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Osseous Variations of the Hypoglossal Canal Area Published: 2009.03.01 Authors’ Contribution: Georgios K

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Osseous Variations of the Hypoglossal Canal Area Published: 2009.03.01 Authors’ Contribution: Georgios K © Med Sci Monit, 2009; 15(3): BR75-83 WWW.MEDSCIMONIT.COM PMID: 19247236 Basic Research BR Received: 2008.01.08 Accepted: 2008.03.31 Osseous variations of the hypoglossal canal area Published: 2009.03.01 Authors’ Contribution: Georgios K. Paraskevas1ADE, Parmenion P. Tsitsopoulos2BEF, A Study Design Basileios Papaziogas1AC, Panagiotis Kitsoulis1CD, Sofi a Spanidou1D, B Data Collection 2 C Statistical Analysis Philippos Tsitsopoulos AD D Data Interpretation E Manuscript Preparation 1 Department of Human Anatomy, Aristotle University of Thessaloniki, Thessaloniki, Greece F Literature Search 2 Department of Neurosurgery, Hippokration General Hospital, Aristotle University of Thessaloniki, Thessaloniki, G Funds Collection Greece Source of support: Self fi nancing Summary Background: The hypoglossal canal is a paired bone passage running from the posterior cranial fossa to the na- sopharyngeal carotid space. Hyperostotic variations of this structure have been described. Material/Methods: One hundred sixteen adult cadaveric dried skull specimens were analyzed. Several canal features, dimensions, and distances relative to constant and reliable landmarks were recorded. Results: One osseous spur in the inner or outer orifi ce of the canal was present in 18.10% of specimens (42/232). Two or more osseous spurs were evident in 0.86% of specimens (2/232). However, com- plete osseous bridging, in the outer or inner part of the canal, was evident in 19.83% of specimens (46/232). Osseous bridging extending through the entire course of the canal was visible in 1.72% of the specimens (4/232). The mean lateral length of the canal was 10.22 mm, the mean medial length was 8.93 mm, the mean transverse and vertical diameters of the internal orifi ce were 7.44 mm and 4.42 mm, respectively, and the mean transverse and vertical diameters of the external or- ifi ce were 6.15 mm and 3.91 mm, respectively. The mean inclination of single hypoglossal canals was 42.3° and 32.4° on the right and left side, respectively. Conclusions: A detailed and accurate evaluation of the hypoglossal canal topographic anatomy with regard to specifi c, standard osseous landmarks was performed. Additional data with respect to several mor- phologic features of the hypoglossal canal area also was obtained. Results of this study provide im- portant information that will enable effective and reliable surgical intervention in the area of the hypoglossal canal. key words: hypoglossal canal • anatomy • morphology • surgical approaches • skull base • jugular tubercle Full-text PDF: http://www.medscimonit.com/fulltxt.php?ICID=869578 Word count: 3441 Tables: 5 Figures: 7 References: 36 Author’s address: Georgios Paraskevas, Department of Human Anatomy, Aristotle University Medical School, P.C: 54124, P.O. Box: 300, Thessaloniki, Greece, e-mail: [email protected] Current Contents/Clinical Medicine • IF(2007)=1.607 • Index Medicus/MEDLINE • EMBASE/Excerpta Medica • Chemical Abstracts • Index Copernicus BR75 Basic Research Med Sci Monit, 2009; 15(3): BR75-83 BACKGROUND ed with an electronic goniometer. In cases of a double hy- poglossal canal, the inclinations of both canals, the length The hypoglossal canal is a bony canal located in the oc- of the septum in partially divided hypoglossal canals, and cipital bone. It lies in the epiphyseal junction between the the distances between the medial and lateral internal ori- basal portion and the jugular process of the occipital bone fi ces of both canals were also recorded with the use of an [1,2]. Variations of the hypoglossal canal are not uncom- electronic goniometer and an electronic digital caliber. mon. Different types, such as bridging and double canals, Finally, associations of partially and totally divided hypo- have been reported, and several attempts have been made glossal canals with adjacent structures, such as jugular fo- to describe them thoroughly [3,4]. ramen bridging, the posterior condylar canal, and occipi- tal condyle morphology, were registered. Differences were Tumor lesions of the skull base in this area were considered measured and analysed using t-test and the level of signifi - to be inoperable not long ago. The surgical approaches are cance was set at p<0.05. technically demanding and complicated, and removal of the lesions is always problematic. However, the introduction of RESULTS advanced microsurgical tools (high-speed drills, suction-ir- rigation devices, microinstruments, etc) has improved re- Two hundred thirty-two hypoglossal canals were examined section and curability of these lesions [2,5,6]. from a total of 116 skulls. The skulls were from 62 men and 54 women. The position of the hypoglossal canal was con- To identify the exact osseous characteristics and topograph- sistently located in the occipital bone just anterior, inferi- ic relations between the canal and adjacent structures rel- or, and slightly medial to the anterior-inferior edge of the ative to stable and reliable anatomic landmarks, we exam- jugular foramen. The canal extended slightly anteriorly in ined variability in the morphology of the hypoglossal canal an inferior-medial to superior-lateral direction. in a large number of specimens. A second aim of this study was to investigate the association of specifi c canal types with Osseous variations in the hypoglossal canal were identi- neighboring anatomic structures. Clinical aspects regarding fi ed (Table 1). One osseous spur located either in the in- surgical intervention in this area are discussed. ternal or external orifi ce of the canal (type 2) was present in 42 canal specimens (18.10%; Figure 1A). Two or more MATERIAL AND METHODS osseous spurs (type 3) were visible in 2 canal specimens (0.86%; Figure 1B). Complete osseous hypoglossal bridg- One hundred sixteen dried skulls from patients aged 20–80 ing of the internal or external portion of the canal (type years at the time of death were used in this study. The 4) was evident in 46 canal specimens (19.83%; Figure 1C). material examined included skulls from the collection Finally, complete osseous bridging (double canal) extending of the Department of Anatomy of Aristotle University of along the entire canal (type 5) was found in 4 sides (1.72%; Thessaloniki. All skulls were from white patients. Data were Figure 1D). Type 1 corresponds to a single canal according collected from both male and female specimens because to the classifi cation of Hauser and De Stefano [3], and in slight sex differences in the incidence of anterior condylar the present study was found in the majority of specimens canal variations have been reported [7,8]. The occipital (59.49%) (Table 1). bones were checked carefully to ensure that they contained the occipital condyle and that the hypoglossal canals were Measurements of canal inclination in nondouble hypoglos- intact bilaterally. Surrounding bony structures were metic- sal canals relative to the midsagittal plane and the distance ulously identifi ed and preserved. The hypoglossal canals of the center of the internal orifi ce of double hypoglossal were clearly delineated. canals from the midpoint of the condylar portion of the oc- cipital bone are shown in Table 2A and Figure 2. In addition, Several measurements were obtained. First, the exact mor- measurements of canal inclination in cases of divided hypo- phology of the hypoglossal canals was recorded. Dimensions, glossal canals (type 4 and type 5) were obtained (Table 2B). such as the lengths of the lateral and medial walls and the The mean transverse and mean vertical diameters of the in- transverse and vertical diameters of the internal and exter- ternal orifi ce were 7.44 mm and 4.42 mm, respectively (Table nal orifi ces of the canal, were calculated with the aid of an 3A). The mean transverse and mean vertical diameters of the electronic digital caliper. The relative position of the in- external orifi ce were 6.15 mm and 3.91 mm, respectively. In ternal orifi ce of the canal with respect to the adjacent sta- cases of partially and totally divided hypoglossal canals, the ble anatomic landmarks, thus the distance of the internal mean medial length was 9.56 mm, the mean lateral length orifi ce of the canal from the midpoint of the the condylar was 11.64 mm, the mean transverse and vertical diameters portion of the occipital bone, the vertical distance from the of the medial internal orifi ce were 4.51 mm and 5.12 mm, internal orifi ce to the lateral border of the foramen mag- respectively, the mean transverse and vertical diameters of num and to the medial border of the sigmoid sulcus, and the lateral internal orifi ce were 2.71 mm and 2.62 mm, re- the distance to the ipsilateral edge of the transverse diam- spectively, and the mean transverse and vertical diameters eter of the foramen magnum were also measured with an of the external orifi ce were 7.12 mm and 6.51 mm, respec- electronic digital caliper. Similarly, the distance from the tively (Figure 3; Table 3). external orifi ce of the hypoglossal canal to the midpoint of the anterior border of the foramen magnum and the verti- The mean medial length of the canal was 8.93 mm, whereas cal distance of the external orifi ce from the lateral border the mean lateral length was 10.22 mm (Table 3A, Figure 4). of the foramen magnum was registered with the aid of an The mean vertical distance from the center of the internal electronic digital caliper. The inclination of the hypoglos- orifi ce of the canal to the lateral border of the foramen mag- sal canal relative to the midsagittal plane also was record- num was 7.41 mm, to the medial border of the sigmoid sul- BR76 Med Sci Monit, 2009; 15(3): BR75-83 Paraskevas GK et al – Osseous variations of the hypoglossal canal area Table 1A.
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