MENINGITIS,, The brain is enveloped by three membranes called the meninges. Next to the skull comes the dura mater, then the arachnoid and innermost is the pia mater. These three membranes are prolonged from the brain in three envelopes of the spinal cord_ Meningitis is an inflammation of the meninges of the brain or of the spinal cord. It is very rarely a primary condition, but is usually sec ondary to infection from micro-organisms of many types, or results from chronic poisonings such as lead, alcohol, etc. Hence modern medi cine speaks of various meningitides rather than one meningitis. When the surface of the brain is wounded by some object breaking through the skull, or a piece of broken bone of the skull, thrust inward by some blow, an artery is ruptured and the blood flows between the membranes. Such a condition is called traumatic meningeal hxmorrhage. When the dura mater becomes inflamed after a wound, or after inflammation of other parts of the head, as the ears, teeth, etc., there results a condition called pachymeningitis externa. In flammation of the meninges, however, is gen erally confined to the pia mater and the arach noid and is then called leptomeningitis. Pachymeningitis, inflammation alone or chiefly of the dura mater, may extend to the other membranes. Inflammation of the cerebral meninges is cerebral meningitis; of the spinal meninges, spinal meningitis; of those of the brain and spinal cord together, cerebro-spinal meningitis. Ascending meningitis is a menin gitis ascending from the lower part of the spinal cord.
Pachymeningitis has one form involving the external surface of the dura mater and result ing from blows or other injuries, and from osseous growths. There may he no well-de fined symptoms, but usually is local headache and tenderness on pressure. The onset is usu ally sudden. Many cases of meningitis of the type called are not other than pachy meningitis. If the dura mater, which is nor mally free, is hound to the skull by fibrous exudation, and especially if pus forms and hwmorrhages occur, there are symptoms pressure. Inflammation of the internal portion of the dura mater may result from the exten sion of inflammation from adjacent parts, such as the ear, the frontal or the ethmoidal sinus; or it may attend cases of pernicious anwmia, chronic syphilis, tuberculosis and chronic wast ing diseases. It occurs chiefly in old age, but
has been seen in children. There are fibrinous deposits and extravasation of blood in cysts (hxmatoma), and occasionally pus forms. The brain is anaemic. sometimes softened. The symptoms are those of irritation — convulsions, vomiting, dilated pupils which are not affected by exposure to light, a slow irregular pulse, etc.—and those of compression or pressure— coma, etc. Pachymeningitis is usually fatal.
Cerebral meningitis (simple or cerebral meningitis), in the acute form, is not common, and is most apt to occur in men engaged in hard mental pursuits. It may be caused by injuries, by sunstroke, by spirituous liquors, etc., and is very dangerous, death usually occurring in from three to eight days. The brain is reddened and covered more or less with pus and coagulated fibrin or lymph, and its superficial layer is soft ened. There is almost always watery effusion into the brain-cavities. The symptoms are those of three stages: (1) Headache; (2) de lirium; (3) coma. At first there• may be slight fever, some photophobia, frequency and irregu larity of the pulse and some contraction of the pupils. There is a disposition to vomit, a slowness in movements of the bowels and often hypersesthesia. Then comes delirium, which may or may not be active ; the patient talks much and tries to get out of bed; does not obey readily. There is more or less trembling of the limbs, with difficulty in moving them. One pupil is likely to be dilated. Sometimes strabismus occurs; the pulse is very irregular; and paralysis begins. Then follows coma, loss of sense, sensation and of voluntary motion; there is sighing, the pulse is frequent and weak, the pupils do not respond readily to light and the capillaries of the skin and eye are con gested. Recovery from this disease cannot oc cur after the period of coma begins.