APHASIA   [ back to Glossary Index ]
Aphasia is the inability to understand or communicate ideas through speaking, reading or writing. Examples are misuse of words, circuitous substitution of words,  repetition of words (perseveration), and inability to name objects, people or places. Aphasia thus involves impairment of the cognitive aspects of language; which should be distinguished from dysarthria which is impairment of the motor aspects of speech due to limitations on use of the jaw, tongue or larynx to produce articulate speech. Paul Broca is credited with discovering the physical site of brain damage underlying certain cases of aphasia, the posterior part of the 3rd left frontal convolution, which since then has been called Broca's area. This discovery in 1861 is viewed by many as the birth of neuropsychology.

Broca stumbled on this momentous advance when he was asked to examine an adult male patient who could only make the sound "Tan" which he repeated over and over. Four days later the patient died, and when Broca examined his brain he found it completely normal except for a lesion over the tip of the left temporal pole. In every subsequent case of an aphasic patient  that he autopsied, Broca found a lesion in the same spot, which made him confident he had physically located the speech center in the brain. Because every person's brain has different patterns of gryi (ridges) and sulci (valleys), neurosurgeons who plan to operate on a patient's brain to remove tissue (e.g. to relieve severe, drug-resistent epilepsy) must map the patients' brain to avoid cutting out a part of Broca's area.  TBI to the left side of the brain can cause temporary or permanent aphasia along a spectrum from very mild to very severe. Referral to a speech and language therapist is the best way to deal with the problem. Spontaneous aphasia in the absence of cranio-cerebral trauma may be due to stroke, brain tumor or Parkinson's disease.