Aphasia is a disorder affecting the processing, formulation and comprehension of spoken and written language resulting from a disease or trauma. Most commonly aphasia occurs secondary to cerebral infarction involving the left cerebral hemisphere. Cerebral haemorrhage of this region will likewise cause aphasia. Speech disorders of some kind occur in over half of patients with acute cerebrovascular disease. Sudden deterioration in the ability to speak is one of the warning signs of disturbed cerebral circulation. The character of aphasia is linked to the location and extent of the cerebral lesion. Aphasia may be accompanied by disturbances of other higher brain functions, including: articulation through the speech organs (dysarthria) memory functions (amnesia) perception (agnosia) voluntary movements (apraxia).