Evaluation of Tongue Movement in Subacute Stroke Patients without Speech Difficulties Using Dynamic Ultrasonographic Analysis-A Preliminary Study

Objective: Reduced speed and range of tongue motions have been frequently observed in post-stroke patients even though there are is obvious decrease in speech intelligibility during natural conversations. The subtle change in tongue function may represent underlying problems. This research collected the dynamic tongue images during the production of consonant-vowel syllables by ultrasonography for analysis and quantification of subtle changes in the coordination of tongue motions. Methods: We obtained the ultrasound tongue images from 10 subacute stroke patients without obvious speech intelligibility and 10 healthy age-controlled controls by fixing the ultrasound probe (model GP 3.5 MHz, Interson, Pleasanton, CA, USA) at the midline sagittal axis of the chin. The participants were asked to produce syllables /ka/, /ki/, /ku/, /ta/, /ti/, and /tu/ with comfortable pitch and loudness. The displacement of the surface top of tongue dorsum corresponding to a syllable between two images was acquired from 5 successive ultrasonographic images extracted from the production at the rate of 12 frames per second. The displacement of tongue top between two successive frames represents the tongue motion during syllable production. Results: The total distance of tongue displacement within the five extracted images were significantly reduced in the stroke patients (p ＜ 0.05, Mann-Whitney U test), and the total displacement of tongue movement of the first 3 frames further showed significant difference between the stroke and control groups during the consonant-vowel transition of the /t/-leading syllables. Conclusion: The decreased retraction range of the tongue could be observed by ultrasonographic dynamic image analysis in stroke patients indicating an altered tongue function even no obvious articulatory errors were observed. Analysis of subtle changes in tongue motion has a potential for basic and clinical research.

關鍵字

articulation ； consonant-vowel ； dynamic image analysis ； subacute stroke ； ultrasound

並列摘要

目的：中風後患者即使在自然交談中語音清晰度沒有明顯的變化，但舌頭運動的速度和範圍的降低還是會有變化。這些舌頭的細微變化仍可能造成交談及吞嚥的潛在問題。本研究展現一種舌頭超音波動態影像分析新方法，測量舌頭在發出子母音（consonant-vowel）構成的音節（syllable）時舌頭動作的協調性是否有細微的變化。方法：我們募集10位亞急性中風（subacute stroke）患者和10位年齡匹配的健康受試者作為對照組，以超音波（GP 3.5 MHz, Interson, Pleasanton, CA, USA）置於下巴中線，以每秒12幀的速率蒐集舌頭發音時縱切的動態影像。語音材料為音節/ ka /，/ ki /，/ ku /，/ ta /，/ ti / 和/ tu /，發聲狀況則為舒適音高與響度（comfort pitch and loudness）。從音節產生中提取包括最大位移之連續5禎（frame）超音波影像，每禎影像獲取舌背頂點的位置，之後再比較連續兩幀之間頂點位置的變化也就是位移。該位移可用以代表該音節舌頭的運動。結果：中風組舌頭位移的總距離顯著減小（p ＜ 0.05, Mann-Whitney U test）。並且在以/t/為首的子母音語料中，構音運動前三禎影像，也就是子母音過渡期，舌頭向後移動範圍，中風組和對照組之間有顯著的統計差異（p ＜ 0.05, Friedman repeated measures of analysis of variance on ranks）。結論：本研究顯示腦中風患者即使能說話沒有明顯的發音錯誤，但實際上他們的舌頭功能已經下降且受到影響。以超音波動態影像分析可以觀察到某些構音時舌頭後縮回的範圍明顯減小。以超音波動態影像分析觀察舌頭的構音，可以看到舌頭動作的細微變化，未來在基礎醫學與臨床研究上都是很有潛力的發展。

並列關鍵字

舌運動；超音波；構音；動態影像分析；亞急性中風

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