Lip smacking, in a medical context, is often referred to as an oral or buccal-lingual-masticatory automatism. This repetitive movement can be alarming, leading to concern about serious neurological conditions like dementia. While lip smacking can be a manifestation of a deeper brain issue, it is not a singular, guaranteed sign of cognitive decline. The behavior has a range of potential origins, from structural brain damage to medication side effects to common oral habits. Understanding the context, pattern, and accompanying symptoms is necessary to determine if the behavior is a benign habit or a sign of an underlying neurological disorder.
The Direct Link to Dementia
Lip smacking is generally rare as an initial or standalone symptom in the most common forms of dementia, such as Alzheimer’s disease. However, it can appear in the later stages of certain neurodegenerative conditions as an involuntary movement. These movements are considered automatisms, which are automatic actions performed without conscious thought.
The appearance of these oral movements is most closely associated with a specific group of disorders known as Frontotemporal Dementia (FTD). In FTD, the deterioration of the frontal and temporal lobes of the brain can lead to behavioral changes, including a symptom called hyperorality. This condition involves an excessive focus on the mouth, manifesting as compulsive behaviors like repeated lip smacking, chewing, or exploring objects with the mouth.
This motor symptom is a result of damage to the brain areas that coordinate learned motor skills and regulate impulses. When lip smacking is due to advanced dementia, it is usually accompanied by other more prominent cognitive and behavioral deficits. These typically include severe memory loss, language difficulties, loss of inhibition, or significant changes in personality.
Drug-Induced Involuntary Movements
A common cause of persistent lip smacking in older adults is a movement disorder known as Tardive Dyskinesia (TD). This condition is an involuntary, repetitive body movement that often affects the face, tongue, and jaw muscles. The name means “late-appearing abnormal movement,” as symptoms often develop after months or years of medication use.
Tardive Dyskinesia is caused by the long-term use of medications that block dopamine receptors in the brain, which are the chemical messengers responsible for controlling movement. These are primarily certain psychiatric medications, known as antipsychotics, used to treat conditions like schizophrenia or bipolar disorder. Certain anti-nausea medications, like metoclopramide, can also cause TD.
The chronic blockade of dopamine receptors creates a hypersensitivity in the brain’s movement control centers, leading to uncontrolled movements. Lip smacking, along with grimacing, tongue protrusion, and chewing motions, is a hallmark symptom of TD. TD is a drug-induced movement disorder distinct from the cognitive impairment of dementia, though the two can co-occur in patients taking these medications.
Lip Smacking as a Sign of Seizure Activity
Lip smacking is recognized as a sign of a focal onset seizure, a specific type of electrical disturbance in the brain. These seizures begin in one area, most often the temporal lobe, which is involved in memory, emotion, and sensory input. The resulting movement is a form of automatism caused by abnormal electrical activity.
During a focal onset seizure, the person may appear awake but have an impaired awareness of their surroundings. The automatism involves repetitive, non-purposeful behaviors that can include lip smacking, chewing, hand fumbling, or repetitive walking. These episodes typically last from 30 seconds to a few minutes.
A seizure-related episode is distinct from TD or dementia due to its sudden onset and brief, self-limiting nature, often followed by confusion. Recognizing lip smacking in this context is important because seizures require immediate neurological evaluation and treatment, typically with anti-seizure medications, to stabilize the erratic electrical signaling in the brain.
Non-Neurological and Common Causes
Lip smacking can frequently be traced back to non-neurological origins. Many people develop subtle oral habits over time, especially in response to anxiety or stress. These habits are generally intermittent and often tied to specific emotional triggers or situations.
Physical or mechanical issues in the mouth can also prompt the behavior. For people who wear dentures, an ill-fitting or loose prosthetic can cause discomfort that leads to the mouth constantly adjusting through subtle movements, including lip smacking and chewing. Dry mouth, or xerostomia, can also cause a person to involuntarily smack or pucker their lips to stimulate saliva flow or moisten the oral tissues.
If the behavior is new, persistent, or accompanied by other changes in movement, speech, or cognition, a medical consultation is warranted. A doctor can perform a full neurological exam and review the person’s medication history to distinguish between a benign habit and a serious underlying condition.