A system of practical medicine. By American authors. Vol. 5

by Unknown

HYPERTROPHY OF THE BRAIN.

INTRODUCTION.—Notwithstanding the numerous measurings and weighings of human brains made in the course of time by different investigators, no absolute standard measure or weight has as yet been established by which we can accurately determine a pathological increase or decrease in the size and weight of this organ. The want of such a standard is principally due to the difference generally existing in the dimensions and weights of even a certain number of brains taken from individuals belonging to the same race or nation. The same difficulties are met with in the attempt at establishing a rule by which to measure the mental capacity of a certain brain, for the question has as yet not been solved whether this capacity depends upon the quantity or quality of the brain-substance. In speaking of hypertrophy of the brain, therefore, we must keep in mind that a large brain must not be considered hypertrophied unless there exists a disproportion between its size and that of the cavity from which it was removed; in other words, when its growth or hypertrophy meets a resistance at the inner walls of the cranial cavity. According to Virchow, a further distinction must be made between the increase (hyperplasia) of the nervous elements themselves and that of the supporting connective tissue, the neuroglia. To the latter condition particularly corresponds the peculiar doughy consistence of the white substance of hypertrophied brains.

ETIOLOGY.—Hypertrophy of the brain is sometimes congenital, and then associated with dwarfishness and a defective development of the cranium. Generally, however, it is an extra-uterine affection, originating mostly during infancy and childhood, though it is also met with at the age of puberty, and even in adult life. The male sex is more predisposed to the affection than the female. When hypertrophy of the brain occurs during infancy, it is almost always associated with an excessive development of the lymphatic glands, with a defective involution of the thymus gland, and with rachitis, but generally without cachexia. No special exciting cause can be assigned to the affection during youth or adult age, though it has been stated that during these periods of life the disease may supervene upon tubercle or carcinoma of the brain. Repeated active or passive congestion (Rokitanski, Andral), as well as the introduction of lead into the system, has also been supposed to incite the disease.

PATHOLOGICAL ANATOMY.—Directly after the removal of the vault of the cranium, and on cutting through the dura mater, the brain, as if liberated from pressure, is observed to swell out to such a degree as to render the replacement of the removed skull-cap impossible. The enveloping membranes are found closely adapted to one another and to the brain; they are very thin, bloodless, and dry, and their vessels are empty and pressed flat. The hemispheres of the cerebrum are large, and their convolutions, mutually pressing against one another, are flattened at their surfaces, so that the intervening sulci are hardly recognizable. After the removal of the brain from the skull the abnormal dimensions of the cerebrum present a remarkable contrast to the normal size of the cerebellum, pons, and medulla oblongata, which also appear flat and broad from pressure. When a horizontal section is made through the hemispheres of the cerebrum and a little above the corpus callosum, the centrum ovale appears unusually large. The cavities of the ventricles are very narrow, their walls touching one another. There is no serum in the pia mater or in the ventricles. The substance of the brain is pale, bloodless, and dry. The white substance, upon which the hypertrophy particularly depends, is of a doughy consistence, comparable to the boiled white of an egg or cheese, whilst the gray substance is so pale as to be hardly distinguishable from the former.

The condition of the skull is, according to Rokitanski,¹ as follows: In cases in which the hypertrophy of the brain has advanced to a high degree, and in which the sutures of the skull are united, the bones of the cranium are found thinner and their inner table roughened by absorption. This is especially the case in the bones which form the vault of the cranium. The holes or other deficiencies found at the base of the cranium in the plates of the frontal, ethmoid, and sphenoid bones are not entirely due to the absorbing process, but rather to the thinness of these bones. In infants the cavity of the cranium enlarges in proportion to the hypertrophy of its contents; the head then resembles in form so much that of hydrocephalus that it may lead to errors in diagnosis. In some cases in which the disease rapidly develops to a high degree there is observed on the infant's skull a loosening and separation of the sutures of the cranial vault, with red coloration and suffusion of their cartilages.

¹ Lehrbuch der Pathologischen Anatomie, 3d ed., 1855, vol. ii. p. 431.

SYMPTOMS.—There is a gradually increasing muscular weakness, manifesting itself especially in the lower extremities, and giving rise to an unsteady, stumbling gait and frequent falling, caused perhaps by the excessive weight of the head, and also an inability of securely grasping objects. Besides these disturbances of motion, epileptic spasms appear, at first light in degree and at long intervals, but becoming later on in the course of the disease more frequent and severe. Continuous or intermittent attacks of headache almost always accompany the disease, and, furthermore, vertigo, tinnitus aurium, photophobia, and dimness of sight with dilatation of the pupil; general sensation also becomes blunted, but without ever amounting to anæsthesia. In a number of cases there is no disturbance of the psychical functions, though in others symptoms of mental excitement amounting even to delirium have been observed. Most frequently the intelligence sinks from the beginning of the disease, to end in complete idiocy. The pulse also has been observed to fall considerably during the last stage.

The COURSE of the disease is, according to Andral and Hasse,² almost always chronic, and if an acute development of the affection has been spoken of, it may be supposed that the latter has commenced a considerable time previous to the manifestation of the symptoms during the last stage. Andral divides the disease into two stages, of which the first is chronic and frequently latent, whilst the other is more acute and leads to a rapid fatal termination. In most cases death is caused by such intercurrent affections as give rise to irritation and hyperæmia of the brain, and thus increase the already abnormal pressure upon this organ.