純粋発語失行3例における構音の継時的変化と改善機序に関する一考察

A study on the successive changes in articulation and mechanism of improvement in three cases of pure apraxia of speech

　純粋発語失行3例における構音症状の継時的変化を報告した．対象は中等度から軽度まで改善を認めた純粋発語失行3例である．方法は単語および複合語の復唱課題を行い，初回評価時と再評価時における誤反応パタンを聴覚印象評価に基づき分析した．その結果，初回評価時に「置換」および「歪んだ置換」であった8割以上の音素が，再評価時に「明瞭」または「歪み」へと変化した．初回評価時に「歪み」であった音素も半数以上が「明瞭」へ変化した．「歪み」が再評価時にも残存した音素のうち，/t‿s/や/ɕ/などは複数例で一致した．本3例では「置換→明瞭」「歪んだ置換→明瞭」「歪み→明瞭」「置換→歪み」「歪んだ置換→歪み」といった改善パタンが確認された．この結果から，改善過程には置換および歪んだ置換から歪み，歪みから明瞭な音声という段階性があると考えられた．また，発語失行の構音症状の改善過程は音素の構音動作の複雑さによって異なる可能性が示された．

　We report on the change over time of articulation errors in three cases of pure apraxia of speech. Each participant exhibited moderate apraxia of speech, which improved to a mild level over time. The study employed a word and compound word repetition task, with error pattern analyses based on auditory impression ratings at the initial and follow-up assessments. Results showed that over 80% of phonemes initially classified as “substitution” and “distorted substitution” improved to “clear articulation” or “distortion” at re-evaluation. Additionally, over half of the phonemes marked as distorted at the initial assessment changed to clear articulation. Of the phonemes that were classified as “distortion” at re-evaluation, /t‿s/ and /ɕ/ were consistently present across all three cases. Improvement patterns identified across the cases included transitions “from substitutions to clear articulation,” “from distorted substitutions to clear articulation,” “from distortion to clear articulation,” “from substitutions to distortion,” and “from distorted substitutions to distortion.” These findings suggest a graded trajectory of improvement, changing from substitution and distorted substitutions to distortion, ultimately to clear articulation. Moreover, the results indicate that the improvement of articulatory symptoms in apraxia of speech might be influenced by the articulatory complexity of phonemes.