[Myokymia-hyperhydrosis syndrome (Isaacs syndrome)].
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Isaacs syndrome.
Although Isaacs syndrome is known by several names including neuromyotonia and quantal squander, it bears some resemblence to other syndromes characterized by muscular stiffness such as stiff-man syndrome. The purpose of this paper is to examine pertinent clinical findings about Isaacs syndrome. A patient who presented cramping pain in both thighs and difficulty releasing his grip is described. Physical examination revealed myokymia in all four extremities, hyporeflexia, and hypertrophy of the thenar musculature. Electromyographic studied show continuous motor unit activity at rest. The patient was treated with phenytoin and showed almost complete symptom resolution over a 24-hour period. Clinical and electromyographic examinations in conjunction with the rapid response to phenytoin are diagnostic characteristics of Isaacs syndrome.
Adult↗
[Syndrome of constant muscle fiber activity (Isaacs syndrome)].
Two cases with expressed signs of a permanent muscular tension in the extremities with fasciculation (the Isaacs syndrome) and difficulties in self-service are described. In both cases the diagnosis was verified by typical EEG changes and a good effect from the use of a diphenylhydantoin or finlepsin.
Adolescent↗
[A case of Isaacs' syndrome associated with dextrocardia].
INTRODUCTION: Isaacs syndrome is a disorder of unknown etiology characterized by muscular rigidity, cramps and myokymias. Described by Isaacs in 1961 and called by him as continuous muscular activity syndrome. There are few reports in Latino american countries. CLINICAL CASE: A 31 year-old man with sustained muscular contractions in lower limbs and diffuse myokymias since he was eighteen-year old. Dextrocardia was disclosed on clinical examination. CONCLUSION: We report the case of a patient with Isaacs syndrome and dextrocardia.
Adult↗
[Clinical recovery from Isaacs' syndrome].
A patient with Isaacs' syndrome (previously reported in 1966) has been clinically normal since 1972. The possibility of an outcome of this type has been reported by Isaacs and Heffron (1974) and in subsequent reports. This does not provide an explanation for the syndrome of continuous muscle fiber activity but constitutes an additional clinical feature.
Adult↗
Hypoxia-sensitive hyperexcitability of the intramuscular nerve axons in Isaacs' syndrome.
A case of Isaacs' syndrome with Trousseau's phenomenon is reported. Myokymia, pseudomyotonia (difficulty relaxing after forceful contraction), and ischemia-induced carpal spasm (Trousseau's phenomenon) were not abolished by nerve block distal to the cuff or by intravenous infusion of calcium. Inhalation of oxygen suppressed the pseudomyotonia and Trousseau's phenomenon, but myokymia persisted. Phenytoin abolished all types of abnormal discharges. The morphological abnormality in biopsied short peroneal muscle consisted of intraterminal and ultraterminal sprouting. We postulate that the trigger zone for abnormal discharge in our case is in the distal segment of the intramuscular nerve axon, including the nerve terminal. Hypoxia-sensitive hyperexcitability of the axon membrane might be responsible for the generation of pseudomyotonia and Trousseau's phenomenon, although the mechanism underlying myokymia remains unknown.
Adult↗
Acquired neuromyotonia (Isaacs' syndrome): a case report with autonomic physiologic studies.
Acquired neuromyotonia (Isaacs' syndrome) is a rare disorder characterized by hyperexcitability of peripheral motor nerves. The cardinal features consist of myokymia, pseudomyotonia and contracture of hands and feet. The diagnosis of Isaacs' syndrome is based on the clinical features and classic electromyographic findings. Serum antibodies against Voltage-Gated Potassium Channels (VGKCs) are detected in some cases. The authors report a 17 year-old man presented with difficulty in walking, writing and respiratory discomfort for 7 months. His body weight had decreased from 120 to 70 kilograms during that period. Physical examination was remarkable for profound sweating. Muscles were in a state of contraction, action myotonia without percussion myotonia, myokymia and carpopedal spasm. Electromyography showed classical neuromyotonic and myokymic discharges. The investigations for conditions associated with Isaacs' syndrome were unrevealing. VGKCs antibody were not performed. Treatment with carbamazepine resulted in substantial improvement of the symptoms within 7 days.
Adolescent↗
Peripartum management of a patient with Isaacs' syndrome.
PURPOSE: To describe the peripartum management of a patient with Isaacs' syndrome with specific reference to the anaesthetic implications of the disease process. Associated medical problems included obesity, pregnancy induced hypertension and a difficult airway. CLINICAL FEATURES: This 30-yr-old gravida V para 0 woman presented to the anaesthesia consultation clinic at 37-wk gestation to discuss pain relief options for labour and delivery. She had a history of Isaacs' syndrome (a peripheral motor neuron disorder), congenital heart disease (ASD and VSD), treated Hashimotos thyroiditis, obesity and a family history of haemachromatosis. On the day of consultation, she was hypertensive and peripheral oedema was noted. Her urine showed trace protein. Four days later, she presented to the labour suite and her cervix was 9 cm dilated. An epidural anaesthetic was given without difficulty and she had an uneventful labour and delivery course. There were no subsequent neurological complications. CONCLUSION: Isaacs' syndrome is an extremely rare peripheral motor neuron disorder. This patient was successfully managed with epidural analgesia for labour and delivered a healthy child with no congenital anomalies.
Adult↗
Reversible F-wave hyperexcitability associated with antibodies to potassium channels in Isaacs' syndrome.
We report a case of Isaacs' syndrome showing F-wave hyperexcitability which was reversible after either epidural block or plasmapheresis. A 14-year-old girl with progressive muscle cramp and myokymia in the legs showed high amplitude, long duration, polyphasic F-waves after either tibial nerve or peroneal nerve stimulation. Potassium current of PC-12 cell membrane was suppressed by her serum, IgM of which strongly reacted with proteins of approximately 50 kDa of the lysates of a PC-12 cell line. After an epidural nerve block with 1 per cent lidocaine 10 ml, the myokymia temporally improved, during which time the hyperexcitable F-waves became normalized. We treated her with double filtration plasmapheresis, which resulted in remarkable improvement of myokymia; simultaneously, the abnormal F-waves showed a decrease in amplitude, duration, and in the number of phases. We concluded that there was hyperexcitability of the proximal site of motor fibers in our patient, and possible immune mechanisms gave rise to the myokymia and unusual F-wave features.
Adolescent↗
Isaacs' syndrome: clinical and electrophysiological response to gabapentin.
A patient with Isaacs' syndrome had generalized muscle spasms, twitching, and progressive muscle stiffness for 21 years. Electrodiagnostic study showed continuous spontaneous motor-unit activity and the presence of M-wave afterdischarges. He responded dramatically to treatment with carbamazepine but developed a drug rash; his treatment was changed to gabapentin with continued improvement. Subsequent nerve conduction studies showed decreased amplitude and later an absence of M-wave afterdischarges. Gabapentin thus appears to be an effective treatment for Isaacs' syndrome.
Action Potentials↗
[Syndromes of permanent contracture (stiff-man syndrome of Moersch and Woltman; Isaacs' syndrome of continual activity of the muscle fibers, other permanent contractures). Attempted classification and pathogenic interpretation. Discussion of the role of the interneurons and of the terminal expansion of the motoneuron].
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Carbamazepine↗
Serum of Isaacs' syndrome suppresses potassium channels in PC-12 cell lines.
Blockage of K+ channels in nerve terminals by immunoglobulin is the speculated pathomechanism of Isaacs' syndrome. Using patch-clamp technique (whole-cell clamp), we investigated the effects on K+ current of serum taken from 2 patients with Isaacs' syndrome employing the clonal cell line PC-12. The addition of a patient's serum to the perfusion solution had little effect on the K+ current of P-12 cells. In contrast, K+ current was reduced by 25-80% when cells were cultured for 3-6 days with 2% serum as compared to control serum values. Suppression of the K+ current appears to develop gradually over the period of culture. Our results suggest that the pathomechanism of Isaacs' syndrome is caused by K+ channel suppression via a humoral factor(s) in the serum, which subsequently induces nerve hyperexcitability.
Adult↗
Isaacs' syndrome as a potassium channelopathy of the nerve.
Isaacs' syndrome (acquired neuromyotonia) is an antibody-mediated potassium channel disorder (channelopathy). The target channel proteins of the antigens are voltage-gated potassium channels (VGKCs), especially dendrotoxin-sensitive fast potassium channels. The suppression of voltage-gated outward K(+) current by antibodies induces hyperexcitability of the peripheral nerve. Patch clamp studies show that antibodies may not directly block the kinetics of VGKCs but may decrease channel density. Electrophysiological, pharmacological, and immunological findings indicate that the site of origin of spontaneous discharges is principally in the distal portion of the motor nerve and/or within the terminal arborization. The spectrum of potassium channelopathies is expanding. The existence of antibodies against VGKCs should be considered in patients who present with generalized nerve hyperexcitability of undetermined etiology.
Humans↗
Creatine kinase (CK)-linked IgA in Isaacs' syndrome. An immune complex disease?
Electrophoresis of serum from a patient with Isaacs' syndrome revealed an atypical creatine kinase (CK) isoenzyme pattern which contained an extra band migrating between CK2(MB) and CK3(MM). Immunofixation demonstrated that the extra band was a complex of CK3(MM) and IgA. The presence of this complex seemed to correlate with increased serum CK levels which were associated with the aggravation of symptoms. Immunofluorescence studies on muscle biopsy samples revealed the presence of the complex in the muscle fiber membrane and motor endplate. The existence of CK-linked IgA in an Isaacs' syndrome suggests that an immunological abnormality may play a role in the pathological process of this rare syndrome.
Chemical Phenomena↗
Isaacs' syndrome associated with myasthenia gravis, showing remission after cytoreductive surgery of pleural recurrence of thymoma.
We report a patient with Isaacs' syndrome associated with myasthenia gravis and pleural recurrence of thymoma, who showed severe limb pain attributed to hyperexcitability of sensory nerves. Myokymia and severe pain were successfully treated with cytoreductive surgery and intraoperative hyperthermic intrathoracic perfusion chemotherapy, but neither pharmacotherapy nor plasma exchange showed obvious clinical effects. Pleural thymoma in our patient may have caused Isaacs' syndrome, probably by unconfirmed humoral immune mechanisms. Cytoreductive treatment for recurrent thymoma should be actively considered as a potent therapeutic option in refractory patients with disabling neuromyotonia symptoms.
Adult↗
[Isaacs syndrome: long-term improvement with intravenous polyvalent immunoglobulins].
A 35 year-old man developed a syndrome with muscle cramp, myokimia, generalized, fasciculations, excessive sweating, sleep disorders and severe impairment. It was a syndrome of continuous muscle fiber activity--or Isaacs syndrome--with central disorders (this may be called "Maladie de Morvan"). Previous reports have suggested that Isaac's syndrome might be an autoimmune disorder. Moreover, high doses intravenous immunoglobulins were given resulting in a substantial improvement six months after the onset of this treatment.
Adult↗
A case of Isaacs' syndrome with associated central nervous system findings.
We report a 44-year-old female with Isaacs' syndrome, peripheral motor neuropathy, and features of central pontine myelinolysis (CPM). The patient presented with stiffness and muscle spasms accompanied by profound sweating. She also had bilateral Babinski signs. Electrodiagnostic abnormalities were characteristic of Isaacs' syndrome. Magnetic resonance imaging demonstrated features of CPM. She gained modest relief from baclofen, valproate, and diazepam. She improved dramatically following plasmapheresis and continued to recover on prednisone. She was weaned from steroids without relapse.
Adult↗
[Isaacs' syndrome. Diagnosis and differential diagnosis of neuromyotonia].
Neuromyotonia is a clinical and electrophysiological syndrome of spontaneous muscle fiber activity due to hyperexcitability of peripheral nerve origin causing generalised, visible myokymia and muscular cramps. Electromyography shows abnormal doublet and triplet discharges of high intraburst frequency as well as myokymic and neuromyotonic discharges. Fasciculations and fibrillation potentials are common. Most commonly, neuromyotonia is an acquired immune-mediated disorder (Isaacs' syndrome) showing elevated antibody levels against presynaptic, voltage-gated, potassium channels. Some of these patients have additional autonomic (hyperhidrosis) and/or CNS symptoms similar to those from limbic encephalitis (referred to then as Morvan's syndrome). We report on a patient with Isaacs' syndrome and discuss the clinical and electrophysiological features, pathophysiology, diagnosis, and differential diagnosis of diseases with peripheral nerve hyperexcitability.
Diagnosis, Differential↗