| Neuromuscular/sensory dysfunction | |
| Mental retardation | |
| Cerebral palsy | |
| Parkinson's disease | |
| Pseudobulbar* | |
| Bulbar palsy* | |
| Stroke* | |
| Hypersecretion † | |
| Inflammation (teething, dental caries, oral-cavity infection, rabies) | |
| Medication side effects (tranquilizers, anticonvulsants) | |
| Gastroesophageal reflux | |
| Toxin exposure (mercury vapor) | |
| Anatomic ‡ | |
| Macroglossia (enlarged tongue) | |
| Oral incompetence | |
| Dental malocclusion | |
| Orthodontic problems | |
| Head and neck surgical defects (i.e., “Andy Gump” deformity) | |