Neurophysiology of swallowing: effects of age and bolus type.

This study examined age-related changes in swallowing from an integrated biomechanical and functional imaging perspective in order to more comprehensively characterize changes in swallowing associated with age. We examined swallowing-related fMRI brain activity and videoflouroscopic biomechanics of three bolus types (saliva, water and barium) in 12 young and 11 older adults. We found that age-related neurophysiological changes in swallowing are evident. The group of older adults recruited more cortical regions than young adults, including the pericentral gyri and inferior frontal gyrus pars opercularis and pars triangularis (primarily right-sided). Saliva swallows elicited significantly higher BOLD responses in regions important for swallowing compared to water and barium. In separate videofluoroscopy sessions, we obtained durational measures of supine swallowing. The older cohort had significantly longer delays before the onset of the pharyngeal swallow response and increased residue of ingested material in the pharynx. These findings suggest that older adults without neurological insult elicit more cortical involvement to complete the same swallowing tasks as younger adults.

Early deficits in cortical control of swallowing in Alzheimer's disease.

The goal of this study was to determine whether functional changes in cortical control of swallowing are evident in early Alzheimer's disease (AD), before dysphagia (swallowing impairment) is evident. Cortical function was compared between an early AD group and a group of age-matched controls during swallowing. Swallowing oropharyngeal biomechanics examined from videofluoroscopic recordings were also obtained to more comprehensively characterize changes in swallowing associated with early AD. Our neuroimaging results show that the AD group had significantly lower Blood-Oxygen-Level-Dependent (BOLD) response in many cortical areas that are traditionally involved in normal swallowing (i.e., pre and postcentral gyri, Rolandic and frontal opercula). There were no regions where the AD group showed more brain activity than the healthy controls during swallowing, and only 13% of all active voxels were unique to the AD group, even at this early stage. This suggests that the AD group is not recruiting new regions, nor are they compensating within regions that are active during swallowing. In videofluoroscopic measures, the AD group had significantly reduced hyo-laryngeal elevation than the controls. Although, swallowing impairment is usually noted in the late stages of AD, changes in cortical control of swallowing may begin long before dysphagia becomes apparent.

Simultaneous estimation of tongue volume and fat fraction using IDEAL-FSE.

PURPOSE: To determine whether high-resolution, high signal-to-noise ratio (SNR) images of the tongue acquired with IDEAL-FSE (iterative decomposition of water and fat with echo asymmetry and least squares estimation) will provide comparable volumetric measures to conventional nonfat-suppressed FSE imaging and to determine the feasibility of estimating the proportion of lingual fat in adults using IDEAL-FSE imaging. MATERIALS AND METHODS: Healthy volunteers underwent magnetic resonance imaging of the tongue using both IDEAL-FSE and conventional FSE sequences. The tongue was manually outlined to derive both volumetric and fat fraction measures. Intraclass correlation coefficients (ICCs) were computed for intrarater measurement reliability and Spearman's rank correlation tested the relationship between IDEAL-FSE and conventional volumetric measures of the tongue. RESULTS: IDEAL-FSE imaging yielded almost identical volumetric measures to that of conventional FSE imaging in the same amount of scan time (IDEAL-FSE mean 64.1 cm(3); conventional mean 63.3 cm(3); r = 0.988, P < or = 0.01). The average fat signal fraction across participants was 26.5%. Intrarater reliability was excellent for all measures (ICC > or = 0.92). CONCLUSION: Our results indicate that IDEAL-FSE provided similar lingual volume estimates to conventional FSE imaging obtained in both the current and previous studies. IDEAL-FSE measures of lingual fat composition may be useful in studies that aim to increase lingual muscle strength and volume in swallowing and speech-disordered populations.