HYPERTROPHY.—Trophic changes are not limited to the process of atrophy. There are conditions of hypertrophy of supposed nervous origin. Samuel considers the hypertrophy of one testicle which attends atrophy of the other from section of its nerve as an example of this. It has been ascertained that one kidney hypertrophies when the other is atrophied or extirpated. When the spleen is removed the lymphatic glands increase in size. But these facts are capable of another explanation—viz. that increased demand upon the organ leads to its increased growth. Hypertrophy of the skin and of the tongue is seen in cretins in contrast with the deformity of the body and atrophy of the limbs. A hemihypertrophy of the face has been noticed in several cases, the counterpart of hemiatrophy; and in one case a unilateral hypertrophy of the entire body was observed.85 The local thickening of the skin known as ichthyosis hystrix, and other hypertrophies of the skin, certain deposits of pigment, and vitiligo, have been ascribed to nervous causes. Mitchell has recorded cases of abnormal growth of the nails and hair after injuries to the nerves, and similar phenomena have followed central lesions. He has also described a thickening of the skin of the first three fingers and of the back of the hand following a wound of the brachial plexus. These conditions of the skin and its appendages indicate an abnormal activity in the cells of the affected part, a rapid metabolism and reproduction, resulting in an undue production of tissue, apparently dependent on nervous impulses reaching the cells from a distance. The insane ear may be mentioned in this connection as a trophic disturbance due to central lesion.
85 Ziel, Virchow's Archiv, xci., S. 92.
MYXŒDEMA (cachexie pachydermique) is a disturbance of nutritive processes characterized by a production of mucin, which is deposited in all the tissues of the body, but especially in the subdermal connective tissue.86 It is considered by the majority of authors a trophic neurosis, and is therefore considered here.
86 Sir William W. Gull, “On a Cretinoid State supervening in Adult Life,” Trans. Clin. Soc. London, 1874, vol. vii. p. 170; Ord, “On Myxœdema,” Med.-Chir. Trans., 1878, vol. lxi. p. 57; Mahomed, Lancet, 1881, ii. No. 26; Hadden, Brain, 1882; W. A. Hammond, Neurological Contributions, 1881, i. p. 36; Ballet, Archives de Neurologie, 1881, vol. iii. p. 30; Schmidt's Jahrbucher, vol. clxxxix. p. 30, and cxcviii. 264; “The Brown Lectures,” Victor Horseley, Lancet, Jan., 1886.
PATHOLOGY.—In the few autopsies which have been made an increase in the connective tissue of all the organs has been found, in the meshes of which a thick, transparent, slimy substance (called animal gum), consisting of mucin, is present. This may compress and destroy the parenchyma of the organs involved. There is also found a thickening of the coats (adventitia and media) of the vessels. An atrophy of the thyroid gland has occurred in every case, and experimental extirpation of the thyroid in animals produces symptoms so nearly identical with those of myxœdema that this is considered the chief pathological feature of the disease. Whether this atrophy is due to a compression by the mucin deposited, or is due to a disease of the trophic centres of the thyroid in the medulla, or is a primary affection of the gland, remains to be determined.
ETIOLOGY.—The actual causation is unknown. Cold and mental shock have been considered exciting causes in some cases. Women are much more liable to the disease than men, and it develops after the age of forty in the majority of cases. It may occur in childhood and result in a cretinoid state. Syphilis and tuberculosis do not appear to be etiological factors.
SYMPTOMS.—The disease begins gradually, and the nervous symptoms or the local œdema may appear together or in succession. The patient notices a thickening of the skin, which becomes dry, rough, and scaly. The thickening is uniform and involves the entire body. It is most marked where the subdermal connective tissue is loose, as in the cheeks, lips, eyelids, and in all parts where the skin is thrown into folds. The hands and feet do not escape. The thickened skin is hard, and does not pit on pressure, thus differing from ordinary œdematous swelling. It appears of a waxy color, and is free from perspiration, the sweat-glands becoming atrophied from pressure. The hair may fall out or become woolly and brittle, and may change its color. In a few cases spots of pigment have appeared on various regions.87 The nails are brittle. The teeth are carious. The mucous membranes show similar changes, and the mouth and tongue, rectum and vagina, may be so swollen as to impair their respective functions. Digestive disturbances, constipation alternating with diarrhœa, and uterine hemorrhages, which occur, are ascribed to this cause. Albumen is occasionally found in the urine, but is not a constant symptom. The nervous symptoms are constant. The patients complain of paræsthesiæ and anæsthesia of the extremities or over the entire body, and the special senses may be impaired, as well as the tactile sense. They are very liable to severe attacks of neuralgia. They suffer from subjective sensations of cold, and are easily affected by changes of temperature. Motion is interfered with; tremors occur early; movements become slow and awkward; the gait is unsteady; the voice is rough and nasal; but no true paralysis or muscular atrophy has been observed. The patella-tendon reflex is occasionally lost, but not in all cases.
87 Allan McLane Hamilton, Journ. Nerv. and Ment. Dis., 1885, April, p. 180.
These symptoms have been ascribed to the pressure of the mucin upon the terminal filaments of the nerves, and also to changes in the central nervous system. That the latter theory is probably correct is shown by the occurrence of mental symptoms in the majority of cases. The patients become apathetic and all mental action is slowly performed. Indifference to surroundings, loss of memory, and inability to concentrate the attention may be succeeded by transient delirium, hallucinations, and occasionally by delusions of persecution, and the patient finally lapses into a state of imbecility. If the disease develops in early life, education is impossible, and the patient remains in an infantile condition.
Whether the changes in the nervous system are due to pressure by deposit of mucin (Hadden), or are due to an altered nutrition of the most delicate tissues of the body consequent upon the general metabolic derangement (Horseley), is undetermined. In experimental myxœdema the degenerative processes have been found in the nerve-cells.