Relationship between Dysphagia and Serum Substance P Level in Chronic Central Nervous Disease

Purpose: We compared serum substance P (SP) levels in underlying diseases and dysphagia, or its absence, in patients with cerebrovascular disease, neurodegenerative disease or Alzheimer’s disease, to investigate the relationship between dysphagia and serum SP in chronic central nervous disease. Methods: Subjects comprised 94 patients admitted to a hospital or nursing home during the 5 years between April 2007 and April 2012 with central nervous symptoms. Serum SP levels were measured by enzyme immunoassay, and video endoscopy using a nasal endoscope in all subjects to objectively evaluate swallowing function. Results: Serum SP level was very similar in central nervous disease without dysphagia and controls without central nervous disease. Conversely, serum SP level was significantly lower in central nervous disease with dysphagia. When comparing underlying diseases, serum SP was significantly lower in Parkinson’s disease than in other disease groups (cerebrovascular disease, Alzheimer’s disease). Looking at changes in serum SP levels over time after disease onset, SP level was significantly low in subjects without dysphagia at the time of onset who went on to develop dysphagia during the disease course, whereas serum SP level tended to be higher in subjects with dysphagia at the time of onset and improvement during the disease course. With Parkinson’s disease and cerebrovascular disease, serum SP was low, particularly in subjects thought to have severe damage to the basal ganglia. Conclusion: Serum SP is generally thought to decrease in patients with cerebrovascular disease accompanied by dysphagia, but these results suggest that serum SP levels can be expected to improve to some extent, even if dysphagia is present at disease onset, assuming, for example, that some basal ganglia function remains. Positive therapeutic interventions such as swallowing rehabilitation should be promoted in such patients, with the goal of improving swallowing function.