Retroflex Tongue as a Non-Invasive Neurological Marker of Functional Severity in Older Adults With Ischemic Stroke: A Retrospective Observational Study

Yungsheng Huang¹Hen-Hong Chang¹John Y Chiang²Po-Chi Hsu^1*Lun-Chien Lo^1*

• ¹China Medical University (Taiwan), Taichung, Taiwan
• ²National Sun Yat-sen University, Kaohsiung, Kaohsiung County, Taiwan

With the growing global burden of ischemic stroke in aging populations, there is increasing interest in simple and non-invasive neurological markers to support early risk stratification and functional prognosis. Retroflex tongue (RT) and tongue deviation (TD) are observable signs of cranial nerve dysfunction; however, their comparative predictive value for stroke severity remains unclear.In this retrospective observational study, 308 older adults (mean age: 69.1 years) hospitalized with ischemic stroke were enrolled. Tongue motor function was evaluated using an automatic tongue diagnosis system (ATDS). Deviation angles were measured, and the presence or absence of RT was assessed by trained traditional Chinese medicine physicians. Stroke severity and functional outcomes were evaluated using the National Institutes of Health Stroke Scale (NIHSS), Barthel Index, and length of hospital stay.Among the 308 patients, 59 (19.2%) exhibited TD and 249 (80.8%) did not. No significant differences were found in baseline characteristics between TD groups, except for deviation angle (TD: 9.72° ± 8.91° vs. non-TD: 6.40° ± 7.84°, p = 0.011). Patients without RT had significantly worse clinical outcomes, including longer hospital stays (32.0 vs. 25.9 days, p = 0.007), higher NIHSS scores (14.1 vs. 8.9, p < 0.001), and lower Barthel Index scores (18.6 vs. 35.0, p < 0.001), compared to those with RT. In contrast, TD showed no significant association with these outcomes. Multivariate regression identified non-RT as an independent predictor of stroke severity. ROC analysis supported the discriminative value of RT (AUC = 0.703 for NIHSS ≥ 9; AUC = 0.712 for Barthel ≤ 17), whereas TD showed poor predictive ability (AUC = 0.524 and 0.570, respectively).Absence of retroflex tongue is more strongly associated with stroke severity and functional impairment than tongue deviation. As a simple, observable motor sign, RT may serve as a practical bedside indicator for early neurological assessment. However, given its preliminary status, further validation in prospective, multi-center studies is warranted before clinical application.