Orofacial Dyskinesia in Parkinson's Disease
The lip smacking behavior observed in Parkinson's disease is formally called orofacial dyskinesia, which is characterized by repetitive, involuntary movements of the mouth, lips, and tongue that can include lip smacking, chewing, and tongue movements.
Clinical Features of Orofacial Dyskinesia
Orofacial dyskinesia in Parkinson's disease presents with several characteristic features:
- Involuntary spasms causing arrhythmic movements of the tongue, sometimes with protrusion and drooling
- Opening of the mouth, clenching of teeth
- Pursing and retraction of the lips
- Repetitive lip smacking and chewing movements that can interrupt speech 1
These movements typically last from seconds to a minute or two and occur in a repetitive pattern.
Pathophysiology
The pathophysiological mechanism of orofacial dyskinesia in Parkinson's disease involves:
- Dopaminergic receptor dysfunction, particularly D1 receptors, which play a crucial role in causing this condition 1
- Can occur as a side effect of long-term treatment with levodopa (L-dopa), the primary medication used to treat Parkinson's disease 1, 2
- May also develop as part of the disease progression itself due to dopaminergic imbalance in the basal ganglia
Relationship to Treatment
Orofacial dyskinesia in Parkinson's disease can occur through two main mechanisms:
Levodopa-induced dyskinesia: Long-term exposure of the dopamine-depleted parkinsonian brain to exogenous dopaminergic agents can cause preferential inhibition of specific putaminal neurons that project to the lateral segment of the globus pallidus, leading to disinhibition of lateral pallidal neurons and physiological inhibition of the subthalamic nucleus 2
Antipsychotic-induced dyskinesia: When antipsychotics are used to treat psychosis in Parkinson's disease, they can exacerbate motor symptoms by blocking dopamine receptors in the nigrostriatal pathway 3
Management Approaches
Management of orofacial dyskinesia in Parkinson's disease involves:
Adjustment of dopaminergic medications (levodopa) to find the optimal dose that controls parkinsonian symptoms while minimizing dyskinesias 4
For patients requiring antipsychotics for psychosis:
- Pimavanserin should be considered as first-line treatment due to its serotonergic mechanism without dopaminergic blockade
- Clozapine in low doses as second-line treatment
- Quetiapine in low doses as third-line treatment 3
For dyskinesias related to levodopa therapy:
- Adjustment of levodopa dosing schedules
- Consideration of advanced treatments such as levodopa-carbidopa enteral suspension or deep brain stimulation for patients with medication-resistant symptoms and dyskinesias 4
Monitoring and Prevention
- Regular evaluation of abnormal movements, especially during prolonged treatment with dopaminergic or antipsychotic medications 3
- Close monitoring of motor symptoms and adjustment of antiparkinsonian medication to maintain balance between symptom control and dyskinesia 3
- Early recognition and intervention are crucial to prevent worsening of dyskinesias
Orofacial dyskinesia represents one of the challenging aspects of Parkinson's disease management, reflecting the complex balance between treating the primary motor symptoms of the disease while minimizing treatment-related complications.