As a general rule, neuralgia of the limbs requires to be treated with a more powerful current than neuralgia of the face (twenty cells instead of ten). In the latter case, indeed, it is necessary to be exceedingly cautious (commencing with five cells), since a current of high power has been known to produce most serious effects upon the deeper-seated organs; the retina has been permanently paralyzed, by too strong a current applied on the face, and still graver dangers attend the incautious use of galvanization of the brain or of the sympathetic, of which we have now to speak.
Galvanization of the brain is a remedy chiefly employed in true migraine, and is certainly very effective in that disease. I have not found it useful to apply the current in the long axis of the cranium, but transmitted from one mastoid process to the other it has proved most useful; and I am glad to find that my experience on this point coincides with that of Eulenburg. But the use of this remedy is highly perilous in careless hands. In working with either Daniell's or Weiss's battery, it is necessary to use at first only three or four cells, and to increase the number only with the greatest caution. The sittings should never last more than half a minute; but the slightest giddiness should make us stop even sooner. On the other hand, the applications ought to be made daily, and usually twice a day. Ten cells (Daniell or Weiss) is the utmost that will ever be required, few patients will bear so much; and, apart from the possibility of more serious mischief, there is nothing which annoys and frightens patients more seriously than the sudden and intense vertigo which over-galvanization of the brain may induce.
Even more ticklish than the galvanization of the cerebral mass is galvanization of the sympathetic. I am not going to raise here the vexed question in physiological electricity as to the possibility of a galvanization the effects of which shall be accurately limited to the sympathetic. The fact is unquestionable, that very powerful and peculiar effects, utterly unprocurable in any other way, can be produced by placing one pole on the superior cervical ganglion (just behind and below the angle of the jaw) and the other on the manubrium sterni. This is a mode of galvanization which has been highly praised, more especially by Remak, and after him by Benedikt, but it has yielded rather disappointing results in neuralgia in my hands. Either I have not observed any distinct effect at all, or, if a current even a very little too strong were applied, I have repeatedly seen most uncomfortable, and sometimes very alarming, symptoms. I shall not easily forget a patient who applied at the Westminster Hospital, suffering from a severe form of facial neuralgia, and who was persuaded to come to my house and have his sympathetic galvanized. I used only twenty cells of Daniell, but the current had not been applied more than a few seconds when the patient fell on the floor, and remained in a state of half swoon for a considerable time. I allude to this and other less dangerous accidents that I have seen follow galvanization of the sympathetic, not with the view to prove that the method is useless in trigeminal neuralgia--I should certainly hesitate to say that, considering the large amount of respectable evidence in its favor--but I think that it is a procedure requiring the utmost caution, and meantime I have not personally found it nearly so useful as the methods already described.