A system of practical medicine. By American authors. Vol. 3

by Unknown

Anæsthesia.

DEFINITION.—Diminished sensibility of the mucous surfaces dependent upon lesion of the nerve-centres, alteration of the conductivity of the nerve-trunks, or upon disease in their terminal distributions. It is usually bilateral, but may be limited to one side. This alteration of the sensitive condition of the mucous membranes is usually observed after diphtheria. It is also met with in bulbar paralysis. In this last condition it is only one of the phenomena of paresis or paralysis involving several different organs. It is not, therefore, properly a disease of the larynx, and the consideration of it will not be embraced in this article. It has been stated that hysteria is frequently accompanied with anæsthesia of the larynx. Von Ziemssen, Chairou, and Schnitzler have published cases. It seems very improbable that this condition of the organ is so generally present in hysteria as is claimed by Chairou. It is, however, certain that anæsthesia as well as hyperæsthesia of the larynx exists as a complication of hysteria. In the later stages of all exhaustive diseases, as cholera, etc., the sensibility of this organ is either diminished or abolished. This is not, however, a true paralysis in the sense in which we generally use the term. It is only one of the manifestations of the general failure of the life-forces. The special senses, the reflex functions, all share in this paresis, this severing of the relationships of life. Anæsthesia of the larynx is usually confined to the parts supplied by the superior laryngeal nerves, and is sharply limited by the edges of the vocal bands. If there is anæsthesia of the parts below these bands, it is of much less significance and hardly requires our consideration.

ETIOLOGY.—So far as we know, there are no predisposing causes. The chief exciting cause of this affection is unquestionably diphtheria. It is, in fact, a sequel of diphtheria. It will hardly be necessary to repeat here what the reader will find fully discussed in the sections devoted to diphtheritic inflammation of the fauces and adjacent parts: we are mainly concerned with the phenomena. Just how this morbid process produces paralysis is not known. It is believed by some observers that the disease is produced by the alteration of the nutrition of the parts during the progress of the diphtheria. It is stated that the parts most nearly related to the seat of the exudation are most likely to become involved. This is thought to sustain the theory of the direct propagation of the morbid changes from the mucous surfaces to the nerves and muscles. That the paralysis following diphtheria is not, however, produced alone in this manner seems to be made evident by the fact that distant parts, parts which have not been at all involved in the disease, do nevertheless become affected with paralysis. This paralysis develops when the general health and the nutritive changes are all improving. It is quite evident, therefore, that the loss of power in the laryngeal muscles, as well as the altered sensibility, in part at least, must be due to some lesion of the nerve-centres. In addition to the causes above noted, anything which impairs or destroys the function of the superior laryngeal nerve may produce this affection. In the anæsthesia from hysteria we know only the fact, but do not know just how the derangements of the nerves in a distant part, or in the nerve-centres perhaps, are so reflected as to change the function of this organ. The hyperæsthesias, the paræsthesias, and the anæsthesias of hysterical character are all probably produced in the same manner. Anæsthesia in bulbar paralysis is easily understood, but need not, for the reasons already given, engage our attention.

SYMPTOMS.—This condition is usually associated with paresis or paralysis of the muscles of the part. One of the first symptoms of loss of sensibility is, therefore, a failure of the constrictors of the larynx to protect the organ from the intrusion of foreign substances in the form of food and drink. Particles swallowed find entrance into the respiratory tube, and this with no sense of discomfort. If the paralysis is complete both above and below the glottis, the intrusion of these substances is not recognized. There may be no cough or spasm to indicate the fact. In the mean time, the particles of food descend into the bronchi, and may become the exciting causes of broncho-pneumonia. It is often noticed after tracheotomy for diphtheria that food and drinks gaining access to the respiratory tract are discovered at the tracheal opening. In several cases within the knowledge of the writer this fact has led the operator to fear that the posterior wall of the trachea had been opened. In all cases in which the pharynx is in a state of paresis a careful examination should be made by means of the laryngeal mirror.

There are no subjective symptoms, and this fact makes it probable that the affection is more common than has been supposed. The patient complains neither of pain nor of any other discomfort. This statement is only true, however, when there is simple loss of sensation. There may be paræsthesia associated with partial anæsthesia. In such cases there will be noted the usual symptoms of paræsthesia. In hysterical forms of anæsthesia the appearance of the parts is often variable from day to day. The location of the disordered function is well defined at the time of one examination, while at the next the condition may be quite different. It is stated by Thaon⁶ that in one-sixth of the cases of hysteria the larynx is in some way affected. The epiglottis is more usually the seat of the affection in the hysterical variety. Several authors have noted that with the laryngeal disorder there is often a zone of modified sensation beneath the chin and on each side of the larynx. This sometimes amounts to absolute loss of cutaneous sensibility.

⁶ Loc. cit.

COURSE AND TERMINATION.—According to Mackenzie, Von Ziemssen, and others, the anæsthesias following diphtheria usually terminate in recovery. It is quite possible, however, that the literature of the subject does not give us elements on which to base an opinion. I am inclined to think that cases die from this disorder in which the nature of the affection is never recognized. It is quite certain that paralysis of the fauces is not unattended with danger. It is also probable that in many of these cases the real danger is not so much from the loss of muscular power in the pharynx, and consequent inability to swallow, as from the fact that the larynx is not protected from the introduction of foreign substances, that the intrusion of these substances is not recognized, and the consequent disorders of the lungs become the cause of death more frequently than has been supposed.

DURATION.—Paralysis of the sensory nerves of the larynx usually lasts only a few weeks. When a result of diphtheria it disappears with the motor trouble with which it is associated. As a complication of hysteria, or rather when hysterical in character, it may last indefinitely. When dependent upon changes in the centres from which the pneumogastrics are derived it has a history commensurate with that affection.

The PATHOLOGY AND MORBID ANATOMY have been suggested in the discussion of the cause and symptomatology of the disorder. The question of the local or general changes in the diphtheritic variety is noted in the history of the disease.

The DIAGNOSIS is made mainly by the examination with the laryngoscope. The probe will at once determine the presence or absence of the sensibility of the mucous membrane of the parts. In addition to touch, electricity may be employed. In these cases the alteration involves both the tactile and reflex sensory functions. There will therefore be neither cough nor spasm resulting from a mechanical irritation. The surfaces are usually quite normal in color and form. The epiglottis is erect, abnormally so, and there will often be more or less paresis, or even complete paralysis, of the other muscles of the organ. In some cases the difficulty in deglutition due to derangement of the reflex functions may be also suggestive of alterations of sensation in the parts within the larynx, but it is only a suggestion.