## 4 Discussion  
Our findings showed that PP, SB and APAD were significantly correlated with the occurrence of MCI and this is in agreement with other studies [1]. The lateral radiographs only provide a sagittal view while a computed tomography examination may be helpful to confirm this diagnosis; however, [PERSON] et al. [17] demonstrated that the presence of skeletal variations in the cervical vertebral anatomy exhibited a high concordance between lateral radiographs and CBCT (cone beam computed tomography) radiographs, therefore the lateral radiographs are often sufficient to identify skeletal abnormalities in the cervical vertebral section. Moreover, it is important to highlight that each subject was not treated orthodontically before the radiographs were taken; in fact, orthodontic patients may exhibit some anatomical variants but not MCI because of the improvement due to the orthodontic treatment. Furthermore, patients of the control group had some orthodontic problems; however, a normal control group without any orthodontic problem was not included since, in a retrospective study, only the patients with orthodontic problems were allowed to perform lateral cephalograms. Since these skeletal anomalies seem to be detectable radiographically at an early age, this could help the clinician to suspect a possible dental displacement. [PERSON] et al. stated that the presence of PP was independent of age, therefore PP cannot be considered exclusively as a process of calcification or ossification due to aging but it is congenital in origin [18]. [PERSON] et al. [19] found a non-statistically significant association between increased sella bridging and palatally displaced canine while [PERSON] et al. [7] observed an increased SB in subjects with MCI. It was observed that the sellae length was almost immutable, whereas the depth and diameter changed with growth, thus the morphological aberration about its length occurs during pre-natal growth while post-natal modification is responsible just for the variations in size [20]. Sella turcica shape does not depend on patients' age in the age range of 6 through 21 and there could be an x-linked genetic disorder behind SB as it has been shown for the MCI: However, most cases of SB are detected at early stages in life calcification may continue over time [16]. The atlas develops during the seventh week of gestation, the fusion of the posterior arch synchondrosis usually occurs at age 5 years and the ossification is complete at 7 years of age [2]. Morphological defects of atlas (C1) are therefore congenital and they can be found in patients' radiographs at an age that is considered the minimum age for collaboration and the minimum age for requiring radiological investigations. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**MCI (Not Severe)**} & \multicolumn{3}{c}{**MCI (Severe)**} \\ \hline  & **RRR** & **IC 95\%** & \(p\)**-Value** & **RRR** & **IC 95\%** & \(p\)**-Value** \\ \hline Ponticulus posticus, (\%) & & & & & & \\ Grade 1 a  & 1 & & & 1 & & \\ Grade 2 & 1.86 & 0.70–3.03 & **0.002** & 1.45 & 0.14–2.77 & **0.030** \\ Grade 3 & 2.05 & 0.26–3.84 & **0.024** & 2.41 & 0.62–4.20 & **0.008** \\ Grade 4 & 1.26 & 1.25–4.15 & 0.124 & 1.48 & \(-\)0.43–3.06 & 0.140 \\ \hline Sella Bridging, (\%) & & & & & & \\ Grade 1 a  & 1 & & & 1 & & \\ Grade 2 & 1.06 & \(-\)0.22–2.34 & 0.105 & 0.74 & \(-\)0.50–1.99 & 0.241 \\ Grade 3 & 2.00 & 0.54–3.45 & **0.007** & 0.71 & \(-\)0.90–2.34 & 0.384 \\ \hline Atlas posterior arch & & & & & & \\ deficiency, (\%) & & & & & & \\ Improbable a  & 1 & & & 1 & & \\ Possible & 1.25 & \(-\)0.39–2.91 & **0.014** & 1.96 & 0.40–3.53 & **0.014** \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Estimated relative risk ratios of having severe or not severe MCI by multinomial logistic regression. PP, SB and APAD can be related to medically relevant signs and symptoms: patients with APAD may show head and neck pain [3].