The tetany It is a symptomatic entity that produces an involuntary muscle spasm or contracture due to increased excitability of the peripheral nerves. It is a symptom but also a clinical sign, since its manifestation is subjective and objective.
Muscle spasms occur predominantly in the extremities and facial region, being less frequent in other locations; tetany can be a generalized symptom, although this is extremely rare. The clinical manifestations of this pathology are annoying, even painful, worrying those who suffer from it.
Tetany is usually preceded by neurological symptoms such as paresthesia, but muscle contracture occurs later, replacing the initial symptoms. It can have multiple causes, predominantly as a consequence of metabolic disorders.
The decrease in calcium in the blood is probably the main cause of this symptom. A difference must be made between tetany and tetanus. Tetany is a symptom of metabolic imbalances, while tetanus is due to bacterial infection by Clostridium tetani.
Tetanus is a disease characterized by a bacterial neurotoxin that produces severe muscle spasms; this pathology is life threatening. Identifying the causes of tetany is necessary to establish the most appropriate treatment for its cure..
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Although tetany is recognized as a symptom, its clinical presentation implies a set of symptoms that could be considered as a syndrome.
The neurological alteration that is observed depends on the hyperexcitability of the peripheral nerves, produced by chemical and metabolic imbalances.
Normal muscle contraction occurs by stimulation of a motor nerve that acts at the level of the neuromuscular plate. The stimulus is due to an action potential that requires the exchange of electrolytes at the cellular level. The alteration of the action potential and its effect on the muscle will produce the symptoms seen in tetany.
The first symptoms of tetany may appear in the form of paresthesia and, if the triggering stimulus persists, muscle contracture appears.
Paresthesia is described as an unpleasant sensation, expressed as tingling, burning, numbness, or "pricks." The symptom is transitory, localized and without consequences. Paresthesia is triggered by stimulation of a peripheral nerve, due to the effect of low oxygenation, compression, or a deficit of electrolytes in the blood.
Paresthesia is a sensory manifestation, unlike contraction. It occurs in localized areas of the body, especially in the extremities (hands and feet) and face.
Fasciculation is the involuntary movement of localized muscle fiber groups due to the depolarization of motor neurons over small areas.
Fasciculation is seen if the muscle groups are under the skin, and is common in the eyelids and fingers.
Tetany itself manifests as muscle contraction predominantly in the hands and feet, producing involuntary extension or flexion.
Muscle contracture is usually accompanied by functional limitation and even pain; however, it is reversible in most cases.
The contracture that occurs in the fingers of the hands produces extension together with a flexion of the metacarpophalangeal joint; on the toes the fingers will appear flexed.
Lockjaw consists of the sustained contraction of the masseter (masticatory) muscles, with a decrease in the opening of the mouth. Lockjaw is a common sign and symptom of tetanus, but can also be seen in tetany.
Perhaps the most severe symptom of tetany is laryngeal muscle contracture or laryngospasm. In relation to other symptoms, laryngospasm is less frequent; however, when it appears it poses a risk to life.
Chvostek and Trosseau clinical signs are not symptoms, but are diagnostic methods when tetany is suspected..
The Chvostek sign consists of a facial motor response by stimulating the earlobe. The response consists of elevation of the labial commissure and nasal wing of the stimulated side.
Trousseau's sign is a motor response in the hands induced by pressure on the brachial artery. The pressure exerted on the artery by inflating the cuff of a sphygmomanometer will cause spastic contracture of the hands. The sign appears as a consequence of the transient ischemia triggers the appearance of the symptom.
The causes of tetany are multiple and are directly or indirectly related to the mechanisms responsible for muscle contraction..
The main cause of tetany is hypocalcemia; that is, low blood levels of calcium, as in hypoparathyroidism. Other causes of tetany are: hypocapnia, hyperphosphatemia, hyperkalemia, hypomagnesemia, and clostridial toxins.
It is defined as a low concentration of ionic calcium in the blood. Calcium regulates muscle contraction and the generation of nerve impulses.
When calcium decreases in the blood, sodium intake increases to the nerve cell, triggering action potentials that will produce muscle contraction..
Hypocalcemia occurs from dysfunction or surgery of the parathyroid glands, leading to hypoparathyroidism. Vitamin D is necessary for the absorption of calcium; decreasing their intake or increasing their losses (vitamin D deficiency) produces hypocalcemia. Calcium deficiency also occurs in severe pancreatitis.
Decrease in the concentration of carbon dioxide in the blood, secondary to the increase in oxygen. Carbon dioxide allows the release of ionic calcium bound to albumin. Low levels of carbon dioxide cause a decrease in ionic calcium in the blood.
Hyperventilation generates increased oxygen concentration (hyperoxemia) in the blood, which displaces carbon dioxide. Respiratory illnesses or anxiety can cause hyperoxemia, such as asthma and hyperventilation syndrome.
High phosphorus or phosphates produce a competitive decrease in calcium, so it will reduce its action.
Elevation of potassium levels in the blood that exceed its normal limit causes muscle spasms. Potassium takes part in the generation of the nervous impulse and the muscular contraction; that is why it is capable of producing muscle spasm in tetany.
Hyperkalemia is caused by increased intake or metabolic alteration, such as that produced in kidney disease. Trauma, burns, rhabdomyolysis, vomiting, and some medications contribute to increased blood potassium.
Magnesium is responsible for regulating both calcium and potassium levels; in addition, it participates in muscle function. Hypomagnesemia means depletion of magnesium, loss of its regulatory function, and causes muscle tetany.
Both Chlostridium tetani and Chlostridium botullinium produce a toxin that is capable of acting on the motor endplate.
The release of neurotransmitters at the neuromuscular junction caused by toxins produces intense muscle spasms, characteristic of infection.
It can be said that some diseases that more frequently can cause tetany are the following:
- Hypoparathyroidism.
- Acute and chronic kidney disease.
- Pancreatitis.
- Liver failure.
- Hepatic cirrhosis.
- Hyperventilation due to respiratory illness or anxiety.
- Intestinal malabsorption syndrome.
- Rickets.
- Vomiting.
- Chronic diarrhea.
The treatment of tetany should be oriented, first of all, to regain the metabolic balance of the patients; this is achieved once the cause is known.
A thorough history and a detailed clinical examination will guide the physician in the diagnosis of the disease causing tetany. In general, it should be taken into account:
- Correct calcium deficiency with the use of supplements of this mineral, either oral or parenteral use.
- Correct electrolyte disturbances.
- Treat diseases that cause electrolyte and respiratory imbalances.
- Tetanus, as a cause of tetany, can be prevented by immunization with toxoids. If the disease occurs, it will be treated with the use of specific antitoxins and human immunoglobulin..
- Hyperventilation syndrome will also require psychological counseling and the use of anxiolytics.
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