CEREBRAL ABSCESS.
Definition.—Cerebral abscess is a focal suppurative encephalitis affecting either the gray or white matter or both. The abscess may be single or there may be several separate foci of suppuration. (See, also, ENCEPHALITIS.) Symptoms.—The symptoms may be of acute rapid onset or they may develop slowly and insidiously during several weeks or even months. Clinically- the symptoms are divisible into those which are general and those which are local or focal, the former being those of general diffused cerebral compression or irrita tion, the latter representing perversion or interruption of motor, sensory, or special function, varying according to the anatomieal site of the abscess. Among the general symptoms which are most common are headache and lassi tude, perversion of the intelligence and the emotions, disturbances of sleep and of consciousness, vertigo, vomiting, con vulsions, and sometimes optic neuritis. These general symptoms will vary some what in degree and character, according to the mode of onset. When the abscess produces symptoms rapidly the headache is more intense; as a rule, there is a more active or decided involvement of intelligence and consciousness, some times manifesting itself in acute delir ium or in profound somnolence or semi coma; there may be rigors, with an abrupt and decided rise of temperature, and the whole picture suggests an active meningitis from which, indeed, it niay be, and often is, difficult to distinguish it. General convulsions are not uncom mon in cases with acute onset. When the symptoms are of slow gradual devel opment they are usually much less in tense in degree. The headache is rela tively mild; the vertigo may be slight; vomiting may be absent or occur only rarely; instead of somnolence or coma there may be simple apathy, and a state of simple mental confusion with irrita bility may appear instead of delirium. The temperature in such cases is usually normal or subnormal; occasionally these patients will exhibit periods of remis sion attended with a very dangerous semblance of well-being and comfort. Sooner or later the disease becomes ag gressive, and evidences of focal disturb ance may be observed by which the site of the abscess may be determined. These
focal symptoms will vary, as has been stated, in accordance with the function of the brain-area affected by the abscess. There are several methods of approach— short-cuts, so to speak—to a considera tion of the focal symptoms. Brain-ab scess is apt to develop in certain areas according to the cause with a constancy which is of decided value in localization. When due to an extension front ear dis ease, for example, the abscess is nearly always found in one of three localities: the temporo-sphenoidal lobes, the cere bellum, or the pons-meclulla region. More than half of all cases are located in the temporo-sphenoiclal lobes or the cerebellum. If the pus enters through the medium of a secondary phlebitis of the lateral sinus the abscess will quite probably be found in the cerebellum.
If the pus enters the superior petrosal sinus it will be found in the cerebrum and probably in the temporal lobe. When caused by trauma the abscess usually bears some relation in its location to the site of the trauma, though sometimes the pus-formation is at a remote part of the brain front the seat of injury, as, for ex ample, in the occipital lobe, the blow having been received over the frontal region.
Cerebral abscess, when due to necrosis or disease of the bones of the face, is frequently located in the frontal lobes or at the base; when from syphilis or tuberculosis, its site is, as a rule, the motor convexity, the base, or the cere bellum. Pyremia and other constitu tional infections are apt to induce multi ple abscesses, which seem rather prone to develop in the distribution of the middle cerebral artery of the left hemi sphere. The data, of cerebral localiza tion should be applied in determining the site of the abscess in each instaiace. The principles of localization in cases of uncomplicated brain-abscess located in active regions apply with unusual con stancy, the diffusion of symptoms being less than in tumor, hmmorrhage, or any other focal disease.