To clarify the anatomical correlations of the sphenoid sinus with surrounding structures in the normal Korean population, and to identify surgical landmarks for safe sellar floor dissection in the anterior skull base by endoscopy and microscopy.
We reviewed the 196 brain magnetic resonance imaging findings showing a normal appearance, and measured the distances between anatomical landmarks.
The mean distances from the base of the columella to the anterior wall of the sphenoid sinus and the sellar floor were 69.71±4.25 mm and 86.26±4.57 mm, respectively in the over 15 age group, and showed the smallest degree of variation among the measurements. The mean angles between the floor of the nasal cavity and the straight line connecting the base of the columella and the sellar floor were 29.45±3.25° and 24.75±4.00° in the over 15 and under 15 age groups, respectively. The mean values of both distances and angles increased with age until 15 years after which no further increases were evident. There were no significant differences in the measurements between males and females or among subjects with different degrees of pneumatization in the over 15 age group.
The distances from the base of the columella to the sellar floor and the anterior wall of the sphenoid sinus, which were consistent among individuals, could be used as a surgical indicator to investigate the sellar floor in endoscopic or microscopic transsphenoidal approaches.
The endoscopic and microscopic transsphenoidal approach has become a standard procedure for the removal of pituitary tumors as it has numerous advantages compared to the transcranial approach
We reviewed all results of brain magnetic resonance imaging (MRI) conducted at our hospital between July and December 2009. The majority were conducted during evaluation of patients presenting with neurological symptoms, such as seizure or headache. Among these, we found 196 MRIs that showed a normal appearance. We reviewed MRIs of normal anatomy as patients with problems in pituitary tend to have variable sizes in anatomical structures. The patients ranged in age from 1 to 86 years (mean : 45.64±24.29 years), and were distributed evenly throughout all age ranges. The gender distribution was 87 males to 109 females.
We selected three candidates for surgical landmarks that could be found easily during surgery : the base of the columella (BOC), the most inferior portion of the anterior wall of the sphenoid sinus (AS), and the planum sphenoidale (PS). Although the distance from anterior nasal spine (ANS) to sphenoid anterior wall had been well reported, ANS is not exposed during endoscopic surgery. So, we chose base of columella, which is always noticeable during endoscopic approach, as candidate for surgical landmark. We measured the distances from BOC to AS and PS was taken and the angle between the floor of the nasal cavity and the straight line connecting BOC and sellar floor (SF) was also measured (
In the over 15 age group, the average distances between the BOC and AS and between BOC and SF were 69.71±4.25 mm and 86.26±4.57 mm, respectively, and also showed the smallest degree of variation, indicating that the distances were consistent among individuals. The mean angle between the floor of the nasal cavity and the straight line connecting BOC and SF (which is related to the direction of the microscope or endoscope during surgery) was 29.45±3.25° in the over 15 age group and 24.75±4.00° in the under 15 age group. The craniocaudal length between the anterior wall of sphenoid sinus and sella was 16.22±2.92 mm and the average of sellar height was 8.54±2.06 mm in the over 15 age group. The mean intercarotid distance (ICD) in the axial cut was 17.61±3.06 mm in the over 15 age group and 13.21±2.28 mm in the under 15 age group (
With regard to the degree of pneumatization of the sphenoid sinus, the study population included 15 cases of conchal pneumatization (7.7%), 14 cases of presellar type pneumatization (7.1%), 82 cases of sellar type pneumatization (41.8%), and 85 cases of postsellar type pneumatization (43.4%). As maturation of the sphenoid sinus is not completed until 15 years of age, patients were divided into two groups above and below this age
We analyzed changes in the distances and angles with age by dividing the patients into age groups at intervals of 3 years (
The endoscopic and microscopic transsphenoidal approach is considered the standard approach for surgical treatment of pituitary tumors
Despite these developments in surgical technique and equipment, sellar floor dissection remains challenging, particularly when the sphenoid sinus is poorly pneumatized or the sellar bulge is poorly demarcated. Hamid et al.
There is a paucity of reports regarding safe dissection of the sellar floor in such cases, although there have been many radiological and anatomical studies analyzing anatomical features of the sphenoid sinus. Here, we measured the distances and angles between the sellar floor and surgical landmarks in 196 healthy brain MRIs. Although the distances between these bony structures may be somewhat inaccurate in MRI in comparison to computed tomography (CT), MRI can provide relatively sharp delineation of important soft tissue structures, such as the carotid artery, sella turcica, sella floor, and the air-filled sphenoid sinus wall. We chose MRI as it is favored over CT as a preoperative evaluation in surgery involving pituitary adenomas, and can yield precise measurements comparable to those obtained by CT.
We calculated both the mean values and standard deviation of all measurements obtained to allow evaluation of consistency and possible application to surgery (
The mean ICD in the present study was 17.61±3.06 mm, which was larger than that reported previously
Previous studies regarding the normal development of the sphenoid sinus indicated that the onset of initial pneumatization varies from 6 months to 4 years of age, and that pneumatization is completed by 12 to 14 years
All measurements were significantly larger in the over 15 age group than in the under 15 age group. Interestingly the angle between the nasal floor and the line connecting the BOC and SF was also smaller in the under 15 age group. Taken together, these observations suggest that surgeons should maintain a lower angle with the endoscope or microscope in pediatric patients than in adult patients. We studied the relationships between the distances and angles with age by dividing the patients into study groups at intervals of 3 years (
We examined the changes in the distances and angles related to the degree of pneumatization, but found no significant differences between the study groups. These results suggest that the relative locations of SF and surgical landmarks are consistent regardless of pneumatization of the sphenoid sinus. In addition, these observations suggest that the measurements obtained in the present study would be applicable in patients with varying levels of pneumatization in the sphenoid sinus.
The distances between the BOC and both SF and AS were consistent among individuals older than 15 regardless of pneumatization of the sphenoid sinus. These distances could therefore be used as surgical landmarks to investigate the sellar floor with the mean angle between the nasal floor and the line connecting the BOC and SF, particularly in patients with poor pneumatization of the sphenoid sinus or an inapparent sellar bulge.
Measurement of the distances between the base of the columella (BOC) and the anterior wall of the sphenoid sinus (AS) and between the BOC and the sellar floor (SF) on T1 weighted fast spin-echo sagittal images of the brain. We measured the line drawn between the BOC and the SF (double arrowed line) and determined the shortest distance between the BOC and the AS (dashed line) on that line. In addition, the angle (asterisk) between the nasal cavity floor and the line connecting the BOC and the SF was measured.
Measurement of the anteroposterior distances between the anterior wall of the sphenoid sinus (AS) and the sellar floor (SF) and the craniocaudal distances between the planum sphenoidale (PS) and the SF on T1 weighted fast spin-echo sagittal images of the brain. We chose one point on the SF at which the perpendicular bony wall from the tuberculum sella turns horizontally, and measured the distance between the AS and the SF (horizontal line) and determined the shortest distance between the horizontal line and the PS (vertical line).
The shortest distances between both internal carotid arteries and the anterior-most portions of the cavernous segment (C4) were measured on T2 weighted fast spin-echo axial images of the brain (double arrow).
Mean values of the distance in patients grouped according to age at intervals of 3 years. A : Changes in distance between the base of the columella (BOC) and the sellar floor (SF) with age. B : Change in distance between the BOC and the anterior wall of the sphenoid sinus (AS) in relation to age. Mean values of the distance increased until age 15 and then showed a plateau.
Mean values and standard deviation of the distances and angles in the over and under 15 age groups
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Distribution of pneumatization of the sphenoid sinus in over and under 15 age groups
Mean values and standard deviation of all measurements with varying pneumatization of the sphenoid sinus. There were no significant differences between groups in any measurements (one-way ANOVA)
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