Date Presented 03/27/20
A noninvasive application of vagal nerve stimulation, taVNS, stimulates the auricular branch of the vagal nerve. In a first-in-neonates application, infants who received taVNS for oral feeding dysfunction also showed improvements in head control and brain neuroimaging of major white-matter tracts. These exploratory results are promising and promote future studies of taVNS to improve motor abilities in infants with feeding difficulties or motor disorders.
Primary Author and Speaker: Shelby Davis
Additional Authors and Speakers: Amy Reiner, Hannah Haskin, Patty Coker-Bolt, Turki Aljuhani
Contributing Authors: Mark George, Bashar Badran, Dorthea Jenkins
PURPOSE: Vagal nerve stimulation (VNS) has been shown to promote neuroplasticity and improve motor function in adults post-stroke when paired with a motor task [1]. A non-invasive application of VNS, transcutaneous auricular VNS (taVNS), stimulates the auricular branch of the vagal nerve. In a first-in-neonates application, infants who failed to achieve full oral feeds received 2-3 weeks of daily taVNS-paired with bottle feeding [2]. With taVNS, 58% successfully attained full oral feeds (responders) vs 42% who received gastrostomy feeding tube (non-responders). For a secondary outcome, we hypothesized that the Specific Test of Early infant motor Performance (STEP) [3] and brain neuroimaging before and after treatment may show taVNS treatment effect. 1) taVNS responders will have greater change in total score on the STEP than non-responders following taVNS treatment 2) taVNS responders will have greater change in scores on specific STEP items relating to head control than non-responders following taVNS treatment 3) White matter tract maturity will differ in taVNS infants performing high vs low on STEP items related to head control.
DESIGN: Prospective cohort study with convenience sample of at-risk infants enrolled into taVNS feeding study. Infants failed oral feeding trials and were referred for a g-tube placement. Infants received taVNS paired with bottle feeds 1-2x a day for 2 weeks.
METHOD: Infants’ motor abilities analyzed using STEP, neuroimaging with Diffusion Kurtosis Imaging (DKI), both at the start and end of taVNS treatments. Data analyzed using independent sample t-test, Spearman correlation, and Tract Based Spatial Statistics for whole brain DKI.
RESULTS: 15 infants completed this study (n=9 responders, n=6 non-responders). There were no significant differences in weight and gestational age between groups. There were more females in responder group (n=6 females). While change in Total STEP scores were not significantly different between responders and non-responders (p=0.2), scores for head movements in 3 positions – Supine with Stimulation (p=0.025), Rolling by Arm (p=0.040), and Head Control in Supported Sitting improved significantly (p=0.025) in responders to taVNS treatment. Infants with lower scores on STEP items Prone Extension and Head Control in Supported Sitting had significantly lower values (p<0.05) of axonal integrity (fractional anisotropy) in major white matter tracts (corpus callosum, external capsule, optic radiation, inferior frontal occipital fasciculus, anterior and posterior limb of internal capsule, cerebellum, corticospinal tract) related to sensorimotor integration and motor control when compared to higher scoring infants. Additionally, specific STEP items Rolling by Leg and Prone extension, and Total STEP Score after treatment had significant correlations to similar white matter tracts (r=0.60-0.80, p<0.05).
CONCLUSION: taVNS responders had greater improvements in STEP items related to head control than non-responders. Infants who performed well on the STEP items of head control had higher white matter integrity in specific tracts, which appear to be responsive to taVNS-paired feeding treatment. Limitations of our study include small sample and lack of control group.
IMPACT STATEMENT: This is the first study to demonstrate that neuromodulation, particularly taVNS, may have contributed to changes in motor function of infants. Findings could improve understanding of neuromodulation techniques, as well as the safety and feasibility of taVNS, on at-risk infants. Although this study is exploratory, our results are promising and promote future studies of taVNS to improve the motor and functional abilities infants with feeding difficulties, other motor problems, or neurodevelopmental disorders.
References
Redgrave JN, Moore L, Oyekunle T, et al. Transcutaneous Auricular Vagus Nerve Stimulation with Concurrent Upper Limb Repetitive Task Practice for Poststroke Motor Recovery: A Pilot Study. Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association. 2018;27(7):1998-2005.
Badran, B. W., Jenkins, D. D., Devries, W. H., Dancy, M., Summers, P. M., Mappin, G. M., . . . George, M. S. (2018). Transcutaneous auricular vagus nerve stimulation (taVNS) for improving oromotor function in newborns. Brain Stimulation, 11(5), 1198-1200. doi:10.1016/j.brs.2018.06.009
Gower, L., Jenkins, D., Fraser, J. L., Ramakrishnan, V., & Coker-Bolt, P. (2018). Early developmental assessment with a short screening test, the STEP, predicts one-year outcomes. Journal of Perinatology, 39(2), 184-192. doi:10.1038/s41372-018-0234-4
