There are broadly three stages to human speech :
There are different types of speech and voice problems. One of the more common problems is slurred speech which is known medically as dysarthria. It involves forming the words through controlling the muscles of speech. It differs from another condition known as dysphonia where the formation of sound in the voice box is impaired leading to a hoarse voice or just a whisper tone.
Slurred speech can be an important indicator of impending conditions like a stroke. Here a person may have recurrent episodes of stroke-like symptoms which are temporary. This is known as transient ischemic attack (TIA). Sometimes it can be the first or only symptom of a mild stroke. It is therefore important that sudden onset of slurring be taken as a serious sign and investigated immediately before there is any permanent implications.
Various parts of the mouth and upper airway are responsible for the speech – articulation. These areas are known as the places of articulation and includes the lips, tongue, palate, teeth, uvula, pharynx (throat), glottis and epiglottis. A structural problem in any of these areas may be responsible for slurred speech. The muscles in these areas may also be the site of the problem either due to muscle disorders itself, the nerves stimulating these muscles or the brain centers that coordinate the muscle activity.
Therefore the following diseases and conditions may be responsible for slurred speech :
Slurred speech can also occur secondarily as a complication in other diseases like with mouth ulcers, oral thrush (candidiasis of the mouth), temporomandibular joint dysfunction and other jaw problems.
Depending on the site of the problem and mechanism by which it occurs, dysarthria can be classified as :
There may also be associated symptoms such as difficulty swallowing, muscle twitching, sensory disturbances like blurred vision or even blindness, difficulty with eye movement, weakness, tremors and muscles stiffness.
There is no definitive treatment for slurred speech. It is dependent on the cause. Often the causative condition especially in the elderly is incurable but physical and occupational therapy may provide some degree of rehabilitation. Treating the underlying condition where possible will alleviate the degree of slurring provided that there is no permanent tissue damage to the brain centers, nerves or muscles of speech. Substance induced dysarthria whether caused by alcohol, medication or illicit drug use tends to resolve completely after discontinuing the causative substance.