Periodic paralysis

Introduction to periodic paralysis Periodic paralysis, also known as periodic paralysis, refers to a group of myopathy that is characterized by recurrent skeletal muscle flaccid paralysis. According to the change of serum potassium content at the time of onset, it can be divided into three types: low potassium type, positive potassium type and high potassium type. According to the cause can be divided into two categories of primary and secondary. Primary means that the pathogenesis is still unknown and hereditary; secondary is the cause of blood potassium changes caused by other diseases, and periodic paralysis usually refers to the former. basic knowledge The proportion of patients: the incidence of hyperthyroidism is about 0.04%-0.09% Susceptible people: no specific population Mode of infection: non-infectious Complications: sudden death, difficulty swallowing

Periodic paralysis

(1) Causes of the disease

Low-potassium periodic paralysis is mostly distributed in China. European and American countries are more common in hereditary or familial, and sporadic only accounts for 20%. Therefore, it is called familial periodic paralysis, which is autosomal dominant, and the gene is located in 1q31~ 32, linked to the dihydropyridine receptor gene, may be caused by a genetic mutation.

Hyperkalemia (high potassium) periodic paralysis, also known as hereditary hereditary myasthenia gravis, tonic and periodic paralysis, is an autosomal dominant myalopathy, which has been found in 17q23.1~25.3 in recent years. The skeletal muscle sodium channel subunit gene (SCN4A) has a mismatched mutation, and high potassium and positive potassium periodic paralysis are associated with this genetic mutation and are considered to be a skeletal muscle sodium channel disease.

(two) pathogenesis

The pathogenesis of this disease is still unclear. Most people think that potassium metabolism disorder and imbalance of potassium balance inside and outside the muscle cells are the main causes of seizures. They are also related to the distribution of other ions inside and outside the membrane and the functional changes of ion channels on the cell membrane. Metabolic processes and endocrine hormones such as insulin, adrenaline and adrenocortical hormone also have a wide-ranging effect on potassium metabolism.

In recent years, it has been found that the skeletal muscle sodium channel subunit gene (SCN4A) located at 17q23.1 to 25.3 has a mismatch mutation, and high potassium and positive potassium periodic paralysis is associated with this gene mutation, and is considered to be a kind. Skeletal muscle sodium channel disease, these mutations can cause structural changes in sodium ion channel protein; low potassium periodic paralysis is considered to be an L-type skeletal muscle calcium channel (dihydropyridine receptor) disease, dihydropyridine receptor gene Located at 1q31~32, mutations in the gene can cause abnormalities in L-type calcium channels. The function of these ion channels is abnormal, which may cause changes in ion distribution and membrane potential inside and outside the membrane of the muscle cells, causing the muscle fibers to lose excitability and cause skeletal muscle spasm.

Periodic paralysis prevention

In patients with periodic paralysis, the interval between seizures is normal, and those with frequent seizures may have persistent muscle weakness and even muscle atrophy. Generally speaking, after middle age, most patients have a gradual decrease in seizures and stop.

Periodic paralysis should avoid all kinds of known causes such as chills, excessive fatigue, full meals, high-sugar diet or alcohol abuse. Frequent periodic paralysis should be focused on hyperthyroidism, persistent low-potassium palsy should be corrected. Detailed cause examination, except for chronic renal failure or adrenal cortex.

Periodic paralysis complications Complications, sudden death, difficulty swallowing

Patients with periodic paralysis may have persistent muscle weakness and even muscle atrophy in patients with frequent episodes. Individual patients may still have arrhythmia during intermittent periods, often with sudden death due to ventricular tachycardia.

1. Hypokalemia periodic paralysis may cause chest tightness due to diaphragmatic muscles, respiratory muscles, myocardial and other paralysis, palpitations, difficulty breathing, slow heartbeat, irregular heartbeat, dysuria, chewing weakness, eating cough, difficulty swallowing, The speech is unclear.

2. The incidence of normal blood potassium periodic paralysis is more than 10 years old.

3. Hyperkalemia periodic paralysis can be complicated by limb paralysis, sometimes accompanied by mild dysphagia.

Periodic paralysis symptoms Common symptoms Limb symmetry Soft palpation Sensory disorder Overeating Gain muscle hypertrophy Breathing difficulty Abdominal wall reflexes weakened or disappeared Tensile drunk renal interstitial damage

Low potassium type

Is the most common type, the disease can occur at any age, more common in 20 to 40 years old, more men than women, mostly in the country, a few family history, autosomal dominant, some before the attack There may be gluttony, alcoholism, high-sugar diet, fatigue, strenuous activity, emotional stress, the application of adrenal cortex hormones and cold and other incentives, mostly in the nighttime sleep or wake up in the morning when the disease occurs, also in the nap when the disease, wake up found limbs soft palate , numbness, soreness, weakness, severe cases may have respiratory muscle paralysis, breathing difficulties.

The limbs are bilaterally symmetrical, the proximal end is heavy, and it can only affect the lower limbs. When the limbs are affected, the lower limbs are generally heavy. Sometimes the cervical muscles are weak, the head lifting is difficult, and the limbs are different, and the muscles can be paralyzed to the whole body. The weakness usually reaches a peak within a few hours. When the examination is found, the muscle tension is reduced, the tendon reflex is reduced or disappeared, the disease has no sensory disturbance, no pyramidal tract sign, and the brain innervation muscle is generally not involved.

Some patients have oliguria or urinary retention. Cardiac auscultation can be found that heart sounds are low and blunt, tachycardia, heart rhythm disorder, severe cases may have blood pressure drop, severe heart rhythm disorder, treatment may not occur in time, cardiac arrest may occur or death due to respiratory muscle paralysis .

The episode usually lasts for several hours to several days, usually recovers completely within 1 week. The frequency of seizures varies from person to person. Many people can have seizures every day. The lesser ones only have one episode in life. The symptoms of hyperthyroidism are more frequent and the course is longer. And frequent episodes, there may be persistent physical weakness after the attack.

Serum potassium decreased (<3.5mmol/L) at the onset, urinary potassium excretion decreased, ECG showed hypokalemic changes, such as QT interval prolongation, ST segment decreased, T wave decreased, u wave appeared and often merged with T wave .

2. High potassium type

Less common, is an autosomal dominant genetic disease, mostly onset and daytime onset before the age of 10, often induced by cold or oral potassium, the lower extremity of the lower limb is also heavy, can also affect the upper limbs and trunk respiratory muscles, Duration varies from a few minutes to a few hours, usually around 1h. Some patients may be accompanied by muscle rigidity, which affects the facial and hand muscles. In the cold, the serum potassium increases, up to 6~ 8mmol/L, the electrocardiogram showed a high potassium change, the T wave was high, and the QT interval was shortened.

3. Positive potassium type

Rarely seen, it is also an autosomal dominant genetic disease. It usually starts before the age of 10, and often has halophilic and polydipsia before the attack. Most of the symptoms are weak after sleeping or early in the morning. The symptoms are similar to low potassium. However, the duration of inability to continue is mostly over 10 days. The reduction of salt intake or potassium supplementation can be induced, and the serum potassium at the time of attack is normal.

Periodic paralysis

1, serum potassium hypokalemia cycle paralysis serum potassium is low, can be as low as 1.5mmol / L, but the reduction level can be inconsistent with the clinical muscle weakness signs, urinary potassium reduction, large potassium excretion during recovery, hyperkalemia cycle paralysis At the time of onset, serum potassium and urinary potassium were elevated, and serum potassium increased by 7-8 mmol/L. Normal potassium potassium cycle was normal.

2, serum creatine kinase subunit B (S-CKB) activity increased, serum myosin content increased, seen in hypokalemia periodic paralysis.

3, ECG changes

(1). Low potassium type electrocardiogram showed low potassium changes, showing PR interval, QT interval prolonged, QRS wave widened, ST segment moved down, high towering u wave appeared, and there were different degrees of atrioventricular block in heavy weight, ventricular Premature beats or other heart rhythm disorders, EMG examination showed severe muscle excitability in patients with severe symptoms, decreased motor unit potential, decreased amplitude, and no induced action potential in electrical stimulation.

(2). The high potassium type electrocardiogram showed a hyperkalemia change, and the T wave was elevated and pointed.

Periodic paralysis diagnosis

Diagnostic criteria

Paroxysmal flaccid paralysis, loss of sputum reflexes, and loss of electrical excitability, as the interictal period is normal, the induction test is more helpful for the diagnosis.

First, medical history and symptoms:

Young adults are more common, may have a family history, often induced by cold, full meal, fatigue; often in the middle of the night, early morning or after a nap acute onset, and recurrent episodes of soft limbs as the main performance.

Second, physical examination found:

1. The degree of limbs is not flaccid, often starting from the lower extremities, the proximal end is heavier, severe respiratory muscle involvement, muscle pain, no sensory disturbances, most of the recovery to a few hours to a day or two, up to a week.

2. When the myocardium is involved, there may be bradycardia, premature ventricular contractions, and elevated blood pressure.

3. Hypokalemia caused by rickets, Guillain-Barré syndrome and hyperthyroidism, hyperaldosteronism, gossypol poisoning, renal tubular acidosis, etc. should be excluded.

Third, auxiliary inspection:

The blood potassium level decreased during the attack, and the electrocardiogram showed a low potassium change. The response of the muscles to DC stimulation is diminished.

Differential diagnosis

Other diseases that can cause similar paralysis should be identified. The most impressive clinical practice is the identification of GBS and cerebrovascular accidents, especially ischemic cerebrovascular disease and transient cerebral insufficiency.

1. Primary aldosteronism often has recurrent limb weakness and hypokalemia, but the initial onset is older, the duration of each episode can last for several months, the symptoms are slower and often difficult to recover. Normal; in addition, there are still high blood pressure, nocturia and so on.

2. Acute infectious polyneuritis Most patients have a history of upper respiratory tract or digestive tract infection from a few days to several weeks before the onset of symptoms. The symptoms gradually increase after onset, reaching a peak within 1 to 2 weeks, after the condition is stable 2 to 4 Weekly recovery, cerebrospinal fluid examination can be found in the phenomenon of protein cell separation; and periodic sputum episodes peak or recovery time is shorter, accompanied by a decrease or increase in serum potassium, generally without obvious sensory loss.

3. Myasthenia gravis is characterized by partial or all skeletal muscle susceptibility to fatigue, increased activity, improved after rest, effective for cholinesterase inhibitors, 90% of patients with blood AchR-Ab positive.

4. Acute sputum poisoning There may be quadriplegia, drooping eyelids, difficulty in pronunciation and dysphagia, gastrointestinal tremors, nausea and vomiting, diarrhea and other gastrointestinal symptoms, as well as eating salt or drug history with excessive bismuth.

5. Polymyositis Slow onset, with fever, muscle pain, Raynaud's phenomenon, increased blood CPK, duration is rarely shorter than weeks or months.

6. Hypokalemia is mostly caused in the cotton-producing area and the history of eating cottonseed oil. In addition to the weakness of the paroxysmal limbs, it is often accompanied by gastrointestinal symptoms and is effective for the treatment of potassium chloride.

7. Hyperthyroidism combined with low-potassium periodic cookware, hyperthyroidism, clinical manifestations, T3, T4 increased, periodic sputum cessation after normal thyroid function.

Other hypokalemia

(1) renal tubular acidosis: the distal defects of the distal convoluted tubule can not be acid and potassium, low potassium and high chlorine, urine pH increased.

(2) hypokalemia caused by diuretics, vomiting and diarrhea.

8. The rickets are stimulated by mental factors, and there are more episodes during the day. There are no obvious features of the distal and distal tendons of the limbs. The tendon reflex is not weakened, and the myoelectric stimulation response is normal.

9. Hypokalemia and periodic paralysis should be differentiated from Guillain-Barré syndrome. The disease starts faster and recovers faster. The limbs are delayed, no respiratory muscle paralysis and cranial nerve damage, no feeling. Obstacles and nerves and irritations, cerebrospinal fluid examination is normal, blood potassium is low, potassium supplementation is effective, and there is a history of recurrent attacks; while Guillain-Barré syndrome has a history of pre-infection and autoimmune response, acute or subacute Disease, progress no more than 4 weeks, may have different degrees of respiratory muscle paralysis and cranial nerve damage, cerebrospinal fluid examination showed protein-cell separation, electrophysiological examination early F wave or H reflection delay, blood potassium test results are normal, no previous recurrent Medical history.

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