Speech can be negatively influenced by abnormalities in the structures responsible for making words. Thickening of the vocal cords or tumor growth on the vocal cords can deepen the tone of speech. A cleft palate, a congenital anomaly, can be a serious impediment of speech. A cleft lip with the palate intact is a lesser problem, but may still interfere with the proper formation of words. Fortunately, surgical correction of either of these impediments is easily carried out.
Traumatic changes that cause loss of part of the tongue or interfere in the movement of the jaw also can result in speech changes. Extended speech therapy can help to make up for the loss in articulation.
A stroke can interfere with the function of the speech center or cause of motor control over the muscles used in speech because it destroys the part of the brain controlling nerves to those structures. Destruction of the speech center can render an individual unable to form meaningful sentences or words. Once destroyed, brain tissue is not regenerated. Loss of the speech center may mean a life without the ability to talk. In this case, the patient may need to rely solely on the written word. Recognition of speech and language is centered in a part of brain apart from the speech center so a patient still could recognize what was said to him or her.
Roiphe, A.R. "Talking Trouble." Working Woman 19 (October 1994): 28-31.