140 Tetany
Tetany is a symptom complex characterized by painful and prolonged contractions of the (generally smooth) muscles. These often appear as convulsions and are usually triggered by hypocalcemia.
Adult varieties of the condition that result from calcium or magnesium deficiencies include maternal tetany, parathyroid tetany, osteomalacic tetany, and magnesium tetany. Alkalosis can also produce tetany. Examples include gastric tetany and hyperventilation tetany, following a lengthy period of forced inspiration and expiration. Another form of the disease — grass tetany caused by magnesium deficiency - is found in cattle. Despite these many forms, however, the disease occurs chiefly in infants (neonatal tetany) and young children (infantile tetany) in whom it is normally associated with rickets. It affects males far more than females and, in the absence of proper treatment, frequently proves deadly.Distribution and Incidence
Because tetany has so often been confused with tetanus, very few data are available on the geographic distribution of the disease. It probably occurs worldwide in the temperate zones, with the highest frequency of neonatal tetany among bottle-fed, black, and prematurely bom infants. An abundance of year-round sunshine and, hence, vitamin D may have the effect of reducing the incidence of infantile
tetany in the tropics. The incidence of neonatal tetany recorded at New York Hospital between 1940 and 1958 was between 1 per 500 and 1 per 700 births.
Etiology
Tetany is a disease whose etiology is incompletely understood. It was originally associated with calcium deficiency and more recently with magnesium deficiency, although it can also be produced by alkalosis. The disease can follow the removal or incapacity of the parathyroid glands and can be a complication of alcoholism and a consequence of prolonged diarrhea and vomiting.
Protein-energy malnutrition (PEM) may also precipitate the disease.As a rule, neonatal tetany strikes during the first 14 days of life, and the spasms, twitches, rigid body, and turned-down corners of the mouth (carp mouth) that it produces are nearly identical to the symptoms of neonatal tetanus. Full-term newborn infants generally have significantly higher levels of serum calcium than do their mothers. However, these levels fall rapidly during the first 2 or 3 days of life, and perhaps the high phosphorus content of cow’s milk places the bottle-fed baby at special risk from tetany because it impairs the alimentary absorption of calcium. Another contributing factor is, doubtless, parathyroid immaturity, whereas still another can be the poor nutritional status of the mother. Maternal tetany can develop in malnourished and multiparous mothers whose serum calcium falls with each succeeding pregnancy. Thus there is a positive correlation among frequent pregnancies, maternal dietary deficiency, and hypocalcemic (or hypomagne- semic) convulsions in infants.
At greatest risk are infants born prematurely, born with low birth weights, and born of multiparous or diabetic mothers as well as those who are products of a difficult labor. Males are much more susceptible than females, suggesting that an androgen may be involved. The peak incidence of neonatal tetany for full-term infants occurs about the sixth day of life, and the disease seldom appears before the third day. In those who are born prematurely or whose mothers suffered a difficult birth, the condition frequently develops within the first 24 hours.
Infantile tetany, the most common form of the disease, occurs chiefly between 6 months and 2 years of age and is the most prevalent between 4 and 8 months of age. As with neonatal tetany, males again predominate among the victims, and bottle-fed babies are at substantially greater risk than their breast-fed counterparts. In neonatal tetany, vitamin D has the para-
VΠI.
Major Human Diseases Past and Present doxical effect of raising the incidence of hypocalcemia, perhaps because of its suppressive effect on the parathyroid glands. But a deficiency of vitamin D to promote the absorption of calcium is strongly implicated in the etiology of infantile tetany, and indeed, evidence of rickets is nearly always present. The disease is much more frequent during the winter months when sunlight and, thus, vitamin D are in shortest supply. Because of pigment, black children in temperate zones have in the past proved the most susceptible to rickets during these months. Doubtless they are also more susceptible to infantile tetany than are their white counterparts.Clinical Manifestations and Pathology
Tetany, characterized by neuromuscular irritability, is often signaled by a tingling sensation in the fingers, and it may become impossible to open and close the hands. Carpopedal spasms (of the wrist and ankle joints) are common, as are stiffness, pain, and spasms in other muscles. Vomiting is also common. Infants in particular may develop a rigid face, “carpmouth,” and body — all symptoms that mimic neonatal tetanus. Mental symptoms include hallucinations, dullness, and distortion. Cardiac spasms may develop, and coma, along with respiratory failure (following asthma-like attacks), leads to death. Mortality from neonatal tetany is low today in developed countries because of treatment with calcium. However, in the 1950s and previously, it has been suggested that over half of the victims died. Necropsy findings of hyperplasia of parathyroid glands are confined to children fed cow’s milk.
History
It is probable that tetany due to mineral (and perhaps vitamin D) deficiencies has always plagued humankind to some limited extent. In children the convulsions of tetany in the past were often attributed to “teething.” But it was not until the beginning of the nineteenth century, with increased bottle feeding, that a syndrome resembling tetany was first described in England (Clarke 1815).
Frangois Remy Lucien Corvisart gave the syndrome its name in 1852, and in 1854 Armand Trousseau described tetany in lactating women. In 1881 H. Weiss observed that tetany appeared on occasion in patients whose goiter had been removed, and in the 1880s the disease appeared in near-epidemic proportions in Vienna. Yet August Hirsch (1883-6) had nothing to say about tetany in his massive Handbook.In 1913 E. Kehrer penned a description of neonatal tetany and suggested the administration of cal-
cium salts in its treatment, but according to Paul D. Saville and Norman Kretschmer (1960), the first satisfactory chemical study was the work of J. Howland and W. M. Marriott (1918). It was this work that distinguished rickets from tetany and reported a substantial reduction of serum calcium in infantile tetany patients. It also reported that the administration of calcium salts would relieve the symptoms.
Alfred Hess (1929) pointed out that in the United States the peak incidence of tetany was in the early spring, that cases seldom developed in the summer, and that the black young were “markedly susceptible.” This suggests a role for vitamin D, given its shortage during the winter months in temperate climates and the difficulties blacks have had historically with vitamin D while wintering in those climates.
During the late 1950s and early 1960s, much attention was focused on the disease, and Arthur Bloomfield (1959) and Saville and Kretchmer (1960) surveyed the literature on what had been an important killer of the young. Subsequently, however, as more has been learned about mineral metabolism and as the disease has gone into decline, so has the name “tetany.” Although it is still in the literature, the tendency since the 1960s has been to write of hypocalcemic and Iiypomagnesemic, rather than tetanic, convulsions.
’ Kenneth F. Kiple
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