Review of the Diagnosis and Treatment of Periodic Paralysis.

Periodic paralyses (PPs) are rare neuromuscular disorders caused by mutations in skeletal muscle sodium, calcium, and potassium channel genes. PPs include hypokalemic paralysis, hyperkalemic paralysis, and Andersen-Tawil syndrome. Common features of PP include autosomal dominant inheritance, onset typically in the first or second decades, episodic attacks of flaccid weakness, which are often triggered by diet or rest after exercise. Diagnosis is based on the characteristic clinic presentation then confirmed by genetic testing. In the absence of an identified genetic mutation, documented low or high potassium levels during attacks or a decrement on long exercise testing support diagnosis. The treatment approach should include both management of acute attacks and prevention of attacks. Treatments include behavioral interventions directed at avoidance of triggers, modification of potassium levels, diuretics, and carbonic anhydrase inhibitors. Muscle Nerve 57: 522-530, 2018.

Lessons learned from muscle fatigue: implications for treatment of patients with hyperkalemic periodic paralysis.

Hyperkalemic periodic paralysis (HyperKPP) is a disease characterized by periods of myotonic discharges and paralytic attacks causing weakness, the latter associated with increases in plasma [K(+)]. The myotonic discharge is due to increased Na(+) influx through defective Na(+) channels that triggers generation of several action potentials. The subsequent increase in extracellular K(+) concentration causes excessive membrane depolarization that inactivates Na(+) channels triggering the paralysis. None of the available treatments is fully effective. This paper reviews the capacity of Na(+) K(+)ATPase pumps, KATP and ClC-1 Cl(-) channels in improving membrane excitability during muscle activity and how using these three membrane components we can study future and more effective treatments for HyperKPP patients. The review of current patents related to HyperKPP reinforces the need of novel approaches for the treatment of this channelopathy.

Successful treatment of hyperkalaemic periodic paralysis in a horse during isoflurane anaesthesia.

HISTORY: A 3-year-old, 400 kg, gelding Quarter Horse was presented for investigation of epistaxis. PHYSICAL EXAMINATION: The horse was bright, alert and responsive with rectal temperature, heart rate and respiration rate within normal limits. MANAGEMENT: During a second general anaesthetic for surgical treatment of guttural pouch mycosis by balloon-tipped catheter occlusion of the right major palatine artery and ligation of the right external carotid artery, signs consistent with hyperkalaemic periodic paralysis (HYPP) were exhibited. These included concurrent hyperkalaemia, hypercapnoea, sinus tachycardia, and muscle fasciculations in the presence of normothermia. Stress associated with an acute haemorrhage pre-operatively, and intra-operative hypercapnoea may have precipitated the episode. There were no signs of HYPP during a general anaesthetic, 1 week earlier, when an initial attempt at surgical treatment of guttural pouch mycosis was performed. Treatment consisted of fluid therapy and administration of calcium gluconate (0.1-0.2 mg kg(-1) minute(-1)), dextrose 5% (5 mL kg(-1) hour(-1)) and insulin (0.05 IU kg(-1)). Treatment resulted in the resolution of clinical signs and an uneventful recovery. FOLLOW-UP: The diagnosis of HYPP was confirmed by DNA analysis post-operatively. CONCLUSIONS: Clinical cases of intra-operative HYPP can present despite a previous history of uneventful general anaesthesia. Rapid diagnosis and treatment can result in the successful management of HYPP. This report documents an unusual presentation of HYPP, a disease that remains present in the Quarter Horse population.

Atypical arrhythmic complications in familial hypokalemic periodic paralysis.

Familial hypokalemic periodic paralysis is an autosomal dominant muscle disorder characterized by episodic attacks of muscle weakness, accompanied by a decrease in blood potassium levels. It is based on genetic mutations in the genes CACNA1S (most frequent, encoding the skeletal muscle calcium channel) and SCN4A (10% of cases, encoding the sodium channel). Few cases have been reported with cardiac dysrhythmia. We report a rare case of a patient with a novel SCN4A mutation who presented, on ECG, extreme bradycardia and syncopal sinus arrest that required a temporary pacemaker implant

Periodic paralysis.

Periodic paralyses are rare diseases characterized by severe episodes of muscle weakness concomitant to variations in blood potassium levels. It is thus usual to differentiate hypokalemic, normokalemic, and hyperkalemic periodic paralysis. Except for thyrotoxic hypokalemic periodic paralysis and periodic paralyses secondary to permanent changes of blood potassium levels, all of these diseases are of genetic origin, transmitted with an autosomal-dominant mode of inheritance. Periodic paralyses are channelopathies, that is, diseases caused by mutations in genes encoding ion channels. The culprit genes encode for potassium, calcium, and sodium channels. Mutations of the potassium and calcium channel genes cause periodic paralysis of the same type (Andersen-Tawil syndrome or hypokalemic periodic paralysis). In contrast, distinct mutations in the muscle sodium channel gene are responsible for all different types of periodic paralyses (hyper-, normo-, and hypokalemic). The physiological consequences of the mutations have been studied by patch-clamp techniques and electromyography (EMG). Globally speaking, ion channel mutations modify the cycle of muscle membrane excitability which results in a loss of function (paralysis). Clinical physiological studies using EMG have shown a good correlation between symptoms and EMG parameters, enabling the description of patterns that greatly enhance molecular diagnosis accuracy. The understanding of the genetics and pathophysiology of periodic paralysis has contributed to refine and rationalize therapeutic intervention and will be without doubts the basis of further advances.

Diagnostics and therapy of muscle channelopathies--Guidelines of the Ulm Muscle Centre.

This article is dedicated to our teacher, Prof. Erich Kuhn, Heidelberg, on the occasion of his 88th birthday on 23rd November 2008. In contrast to muscular dystrophies, the muscle channelopathies, a group of diseases characterised by impaired muscle excitation or excitation-contraction coupling, can fairly well be treated with a whole series of pharmacological drugs. However, for a proper treatment proper diagnostics are essential. This article lists state-of-the-art diagnostics and therapies for the two types of myotonic dystrophies, for recessive and dominant myotonia congenita, for the sodium channel myotonias, for the primary dyskalemic periodic paralyses, for central core disease and for malignant hyperthermia susceptibility in detail. In addition, for each disorder a short summary of aetiology, symptomatology, and pathogenesis is provided.

Genotype-phenotype correlation and therapeutic rationale in hyperkalemic periodic paralysis.

Familial hyperkalemic periodic paralysis (PP) is a dominantly inherited muscle disease characterized by attacks of flaccid weakness and intermittent myotonia. Some patients experience muscle stiffness that is aggravated by cold and exercise, bordering on the diagnosis of paramyotonia congenita. Hyperkalemic PP and paramyotonia congenita are allelic diseases caused by gain-of-function mutations of the skeletal muscle sodium channel, Nav1.4, which is essential for the generation of skeletal muscle action potentials. In this review, the functional and clinical consequences of the mutations and therapeutic strategies are reported and the differential diagnoses discussed. Also, the question is addressed of whether hyperkalemic PP is truly a different entity than normokalemic PP. Additionally, the differential diagnosis of Andersen-Tawil syndrome in which hyperkalemic PP attacks may occur will be briefly introduced. Last, because hyperkalemic PP has been described to be associated with an R83H mutation of a MiRP2 potassium channel subunit, evidence refuting disease-causality in this case will be discussed.

[Gamstorp's disease in a Marseilles family]. / Maladie de Gamstorp. A propos d'une famille marseillaise.

BACKGROUND: Primary periodic palsy is a group of muscular diseases transmitted by autosomal dominant inheritance. The characteristic features are flaccid muscular deficiency, abolition of reflexes, and dyskalemia. CASE REPORT: A 36-year-old woman presented a 5-year history of acute episodes of myalgia, muscle contracture, and muscle paralysis involving first the hand, then all four limbs and the face, sparing the respiratory muscles. The symptoms totally regressed spontaneously within one hour or in a shorter time if the patient ingested sugar. Demonstration of hyperkalemia during an acute episode led to the diagnosis of transfer hyperkalemia typical of Gamstorp's disease. Several members of the family presented identical symptoms. DISCUSSION: Despite progress in our understanding of this disease, diagnosis is often made late. The diagnostic strategy is however quite simple: serum potassium during an acute episode and provocation test with fasting and rest.

Therapy in myotonic disorders and in muscle channelopathies.

Myotonia and muscle weakness are cardinal features of myotonic disorders including the myotonic dystrophies and the non-dystrophic myotonias. Despite the recent progress in molecular genetics of these myotonic disorders, the precise mechanisms responsible for myotonia and for permanent or episodic muscle weakness are still unclear. Treatment has been mostly symptomatic, independent of the disease process involved. Moreover, there have been few randomized controlled trials of treatment for myotonic disorders and consequently no standardized treatment regimens are available. We present a review of selected treatment trials in the myotonic disorders and in muscle channelopathies, and discuss, on the basis of our experience in the myotonic disorders, the limits and advantages of treatment trials in this field. Future genotype-phenotype correlations using the patch-clamp technique are also illustrated.