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ORIGINAL ARTICLE
Year : 2022  |  Volume : 29  |  Issue : 1  |  Page : 27-32

Size and shape of sella turcica among Down syndrome individuals in a Nigerian population


Department of Dental Surgery, Orthodontic Unit, Federal Medical Centre, Keffi, Nasarawa State, Nigeria

Date of Submission15-Jun-2021
Date of Acceptance19-Jul-2022
Date of Web Publication15-Nov-2022

Correspondence Address:
Dr. Osaronse Anthony Aghimien
Department of Dental Surgery, Orthodontic Unit, Federal Medical Centre, Keffi, Nasarawa State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/wajr.wajr_29_21

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  Abstract 


Background/Aims: This study was conducted to determine the size and shape of sella turcica (ST) among Down syndrome (DS).
Materials and Methods: The size of the ST was determined among 29 DS (mean age 13.76 ± 2.41 years), while the shape of the ST was among 25 DS individuals (mean of 13.84 ± 2.41 years) who met the inclusion criteria. Statistical significance of linear measurement in relation to gender was evaluated using an independent t-test, while Chi-square test was used to analyze the occurrence and significance of the shape. A statistically significant level was set at P < 0.05.
Results: ST length (STL), depth (STD), and anterior–posterior diameter (STAPD) were 9.00 ± 3.23 mm, 7.61 ± 1.51 mm, and 10.45 ± 2.79 mm, respectively. Female DS had a larger value for STD and STAPD than males (P > 0.05). The pyramidal shape of the dorsum sella accounted for the largest deviation (28.3%) in shape. A change in shape of the ST tend to affect the depth (F = 1.669, P = 0.204) and diameter (F = 1.425, P = 0.263) than its effects the length.
Conclusion: The depth and diameter of ST were observed to be larger than normal individuals within the same age range documented in the literature. Abnormal deviation in the shape of sell turcica may have contributed to the variation in the length, depth, and diameter. A deviation in the size and shape of ST could be considered etiological factor in the development of malocclusion among Down syndrome individuals.

Keywords: Down syndrome, sella turcica, shape, size


How to cite this article:
Aghimien OA. Size and shape of sella turcica among Down syndrome individuals in a Nigerian population. West Afr J Radiol 2022;29:27-32

How to cite this URL:
Aghimien OA. Size and shape of sella turcica among Down syndrome individuals in a Nigerian population. West Afr J Radiol [serial online] 2022 [cited 2022 Dec 7];29:27-32. Available from: https://www.wajradiology.org/text.asp?2022/29/1/27/361185




  Introduction Top


The sella turcica (ST), also called the hypophyseal fossa is a saddle-shaped area in the sphenoid bone located in the middle cranial fossa.[1] It is bounded anteriorly by tuberculum sellae, posteriorly by dorsum sellae, and inferiorly by the bony roof of the sphenoid air sinus.[2] Anterior to the ST is the anterior cranial base while the posterior cranial base is distal to it. The ST houses the hypophyseal gland and any abnormality in the development of the gland could affect its size and morphology.[3],[4] It forms an important landmark to which the jaws are related to the anterior cranial base and for analyzing pathologies of the pituitary gland or several syndromes affecting the craniofacial region.[3] Several studies on the ST in different population have revealed possible variations in the sizes and morphology of ST among normal individuals which may be due to ethnic or racial differences.[5],[6],[7],[8],[9],[10] The size and morphology of the ST can be altered by various craniofacial defects and syndromes.[11] These conditions include cleft lip and palate, Down syndrome (DS), William syndrome, and fragile X-syndrome among others.[12],[13],[14],[15],[16],[17]

DS is a common chromosomal disorder caused by nondisjunction or translocation of the extra 21st chromosome.[18] The gene mutation in DS is reported to cause premature fusion of the cranial sutures and resultant reduction of the cranial base or an increased cranial base.[19],[20],[21],[22],[23] The S-point is an anatomic landmark located on the lateral cephalometric radiograph within the ST, therefore deviation in its size and morphology has been correlated with certain malocclusion traits with larger ST size being reported to be more prevalent in class III malocclusion, while smaller size sella turica was more common in class II malocclusion.[3],[24],[25],[26],[27],[28] As an individual advances in age, the size of the ST tends to increase also.[29],[30] The dimension tends to vary with race, as a lesser dimension has been reported in Africans when compared to Caucasians.[7] There is the scarcity of information on the sizes and morphology of ST among DS individuals in our environment which could have contributed to the development of malocclusion among DS in our environment.[31],[32] Although it has been established that reduced anterior cranial base and the reduced maxillary length among DS may have contributed to the development of class III malocclusion,[19],[20],[21] it is also important to ascertain if the deviation in the size and morphology of ST in DS would be a pointer to development of this malocclusion traits. Studies on the size and morphology of ST appeared skewed toward normal individuals with very few studies on DS.[14] Saudis individuals with DS were observed to have a larger length and diameter of ST with abnormal deviation in the normal shape.[14] The abnormal deviation in the shape of ST observed among the Saudi DS corroborates the earlier findings made by another author, that abnormal ST shape was present in 23% of the group Russians with DS.[13] This present study was conducted among a certain group of DS individuals in Nigeria with the aim of documenting findings in this environment and comparing the findings with observations made by several studies on normal and DS individuals in the literatures.


  Materials and Methods Top


Study setting

The study was conducted among DS individuals recruited from special need schools and homes within Benin City metropolis, Edo state Nigeria and also from Ibadan City metropolis, Oyo state (South-West, Nigeria).

Sampling method

DS participants were recruited using the convenience sampling method due to the peculiarity of this individuals and the age range being considered.

Study design and study population

A cross-sectional descriptive study was conducted among the DS participants between 10 and 20 years of age.

Thirty-eight DS individuals were initially recruited for the study. Twenty-two DS individuals were recruited from special need schools/homes in Benin City metropolis (South-South, Nigeria) and another 16 DS individuals were recruited from special need schools/homes within Ibadan City metropolis (South-West, Nigeria). All the DS were clinically classified using the Fried diagnostic index.[33] Lateral cephalograph of those recruited from the Benin metropolis were taken at Shalom Dental Clinic in Benin City while those from the Ibadan City metropolis were taken at the Dental Centre of the University College Hospital, Ibadan.

The inclusion criteria included; those within the study age group, individuals for whom informed consent had been given. Individuals with previous orthodontic treatment, those with difficult neck stability and those with distorted radiographs were excluded.

Following the inclusion criteria, only 29 participants were evaluated for the length, depth, and diameter of the ST, while 25 met the criteria for the shape of the ST to be evaluated. The mean age of the participants included in the length, depth, and diameter of the ST was 13.76 ± 2.41 years, while the mean age of the participants evaluated for shape was 13.84 ± 2.46 years

Ethical consideration

Ethical approval (ADM/E 22/A/VOL VII/1236) for this research protocol was obtained from the University of Benin Teaching Hospital Ethics and Research Committee before data were collected. Written informed consents were obtained from the parents and guardians of the DS individuals before they were recruited for the study.

The linear dimensions of the ST were measured using Vernier caliper traced on a matte acetate paper using a pointed HB pencil under a lightbox. Evaluations of the linear dimensions of the ST were done at two different session of 2 weeks interval for intra-assessor reliability assessment which was 0.79.

Data analysis

The data were analyzed using IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY (USA): IBM Corp. Statistical significance between frequencies of occurrence of the linear measurement was evaluated using an independent t-test. Chi-square test was used to analyze the occurrence and significance of the categorical data (shape). One-way ANOVA was used to test the effect of change in shape on the linear dimensions of ST among the DS. A statistically significant level was set at P < 0.05.

Lateral cephalometric measurement of sella turcica

The ST on each lateral cephalometric radiograph was be traced on a thin acetate paper under optimal illumination. The tuberculum sella, sella floor, dorsum sella will be outlined on the lateral cephalograph. All reference lines used in the study were located in the mid-sagittal plane. A schematic representation of the landmark is shown in [Figure 1], while a lateral cephalograph of a DS participant recruited for the study is shown in [Figure 2].
Figure 1: Reference points and lines according to Kisling.[20] TS – Tuberculum sella; DS- – Dorsum sella; BPF – Base of the pituitary fossa; L – Length of the sella turcica; D – Diameter of the sella turcica; APD – antero-posterior diameter of the sella turcica

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Figure 2: Lateral cephalograph of a Down syndrome participant (a) recruited for the study with the location of the sella turcica highlighted (b)

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  • Tuberculum sella: The most anterior point on the contour of ST
  • Sella floor: The deepest point on the floor of the ST
  • Dorsum sella: The posterior wall of the ST.


Size of sella turcica

Three linear measurements of the ST which include length, diameter, and depth in mid-sagittal plane were obtained according to the method described by Kisling, as shown in [Figure 1].[20]

Length

The distance between the tuberculum sella to the tip of dorsum sella.

Depth

A line perpendicular to the length and to the deepest point on the floor.

Antero-posterior diameter

Line drawn from the tuberculum sella to the most posterior point on the posterior inner wall of the fossa.

Morphology (shape) of the sella turcica

The different morphological appearances of the ST described by Axelsson et al.[16] was be used to classify shapes of ST in this study [Figure 3]. They include:
Figure 3: The different types of sella turcica according to Axelsson et al.[16] (a) normal sella turcica, (b) oblique anterior wall, (cs) double contour of the floor, (d) sella turcica bridge, (e) irregularity in the posterior part of the sella turcica, (f) pyramidal shape of the dorsum sella

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  1. Oblique anterior wall
  2. ST bridging
  3. Double contour of the floor
  4. Irregularity (notching) in the posterior part of the dorsum sella
  5. Pyramid shape of dorsal sella.



  Results Top


The average mean values of the ST length (STL), depth (STD), and anterior-posterior diameter (STAPD) is shown in [Table 1]. Female DS narrowly had a larger value for STD and STAPD than male DS participants but were not statistically significant, as shown in [Table 2]. Majority of the DS participants had normal shape of ST (56.0%) while about 44% had an abnormal shape of the ST. The pyramidal shape of the dorsum sella accounted for the largest proportion (28.3%) of morphological deviation from normal ST shape, followed by notching of the posterior wall with oblique anterior wall least represented with 4%, [Table 3]. [Table 3] also shows gender variations in the distribution of the morphology of the shape of the turcica with most of the female DS (57.1%) appearing normal. Pyramidal shape of the dorsum sella occurred more frequently in males (36.7%) than females (28.6%) DS. All the DS participants with notching of the posterior wall were males, accounting for 21.4% of presentation among the males. The impact of morphological deviation on the linear dimensions of the ST was evaluated using one-way ANOVA shown in [Table 4]. The result showed that the STD (F = 1.669, P = 0.204), followed by the STAPD (F = 1.425, P = 0.263) were mainly affected, although not statistically significant.
Table 1: Distribution of the average mean values dimensions of the sella turcica

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Table 2: Distribution of the dimensions of the sella turcica in relation to gender

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Table 3: Distribution of the morphology of the sella turcica

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Table 4: Effect of change in shape on linear dimension of sella turcica

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  Discussion Top


The size and shape of the ST have majorly been reported among normal population.[5],[7],[16]

However, some authors have compared the size and shape of ST of DS with controls.[3],[15] Observations made concerning the dimension and shape of ST among DS in this present study will be compared to normal control value in the region where this study was conducted and also with the pattern of occurrence in studies conducted between DS and normal individuals.

In comparison with the norms proposed by a previous author for normal individuals with different skeletal patterns[5] with participants of a similar age range of this present study, it was observed that DS had a larger anterior-posterior diameter and depth of ST. This pattern, therefore, agrees with the observation made by the previous author.[3] The observation made in this present study also corroborates results among 7–12 years old group in the depth and diameter of ST and among 13–20 years old in the length and diameter of ST in the study conducted by another researcher.[15] Divers views exist, especially in relation to the age when the dimension of ST of DS are compared to normal individuals.[3],[15] Alkofide reported a larger STL, depth, and diameter than normal individuals aged 12–22 years[3] while varying observation was made by another author in another case–control study between DS and normal population in relation to the various age range.[15]

The length of ST of DS in the present study in comparison with previously studied normal individuals appeared shorter which is at variance with the observation made by the other authors.[3],[15] The length of ST of DS in this present study was, however, noted to be larger than observation made among another group of non-DS normal individuals in Nigeria.[9] This corroborates the observation made by ALkofide among Saudi DS individuals that dimensions of ST in DS are larger than normal individuals of the same age.[14] Larger dimensions of ST among normal Nigerian individuals in comparison with the observation among DS in this present study has been reported author.[7] This could be attributed to the adult population recruited in the study conducted by the author,[7] which further reemphasizes the influence of age in the dimension of DS.[29],[30] The alteration in the size of the ST observed in this present study may be related to depression of the base of the anterior wall of DS fetus previously reported.[34] When other craniofacial syndromes like William syndrome and cleft lip and palate are considered, their ST dimensions appeared smaller than the control as against that of DS.[3],[29] The present study shows that the diameter and depth of the ST were larger among female DS while the length was larger among male DS. This pattern is replicated among normal individuals in a previous study[5] but at variance with an earlier study conducted among DS with males having greater dimensions in STL, depth, and diameter.[15] The size of the ST tend to vary with the skeletal pattern with a larger length and diameter of ST tending toward the development of class III skeletal pattern.[25] Findings from this present study are therefore suggestive that the dimension of ST in DS may have contributed to the development of malocclusion in DS.

DS individuals have a high tendency to develop abnormal shapes of the ST.[3] The present study revealed a high percentage (44%) of abnormal shapes of the ST. While the pyramidal shape of the dorsum sella accounting for the highest morphological deviation in the present study, the oblique anterior wall had earlier been reported to be more prevalent by a previous author.[3] The racial difference and population size of the study could have accounted for the difference observed.

An earlier study had reported type 1 ST with almost normal shape and mild obliqueness of the anterior as most prevalent in a postnatal study among DS <12 years of age.[13] This present study reported 56% of normal ST among the DS individuals. The change in shape tends to mainly affect the depth and diameter of the ST in DS although not statistically significant. This further strengthens the findings of larger depth and diameter among DS in this present study and as reported in the literature.[3],[15]


  Conclusion Top


This present study, therefore, revealed that the depth and diameter of ST among DS were larger than those of normal individuals documented in the literature conducted in the same region.

The length of the ST was observed to either be shorter or larger when compared with studies conducted among normal individuals.

The present study also shows that the diameter and depth of the ST were larger among female DS while the length was larger among male DS.

A high percentage (44%) of DS individuals had deviation in the shape of the ST with the pyramidal shape of the dorsum sella (28.3%) accounting for the highest morphological deviation followed by notching of the posterior wall (12.0%).

Observation made in this present study also reveals that a change in the shape of the ST tends to affect the depth and diameter than its effect on the length of the ST.

A deviation in the size and shape of ST should therefore be considered as possible etiological factor in the development of malocclusion among DS individuals.

Recommendation

The present study appears to be the pioneer study of the size and shape of ST among DS in Nigeria; therefore, further studies is recommended for a more comprehensive comparison of the size and shape of ST between DS and normal individuals.

Also, to impact more on the findings among DS individuals, it would be interesting to conduct a study using the CT scan.

Acknowledgement

Sincere thanks to Prof E. O Ajayi and Prof I. N Ize-Iyamu for the enormous support received when this study was been conducted.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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