The third important symptom of tet any, known as Erb's sign, is a greatly exaggerated electrical excitability of the nerves. Weak faradic or galvanic cur rents produce muscular contractions in excess of the normal response. Cathodal closure contractions are found with small currents, but also with moderate cur rents; also cathodal closure tetanus, and anodal opening tetanus, which are not observed in any other condition.
The most convenient test, and one which usually suffices in an affected per son, is the increased mechanical excit ability, a simple touch, a light press ure on nerve, being enough to produce contractions in the muscles supplied by it. It is less painful to the subject than to induce an attack by pressure on a large trunk or artery. (B. Sachs.) Sensory phenomena are few; there are no disturbances of cutaneous sensi bility. Headache, vertigo, nystagmus, and tinnitus aurium are described as co existing. Temperature elevation is only rarely produced, but may be present be cause of some underlying condition.
Respiration is not, as a rule, affected. Dyspncea is sometimes produced by fixa tion of the muscles of the thorax and the diaphragm. The pulse is often in croased in frequency. The urine is rarely affected; it may be increased in amount. Nephritis occurs occasionally. There are seen, at times, certain nutritive dis turbances affecting the hair, nails, etc. The reflexes do not show any character istic alterations, and are, as a rule, nor mal.
The duration of an attack of tetany is most variable. There may be many re missions of greater or less severity, of shorter or longer periods of abeyance.
Diagnosis. — The clinical picture of tetany is thoroughly characteristic, and should be easily recognized.
The position of the hands, the fingers grouped together or held rigidly in this or some other attitude, as in extension, the legs oftentimes affected, as well or both arms and legs firmly adducted, should instantly excite suspicion. On investigation the sign of Trousseau would reveal the condition even during the periods of latency; that of Chvostek (irritability to slight mechanical stimuli) and that of Erb (electrical excitability as described) should make the diagnosis clear. Morse regards the one symptom
pathoguomonie of tetany: the spon taneous intermittent, paroxysmal condi tions of the muscles of the forearms.
Not all the characteristic symptoms are seen in each case, and the absence of some one or other does not vitiate the diagnosis.
The diagnosis of tetany is personally reserved for those alone in whom a spontaneous characteristic contracture occurs, and the habit which has arisen, of describing laryngismus etridulus Chvostek's symptom and Trousseau's phenomenon—as being symptomatic of tetany, is deplored. Cases in which such symptoms are grouped as latent tetany are never transformed into true tetany. It is only by holding strictly to this point of view that the clinical individuality of tetany as a disease can be maintained. Tetany is a disease resembling, in many respects, epilepsy, and having its origin in various predisposing causes, arising frequently in rickety children, without being a manifestation of that disease; frequently in children suffering from gastrointestinal trouble, and occasion ally at the commencement of the infec tious fevers and acute illnesses. The tox ins of ptomaines resulting from these various conditions have a functional rather than an organic effect on the cen tral and peripheral nervous system, pro ducing the characteristic spasm. Romme (Gaz. Hebd. de _fled., Jan. 24, '07).
Results in the study of 7180 eases of convulsions in children: 1. One per cent. of the children applying for treat ment at the Children's Hospital came for convulsions. 2. Ten per cent. of children between five and twelve years of age gave a history of convulsions. 3. Cases that appear to be due to some manifest reflex cause may turn out to be true epilepsy. •. Other cases, where the attacks occur frequently and without apparent cause, may suddenly recover; at least, for a considerable period. 5. Children who have had con• vulsions may be strong and free from nervous tendencies in later life, al though the proportion who have nerv ous tendencies seems to be greater than in those who have not had convulsions. W. X. Bullard and C. W. Townsend (Boston Med. and Surg. Jour.. Mar. 7, 1901).