PARATHYKOID GLANDS 675 



sion of the foot) , a positive Chvostek's sign, often a positive Erb phenome- 

 non, but very rarely a positive Trousseau phenomenon. 



3. Formes frustes of von Frankl-Hochwart. No spontaneous typical 

 muscle spasms, but Trousseau phenomenon positive, leg phenomenon posi- 

 tive, Chvostek's phenomenon positive, and Erb's phenomenon positive. 



4. Chronic tetany with mild recurrent attacks. All signs of tetany 

 present. 



5. Acute attacks of tetany. The most outspoken symptoms of tetany 

 are present. 



These variations in the clinical picture of tetany doubtless depend, 

 according to Chvostek, partly upon the degree of functional disturbance of 

 the parathyroid glands that exists, partly upon variations in the power of 

 the organism to adapt itself to the altered functions of these structures, and 

 partly upon the existence and intensity of releasing factors. Or, it may 

 turn out to be true that tetany of variable severity may occur, owing to 

 metabolic vices that are independent of parathyropathies. 



VIII. Differential Diagnosis of Tetany 



Those modifications of the clinical picture in tetany that are often 

 responsible for confusion with other diseases, nervous or infectious, will 

 next be discussed. The conditions can be classified under three main head- 

 ings, each with several subheadings : 



1. Conditions (other than tetany) in which hyperkinetic phenomena 

 resembling those of tetany may occur, (a) Conditions in which tonic 

 spasms involving the musculature as a whole may occur (tetanus, hydro- 

 phobia, strychnin poisoning, katatonia). (b) Conditions in which tonic 

 spasms that involve local muscular domains occur (crampi musculorum). 

 (c) Myoclonias and fibrillary twitchings. (d) Tics and habit spasms, 

 (e) Conditions in which general convulsive states or fits occur (hysteria, 

 psychasthenia, epilepsy, symptomatic fits). 



2. Conditions (other than tetany) that may simulate the motor 

 pareses sometimes seen in tetany (poliomyelitis, progressive central mus- 

 cular atrophy, peripheral neuritis, progressive muscular dystrophy, myas- 

 thenia gravis, and encephalitis and encephalomyelitis). 



3. Conditions (other than tetany) that may be associated with sensory 

 phenomena resembling those of tetany (acroparesthesias, arthritides, Eay- 

 naud's disease). 



