Definition.—An inflammation of the external layer of the dura mater of the brain.
Etiology.—The most frequent cause is fracture of the skull, with its consequent extravasation of blood. Next in order is caries of the middle ear or of the frontal or ethmoidal sinuses. Syphilis, erysipelas, or carbuncle may also be the exciting-cause.
Pathology.—The dura is thickened, due to infiltration of blood and pus, and these products, collecting between the dura and the skull, are apt to give rise to localized abscess. Where due to syphilis, there is generally marked thickening of the inner table and much pus between the dura and the bone. Where there is an infiltration of pus between the two layers of the dura, dura-arachnitis may follow.
Symptoms.—The symptoms are not well defined in mild cases, and are apt to be overlooked, headache being the only evidence of the lesion. In the more severe types there will be a chill, followed by fever, headache, more or less dullness, which in turn is followed by stupor. Paralysis and convulsions occur in rare cases. Should rigors occur, they would suggest pyemia. There is more or less tenderness over the part affected.
Treatment.—The treatment is mostly surgical, and consists in trephining for the liberation of pus. In the milder cases, counter-irritation, and the properly selected sedative should be used. When due to syphilis, echinacea, Donavan's solution, berberis aquifolium, corydalis formosa, or stillingia will be found useful as well as potassium iodid.