The purpose of this study was to measure treatment outcomes in a group of six adults with chronic dysphagia following acquired brain injury, who each completed 24 sessions of tongue-pressure resistance training, over a total of 11–12 weeks. The treatment protocol emphasized both strength and accuracy. Biofeedback was provided using the Iowa Oral Performance Instrument. Amplitude accuracy targets were set between 20–90% of the patient's maximum isometric pressure capacity. Single subject methods were used to track changes in tongue strength (maximum isometric pressures), with functional swallowing outcomes measured using blinded ratings of a standard pre- and post-treatment videofluoroscopy protocol. Improvements were seen in post-treatment measures of tongue pressure and penetration–aspiration. No improvements were seen in pharyngeal residues, indeed worsening residue was seen in some patients.

Thickened liquids are frequently used in the management of oropharyngeal dysphagia. Previous studies suggest that compression of a liquid bolus between the tongue and the palate in the oral phase of swallowing serves a sensory function, enabling the tuning of motor behavior to match the viscosity of the bolus. However, the field lacks information regarding healthy oral sensory discrimination ability for small differences in liquid viscosity. We undertook to measure oral viscosity discrimination ability for five non-Newtonian xanthan gum-thickened liquids in the nectar- and honey-thick range. Xanthan gum concentration ranged from 0.5 to 0.87 % and increased by an average of 0.1 % between stimuli in the array. This translated to an average apparent viscosity increase of 0.2-fold between adjacent stimuli at 50 reciprocal seconds (/s). A triangle test paradigm was used to study stimulus discrimination in 78 healthy adults in two, sex-balanced age cohorts. Participants were provided 5-ml samples of liquids in sets of three; one liquid differed in xanthan gum concentration from the other two. Participants were required to sample the liquid orally and indicate which sample was perceived to have a different viscosity. A protocol of 20 sets (60 samples) allowed calculation of the minimum difference in xanthan gum concentration detected accurately. On average, participants were able to accurately detect a 0.38-fold increase in xanthan-gum concentration, translating to a 0.67-fold increase in apparent viscosity at 50/s. The data did not suggest the existence of a nonlinear point boundary in apparent viscosity within the range tested. No differences in viscosity discrimination were found between age cohorts or as a function of sex. The data suggest that for xanthan gum-thickened liquids, there may be several increments of detectably different viscosity within the ranges currently proposed for nectar- and honey-thick liquids. If physiological or functional differences in swallowing can be demonstrated for these smaller increments of detectably different viscosity, more narrowly defined categories of thickened liquids for dysphagia management will be warranted.