_Treatment._--The abscess having been localised, the skull must be opened and the pus removed. #Abscess from causes other than Middle Ear Disease.#--From the _nasal passages_, infection may spread to the interior of the skull directly through the walls of the frontal, ethmoidal, or sphenoidal air sinuses, or indirectly by way of the veins, and give rise to a cerebral abscess, usually in the frontal lobe. The symptoms are similar to those of abscess following middle ear disease, but focal symptoms are seldom present. When the abscess is on the left side, apraxia and motor aphasia may be present. Spontaneous evacuation may take place by the abscess bursting into the nose through the cribriform plate. The treatment consists in trephining through the frontal bone or through the temporal fossa, according to the site of the abscess and its seat of origin. The primary focus of infection must also be dealt with. In _infected compound fractures_, an abscess may form in the cortical grey matter within a few days of the injury from direct spread of infection from the bone and membranes. This is usually associated with a spreading lepto-meningitis, the symptoms of which predominate. The condition usually proves fatal, but by opening up the original wound, removing depressed fragments of bone, and establishing drainage, the patient's life may be saved. There is evidence that an abscess may form in the brain after a simple contusion without fracture or other external injury (Ehrenvooth). An abscess may develop in the white matter of the centrum ovale some weeks, or even months, after an injury, particularly if a fragment of bone or a foreign body has been driven into the brain. If the infection has spread along the track of the missile, the abscess is usually near to the seat of the brain injury, but if it is due to spread of a thrombo-phlebitis it may be a considerable distance from it, even on the opposite side of the head. These chronic abscesses are usually in the parietal or frontal lobes, and as the pus is encapsulated they may remain latent for long periods, during which they may cause some degree of headache, neuralgic pains in the distribution of the trigeminal nerve, and occasional rises of temperature. When the abscess becomes active, general symptoms similar to those of other forms of abscess develop, and there may be localised paralysis of the opposite side of the body, the distribution of which depends upon whether the cortical centres or the motor fibres are implicated. The treatment consists in opening up the original wound, removing any depressed bone or foreign body that may be present, and establishing drainage. _Bronchiectasis_ and other infective diseases of the lungs are less common causes of cerebral abscess, which is usually single, and may occur in any part of the brain. _Disease of the bones of the skull_, such as osteomyelitis or syphilis, may be followed by cerebral abscess.