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Unilateral cricothyroid contraction and glottic configuration
G E Woodson1, M P Murry, V Schweizer
1Department of Otolaryngology, University of Tennessee, Memphis 38163, USA.
Journal of Voice : Official Journal of the Voice Foundation
|October 8, 1998
Summary
Unilateral cricothyroid muscle (CT) paralysis diagnosis through physical exam is unreliable. CT muscle contraction causes minimal glottic changes, suggesting current diagnostic methods need re-evaluation for accuracy.
Area of Science:
- Laryngology
- Anatomy
- Physiology
Background:
- Clinical diagnosis of unilateral cricothyroid muscle (CT) paralysis relies on physical examination findings.
- Observed signs like glottic rotation and vocal fold displacement are inconsistently reported, leading to diagnostic controversy.
Purpose of the Study:
- To investigate the three-dimensional effects of cricothyroid muscle contraction on glottic configuration.
- To evaluate the validity of physical examination signs used to diagnose unilateral CT paralysis.
Main Methods:
- Computerized tomography (CT) scans were performed on cadaver larynges.
- Simulated unilateral CT muscle contraction was induced.
- Radiopaque markers were used to quantify changes in glottic dimensions and vocal fold positions.
Main Results:
- Unilateral CT contraction resulted in a minimal posterior glottic rotation (<1 mm).
- Both membranous vocal folds showed equal length increases.
- No significant adduction of vocal processes or alteration in their vertical level was observed.
Conclusions:
- Clinically apparent changes in glottic configuration due to unilateral CT contraction are minimal.
- Physical examination findings are insufficient for reliably diagnosing unilateral CT paralysis.
- Current diagnostic criteria for CT paralysis require reassessment based on objective biomechanical data.