Effects of aging on evoked retrusive tongue actions

Abstract

Objective Tongue strength, timing, and coordination deficits may underlie age-related swallowing function. Retrusive tongue actions are likely important in retrograde bolus transport. However, age-related changes in retrusive tongue muscle contractile properties have not been identified in animal studies. Because previous studies employed whole hypoglossal nerve stimulation that activated both protrusive and retrusive tongue muscles, co-contraction may have masked retrusive muscle force decrements. The hypotheses of this study were: (1) retrusive tongue muscle contraction forces would be diminished and temporal characteristics prolonged in old rats when lateral nerves were selectively activated, and (2) greater muscle contractile forces with selective lateral branch stimulation would be found relative to whole hypoglossal nerve stimulation. Design Nineteen Fischer 344/Brown Norway rats (9 Old, 10 Young Adult) underwent tongue muscle contractile property recording elicited by: (1) bilateral whole hypoglossal nerve stimulation, and (2) selective lateral branch stimulation. Twitch contraction time (CT), half-decay time, maximal twitch and tetanic forces, and a fatigue index were measured. Results For whole nerve stimulation, CT was significantly longer in the old group. No significant age group differences were found with selective lateral nerve stimulation. Significantly reduced twitch forces (old group only), increased tetanic forces and significantly less fatigue were found with selective lateral nerve stimulation than with whole hypoglossal stimulation. Conclusions Retrusive tongue forces are not impaired in old rats. Deficits observed in swallowing with aging may be due to other factors such as inadequate bolus propulsive forces, mediated by protrusive tongue muscles, or timing/coordination of muscle actions.

Shear and extensional rheology of commercial thickeners used for dysphagia management

“…Therefore, the higher the yield stress, the greater the force needed to initiate the flow. This means individuals with weak swallowing reflux may suffer from postswallow residues in case they swallow food of very high yield stress or they have reduced capacity to generate appropriate tongue pressure as mentioned by the group of Becker and Connor (). However, during oral processing and swallowing, the bolus is never static and, therefore, the overall stress required exceeds the yield stress at the levels measured by Steele et al ().…”

The effects of concurrent chemoradiation therapy to the base of tongue in a preclinical model

“…Optimal and reproducible tongue‐to‐force‐gauge suture alignment and angle were achieved using a laser level (Stanley Black & Decker, New Britain, CT). Suture tension was set to 20 mN for all stimulations, as described previously . Tongue force data were acquired from the force gauge at 20,000 samples per second using an analog‐digital converter (Measurement Computing, Norton, MA) and data acquisition software (DAQami v3.0, Measurement Computing, Norton, MA).…”

<em>In Vivo</em> Evaluation of the Mechanical and Viscoelastic Properties of the Rat Tongue

“…Measuring tongue force requires delicate surgical techniques to isolate and bilaterally stimulate the hypoglossal nerves 17,18 . Such techniques have been previously described in rats 5,17,19,20 , rabbits 21 and humans 22,23 , yet with limited visual aids to the investigator. Due to its highly technical nature, the availability of a detailed protocol would significantly improve the accessibility and reproducibility of this technique.…”

“…The stimulatory hook electrodes described in this protocol are placed proximal to the bifurcation of the nerve, causing the whole tongue is stimulated to be stimulated. Other groups have described the use of silicon nerve cuff electrodes in rats 19,32 or rabbits 21 , which allow selective access and stimulation of one or both branches of the hypoglossal nerves. Additionally, the use of injectable anesthetics instead of isoflurane inhalation would provide better access to the submandibular region where the hypoglossal nerves branch.…”