Laryngeal stroboscopy-Normative values for amplitude, open quotient, asymmetry and phase difference in young adults

To provide the normative values for laryngeal stroboscopy (LS) concerning amplitude, open quotient, asymmetry and phase difference in healthy, young subjects.

Prospective case-control study.

Patients treated at a single institute.

A total of 68 healthy subjects were included in the study (35 women, 33 men), aged 18-35 years. After obtaining LS recordings, image processing was performed to attain parameters of vocal fold vibration.

In women, the location of the maximum vibration amplitude is approximately in the 1/3 posterior part of the glottis, while in men, the location is moved to the glottis centre. In males, the relative amplitude vibration of the vocal folds in the 1/3 anterior part of the glottis was significantly higher than in females (P = 0.029). Women showed significantly higher open quotients (OQ) at the posterior part of the glottis than the male subjects (P < 0.001) and men presented significantly higher OQ at the anterior part of the glottis than the females (P < 0.001). The average OQ values for both sexes were almost the same. Females showed significantly higher relative glottal gap area (P = 0.044). Women presented a significantly lower amplitude asymmetry than men (P = 0.002). The weighted absolute left-right phase difference reached up to 24° and remained insignificantly higher in the men than the women (P = 0.142).

The study provides normative values for LS in young adults for the measurement of therapy outcomes in patients with voice disorders and realisation of evidence-based medicine. The LS parametrisation is easy to perform in clinical practice.