Submitted on March 12, 2003
Accepted on August 18, 2003
Changes in pharyngeal corticobulbar excitability and swallowing behavior after oral stimulation
M. Power1, C. Fraser1, A. Hobson1, J. C. Rothwell2, S. Mistry1, D. A. Nicholson3, D. G. Thompson1, and S. Hamdy1*
1 Department of G.I. Science, University of Manchester, Hope Hospital, Salford, Manchester, United Kingdom
2 Sobell Department of Neurophysiology, Institute of Neurology, London, United Kingdom
3 Department of Radiology, University of Manchester, Hope Hospital, Salford, Manchester, United Kingdom
* To whom correspondence should be addressed. E-mail: shamdy{at}fs1.ho.man.ac.uk.
Faucial pillar (FP) stimulation is commonly used in swallowing rehabilitation, yet its physiological basis remains uncertain. We investigated the effects of intra-oral FP stimulation on human corticobulbar excitability and swallowing behavior, to explore the possibility for a central mechanism for functional change. In 10 healthy subjects, corticobulbar projections to pharynx were investigated with transcranial magnetic stimulation, via intra-luminal electrodes, before and up to 1 hour after 10 minutes of electrical FP stimulation with 3 frequencies (0.2, 1, and 5 Hz) or sham and peripheral(median nerve) stimulation. In a second study, swallowing behavior was assessed with videofluoroscopy before and after FP stimulation. FP stimulation at 5Hz inhibited the corticobulbar projection (
-14±6%, p<0.02) and lengthened swallow response time ( +114±24%, p=0.02). By comparison, FP stimulation at 0.2Hz facilitated this projection ( +60±28%, p<0.04), without enhancing swallowing behavior. Neither 1Hz, sham or median nerve stimulation altered excitability. Thus, changes in the corticobulbar excitability to FP stimulation are frequency dependent with implications for the treatment for neurogenic swallowing dysfunction.
