INTRACRANIAL COMPLICATIONS 361 Not infrequently his friends notice a change for the worse in his character. When the abscess is sufficiently large to cause pressure on the internal capsule paresis may develop in certain of the groups of muscles of the opposite side of the body, and even hemiplegia may arise. In such cases there is dorsiflexion on eliciting the plantar reflex. Crossed deafness and crossed facial paralysis sometimes occur. Cases of encephalitis of the temporal lobe associated with convulsions have been recorded. If the abscess is situated on the left side optic aphasia is frequently found, but is a late symptom and by no means constantly present. The purulent collection interferes with the nerve tract connecting the centres for visual and auditory memory- Thus the patient is unable to name such simple objects as a pen, knife or keys, though he may demonstrate by pantomime that he knows how to use them. It will thus be seen that an abscess of the left temporo- sphenoidal lobe is more easy to diagnose than one on the right side. Indeed in cases of bilateral purulent otitis media with well-marked general symp- toms of brain abscess it may only be possible to diagnose the presence of the abscess in the right temporal lobe by finding that the localizing symp- toms of abscess in the left temporal lobe and those of abscess in both lateral cerebellar lobes are absent. It has been stated that the most important signs of abscess of the temporal lobe are sjight weakness; of^ the~oppo$ite-~side of ihe face in its lower half, most obvious when the patient talks or smiles, and absent or diminished abdominal reflexes, with increased knee jerk and extensor or doubtful plantar response on the contralateral side due to pressure of the abscess on the pyramidal tract. Paralysis of the contralateral arm and even of the lower extremity have been described. Anosmia may sometimes be detected, but it is a symptom which may readily escape notice unless specially looked for. Homonymous hemianopia may be present if the abscess is large and extends towards the optic radiation. The usual type of defect is in the superior quadrant. When the patient is alert this sign is easily demonstrated, but when his mental state is impaired it is necessary to take the patient by surprise. The observer stands opposite the patient and makes certain that he (the patient) is looking directly at him. The observer then raises a finger on either side of the patient's face, on a level with the eyes, and says sharply, *Take hold of my finger'. If the patient makes no response he is probably incapable of understanding. If he raises both hands and grasps each of the observer's fingers, it is evident that there is no gross temporal hemianopia. If, however, the patient only raises one hand to grasp one finger, it is then obvious that he does not see the other finger. This method is also of use in the case of young children. Radiological examination may aid the diagnosis, as brain abscesses sometimes contain gas which can be shown by radiographs. Air-encephalography, arterio- graphy or an electro-encephalogram may yield very useful information as a help in diagnosis, but the first is contra-indicated where a cerebellar abscess is suspected and ventriculography should be substituted in its stead. Nystagmus is very rare in temporal abscess and only occurs if the suppura- tion extends backwards to the occipital lobe. Sudden onset of coma with high fever indicates that the abscess has ruptured into the lateral ventricle (see Fig. 186, p. 359). In cases of localized collection of pus on the surface of the brain, beneath the pia arachnoid membrane, there may be a sudden onset of Jacksonian epileptic attacks on the contralateral side.