Fig. 194.—Diagram of Sub-Dural Abscess.
Acute General Lepto-Meningitis.—In bone lesions, particularly compound fractures, infection of the arachno-pia may take place before protective adhesions form, and a diffuse lepto-meningitis results. The open structure of the arachno-pial membrane favours the rapid spread of the infection, which may extend over the surface of the hemispheres, or downwards towards the base (basal meningitis), or in both directions. The process is at first attended with a copious effusion of cerebro-spinal fluid into the arachno-pial space and into the ventricles (serous lepto-meningitis), but this fluid tends to become purulent, the pus forming in a thin layer over the surface of the brain, and in the sulci between the convolutions (purulent lepto-meningitis). The membranes are congested and thickened, the veins of the arachno-pia engorged, and the superficial layers of the cortical grey matter may share in the process (encephalitis).
Clinical features.—The earliest and most prominent symptom is violent pain in the head, often referred to the frontal region, or, in cases starting from middle ear disease, to the temporal region. This is accompanied by a sudden rise of temperature, usually without an antecedent rigor; the temperature remains persistently elevated (102° to 105° F.), and the pulse is small, rapid, and irregular both in rate and force. The patient, especially if a child, is extremely irritable, all his sensations are hyper-acute, and he periodically utters a peculiarly sharp, piercing cry.
Vomiting of the cerebral type—that is, unattended with nausea and not related to the taking of food or to gastric disturbance—is common, and persists through the illness. The bowels are usually constipated. There is an increase in the number of leucocytes in the cerebro-spinal fluid, and organisms also are found in the fluid. As this does not occur in cerebral abscess, examination of the cerebro-spinal fluid may be useful in differential diagnosis. There is a higher leucocytosis in the blood in meningitis than in cerebral abscess.
When the inflammation is most marked over the cerebral hemisphere, there may be paralysis of the side of the body opposite to the seat of the original lesion; sometimes there is erratic rigidity of the limbs, sometimes clonic spasms of groups of muscles. The superficial reflexes disappear early on both sides; the abdominal reflexes being lost sooner than the knee-jerks. In basal meningitis, temporary squinting due to irritation of the ocular muscles, retraction of the head, and an excessively high temperature are usually prominent features. The pupils at first are equally contracted; later they become dilated and fixed. Both optic discs are œdematous and swollen.
Gradually the patient becomes unconscious, shows signs of increasing intra-cranial tension, slowing of the pulse, and laboured respiration, and the condition almost always proves fatal within three or four days.
Treatment.—The treatment consists in removing the source of infection when this is possible, but as a rule little can be done to arrest the spread of the meningitis or to ward off its effects. In cases resulting from a sub-dural abscess in relation to a compound fracture, a sinus phlebitis, or an erosion of the tegmen tympani, an attempt should be made, after exposing this, to purify and drain the meningeal spaces. Temporary relief of symptoms sometimes follows the withdrawal of cerebro-spinal fluid by repeated lumbar puncture, bleeding by leeches or cupping, or the use of an ice-bag or Leiter's tubes. The bowels should be freely moved by purgatives or enemata.
Cerebro-spinal Meningitis.—This form of meningitis, which is due to the diplococcus intracellularis, may occur sporadically, but is more frequently met with in an epidemic form. It is attended with the formation of a profuse sero-purulent exudate, which covers the brain, the cord, the nerves, and the membranes.
The clinical features are similar to those of acute general lepto-meningitis, and in sporadic cases the diagnosis is only completed by discovering the diplococcus intracellularis in the fluid withdrawn by lumbar puncture. Although recovery sometimes takes place, the disease is attended with a high mortality. In the early stages, before the exudate has become too thick, repeated lumbar puncture followed by the injection of Flexner's serum has proved beneficial. Recovery may be attended with paralysis of one or other of the cranial nerves.