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Dentomaxillofacial Radiology (2005) 34, 308–312
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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
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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
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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
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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).
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