MEN'INGI'TIS. An inflammation of the meninges, the membranes covering the brain and spinal cord. These are three in number: the pia muter, lying in contact with the substance of the brain and cord; the durn muter. lining the cra nial cavity and spinal ea nal; and the aroohnoid, a delicate web-like structure lying between the pia and darn. The term Meningitis is specifical ly applied to an inflammation of the pia mater of the brain, described in this article under the heading of Cen Graf Meningitis. Inflammation of the darn, whether of the brain or cord, is called paehgmeningitis, and of the pia. leptorneningitic. 'rim term nrachnitis was formerly used on the supposition that the araehnoid might he t he seat of an independent intlammatory process, but this is no longer believed to be possible. An 'Milani illation involving the meninges of both the brain and cord is t(•rtned rerchro.spinal For convenience of description the subject may he arranged under the following heads: Pacby meningitis, involving the data of the brain and cord; cerebral meningitis, of which two forms are reeognized: tubercular and simple; spinal men ingitis, and epidemic cerebro-spinal meningitis.
PACHYMENiN(aTis. The Jura becomes inflamed on outer from injnries, or by extension from adjacent structures. In the head a common cause is suppurat ivy disease of the middle Par see Emt, section Diseases), and in the spinal dura a Very frequent cause is caries of the The internal surface of the (lima is the seat of a peculiar hemorrhagic inflammation. hiematoma of the (Jura mater. eharacterized by the formation of adventitious membranes, which appear to be repetitions of the nrachnoid, having yell kb rupture, the ext ra va sated blood collecting in the form of cysts eontaining from an mince to a pound of blood. The symptoms of this
rhagie form of paehymeningitis are primarily those of innaintnation and due to pressure, There is some fever, irregularity of the pulse, headache, giddiness, somnolence, gradu ally deepening to ; and there may be ing and convulsions, followed by muscular weak ness and paralysis. The disease affects the dura of both brain and cord, but the symptoms refer able to the latter are often overshadowed by the cerebral effects. The diagnosis is very difficult and the termination almost invariably fatal. The ease may be treated as one of apoplexy (q.v.), but nothing materially alters the course of the affection. A chronic hy1ertrophic form of internal pachymeningitis occurs in the spinal dura, producing an extensive thickening of the membrane. This in turn causes severe compres sion of the cord and spinal nerve-roots. After a first stage of shooting pains along the course of the nerves affected, with muscular twitehiugs and spasms, there gradually supervene anes thesia, paralysis, and atrophy. As the compres sion increases, paraplegia, secondary degenera tion, and rigidity of the paralyzed parts appear. This form of paehymeningitis is due to syphilis, alcoholism, or injury, and is thought by some writers to follow the hemorrhagic form. Treat ment consists of counterirritation over the spine. with remedies for the pain and spasms. When the trouble is syphilitic great improvement may be derived from mereurials and potassium iodide.