The involuntary movement of the tongue, often seen as a subtle or pronounced protrusion in older adults, is medically known as orofacial dyskinesia. This movement disorder involves the muscles of the mouth, jaw, and tongue, and it is common in the geriatric population. This behavior is rarely intentional, instead signaling underlying changes in neurological function, medication side effects, or structural issues within the oral cavity.
Drug-Induced Movement Disorders
One of the most frequent causes of involuntary tongue protrusion in the elderly is an iatrogenic condition called Tardive Dyskinesia (TD). This hyperkinetic movement disorder results from the long-term use of medications that block dopamine receptors in the brain, primarily first-generation antipsychotics. These drugs are used not only for psychiatric conditions but also as anti-nausea agents, such as metoclopramide, which is commonly prescribed for gastrointestinal issues.
The mechanism behind TD involves the continuous chemical blockade of dopamine D2 receptors in the basal ganglia. This chronic blockage leads to receptor supersensitivity, causing them to over-respond when dopamine is released and resulting in involuntary, stereotyped actions.
These movements in the mouth may include lip-smacking, chewing motions, grimacing, and the characteristic involuntary tongue thrusting or protrusion. The movements are typically repetitive and can persist even after the offending medication is discontinued, a persistence that gives the condition the name “tardive,” meaning delayed. Because older adults are more likely to be on multiple medications (polypharmacy), they have a higher risk of developing this side effect from dopamine-blocking agents.
Neurological Causes of Orofacial Dyskinesia
Beyond medication side effects, involuntary tongue movements can be a direct symptom of several neurodegenerative diseases that affect the brain’s control over motor function. Orofacial dyskinesia in this context represents a failure of the brain’s control circuits to properly inhibit unwanted movements.
In cases of advanced dementia, particularly Alzheimer’s disease, involuntary tongue protrusion can occur as a “release phenomenon.” This movement is the re-emergence of primitive reflexes, such as the tongue-thrusting reflex, which are normally suppressed by the frontal lobes early in infancy. As cortical tissue degenerates with disease progression, this inhibitory control is lost, allowing the reflex to reappear.
Movement disorders like Parkinson’s disease and other forms of parkinsonism can also be associated with involuntary mouth movements. While the disease itself may cause tremors in the jaw and lips, the more pronounced, erratic tongue and mouth movements are often dyskinesias induced by the long-term use of levodopa medication. This specific drug-induced dyskinesia is a complication that arises after years of therapy aimed at replacing lost dopamine.
Cerebrovascular events, such as stroke, can also cause an acquired form of involuntary tongue movement, known as post-stroke lingual dystonia. This hyperkinetic disorder occurs when the stroke damages areas of the brain responsible for motor control, such as the basal ganglia, thalamus, or cerebellum. The resulting damage causes a breakdown in the neural communication that dictates smooth, voluntary muscle action, leading to uncontrolled tongue spasms or protrusion.
Physical and Oral Health Contributors
Not all instances of tongue protrusion stem from neurological disease or medication effects; some relate to structural and comfort issues within the oral environment. These non-neurological factors often cause the tongue to move in an attempt to correct a physical problem or respond to irritation.
One common physical contributor is chronic xerostomia, or severe dry mouth, which is highly prevalent in the elderly due to chronic diseases and the side effects of numerous medications. Saliva provides the lubrication necessary for comfortable tongue movement, and its absence causes the oral mucosa to feel dry and sticky. The tongue may involuntarily protrude or move excessively in an attempt to gather moisture or stimulate the production of more saliva.
Structural issues related to tooth loss can also trigger orofacial dyskinesia. In individuals who are edentulous (toothless), the tongue loses the stable physical boundaries normally provided by the teeth and underlying bone structure. The lack of a firm reference point can lead to “edentulous orodyskinesia,” where the tongue, lips, and jaw move hyperactively as the oral system attempts to find a stable resting posture.
Age-related muscle loss, known as sarcopenia, affects the tongue. Reduced muscle strength and endurance impair the tongue’s ability to maintain a stable, controlled position, leading to positional instability. Furthermore, a poorly fitting or new dental prosthesis, such as a denture, can also prompt the tongue to move uncontrollably as it attempts to adjust to the foreign object or dislodge a loose appliance.