International Journal of Dental and Health Sciences Original Article Volume 04,Issue 01
MORPHOMETRIC ANALYSIS OF SELLA TURCICA AND ITS CLINICAL SIGNIFICANCE Priya Damodaran1, Yuvaraj.M2, Priyadarshini.A3, Sankaran.P.K4, Kalaiarasi.P5, Madhu Radhakrishnan6 1. Student, Compulsory Rotarory Residential Internship, Ragas dental college and hospital, Tamil nadu 2. Tutor, Department of Anatomy, Saveetha medical college and hospital, Thandalam, Tamil nadu 3. Tutor, Department of Anatomy, Saveetha medical college and hospital, Thandalam, Tamil nadu 4. Associate professor, Department of Anatomy, Saveetha medical college and hospital, Thandalam, Tamil nadu 5. Student, Compulsory Rotarory Residential Internship, Ragas dental college and hospital, Tamil nadu 6. Student, Compulsory Rotarory Residential Internship, Ragas dental college and hospital, Tamil nadu
ABSTRACT: Sella turcica is an important and commonly used cranial landmark in many ventures. This work aims to measure and study sella turcica size and shape variations which is important for neurologists and neurosurgeons to avoid any damage to the sellar region and in identifying any pathological signs involving pituitary gland. The study was done with 102 dried human skulls where the gender of the skulls was not taken into consideration. The study was mainly concentrated to analyze the parameters of sella turcica. The average of sella turcica length, breadth and depth were calculated to be 10.59mm, 10.76mm and 9.23mm respectively. Most commonly found shape of sella turcica is normal (56.8%). These observations are essential in providing reference standard values. Keywords: Sella turcica, Sella size, Sella shape, Hypophyseal fossa
The Sella turcica, a saddle shaped chiasma, inferiorly by sphenoid sinus, depression, is an important bony entity medially by cavernous sinus, oculomotor which is located in the body of the nerve, trochlear nerve, abducent nerve, sphenoid bone of the middle cranial ophthalmic nerve, maxillary nerve, fossa and is bounded by the two anterior internal carotid artery. and two posterior clinoid processes. The seat of the saddle, the deepest part of The prenatal and postnatal formation of the sella turcica, known as the pituitary gland and sella turcica are hypophyseal fossa along with complex processes. During prenatal tuberculum sellae and dorsum sellae formation, pituitary gland and sella forms the whole of the sella turcica. The turcica, the two important structures are hypophyseal fossa lodges the Pituitary located in the boundary region, gland, the master endocrine gland also separating tissues of different origin and known as the ‘conductor of endocrine development. Origin of the pituitary orchestra’. The roof is diaphragm sella, gland is a result of interaction between which is circular fold of duramater oral ectoderm which gives rise to attached to anterior clinoid process and anterior pituitary and neural ectoderm posterior clinoid process.  Sella turcica gives rise to posterior pituitary. The is surrounded anteriorly by optic pituitary fossa differentiates directly from the hypophyseal cartilage which in
*Corresponding Author Address: Dr. Priya Damodaran. E-mail: [email protected] Priya D.et al, Int J Dent Health Sci 2017; 4(1):77-84 turn is derived from the cranial neural Department of Anatomy of Ragas Dental crest cells of the early chondrocranium. College and Hospital, Uthandi, Chennai, Tamilnadu. Sex of the skulls was not During embryological development, sella taken into consideration but skulls of turcica area is the key point for the extreme ages were avoided. Any migration of the neural crest cells to the abnormalities or fusion of anterior, fronto nasal and maxillary middle and posterior clinoid processes developmental fields. Formation and were noted and excluded. development of the anterior part of the pituitary gland, sella turcica, and teeth The morphometric parameters share in common, the involvement of concentrated in this study are the neural crest cells, and dental epithelial length, breadth, depth (in mid-sagittal progenitor cells differentiate through plane) and also the shape variations of sequential and reciprocal interaction sella turcica. The linear measurements with neural crest-derived mesenchyme. are calculated with Digimatic vernier Posterior part of the pituitary gland caliper and scale. And the measurements develops from the paraxial mesoderm from columella to hypophyseal fossa and which is closely related to notochordal glabella to hypophyseal fossa are also induction.  measured. These values are vital to the neurosurgeons operating in that area. During the postnatal development, deposition of bone on the anterior part SIZE OF SELLA TURCICA: of the interior surface of the sella turcica ceases at an early age, whereas Numerous studies have been done on resorption on the distal part of the sella the size of sella turcica, however the floor and on the posterior wall continues methods differ widely. Due to difference for a longer period of time. Deposition of in the method of measurement, bone was seen on the tuberculum sellae comparisons to other studies should be and resorption at the posterior boundary done with caution. of sella turcica up to 16-18 years of In this current study the parameters are age. determined with the reference methods The purpose of this study is to analyze of Silverman. Figure 1(a) and (b) predominant morphological parameters Sella turcica length is obtained by and various shapes and abnormalities of measuring the distance between the sella turcica and contributing to establish midpoint of tuberculum sellae and reference standard values. midpoint of dorsum sellae.  MATERIALS AND METHODS Sella turcica depth is measured at the The study was conducted on 102 dried deepest part of the sella and is at right human skulls obtained from the
Priya D.et al, Int J Dent Health Sci 2017; 4(1):77-84 angles to the direction of the length of Shape of sella turcica: sella turcica. The morphological variations in sella Sella turcica breadth is measured from turcica have been reported by many the midpoint of the medial margin of researchers through time. The study carotid sulcus of both sides. done by Axelsson in 2004 is used as comparative standards for this study and SHAPE OF SELLA TURCICA: the variations in shape of sella turcica is observed in our study skulls. Frequency The study by Axelsson was used to of each shape is tabulated in Table 3. determine the shape of sella turcica, according to which 5 variations in DISCUSSION : morphology of sella turcica are described apart from normal The anatomy of sellar region is very morphology. much vital for neurosurgeons and the discussion about the parameters The different morphological types of measured in our study is done below. sella turcica are (a) normal sella turcica (b) oblique anterior wall (c) double Size of sella turcica: contour of the floor (d) irregularity in the posterior part of sella turcica (e) A microsurgical anatomical study on 250 pyramidal shape of dorsum sellae. spheroidal blocks from cadavers of Illustrated in figure 2. different ages was performed by Quakinine and Hardy and found that the OBSEVATION AND RESULTS: average transverse width of sella turcica was 12 mm, length was 8 mm, and the Size of sella turcica: average height was 6 mm. Silverman  in his extensive longitudinal radiographic The morphometric parameters of the investigation of 320 subjects from 1 sella were measured on 102 study skulls month to 18 years of age reported that in terms of millimeters. Sex comparison sella turcica was larger in males than in or age factors were not noted in this females except during puberty. study. Measurements were taken and Axelsson studied the size of Norwegian mean values and standard deviation males and females longitudinally from 6 were calculated in table 1. to 21 years of age with normal facial The measurements needed for trans appearance and normal occlusion. The nasal and trans sphenoidal approach depth and diameter in males and (needed during surgery) is also taken in females were similar but the length was this study and their average values and larger in males. Alkofide  studied the standard deviation were calculated and lateral cephalograms of 180 Saudi tabulated in table 2. subjects with an age range of 11-26 years with different skeletal types.
Priya D.et al, Int J Dent Health Sci 2017; 4(1):77-84 Diameter of sella turcica was larger in hypophyseal fossa were measured and class III subjects and smaller in class II the average was found to be 85 mm and subjects. It was found that there were no 80 mm respectively. These statistically significant differences measurements are very helpful to the between males and females in all the surgeons during procedure. three linear dimensions. When linear dimensions were compared with age, Shape of sella turcica: the size of sella turcica was larger in The shape of sella turcica was classified older age group than in the younger age by Gorden and Bell in 1922 by group. According to Preston,  pituitary examining radiographs of children of age fossa increased in size with age and ranging from 1 year to 12 years as found a positive correlation of the area circular, oval, and flattened or saucer- of the sella to age. After 26 years of age, shaped and majority of the subjects had no significant increase was observed on either a circular or oval shaped sella. the size. The dimensional changes in the Other classifications were based on the sella turcica had a significant positive contours of the sella floor, the angles linear trend to length, depth, and formed by the contours of anterior and diameter until 25 years of age. posterior clenoid processes and Our current study gives the mean of sella tuberculum sellae and the fusion of both turcica length, breadth and depth which clenoid processes as sella turcica  aids in obtaining the morphological bridge. In a recent study by Axelsson et knowledge of sella. These mean data can al in 2004, shape of the sella turcica was be used as reference values. This divided into six main types [fig 2]; knowledge of the sella turcica is normal sella turcica, oblique anterior important for neurologists and wall, double – contoured sella, sella neurosurgeons operating in the region of turcica bridge, irregularity (notching) in cavernous sinus or the surrounding the posterior part of the sella and structures helping them to avoid injury pyramidal shape of the dorsum sellae. to structures in the vicinity to the sella In our study the normal variation was turcica. Endoscopical surgery with trans observed in 56.8% of the subjects nasal and trans sphenoidal approaches whereas 39.2% were seen different are the most commonly used variation. The finding of oblique anterior approaches by neurologists and wall in the current study and Axelsson neurosurgeons while operating in the study is similar. The pyramidal shape of hypophyseal or its adjacent area and the dorsum sella was more frequent in since sella turcica serves as an important the current study than Axelsson study. landmark, it is essential to know the size The presence of sella turcica bridge was variations of this region. The distance seen in 6% -16 % of the subjects, from columella to hypophyseal fossa and however none were found in our study. the distance from glabella to 80
Priya D.et al, Int J Dent Health Sci 2017; 4(1):77-84 Similarly the double contour of the floor and to themselves. These relationships was not found in our study. Irregularity provide the orthodontist with a perfect in the posterior part of sella turcica i.e. a study tool in determining the growth of notched appearance is seen in 17.64% an individual through superimposition of whereas in Axelsson study it was found structures on a longitudinal basis, and in 11% of the subjects. The shape during evaluation of orthodontic variations is a significant factor since it treatment results. helps in identifying any enlargement or erosions of the bone which throws some It is traceable for metric analysis which light into diagnosing any pathologies of makes it an excellent source of  the gland. information and thorough knowledge of anatomy of this region is important to Some pituitary adenomas can extend neurologists and neurosurgeons dealing inferiorly, growing downward and with the pathologies and anomalies of invading the sphenoid bone and this region. Pathological enlargement of cavernous sinus. Adenomas greater than the pituitary fossa can be detected by 10mm (macroadenomas) can cause this technique and in diagnosing remodeling of the underlying sphenoid anomalies or tumors of the pituitary bone altering the shape of the sella gland, like pituitary adenoma which is turcica. In such cases it is essential to the commonest tumor of the pituitary know the normal variations of the shape gland. Recognizing variations of the of sella turcica for an appropriate morphology is important in preventing diagnosis and in strategizing treatment damage during surgery. plans. CONCLUSION: CLINICAL SIGNIFICANCE: Approximately 57 percent of the study Sella turcica is an important landmark had a normal sella turcica. The results of readily seen on lateral cephalograms and the current study of sella size and shape acts as a noteworthy reference point in may be used as reference guide in cephalometric analysis which is doubtful cases of pathological commonly done prior to skull based enlargement of the pituitary fossa. procedures.[14,15] In orthodontics, sella Identifying the variations helps in point which is located at the center of preventing damage during surgery. sella turcica is one of the most Growth of the individual can be assessed commonly used landmarks in based on the size of the sella turcica at cephalometrics. Such landmarks are different age period which can be used used to measure the positions of maxilla as a diagnostic tool in orthodontic and mandible in relation to the cranium treatment.
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TABLES: Length of sella turcica Breadth of sella turcica Depth of sella turcica Mean value 10.59mm 10.76mm 9.23mm Standard deviation 1.77 2.24 1.45
Table 1: Mean and standard deviation for length, breadth and depth of sella turcica
Distance from columella to Distance from glabella to hypophyseal fossa hypophyseal fossa Mean value 85mm 80mm Standard deviation 2.11 1.72
Table 2: Mean and standard deviation required for trans nasal and trans sphenoidal approaches.
SELLA TYPE FREQUENCY Normal sella turcica 58 Oblique anterior wall 14 Double contour of the floor 0 Irregularity in the posterior part of sella turcica 18 Sella turcica bridge 0 Pyramidal shape of dorsum sellae 12 Total 102
Table 3: Frequency of morphological shapes of sella turcica
Priya D.et al, Int J Dent Health Sci 2017; 4(1):77-84 FIGURES:
Figure 1: (b) Measuring length and Figure 1: (a) Reference lines used for breadth of sella using a digimatic measuring sella size: TS Tuberculum verniercaliper sellae, DS Dorsum sellae, BPF Base of pituitary fossa; Black line- length of sella; dotted line- depth of sella
Figure 2: Morphological types of sella turcica