The

Carcinoma is a rare tumor, and is always secondary. secondary form is not rarely seen in the muscles in the vicinity of carcinomata of other structures, such as the mammary gland.

Among the parasitic diseases of muscles may be mentioned trichinosis, cysticercus invasion, and hydatid disease. The first occasions disseminated myositis, to which reference has already been made. The other two conditions are rare and not important.

CHAPTER XII.

DISEASES OF THE BRAIN AND ITS MEMBRANES.

THE DURA MATER.

CIRCULATORY DISTURBANCES.

Active hyperemia occurs in the dura in association with tumors, gummata, and other focal diseases. The vessels of the dura surrounding the area of disease become distended and the membrane may be diffusely reddened.

Passive hyperemia may occur under the same circumstances as the above, and also in cases of thrombosis of the venous sinuses. Hemorrhages are usually due to traumatism, and may occur on the outer or inner surface of the dura. Extradural hemorrhages are more common than intradural, especially in cases in which there is fracture of the skull. A collection of blood between the skull and the dura is sometimes designated internal cephalohematoma. Small hemorrhages into the dura may occur in infectious or hemorrhagic diseases and in cases of death from asphyxia.

INFLAMMATIONS.

Inflammation of the dura, or pachymeningitis, may be acute or chronic, and hemorrhagic, suppurative, or productive in character.

Hemorrhagic pachymeningitis occurs more frequently in the aged than in the young, and is not uncommon in the insane. Chronic alcoholism and traumatism seem to be etiologic factors of some importance. In the early stages of the disease the inner surface of the dura exhibits a superficial deposit or membrane of grayish color, with brown or red spots, the former being composed of altered blood-pigment (hematoidin). Often several layers are present, indicating successive exacerbations. Microscopically the membranous deposit is found to consist of soft granulation-tissue

containing numerous thin-walled blood-vessels. Later, diapedesis of blood-corpuscles, or actual hemorrhages, occur, and the diseased area may have the appearances of a simple collection of blood or of a more or less stratified hemorrhagic exudate. Sometimes the amount of exudate and of hemorrhage may be such as to cause considerable cerebral compression, and in other cases death may occur from the hemorrhage itself. Occasionally the blood is in part absorbed, and a serous collection (hygroma dura matris) results. The seat of the disease is usually in the area of distribution of the middle meningeal artery.

Suppurative pachymeningitis may occur in consequence of injuries, caries, or other diseases of the skull. Sometimes it results from purulent softening of thrombi in the venous sinuses, and very rarely it is secondary to leptomeningitis. Not rarely localized suppurative pachymeningitis results from disease of the middle or internal ear, with extension through the petrous bone. The dura becomes thickened by cellular infiltration, is soft and edematous, and not rarely undergoes necrotic change. The disease may be localized or diffuse, and may occasion secondary thickening and adhesions of the dura in cases terminating favorably.

Productive pachymeningitis may be of fibrous or ossifying character. The etiology is often obscure. Some cases follow hemorrhagic or suppurative pachymeningitis; in some the process seems to be primarily productive. Traumatism may cause proliferation of fibrous tissue in the dura. This is especially apt to occur after fractures of the skull in children, when, as a result of its adhesion to the bone, the dura is almost invariably torn. Syphilis is probably a cause of importance. The dura, in the fibrous variety, is simply thickened and more or less attached to the pia-arachnoid and the inner surface of the skull. When firm attachments with the skull are formed, osteophytes are frequently found upon the surface of the bones and in the dura (ossifying pachymeningitis). Osseous plates may be met with in the falx cerebri and tentorium cerebelli.

INFECTIOUS DISEASES.

Tuberculosis may occur in the form of miliary tubercles in association with tuberculous leptomeningitis. It may also be associated with tuberculosis of the bones; and, in rare instances, has been met with as a primary disease of the dura. In the latter cases the disease takes the form of a caseous nodular thickening of the membrane.

Syphilis may occasion a form of diffuse productive pachymeningitis, or gummata. The latter may originate in the dura, and extend to the pia or skull-bones, or they may originate in the

bones and invade the dura secondarily. Gummata in this situation present themselves as more or less flattened nodular growths of grayish color, having a marked tendency to caseous change and to resolution, with formation of circumscribed thickenings and adhesions of the dura.

TUMORS.

Tumors of the dura mater occur with considerable frequency. The most common is probably alveolar sarcoma. This may occur in various situations, either as a flat swelling, or as a somewhat pyramidal mass, with the apex toward the brain, into the substance of which it projects; it is often firmly attached to the skull. Other forms of sarcoma are angiosarcoma, characterized by the proliferation of the cells of the adventitia of the blood-vessels, and a form in which the fibrous tissue so predominates as to make it really a fibroma, although nests of endothelial cells are found scattered throughout it. Other forms of sarcoma, however, also occur, particularly a small round-cell variety, which is usually multiple and the result of metastasis from some other portion. The latter tumors are usually flat, diffuse, and often extensive. They may or may not cause bulging of the skull.

Recent investigations have shown that endotheliomata are among the most common tumors in this region. They usually occur as single irregular masses; but occasionally they are multiple, and it is possible that under these circumstances metastasis has occurred. Ordinarily they produce no disturbances in the brain, but in a few instances pressure-symptoms have been reported. In any of these forms, but particularly in those in which the fibrous connective tissue is in excess, calcareous infiltration is not uncommon. In nearly all cases these tumors may produce erosion of the inner surface of the skull. Hyaline degeneration of the intercellular substance is very common. Among the other tumor-like growths are fibrous changes that may or may not be inflammatory in nature, and lead to circumscribed or diffuse thickening of the dura mater, and usually cause it to adhere densely to the skull. These are most apt to be found in old people. In addition to the round-cell sarcoma, gliosarcoma of the brain and carcinoma of the scalp may give rise to secondary growths in the dura mater, but these are extremely rare.

CYSTS.

Cysts of the dura are usually due to its protrusion through the skull, and the escape into the protruded portions of cerebrospinal fluid. This is spoken of as meningocele. Two varieties are recognized, true and false. True meningocele is pro

duced by the bulging of the dura mater through some congenital fissure in the skull. It is difficult to distinguish this from encephalocele (q. v.). False or spurious meningocele is almost invariably the result of some injury before the third year of life. There is fracture of the skull and effusion of blood. Later the blood is absorbed and replaced by a clear fluid, leaving only a brownish layer upon the inner surface of the cyst. As in early life the dura is adherent to the skull, it is usually torn at the time of fracture; and ordinarily there is also a laceration of the arachnoid, allowing the escape of the cerebrospinal fluid into the sac, which is formed externally chiefly by the pericranium. As a result of pressure, of bone-absorption, or of defective growth, the opening in the skull usually enlarges considerably, and ultimately there is extreme deformity of the head. In cases where the brain has been lacerated at the time of injury, porencephalic cavities may occur, which in some instances have communicated with the lateral ventricles. The commonest situation for these cysts is the parietal bone; but they may occur in the frontal or occipital regions, and in rare cases are multiple.

THE PIA AND ARACHNOID.

CIRCULATORY DISTURBANCES.

Anemia of the pia may occur in cases of general anemia. Active hyperemia is constantly present in the early stages of meningitis. It is also met with in cases of death from alcoholism, and in severe infectious fevers, though in most of these cass microscopic examination discloses the fact that the process is really one of beginning inflammation. The pia is red and the small arterioles are injected. The fluid in the subarachnoid space is in excess, and may be slightly turbid or sanguinolent.

Passive hyperemia occurs in cases of general venous stasis, as in heart-disease, pulmonary disease, and venous thrombosis, The large veins are greatly swollen, and the subarachnoid fluid is excessive.

Hemorrhages.-Small punctate hemorrhages may occur in cases of meningitis, in scurvy, purpura, and the like. Larger hemorrhages between the pia and arachnoid are most commonly due to traumatism, and may sometimes be the result of rupture of aneurysms. The blood in cases of large hemorrhages may cause injurious cerebral compression, if death does not follow the injury itself. Occasionally the blood becomes inspissated and absorbed, the membranes in these instances becoming thickened and pigmented, or it may be encapsulated and the pigment absorbed, giving rise to a clear cyst (hygroma).

Edema of the membranes, or collections of liquid in the sub

arachnoid space (external hydrocephalus), may be due to passive congestion. The membranes are thickened and of a translucent or gelatinous appearance; the subarachnoid fluid causes elevation. of the arachnoid and more or less compression of the cerebral convolutions. Hydrops ex vacuo is a form of dropsical effusion under the arachnoid, resulting from atrophy or hypoplasia of the cerebral convolutions. The space normally occupied by cerebral substance is in these cases filled with cerebrospinal liquid.

INFLAMMATION.

Inflammation of the arachnoid and pia is called leptomeningitis. It is always an infectious process, and may be either acute or chronic.

Etiology. The commonest cause of acute leptomeningitis is the pneumococcus. It is found in about 60 per cent. of all cases, and in these pneumonia is often an associated or primary condition. The pneumococcus may reach the meninges either by the blood- or lymph-channels, or by creeping along the lymphatic spaces in the areolar tissue between the esophagus and vertebral column; occasionally it enters directly from the ear or nasal cavity. Other micro-organisms that have been found are the streptococcus, the staphylococcus, Friedländer's bacillus, the Bacillus pyocyaneus, the bacillus of glanders; the actinomyces, the typhoid bacillus (of which a number of cases have been reported), the Bacillus coli communis, and the bacillus of bubonic plague. Meningitis occasionally occurs in the course of gonorrhea, but no case has as yet been reported in which the gonococcus was certainly demonstrated. Mixed infection is not uncommon, consisting usually of the pneumococcus and one or other of the more common progenic micro-organisms, and the latter are also frequently found associated with the tubercle-bacillus. The cause of epidemic cerebrospinal meningitis is the Diplococcus intracellularis meningitidis, discovered in 1887 by Weichselbaum in six cases that he examined, and subsequently found in other cases by Goldschmidt, Guarnieri, Netter, Faber, and others.

Pathologic Anatomy.-The gross changes may vary from those that are not recognizable macroscopically, to collections of greenish pus in the subarachnoidal space half an inch or more in thickness and covering the entire surface of the brain. In the slightest forms the presence of the condition may be suspected by the slight edema of the arachnoid, and perhaps a small collection of fluid containing flakes along the fissures of the brain. In some cases, however, even this does not occur, and it is impossible, without a microscopic examination, to say that inflammatory processes exist. Microscopically, sections in these cases usually show overfilling of the small vessels with blood, and a greater or less num