What causes lip tremors?

Causes of Lip Tremors

Lip tremors result from diverse etiologies including drug-induced effects, neurological disorders (particularly Parkinson's disease and essential tremor), functional neurological disorders, neonatal drug withdrawal syndromes, and task-specific tremor variants.

Drug-Induced Causes

Medications are among the most common reversible causes of lip tremors and should be evaluated first in any patient presenting with this symptom. 1

Common Offending Medications

• SSRIs/SNRIs (fluoxetine, paroxetine, sertraline, citalopram, escitalopram) cause tremors as a frequent side effect 2
• Antipsychotics and dopamine antagonists can induce parkinsonian tremor including facial involvement 3, 1
• Lithium, valproate, and amiodarone are well-established tremor-inducing agents 1
• Beta-adrenoceptor agonists commonly produce tremor 1
• Stimulants including cocaine and amphetamines cause tremors through dopaminergic mechanisms 2

Risk Factors for Drug-Induced Tremor

• Polypharmacy, male gender, older age, high doses, and immediate-release preparations increase risk 1
• Drug-induced tremor typically resolves after discontinuation, though tardive tremor may persist in some cases 1

Neurological Disorders

Parkinson's Disease

Facial tremors can be an early presenting sign of Parkinson's disease, occurring in approximately 5% of patients with movement disorders. 4

• Parkinsonian lip tremor is primarily a resting tremor (4-6 Hz) that may have postural components 5, 6
• Facial tremor response to acute levodopa challenge shows 92% sensitivity and 93% specificity for predicting final PD diagnosis 4
• Associated with other cardinal features including bradykinesia, rigidity, and postural instability 6
• Re-emergent tongue and lip tremor has been documented in drug-induced parkinsonism (e.g., levosulpiride) 3

Essential Tremor

• Essential tremor is the most common tremor disorder, presenting as postural and kinetic tremor at 4-8 Hz 7
• Can involve the head and lips, responding to primidone, beta-blockers, and benzodiazepines 7
• Task-specific variants exist, where lip tremor appears only during speech (4-5 Hz), improving with beta-blockers or small amounts of alcohol 8

Cerebellar and Intentional Tremor

• Intentional tremor becomes more pronounced during goal-directed movements and is associated with dysarthria and ataxic gait 2, 9, 6
• Caused by multiple sclerosis, Wilson's disease, traumatic brain injury, certain medications, or toxic exposures 9
• Distinguished by its coarse, irregular pattern and "wing-beating" appearance 9

Functional Neurological Disorder

Functional tremor is characterized by variability in frequency and amplitude, and most importantly, its distractibility—stopping when attention is redirected. 5

Diagnostic Features

• Tremor stops with distraction techniques, unlike organic tremors 5
• Variable frequency and amplitude distinguish it from parkinsonian or essential tremor 5
• May have underlying psychological factors, though not all patients have obvious psychological symptoms 5

Management Approach

• Explain to patients that functional neurological disorder is a real neurological condition caused by potentially reversible miscommunication between brain and body 5
• Implement rehabilitation strategies focusing on redirecting attention away from symptoms 5
• Avoid providing adaptive equipment in the acute phase, as this may reinforce maladaptive movement patterns 5
• Occupational therapy focusing on normal movement patterns can be helpful 5

Neonatal Drug Withdrawal

In neonates, lip tremors are a prominent feature of drug withdrawal syndromes, particularly from opioids, benzodiazepines, barbiturates, SSRIs, and alcohol. 2

Specific Drug Withdrawal Patterns

• Opioid withdrawal (neonatal abstinence syndrome) develops in 55-94% of exposed neonates 2
• Alcohol withdrawal presents with tremors, hyperactivity, irritability, and seizures within 3-12 hours of birth 2
• Benzodiazepine withdrawal (diazepam, chlordiazepoxide) causes tremors with onset from hours to weeks 2
• SSRI exposure causes tremors, irritability, and feeding difficulty with onset from hours to days after birth, typically resolving within 1-4 weeks 2
• Barbiturate withdrawal produces severe tremors with onset 1-14 days postnatally 2
• Stimulant exposure (cocaine, methamphetamine) causes neurobehavioral abnormalities including tremors on postnatal days 2-3 2

Clinical Pitfalls and Diagnostic Considerations

The timing, context, and associated features are critical for distinguishing between tremor etiologies:

• Resting tremor suggests Parkinson's disease or drug-induced parkinsonism 6, 3
• Postural/action tremor suggests essential tremor or physiologic tremor 7
• Intentional tremor suggests cerebellar pathology 9, 6
• Distractible tremor suggests functional neurological disorder 5
• Sudden onset, unilateral, or task-specific patterns may indicate dystonic or functional tremor 1

Always obtain a detailed medication history, as drug-induced tremor is common and reversible. 1 Consider acute levodopa challenge in patients with suspected parkinsonian facial tremor, as positive response strongly predicts Parkinson's disease diagnosis. 4