Clinical features, endoscopic images of laryngoscopy and pathological anatomy of vocal cord cysts

This shows that most cases of vocal cord cyst lesions also cause loss of symmetry similar to other benign lesions of the vocal cords.

4.3.5. Periodicity

In our study, 100% (29/29) of patients had periodicity on laryngeal stroboscopic testing. Of these, the majority of patients had irregular periodicity 72.4% (21/29). A small number of patients had regular periodicity on laryngeal stroboscopic testing, accounting for 27.6% (8/29).

This result is similar to the study on vocal cord polyps by Nguyen Thi Hong Nhung (2016) when 42/70 patients, accounting for 60%, had irregular cycles on laryngeal stroboscopic testing [51].

This shows that there is a similarity in the periodicity on laryngeal stroboscopic between vocal cord cysts and vocal cord polyps. The periodicity is the regular movement of the vocal cords, normal, regular and periodic vibration. Because the process of forming the lesion has affected the elasticity, the expansion of the submucosal layer, changing the phase difference, affecting the vibration cycle of the vocal cords.

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4.3.6. Glottic closure phase

In our study, 89.7% of glottis were not closed. This result is also consistent with Nguyen Khac Hoa [41] when 95.6% of glottis were not closed and Shohet [30] was 100% (30/30).

According to the physiology of pronunciation, the closed phase of the glottis requires a balance between the closed phase and the open phase and no physical damage to the vocal cords. A glottal cleft occurs when there is an imbalance between the two phases of closure and opening and the damage is large enough to prevent the two vocal cords from closing.

4.3.7. Vocal cord spasm

According to our study, 1/29 patients had spasm on laryngeal stroboscopic testing, accounting for 3.4%.

The cause is due to the patient abusing the voice for a long time, leading to a disorder in the coordination of the laryngeal muscles, creating an opposition.

resistance. Specifically, the case of vocal cord spasm in our study also had symptoms of prolonged hoarseness that started more than 1 year ago.

4.3.8. Relationship between wave amplitude and hoarseness duration

Wave amplitude decreased in 23/29 patients, accounting for 78.6%. Of which, 3/5 patients in the group with illness duration of less than 1 month had decreased wave amplitude, accounting for 60%, 13/17 patients in the group with illness duration of 1-6 months had decreased wave amplitude, accounting for 76.5%. Notably, 100% (6/6) of patients in the group with illness duration of more than 6 months had decreased wave amplitude.

This shows that the longer the disease lasts, the more it affects the amplitude of the wave. Therefore, patients should be diagnosed and treated early for better results. Wave amplitude depends largely on two factors: mass and stiffness. Causes of reduced amplitude include physical damage to the vocal cords, increased closing pressure, high and loud sounds. Therefore, improving the voice can be overcome by speaking in a low voice, not speaking loudly, limiting speaking, and increasing the flow of inhaled air.

4.3.9.Relationship between laryngeal stroboscopy frequency and age group

The average laryngeal stroboscopic frequency of the study subjects was 213.0 Hz. The 23-35 age group had the highest average laryngeal stroboscopic frequency of 225.4 Hz; in the 36-45 age group, this average frequency was 208.8 Hz and the lowest was in the 46-55 age group with an average laryngeal stroboscopic frequency of 207.3 Hz.

Because the pitch of the voice is directly related to the frequency of the vocal cords' vibration. The frequency is lower and deeper if the vocal cords are longer. According to Hirano M. (1986), the total length of the vocal cords increases gradually until the age of 20 [52]. In this study, we found a decrease in the frequency of laryngeal stroboscopic activity in the age group of 20-55, consistent with the increase in vocal cord length. However, there was a difference in the age group over 55 when the average frequency was 210.3 Hz, higher than the two age groups of 26-45 and 46-55, which can be explained by the small sample size of the research group, causing the difference.

4.3.10. Relationship between laryngeal stroboscopy frequency and gender

Of the 29 subjects participating in the study, 16 were female and 13 were male. The mean laryngeal stroboscopy frequency of females was 245.6Hz, which was higher than the mean frequency of males, 165.5Hz.

Average frequency (F0) is the frequency of vocal cord vibrations per second, measured in Hz. Frequency is inversely proportional to vocal cord length, so frequency in women is usually higher than in men.

4.3.11. Pathological results

In our study, the majority of cysts were mucous cysts (89.7%), while epidermoid cysts accounted for only 10.3%. Our results were similar to those of Nguyen Khac Hoa [41]. However, they were not consistent with Zoran, in 37 patients studied, the results showed 65% of epidermoid cysts and 35% of mucous cysts [20]. The inconsistency may be due to the small sample sizes of ours and Zoran, which were not representative enough.

Mucous cysts are usually located on the free edge of the vocal cords, the cyst shell is covered by 2 thin layers of columnar glandular epithelium. They contain mucous fluid from the mucosa. Mucous cysts develop from blockage of the glandular duct. Epidermoid cysts develop from the consequences of repeated trauma, or remaining epidermal fragments in Reinke's space. The cyst shell is composed of desquamated, keratinized cells. The cyst lumen contains white tissue mixed with cholesterol and keratin crystals. Epidermoid cysts are usually located on the upper surface of the vocal cords [20,30].

CHAPTER 5: CONCLUSION

5.1. Clinical characteristics of vocal cord cysts:

- Vocal cord cysts are mainly found in the 35-45 age group, with an average age of 43.38 ± 10.9.

- The incidence of the disease is higher in women (58.6%).

- Favorable factors that trigger the disease and promote its progression are alcohol and tobacco use (34.4%), voice abuse (24.1%) and internal medical conditions.

- The time from illness to medical examination is mainly within 6 months (75.8%).

- Hoarseness is the main symptom and the reason for medical examination in 100% of cases. Some other common symptoms: feeling short of breath, tiredness when speaking (48.3%) and sore throat (10.3%).

5.2. Laryngeal endoscopic images and pathological anatomy

- The most common tumor location is in the middle third of the vocal cords (96.6%) and occurs equally on both sides (50-50%).

- Laryngoscopy showed: reduced wave amplitude and loss of wave symmetry (78.6%), irregular periodicity (72.4%), and differential closure plane (68.9%).

- The frequency of laryngeal stroboscopic tests decreases with age and is higher in women.

- The main pathological lesion is mucinous cyst (89.7%).

RECOMMENDATION

Although our study has many limitations with small sample size, short research time and retrospective study, we would like to make some recommendations as follows:

1. For family and community

- Use the right voice, suitable for each individual's voice quality.

- Early and thorough treatment of inflammatory diseases in the nose, throat, larynx, and gastroesophageal reflux syndrome at an early stage.

- Limit the use of tobacco and stimulants that contain alcohol.

- Propaganda and advice people to go to the doctor immediately when mild hoarseness symptoms appear to get treatment and achieve the best treatment results.

2. For medical doctors

Benign lesions of the larynx always manifest as hoarseness. Therefore, for patients with signs of hoarseness, laryngoscopy should be indicated to accurately assess laryngeal lesions and thereby assess the condition of the nose and throat. This helps the doctor to make an early and correct diagnosis, thereby providing appropriate treatment.

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