Discussion
Although the mechanisms underlying the asymmetry of the human face has been subject to comprehensive research, no conclusive results have been obtained to date. Several factors including developmental or genetic factors, as well as those related to soft tissue orientation, prenatal stress, and environment (low temperature) have been described in the literature (15, 16). One of the hypotheses proposed by Moss is that the septal deviation has a negative impact on facial development, with the affected side being less well-developed (17). Another hypothesis has proposed that the nasal septum is also asymmetrical and deviated as a result of the development of the facial bones (18, 19).
Hafezi et al. evaluated facial asymmetry in deviated noses and reported that the left side of the nose, left half of the face, and left side of the body were greater in size, and that the nose was deviated to the less well-developed side (20). Furthermore, Ercan et al. (2008) found higher dimensions in the anatomical structures forming the left half of the face in a Turkish cohort. In our study, the bony nasal pyramid was deviated to the right and left in 59.4% and 40.6% of those participants with an asymmetric bony nasal pyramid, respectively. Although the difference was statistically insignificant, a trend for right-sided deviation was observed.
In a previous study examining whether nasal growth differed by sex, the nasal growth was completed at 15.8 and 16.9 years of age in boys respectively, indicating a statistically significant difference (21). In another study evaluating the extent of variation in timing, duration, and intensity of growth in the craniofacial complex during childhood and adolescence, Nahhas et al. reported that, in male adolescents, as opposed to females, the peak velocity of the anteroposterior growth of the maxilla occurred earlier than 14 years of age, and that the growth continued until the age of 20 years, although it was at a lower rate(22). In the current study including male adolescents aged 15, 16, and 17 years, the nasal bony pyramid deviation, caudal septal deviation, and nostril asymmetry did not increase and, on the contrary, a minimal, insignificant degree of reduction was observed. Based on these findings, we can speculate that male adolescents in these age groups reach a stable point during nasal growth.
Caudal septal deviations refer to deviations of the one-third caudal portion of the nose. Although review of the literature reveals several studies on problems (aesthetic and/or functional) associated with the caudal septal deviations and proposing treatment recommendations, there is no study available examining its incidence during adolescence (between 15 and 17 years of age). The classification for septal deviation proposed by Mladina et al. (1987) includes Type 1, 2, and 4 caudal septal deviations and allows a diagnosis to be established by inspection and Cottle’s maneuver. In another study Marin and Mladina (2001) reported that the overall incidence of Type 1, 2, and 4 deviations among patients aged between 15 and 18 years was 40.7%. Although no significant correlation was observed with caudal deviations and sex, Type 1 was the most common type with a significant decline with aging. In the aforementioned studies, no data regarding the side of the deviation were given. In contrast, 25.6% of the participants had caudal septal deviation and, of these, 74.2% were to the right in our study. Since septal deviation has an impact on the size of nostrils, it is not surprising to observe smaller nostrils in participants with septal deviation to the right. Similarly, in 75.5% of the adolescents with asymmetric nostrils, the right nostril was smaller.
In general, questionnaires and performance studies are utilized to evaluate the hand dominance. Among these, questionnaires are more frequently used tools thanks to their practical nature. In this study, we asked participants to choose one of their hand as dominant according to daily tasks such as writing, use of knives and forks, throwing, and tooth brushing. Some large-scale studies have reported a prevalence of 89.6% to 94.1% for right-hand dominance (23). Consistent with these reports, 91% and 9% of our participants were right- and left-hand dominant, respectively. Since nasal deviations without a major trauma are thought to have developmental and genetic underlying mechanisms, we attempted to evaluate the possible relationships between hand dominance and nasal deviations in our study. To the best of our knowledge, there is no study available investigating this potential link. Among our adolescent boys cohort, 61.2% of those with a nasal deviation to the right had right-hand dominance, while 58.3% of those with nasal deviation to the left were left-hand dominant. Although these associations were not statistically significant, a trend in nasal deviations was noted toward the side of the hand dominance.
Furthermore, in those with caudal septal deviation to the right, 76.6% were right-hand dominant, while 50% were left-hand dominant in those with a deviation to the left. Again, these associations were not significant. This might be due to a small number of adolescents with caudal septal deviation and left-hand dominance. In our study, the caudal part of the septum was evaluated through inspection, without the use of any equipment (speculum, endoscope) or imaging studies such as direct X ray or computed tomography. Inspection allows the assessment of the nasal bony pyramid and caudal septum only. This examination method was chosen on the basis of the fact that it was non-invasive and associated with minimal discomfort, suitable for adolescents under 18 years of age with no history of trauma. Although inspection is considered adequate for the accurate evaluation of the asymmetry, quantitative measurements (speculum and endoscopic examination) and imaging studies would allow better quantification of such conditions.
Another main finding of the present study is that 84.6% of those with caudal septal deviation had nasal bone pyramid deviation to the right, and 91.2% of those with a septal deviation to the left had nasal bone pyramid deviation to the left. This finding supports the axiom “as the septum goes, so goes the nose” proposed by Maurice Cottle and suggests that the nasal septum also determines the direction of the external deviation. In this context, it may be worth noting that the importance of the cartilage septum on the development of the nose and maxilla was underscored by Verwoerd and Verwoerd-Verhoef (24).
Nonetheless, there are some limitations to this study. First, no imaging tool such as CT or nasal endoscopy was used for a more accurate evaluation of the septal deviation. Determination of nasal septal deviation was done by purely visual analysis, so there would be many false negatives which would skew the data. Second, the hand dominance was evaluated for the left and right hands and ambidexterity was disregarded. In general, two tests are used to evaluate hand dominance: one for self-report questionnaire and the other one for functional ability and skills. In this study, however, hand dominance was evaluated by questioning the preference of hand during daily living activities such as writing. We used this method to improve the attention of adolescents to the questionnaire. Also, the school setting did not allow for a functional evaluation. Third, this study does not cover girls since it was conducted in schools where only boys attend. We are of the opinion that it will be appropriate to include girls in the next studies to obtain the correct results.