ABSTRACT
Speech disturbance is usually one of two types: dysarthria or aphasia. When it is due to dysarthria – a problem of articulation – the patient will usually be acutely aware of the problem. With aphasia – a problem of language – the patient may not be aware of the problem or is unable to explain it. Dysarthria usually arises from impairment at a subcortical level of muscle control needed to speak clearly. Aphasia arises from impairment, usually at a cortical level, of the thinking processes which underly language. Aphasia usually arises from focal lesions involving the dominant cerebral hemisphere (usually the left, even in left-handed patients) of the brain. Language may also be impaired in dementia and many other neurodegenerative disorders where there is widespread disturbance of function in the cerebral hemispheres.
