Myasthenia gravis causes diffuse muscular weakness along with droopy eyelids, double vision and slurred speech. Weakness of the tongue and pharyngeal muscles results in dysphagia. There is a reduction in the oral preparatory stage along with decreased tongue movements, nasal regurgitation and reduced peristalsis. Other muscular disorders include scleroderma, Raynaud's disease, achalasia and neuromuscular esophageal disorders. All of these patients are commonly seen by neurologists, internists and gastroenterologists, but rarely make it to a rehabilitation specialist for swallowing therapy.
Diseases involving the brain, brainstem and peripheral nerves are more common than muscle disorders.
Strokes and brain injuries account for the majority of swallowing problems. Strokes on both sides of the brain may cause pseudobulbar palsy with emotional lability, slurred speech and dysphagia. Brainstem strokes may involve the lower cranial nerves that affect tongue movements, facial strength and pharyngeal muscles. This results in both spastic and atrophic symptoms with difficulty in tongue control, nasal regurgitation and a delayed swallowing reflex. Multiple sclerosis is a disease of the central myelin, the substance that insulates nerve fibers in the brain and spinal cord.