Aphasia is a brain disorder which affects the sufferer's ability to correctly use language. Those with this condition might find that they make mistakes with their word usage, for instance using the wrong sounds in a word, putting two words together incorrectly or simply choosing the wrong word altogether. The disorder effects writing as well as speaking, and might also make it hard for people living with the affliction to properly understand sentences or words that they hear or read. Etymologically the term comes from the Greek word "aphatos" which means speechless.
There are a number of different kinds of aphasia, each with its own unique symptoms. Broca's aphasia, also known as non fluent or expressive, will cause a person to have huge difficulty in speaking, often only being able to form sentences made of just a few essential words in order to get their meaning across. Unlike sufferers of Broca's, those with the Wernicke kind of the condition are able to speak using long and complete sentences, however they will do so using made up words which do not make any sense. Global aphasia will cause the sufferer to find all forms of communication extremely difficult.
Having looked at the various different kinds of the condition it now seems appropriate to look at the causes of this affliction, and as with most brain disorders it can, not surprisingly, be put down to damage to the brain, in this case, specifically damage to the language center. The language center is usually found in the side of the brain opposite to the hand you write with, so it will be found in the left hand side of the brain if you are right handed and vice versa. The two places in the brain the language center can appear are known as Wernicke's Area and Broca's Area, and damage to either of these parts of the brain will result in the corresponding sub-type of the disorder listed above.
We know that the cause of the condition is damage to the brain, but what exactly are the causes of this? Strokes are the most common cause of the affliction, and these result when the brain is starved of oxygen usually due to a blood clot, which are often caused by smoking, obesity and high blood pressure. It is said that a third of all stroke sufferers experience aphasia to some degree. Traumatic brain injury is another of the major causes of the condition, and this often happens due to a serious fall or a car crash or similar collision. Brain tumours, as well as diseases which cause the brain and nervous system to deteriorate over time such as Alzheimer's or Parkinson's are also thought to be major causes of the language disorder.
To conclude, this brain disorder effects how you are able to use language, and is caused by damage to the language center of the brain, as detailed above, this damage can be a result of any number of neurological or physical conditions.