Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Dentomaxillofacial Radiology (2005) 34, 308–312 q 2005 The British Institute of Radiology http://dmfr.birjournals.org CASE REPORT An enlarged sella turcica on cephalometric radiograph H-P Chang*,1, Y-C Tseng2 and T-M Chou1 1 Faculty of Dentistry and Graduate Institute of Dental Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan; 2Department of Orthodontics, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan A 28-year-old male presented to the Orthodontic clinic for correction of his anterior crossbite due to mandibular prognathism as a result of pituitary adenoma with acromegaly. A radiographic cephalometric analysis and clinical orthodontic examination were made. This article describes in detail the methods of correcting the magnification of cephalometric linear measurements in sellar dimensions (length, depth and width) from lateral and posteroanterior cephalograms. Cephalometric findings revealed that the sella enlarged in all its dimensions with a deepening of the floor in this acromegalic case. We discuss the radiographic diagnosis of an enlarged sella turcica in intrasellar tumours and also emphasise the dentist’s important role in the initial diagnosis of pituitary adenoma cases. Dentomaxillofacial Radiology (2005) 34, 308–312. doi: 10.1259/dmfr/27388408 Keywords: sella; pituitary adenoma; acromegaly; cephalometric cephalograph Introduction The pituitary gland, also known as hypophysis, occupies the hypophyseal fossa, which is the deep depression in the sella turcica. The hypophysis is divided both functionally and embryologically into an anterior and a posterior lobe, the adenohypophysis and neurohypophysis, respectively.1 The most common cause of sellar enlargement is a primary intrasellar pituitary tumour, which is usually a pituitary adenoma.2 Pituitary adenomas are benign tumours located in the sella turcica and usually associated with hypersecretion of pituitary hormones. These hormones include growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), ovarian follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin (PRL). The GH-secreting pituitary adenoma leads to acromegaly, which is a highly disproportionate growth of the mandible and facial bones in post-pubertal patients, mainly a result of reactivation of the subcondylar growth zones and also due to periosteal bone apposition.3 Case report A 28-year-old male presented to the Orthodontic clinic at the Kaohsiung Medical University Hospital for correction *Correspondence to: Dr Hong-Po Chang, Department of Orthodontics, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan; E-mail: [email protected] Received 21 October 2004; revised 25 February 2005; accepted 15 March 2005 of his anterior crossbite due to mandibular prognathism. More than 8 months ago, enlargement of his lower jaw was noticed by his family and friends. Acromegaly caused by pituitary adenoma with excess secretion of GH was then detected by an endocrinologist, and the patient was referred to the neurosurgical department of the university hospital for further surgical treatment where he underwent transsphenoidal microsurgical removal of the pituitary adenoma using the Hardy method (microsurgical transsphenoidal hypophysectomy).4 A routine set of orthodontic diagnostic records was taken, consisting of upper and lower study models, intraoral and extraoral photographs, and radiographs (panoramic radiograph, lateral cephalometric and posteroanterior (PA) cephalometric radiographs) at the first visit to the Orthodontic clinic. He had a concave facial appearance, which is the most noticeable profile characteristic of acromegalic patient.5 The lateral profile indicated marked mandibular prognathism with a prominent chin, enlarged lips, a bulbous nose and prominent supraorbital ridges. Oral examination and study model analysis showed super Class III molar and canine relationships and bilateral posterior crossbite and anterior crossbite with minimal crowding of the lower arch. Cephalometric analysis revealed severe skeletal Class III malocclusion (ANB ¼ 2 8.18; norm in adult male: 3.58 ^ 1.48) with slight maxillary retrusion (SNA ¼ 808; norm: 84.38 ^ 2.58), severe mandibular prognathism (SNB ¼ 888; norm: 80.98 ^ 2.88) and very Enlarged sella turcica H-P Chang et al severe anterior crossbite (negative incisal overjet of 2 11.5 mm; norm: 3.3 mm ^ 1.4 mm). Following combined orthodontic and orthognathic surgical diagnosis, the orthodontic treatment of presurgical decompensation for dentoalveolar compensation6 of proclined maxillary incisors and retroclined mandibular incisors due to Class III skeletal relationship and the orthognathic surgery with bilateral intraoral vertical ramus osteotomy (IVRO)7 for mandibular setback were planned to correct the anterior crossbite and the prognathic mandible, if the acromegalic condition was well controlled and the pituitary adenoma was not recurrent. The patient was followed up for 1 year after the diagnosis in the university hospital. Endocrine studies revealed that the serum GH was not improved to normal level after transsphenoidal hypophysectomy and hormone control, and orthodontic examinations also showed that a slightly continuing growth change of the occlusion and the craniofacial structure. At this time he has not undergone orthognathic surgery. Upon examination of the initial lateral and PA cephalographs, an abnormally sized sella turcica was detected (Figure 1). The anteroposterior dimension (length) was 13.0 mm and the depth was 12.2 mm, which were deduced from measurements from the lateral cephalogram. The width was 16.5 mm, which was deduced from measurement from the PA cephalogram. These values exceeded normal figures for the dimensions of the sella in adult males of the 20 – 29 years age group (norms in sella length: 10.82 mm ^ 1.47 mm, depth: 8.32 mm ^ 1.11 mm, and width: 13.28 mm ^ 1.87 mm).8 The methods of correcting the magnification of cephalometric linear measurements from lateral and PA cephalograms are detailed in the discussion section of this report. The software9 used was written in the “MATLAB 5.3” (Version 2.3; CAESAR Lab, NCKU, Taiwan) and implemented on a 1.0 GHz Pentium III PC. Discussion The radiographic methods for detecting intrasellar tumours include lateral, Towne’s, PA, and axial views/projections of the skull.10 Computerized tomography (CT) scans have also proved helpful to measure the size of the intrasellar contents.11 The best method to determine the extent of sellar enlargement and detect the presence of intrasellar tumours is with magnetic resonance imaging (MRI).12 MRI is superior to CT in that it generates higher soft tissue contrast and has proved to be more sensitive for accurate delineation of sellar tumours and surrounding structures.13,14 Although CT scan and MRI have replaced plain films as the investigation of choice for suspected pituitary abnormalities, it remains nevertheless imperative for the dental and medical practitioners to be aware of the plain film appearance of sella turcica. The dental profession can play an important role in the detection of skull lesions. Orthodontists, in particular, routinely take lateral cephalographs as part of the process of orthodontic diagnosis, treatment planning, and assessment of therapeutic results. Hence they may be the 309 first to observe an abnormality in the sellar region of the cranium. This initial diagnosis by an orthodontist and subsequent investigation and evaluation by an endocrinologist or neurosurgeon might sometimes be lifesaving to the patient. The AP dimension (length) is the longest AP diameter of the sella, while the depth is the longest perpendicular dimension between the diaphragmatic line and the sellar floor.10,15 The sellar floor may be delimited laterally on the PA cephalograph thus yielding the width of the sella.10,15 The sellar floor is recognized in the PA view of the skull film in over 90% of cases and in 100% of cases using tomography.15,16 According to the “law of the similar triangles” the ratio of the corresponding sides is equal. Thus the magnification factor for the lateral cephalogram can be calculated by the following formula: magnification factor ¼ 150/(150 þ 15) ¼ 10/11 (anodeto-midsagittal ¼ 150 cm, midsagittal-to-film ¼ 15 cm). In this patient, the actual sella size was corrected from measurements from the lateral cephalogram. The length was 14.3 mm £ 10/11 ¼ 13.0 mm and the depth was 13.4 mm £ 10/11 ¼ 12.2 mm. The PA cephalogram presents different magnification. The magnitude of enlargement in the PA cephalogram is a function of the distance between the anode and the landmark as well as the distance between the anode and the cephalogram.17 This is the same geometric principle mentioned above in the lateral cephalogram. In this case the magnification factor for the PA cephalogram is the distance between the anode and the transporionic axis (150 cm) plus the corrected distance of the landmark (sella floor) to the transporionic axis measured from the lateral cephalogram (2.98 mm £ 10/11 ¼ 2.71 cm), divided by the distance between the anode and the film (150 cm þ 15 cm ¼ 165 cm). The actual width of the sella was 17.8 mm £ [(150 þ 2.71)/165] ¼ 16.5 mm. The radiographic differential diagnosis of an enlarged sella turcica includes acromegaly, adenomas, craniopharyngioma, empty sella syndrome, gigantism, intrasellar aneurysm, meningioma, Nelson syndrome, primary hypothyroidism, prolactinoma, and variant of normal.2,16,18,19 The most common cause of sellar enlargement is a primary intrasellar pituitary tumour, which is usually a pituitary adenoma.2 Patients with pituitary adenomas may present with symptoms of pituitary dysfunction and visual abnormalities. Sometimes patients with an enlarged sella are asymptomatic or present with only non-specific headaches.2,19 In this patient, no symptoms were present. Enlargement of his lower jaw was noticed by his family, thus triggering the investigation that led to the detection of a pituitary adenoma by an endocrinologist. Ninety per cent of patients with any clinical signs of a pituitary adenoma have an enlarged sella.2 An enlargement of the sella may be with or without bony destruction. In this case the sella enlarged in all its dimensions with a deepening of the floor. The patient had undergone surgical treatment by transsphenoidal microsurgical removal of the anterior pituitary adenoma4 8 months earlier. The surgical defect of the Dentomaxillofacial Radiology Enlarged sella turcica H-P Chang et al 310 Figure 1 (a) Lateral and (c) posteroanterior (PA) cephalographs with corresponding diagrams (b and d) illustrate the method for measurement of sellar dimensions. The surgical defect of the anterior sellar wall between four-to-five o’clock was discernible on the lateral cephalograph. The length measurement represented the longest anteroposterior (AP) diameter of the sella, while the depth measurement was the longest perpendicular dimension between the diaphragmatic line and the sellar floor (b). The width measurement was taken from the PA cephalograph. The diagram (d) indicated method of width measurement for the “rounded edge” sellar floor.26 The actual dimensions (length, depth and width) of the sella were deduced from measurements from the lateral and PA cephalograms. Correction of magnification of these linear measurements was detailed in the discussion anterior sellar wall between four-to-five o’clock is discernible on the lateral cephalograph. The surgical specimen obtained from this patient via transsphenoidal hypophysectomy was diagnosed by the pathological examination with light microscopy as basophilic pituitary adenoma. The pituitary adenomas can be Dentomaxillofacial Radiology subdivided into GH-secreting, ACTH-secreting, PRLsecreting, FSH, LH secreting tumours or mixed type tumours.20 The diagnosis should be pathologically verified by electron microscopy. Clinical symptoms are related to the type of hormone secreted. For instance, GH-secreting adenomas cause elevated blood GH levels, acromegaly in Enlarged sella turcica H-P Chang et al adults and gigantism in children and ACTH-secreting adenomas cause Cushing’s disease or Nelson’s syndrome. Prolactinomas (PRL-secreting adenomas) are marked clinically by amenorrhoea, galactorrhoea or loss of libido. Mixed GH- and ACTH-secreting adenoma generally results in acromegaly, Cushing’s disease or Nelson’s syndrome. Mixed GH- and PRL-secreting adenoma could be correlated to clinical findings, such as acromegaly, amenorrhoea, galactorrhoea or loss of libido. Transsphenoidal selective hypophysectomy is the most efficient and widely used method to treat acromegaly.21,22 However, the acromegalic patients have a substantial risk of recurrence of the pituitary adenoma, which causes growth changes in the facial skeleton even after removal of the pituitary adenoma and hormone control.21 The reported long-term cure rates of transsphenoidal hypophysectomy have been variable. Serri et al22 stated that the overall cure rate was 68%. Endocrine studies and orthodontic examinations should identify no relapse of the GH level or no significant change of the occlusion with the craniofacial structure in the acromegalic patient before the orthognathic surgery is performed for correction of the enlarged mandible and anterior crossbite. The pituitary gland occupies approximately 79% (on the average) of the volume of the sella turcica15 and thus considerable enlargement of the pituitary gland may not actually produce changes which can be seen on routine film of the skull. Roddriguez et al,23 in a prospective study of pituitary adenomas, found that the contents of the sella turcica decreased in height by up to 81%, and on average 311 58% following surgery, reaching their final size by the fourth month in most cases. The most significant reduction occurred during the first month. They concluded that the post-operative MRI appearance of the sella stabilized by 4 months when most of the post-surgical changes have resolved, and that the MRI was not useful for the follow-up of microadenomas (, 10 mm in diameter in the coronal images). A dangerous sequel of pituitary adenoma is known as pituitary apoplexy, which is a life-threatening episode caused by haemorrhagic infarction or necrosis of a pituitary tumour.12,24 Clinical manifestations include the sudden onset of headache, vomiting, signs of meningeal irritation, visual impairment, ophthalmoplegia, and deterioration of consciousness level.24 This initial phase can be life threatening and requires timely prompt treatment. Almost all patients who experience pituitary apoplexy have sellar enlargement that is detectable on lateral skull films.24,25 Therefore, early detection of sellar abnormalities may benefit the patient and sometimes avert a potentially life-threatening event. Acknowledgment The authors wish to thank Dr Yin-Ting Liu for assembling the clinical records examined in this study. This work was supported by research grant from the National Science Council of Taiwan (NSC 90-2314-B-037-087). References 1. Tyrrell JB, Findling JW, Aron DC. Hypothalamus and pituitary. In: Greenspan FS, Baxter JD (eds). Basic and clinical endocrinology. Norwalk, CT: Appleton & Lange, 1994; pp 39 – 47, 99 – 104. 2. Weisberg LA. Asymptomatic enlargement of the sella turcica. Arch Neurol 1975; 32: 483 –485. 3. Tornes K, Gilhuus-Moe O. Correction of jaw deformities subsequent to treatment of acromegaly. Int J Oral Maxillofac Surg 1986; 15: 446 –450. 4. Hardy J. Transsphenoidal hypophysectomy. Neurosurgical techniques. J Neurosurg 1978; 48: 13 –22. 5. Clayton RN. New developments in the management of acromegaly. Should we achieve absolute biochemical cure? J Endocrinol 1997; 155: S23 –S29. 6. Sarver DM, Proffit WR, Acherman JL. Diagnosis and treatment planning. In: Graber TM, Vanarsdall RL Jr (eds). Orthodontics— current principles and techniques (3rd edn). St Louis, MO: Mosby Inc, 2000, pp 3 – 115. 7. Ghali GE, Sikes Jr JW. Intraoral vertical ramus osteotomy as the preferred treatment for mandibular prognathism. J Oral Maxillofac Surg 2000, 58: 313 –315. 8. Ting LL, Liu HM, Huang SC, Huang KM, Hsu JCY. Polytomographic study of normal sella turcica in 959 Taiwanese. Chin J Radiol 1987; 12: 83 –91. 9. Chang HP, Liu PH, Chang HF, Chang CH. Thin-plate spline (TPS) graphical analysis of the mandible on cephalometric radiographs. Dentomaxillofac Radiol 2002; 31: 137 – 141. 10. Keats TE, Sistrom C. Atlas of radiologic measurement (7th edn). St. Louis, MO: Mosby Inc, 2001. 11. Swartz JD, Russell KB, Basile BA, O’Donnell PC, Popky GL. High resolution computed tomographic appearance of the intrasellar contents in women of childbearing age. Radiology 1983; 147: 115 – 117. 12. Cardoso ER, Peterson EW. Pituitary apoplexy: a review. Neurosurgery 1984; 14: 363 – 373. 13. Mikhael MA, Ciric IS. MR imaging of pituitary tumors before and after surgical and/or medical treatment. J Comput Assis Tomogr 1988; 12: 441 –445. 14. Davis PC, Horffman JC Jr, Spencer T, Tindall GT, Braun IF. MR imaging of pituitary adenoma: CT, clinical, and surgical correlation. Am J Neuroradiol 1987; 8: 107 – 112. 15. Di Chiro G, Nelson KB. Volume of the sella turcica. Am J Roentgenol Radium Ther Nucl Med 1962; 87: 989 –1008. 16. McLachlan MSF, Wright AD, Doyle FH. Plain films and tomographic assessment of the pituitary fossa in 140 acromegalic patients. Br J Radiol 1970; 43: 360 – 369. 17. Hsiao TH, Chang HP, Liu KM. A method of magnification correction for posteroanterior radiographic cephalometry. Angle Orthod 1997; 67: 137 –142. 18. Pribram HW, du Boulay GH. Sella turcica. In: Newton TH, Potts DG, (eds). Radiology of the skull and brain. St Louis, MO: CV Mosby, 1971, pp 357 – 405. 19. Kunick JE, Hartman CR, Lufkin BG, Hofeldt FD. Abnormal sella turcica. A tumor board review of the clinical significance. Arch Intern Med 1977; 137: 111 – 117. 20. Howng SL, Wang JR. Ultrastructure of the human pituitary adenoma. Kaohsiung J Med Sci 1987; 3: 661 –667. 21. Long H, Beauregard H, Somma M, Comtois R, Serri O, Hardy J. Surgical outcome after repeated transsphenoidal surgery in acromegaly. J Neurosurg 1996; 85: 239 – 247. 22. Serri O, Somma M, Comtois R, Rasio E, Beauregard H, Jilwan N, et al. Acromegaly: biochemical assessment of cure after long term follow-up of transsphenoidal selective adenomectomy. J Clin Endocrinol Metab 1985; 61: 1185– 1189. Dentomaxillofacial Radiology Enlarged sella turcica H-P Chang et al 312 23. Roddriguez O, Mateos B, de la Pedraja R, Villoria R, Hernando JI, Pastor A, et al. Postoperative follow-up of pituitary adenomas after transsphenoidal resection: MRI and clinical correlation. Neuroradiol 1996; 38: 747 –754. 24. Vidal E, Cevallos R, Vidal J, Ravon R, Moreau JJ, Rogues AM, et al. Twelve cases of pituitary apoplexy. Arch Intern Med 1992; 152: 1893 –1899. Dentomaxillofacial Radiology 25. Fitz-Patrick D, Tolis G, McGarry EE, Taylor S. Pituitary apoplexy: the importance of skull roentgenograms and computerized tomography in diagnosis. JAMA 1980; 244: 59 – 61. 26. Underwood LE, Radcliffe WB, Guinto FC. New standards for the assessment of sella turcica volume in children. Radiology 1976; 119: 651 – 654.