supplementation in McArdle's disease: a strategic case study

A patient-blind study into the effect of a 10-week cessation of long-term vitamin B6 supplementation on B6 status and performance in McArdle's disease is reported. Muscle performance was assessed both subjectively and objectively by an ischaemic fatiguing protocol of the adductor pollicis muscle. Nine weeks after withdrawal of supplementation, vitamin B6 status had changed from adequacy to inadequacy and the force loss during the ischaemic fatiguing protocol had increased at all frequencies studied. The patient reported decreased exercise tolerance after 7 weeks and by the tenth week was experiencing an increase in muscle cramps. Vitamin B6 status and muscle performance may be linked in McArdle's disease and there is potential for enhancement of performance by B6 supplementation.

[Stretching--possibilities and limits]

The basic scientific knowledge about stretching remains incomplete in spite of its wide use in sports and physiotherapy. This article deals with the assessment of the flexibility and with the anatomical and physiological basis and limitations of stretching. The effects of stretching on delayed onset muscle soreness (DOMS), performance and regeneration are discussed. Recommendations are given for stretching as a measure of warming-up and cooling-down, for stretching before exercises, which demand explosive maximum muscle strength, and for stretching after training for strength endurance.

Alterations of motor cortical inhibition in patients with dystonia

Cortical inhibitory mechanisms were investigated with the technique of paired transcranial magnetic stimulation in 10 patients with dystonia of the right arm: six patients had focal, task-specific dystonia (writer's cramp) and three had segmental and one had generalized dystonia. Paired stimuli were delivered in a conditioning-test design during slight voluntary activation of the target muscle, with subthreshold conditioning stimuli at short intervals (3-20 ms) and suprathreshold conditioning stimuli at long intervals (100-250 ms). The amount of inhibition at short interstimulus intervals did not differ significantly between patients and normal subjects. With long interstimulus intervals, patients showed more inhibition of the test response, which was significant at the 150-ms interval. The cortical silent period following a single suprathreshold magnetic stimulus was slightly shorter in patients. No significant difference was detected between the affected side and the unaffected side in patients with unilateral task-specific dystonia, neither in the duration of the silent period nor in the response to paired magnetic stimuli. These results indicate that the different types of motor cortical inhibition are produced by different inhibitory circuits. We propose that the alterations observed in patients with dystonia are the result of impaired feedback from the basal ganglia to motor cortical areas, with the ultimate effect of a flattening of the excitability curve of the cortical motoneuron pool during voluntary muscle activation.

Cylindrical spirals of myofilamentous origin associated with exertional cramps and rhabdomyolysis

We describe the presence of cylindrical spirals on muscle biopsy from a 31-year-old man who developed rhabodomyolysis following a long run. He had a prior history of exertional cramps and myoglobinuria. His maternal grandfather had similar symptoms. Transmission electron micrographs demonstrated continuity between the lamellae of the cylindrical spirals and native myofilaments. Whether these unusual structures confer a derangement in myofilament function is uncertain.

Exertional rhabdomyolysis and exercise intolerance revealing dystrophinopathies

Exercise intolerance associated with myalgias, muscle cramps or myoglobinuria may be associated with a dystrophinopathy. A search for abnormal dystrophin expression (using immunohistochemistry, immunoblot and DNA analysis) was carried out in a series of 15 patients. They were selected because they presented exercise intolerance, negative biochemical tests (lipid, glycogen and mitochondrial metabolism) and abnormal immunohistochemistry with at least one anti-dystrophin antibody (anti-Dys 1, rod domain; anti-Dys 2, C terminus; anti-Dys 3, N terminus). Lack of anti-Dys 1 immunoreactivity was seen in three patients and abnormal immunoreactivity with all three anti-dystrophin antibodies in two. Immunoblot confirmed the dystrophinopathy in these five patients only, and multiplex polymerase chain reaction DNA analysis revealed a deletion in the dystrophin gene in two of these patients, affecting the proximal part of the rod domain in one and the distal part of this domain in the other. The clinical, biological and histopathological features of the five patients reported here, together with the previous cases reported in the literature, are described and reveal that exercise intolerance associated with dystrophinopathy displays characteristic clinical, biological and immunohistochemical features and defines a new dystrophinopathy phenotype. The absence of staining in the rod domain provides a secure diagnosis of this syndrome. Dystrophinopathy is one etiology of idiopathic myoglobinuria, requiring genetic counseling.

Aetiology of skeletal muscle 'cramps' during exercise: a novel hypothesis

The aetiology of exercise-associated muscle cramps (EAMC), defined as 'painful, spasmodic, involuntary contractions of skeletal muscle during or immediately after physical exercise', has not been well investigated and is therefore not well understood. This review focuses on the physiological basis for skeletal muscle relaxation, a historical perspective and analysis of the commonly postulated causes of EAMC, and known facts about EAMC from recent clinical studies. Historically, the causes of EAMC have been proposed as (1) inherited abnormalities of substrate metabolism ('metabolic theory') (2) abnormalities of fluid balance ('dehydration theory'), (3) abnormalities of serum electrolyte concentrations ('electrolyte theory') and (4) extreme environmental conditions of heat or cold ('environmental theory'). Detailed analyses of the available scientific literature including data from recent studies do not support these hypothesis for the causes of EAMC. In a recent study, electromyographic (EMG) data obtained from runners during EAMC revealed that baseline activity is increased (between spasms of cramping) and that a reduction in the baseline EMG activity correlates well with clinical recovery. Furthermore, during acute EAMC the EMG activity is high, and passive stretching is effective in reducing EMG activity. This relieves the cramp probably by invoking the inverse stretch reflex. In two animal studies, abnormal reflex activity of the muscle spindle (increased activity) and the Golgi tendon organ (decreased activity) has been observed in fatigued muscle. We hypothesize that EAMC is caused by sustained abnormal spinal reflex activity which appears to be secondary to muscle fatigue. Local muscle fatigue is therefore responsible for increased muscle spindle afferent and decreased Golgi tendon organ afferent activity. Muscles which cross two joints can more easily be placed in shortened positions during exercise and would therefore decrease the Golgi tendon organ afferent activity. In addition, sustained abnormal reflex activity would explain increased baseline EMG activity between acute bouts of cramping. Finally, passive stretching invokes afferent activity from the Golgi tendon organ, thereby relieving the cramp and decreasing EMG activity.

Impairment of cortical inhibition in writer's cramp as revealed by changes in electromyographic silent period after transcranial magnetic stimulation

Changes in silent period (SP) duration following transcranial magnetic stimulation (TMS) set at 20% above the motor threshold were studied in six subjects suffering from writer's cramp, while performing dystonic movement and during voluntary isometric contraction of the muscles mostly involved in the dystonic movement. Dependency of SP duration on the intensity of preceding muscle contraction was compared on both affected and healthy side. In all subjects SP duration during dystonic contraction was shorter than during voluntary contraction of the similar strength performed with the same hand. Also, in five subjects, SP duration during dystonic contraction was shorter than during voluntary contraction of the similar strength performed with the healthy hand. In addition, the SP duration on the affected side was negatively associated with the intensity of the preceding contraction (i.e. the stronger contraction the shorter SP), while on the healthy side it was not the case. It is concluded that central inhibitory mechanisms are abnormal in writer's cramp.

Leg cramps in children

Most leg cramps are benign and self-limited. Idiopathic nocturnal leg cramp is the most common from of cramps. Occasionally, leg cramps may signify a significant systemic disorder. Investigations are usually not necessary unless indicated by the history or physical examination. Symptomatic treatment consists of stretching the affected calf muscle by forcible dorsiflexion of the foot.

Botulinum toxin treatment of muscle cramps: a clinical and neurophysiological study

Botulinum toxin is now widely used in the treatment of several hyperkinetic movement disorders. To evaluate its efficacy in treating muscle cramping syndromes, we studied clinical and neurophysiological variables before and after botulinum toxin injections into calf muscles and small flexor muscles of the foot in patients with an inherited benign cramp-fasciculation syndrome. At each assessment the clinical severity of cramp was scored and the cramp threshold frequency was measured with repetitive electrical peripheral nerve stimulation. Botulinum toxin injection significantly lowered our patients' clinical cramp severity scores (mean +/- SD: before, 3.80 +/- 0.44; after, 1.40 +/- 0.54), left muscle strength unchanged and significantly increased their cramp threshold frequencies (before, 4.22 +/- 2.26 Hz; after, 10.0 +/- 3.74 Hz). The clinical benefit induced by botulinum toxin lasted about 3 months. Botulinum toxin injections also significantly reduced fasciculation potentials in relaxed muscles (before, 0.86 +/- 0.19 fasciculations/sec; after, 0.45 +/- 0.11 fasciculations/sec). These findings show that local intramuscular injections of botulinum toxin provide effective, safe, and long-lasting relief of cramps possibly by reducing presynaptic cholinergic stimulation of motor nerve terminals and by impairing the input/output function of intrafusal and extrafusal motor end plates.

Bartter's syndrome in pregnancy: a case report and review

Bartter's syndrome is a rare autosomal recessive disorder characterized by hypokalemia, hyperaldosteronism, sodium wasting, normal blood pressure, hypochloremic alkalosis, and hyperplasia of the juxtaglomerular apparatus. We present a 21-year-old African-American nulliparous patient who was referred to our clinic at 9 weeks' gestation with a history of Bartter's syndrome. Her antenatal course was complicated by muscle cramps, which required increasing potassium supplementation. She developed hypomagnesemia in the third trimester of pregnancy, which necessitated magnesium therapy. She delivered an unaffected infant at term. Bartter's syndrome, although extremely rare in pregnancy, requires prompt recognition and careful management, as it may have significant maternal and neonatal implications.