The explanation offered by those who believe in the peripheral theory is, that the affected muscle is always imperfect in its action, but that this imperfection is masked in other combinations by the action of the healthy muscles, so that it is no longer noticeable.
PROGNOSIS.—The prognosis in these affections varies with the conditions found and with the previous duration of the disease.
A favorable prognosis may generally be given where the case is an acute one, and where the disability can be proved to be due to some one of the peripheral conditions previously mentioned. When the condition is in the forming stage, when fatigue, stiffness, tremor, tingling, aching, sense of heat, coldness, or powerlessness are the only symptoms which exist, the disease is quite amenable to treatment and a good prognosis may be given; but, unfortunately, patients are loath to believe that these trivial symptoms, which do not prevent their work, are precursors of any serious trouble, and therefore pay but little attention, if any, to them, so that the physician is seldom consulted during this period.
When positive cramp has made its appearance, it is an evidence of a more advanced stage of the malady, and the prognosis becomes less hopeful, although still the symptoms may be greatly ameliorated, or a complete cure even be effected.
When the cramp has existed for years and is present in many of the finer acts of co-ordination, the case becomes almost hopeless as far as cure is concerned; and even though the part is rested, so far as the disabling occupation is concerned, for months or even years, it will be found to return upon resumption of the old work. Roth96 considers those cases due to central changes totally incurable.
96 Loc. cit.
When a congestion of the nerves or a well-defined neuritis is discovered to be the cause of the trouble, the probability of a favorable termination is rather more hopeful.
Paralysis is to be looked upon as an unfavorable symptom, pointing as a rule to a late stage of the disease.
It may be stated with positiveness that when the premonitory symptoms are neglected and constant work persevered in, the case will go on from bad to worse: periods of amelioration, it is true, may occur, but cramp usually supervenes, and the affection becomes gradually progressive as group after group of muscles becomes implicated, until the part becomes useless for all delicate work.
The probability of the left hand escaping, should it be used to relieve or replace the right, is slight; and for two reasons: 1st. The same predisposition which favored the trouble in the right arm still exists; and, 2d. The proximity of the spinal centres for the two arms is such that the morbid process may easily be conveyed from one to the other, as was shown while considering associated movements.