Key points
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Skull base ligamentous mineralisation is common and seen in most age groups, aside from the posterior petroclinoid ligament, which is has a stronger association with age, reflecting its dural origin.
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Mineralisation of the interclinoid and caroticoclinoid ligaments can increase the risks of several surgical procedures at the skull base (including during the treatment of aneurysms). Knowledge of such structures is important in operative planning.
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Ossified ligaments have been associated with neural impingement syndromes of the abducens nerve (petrosphenoid ligament), oculomotor nerve (petroclinoid ligament), and mandibular nerve branches (pterygospinous and pterygoalar ligaments).
Introduction
Materials and methods
Ligament | Course | Plane used for evaluation |
---|---|---|
Interclinoid ligament | Double oblique sagittal | |
Caroticoclinoid (anterior interclinoid) ligament | Double oblique axial | |
Petrosphenoid (Grüber’s) ligament | Double oblique sagittal | |
Posterior petroclinoid ligament | Double oblique sagittal | |
Pterygospinous (Civinini) ligament | Double oblique sagittal | |
Pterygoalar (Hyrtl-Calori or ‘innominate’) ligament | Extends from the root of the lateral plate of pterygoid process to the infratemporal surface of the greater sphenoid wing, lateral to the foramen spinosum. Historically, complete mineralisation of the pterygoalar ligament was termed the porus crotaphiticobuccinatorius of Hyrtl (derived from the historic term for the mandibular nerve with deep temporal—or crotaphitic—and buccinator branches) [20‐22]. | Double oblique sagittal |
Results
Demographics
Ligament type
Total (n) | Proportion (%) | |
---|---|---|
Interclinoid | 53 | 22.1 |
Petroclinoid | 44 | 18.3 |
Caroticoclinoid | 42 | 17.5 |
Pterygospinous | 41 | 17.1 |
Petrosphenoid | 26 | 10.8 |
Pterygoalar | 15 | 6.3 |
Bilateral | Unilateral | ||||||||
---|---|---|---|---|---|---|---|---|---|
Total | Complete (%) | Mixed* (%) | Partial (%) | Total | Complete (%) | Partial (%) | |||
% |
n
| % |
n
| ||||||
Interclinoid | 45.3 | 24 | 29.2 | 12.5 | 58.3 | 54.7 | 29 | 20.7 | 79.3 |
Caroticoclinoid | 59.5 | 25 | 60.0 | 24.0 | 16.0 | 40.5 | 17 | 52.9 | 47.1 |
Petrosphenoid | 26.9 | 7 | 14.3 | 0.0 | 85.7 | 73.1 | 19 | 26.3 | 73.7 |
Petroclinoid | 56.8 | 25 | 4.0 | 4.0 | 92.0 | 43.2 | 19 | 10.5 | 89.5 |
Pterygospinous | 34.1 | 14 | 7.1 | 42.9 | 50.0 | 65.9 | 27 | 14.8 | 85.2 |
Pterygoalar | 20.0 | 3 | 33.3 | 66.7 | 0.0 | 80.0 | 12 | 16.7 | 83.3 |
Ligament thickness | Mean foramen size | ||||
---|---|---|---|---|---|
Mean (mm) | SD (mm) | Mean (mm2) | SD (mm2) | Range (mm2) | |
Interclinoid | 1.8 | 0.5 | 75.2 | 22 | 43–142 |
Caroticoclinoid | 1.8 | 0.8 | 25.3 | 4.4 | 24–40 |
Petrosphenoid | 1.1 | 0.5 | 7.2 | 5.5 | 2–18 |
Petroclinoid | 1.3 | 0.5 | 39 | 14.5 | 24–60 |
Pterygospinous | 0.95 | 0.3 | 39.9 | 32.9 | 2–112 |
Pterygoalar | 1.2 | 0.4 | 13.3 | 7.2 | 4–25 |
Multiple ligaments
Limited systematic review
Author | Number included | Population | Age range | Mineralisation | Significance | ||
---|---|---|---|---|---|---|---|
Partial | Complete | Both | |||||
Caroticoclinoid ligament | |||||||
Current study | 240 CT studies | UK | 6–80 years | 5% | 10% | 17.5% (includes mixed 2.5%) | – |
Archana et al. [26] | 250 dry skulls | India | – | 6.80% | 5.20%** | 12% | Neurosurgical implications. |
Boyan et al. [27] | 34 dry skulls | Turkey | Adults | 35.3% | Neurosurgical implications. | ||
Brahmbhatt et al. [28] | 50 dry skulls | India | Adults | Not assessed (complete only) | 2/50 skulls (4%) | – | Need for awareness amongst radiologists and neurosurgeons. |
Dagtekin et al. [29] | 15 cadaveric heads + 25 dry skulls | Turkey | – | 10% | 15% | – | Neurosurgical implications. |
Efthymiou et al. [30] | 76 dry skulls | Greece | Adults | 69.3% (of ossified ligaments)—equivalent of 46% of total | 30.7% (of ossified ligaments)—equivalent of 20.4% total** | 74% | Neurosurgical implications. |
Erturk, Kayalioglu, and Govsa [31], | 119 dry skulls + 52 cadaveric heads | Turkey | – | 14.91 | 8.77%** | 35.67% | Neurosurgical implications and relationship with cavernous sinus. |
Fernandez-Miranda et al. [6] | 100 CT angiograms + 50 anatomic specimens | USA | – | – | 20% | – | Importance with respect to endonasal neurosurgery. |
Gibelli et al. [32] | 300 CT head scans | Italy | 18–99 years | – | 8.70% | – | Association between interclinoid and caroticoclinoid bridging. No association with age or sex. |
N. Gupta, Ray, and Ghosh [33] | 35 dry skulls | Nepal | – | 11.40% | 8.60%** | 20% | Neurosurgical implications. |
Keyes 1935 [12] | 2187 dry skulls | USA | 1 day–105 years | – | – | 34.84% | Details of the anatomical features of mineralised ligament. Complete ossification present in cases as young as 21 days. |
Kapur and Mehić [34] | 200 dry skulls | Bosnia and Herzegovina | 19–91 years | 9.75% | 7%** | 16.75% | Neurosurgical implications. |
Lee et al. [35] | 73 dry skulls | Korea | n/s | 11.60% | 4.10% | 15.7% | Neurosurgical implications. |
Miller, Chamoun, and Beahm [3] | 150 maxillofacial CTs | USA | – | – | 41.80% | – | Neurosurgical implications for expanded endoscopic approaches. |
Natsis et al. [14] | 123 dry skulls | Greece | 20–91 years | 36.60% | 23.60% | 60.16% | Association between complete mineralisation and age and bilaterality. |
Ota et al. [2] | 72 CT angiograms for paraclinoid aneurysms | Japan | – | – | – | 16.60% | Use of preoperative CT prior to extradural anterior clinoidectomy. |
Peker et al. [8] | 80 dry skulls | Turkey | – | – | – | 34.2% | Neurosurgical implications. |
Sharma et al. 2018 [5] | 2726 dry skulls | USA | 18–105 years | 42%* | 31%** | – | Neurosurgical implications including risks of injury to the internal carotid artery. |
Skrzat, Mroz, and Marchewka [19] | 80 dry skulls | Poland | Adults | – | 16.3% | – | Neurosurgical implications and effects upon the internal carotid artery. |
Suprasanna and Kumar [36] | 54 CT angiograms | India | 18–70 years | – | – | 22.20% | Importance of imaging in pre-operative planning in treating paraclinoid aneurysms. |
Aggarwal, Gupta, and Kumar [37] | 67 dry skulls | India | – | 13.4% | 3.0% | 16.4% | Neurosurgical implications. |
Interclinoid ligament | |||||||
Current study | 240 CT studies | UK | 6–80 years | 15.4% | 5.4% | 22.1% (includes mixed 1.3%) | – |
Archana et al. [26] | 250 dry skulls | India | – | 2.40% | 1.60%** | 4% | Neurosurgical implications. |
Boyan et al. [27] | 34 dry skulls | Turkey | Adults | 5.9% | 5.9% | 11.8% | Neurosurgical implications. |
Brahmbhatt et al. [28] | 50 dry skulls | India | Adults | – | 2% (1/50 skulls) | – | Need for awareness amongst radiologists and neurosurgeons. |
Cederberg et al. [23] | 255 lateral cephalometric radiographs | USA | 8–76 years | 38.4% | 8.2% | – | Weak association between advancing age and degree of mineralisation. |
Dagtekin et al. [29] | 15 cadaveric heads + 25 dry skulls | Turkey | – | – | 5% | – | Neurosurgical implications. |
Erturk, Kayalioglu, and Govsa [31] | 119 dry skulls + 52 cadaveric heads | Turkey | – | – | 8.18% | – | Neurosurgical implications and relationship with cavernous sinus. |
Gibelli et al. [32] | 300 CT head scans | Italy | 18–99 years | – | 16.00% | – | Association between interclinoid and caroticoclinoid bridging. Potential association with interclinoid mineralisation and age. |
Gupta et al. [38] | 1 | India | – | – | – | – | Case report—misidentification of a mineralised interclinoid ligament as para-posterior communicating artery aneurysm. |
Keyes 1935 [12] | 2187 dry skulls | USA | 1 day–105 years | – | – | 8.68% | Details of the anatomical features of mineralised ligament. Complete mineralisation in cases as young as 6. |
Kucia et al. [39] | 322 lateral cephalograms | Poland | 8–16 years | – | – | 11.80% | Possible association with malocclusion. |
Leonardi et al. [40] | 34 dry skulls | Italy | 8–16 years | 33.7% (controls); 58.8% (cases) | 9.9% (controls); 17.6% (cases) | – | Higher incidence of sellar bridge formation in patients with dental anomalies. |
Marşan et al. [41] | 118 lateral cephalograms | Turkey | Adult females (mean ages 27.2 and 25.8 years) | – | 5% (class I and II); 18% (class III) | – | Association between sella turcica bridging and manifest skeletal class III malocclusions. |
Natsis et al. [14] | 123 dry skulls | Greece | 20–91 years | – | – | 21.95% | Association between complete mineralisation and age and bilaterality. |
Ota et al. [2] | 72 CT angiograms for paraclinoid aneurysms | Japan | – | – | – | 2.8% | Preoperative computed tomography is useful to detect variations in the anatomy around the ACP. When performing extradural anterior clinoidectomy. |
Ozdogmus et al. [13] | 50 autopsy specimens | Turkey | 18–80 years | – | 6% | – | Neurosurgical implications. No significant association between ossification and age. |
Peker et al. [8] | 80 dry skulls | Turkey | – | – | – | 34.17% | Neurosurgical implications. |
Scribante et al. [42] | 78 lateral cephalometric radiographs | Italy | – | 30% (controls) | 13% (controls) | – | Higher incidence of sellar bridge formation in patients with dental anomalies. |
Skrzat, Mroz, and Marchewka [19] | 80 dry skulls | Poland | Adults | – | 13.8% | – | Neurosurgical implications and effects upon internal carotid artery. |
Suprasanna and Kumar [36] | 54 CT angiograms | India | 18–70 years | – | 0.9% | – | Neurosurgical implications. |
Aggarwal, Gupta, and Kumar [37] | 67 dry skulls | India | – | 5.2% | 1.5% | 6.7% | Neurosurgical implications. |
Petrosphenoid ligament | |||||||
Current study | 240 CT studies | UK | 6–80 years | 8.3% | 2.5% | 10.8% | – |
Skrzat et al. [43] | 1 | Poland | – | – | – | – | Neurosurgical implications and possible role in abducens palsy. |
Joo et al. [44] | 10 cadaveric heads | Korea | – | – | – | 25% | Anatomical features that may predispose to abducens palsy. |
Inal et al. [16] | 130 skull bases on CT | Turkey | 20–78 years | 9.8% (right); 9.8% (left) | 2.3% (right); 2.9% (left) | – | Association between mineralisation and advancing age. Neurosurgical implications. |
Özgür and Esen [11] | 523 CT heads | Turkey | 18–100 years | 3.60% | 2.20% | 5.80% | Anatomical features that may predispose to abducens palsy. |
Icke, Ozer, and Arda [45] | 20 cadaveric heads | Turkey | – | – | – | 5% | Neurosurgical implications. Variation in ligament morphology. |
Aggarwal, Gupta, and Kumar [37] | 67 dry skulls | India | – | 3.0% | 2.2% | 5.2% | Neurosurgical implications. |
Posterior petroclinoid ligament | |||||||
Current study | 240 CT studies | UK | 6–80 years | 16.7% | 1.2% | 18.3% (Includes mixed 0.4%) | – |
Cederberg et al. [23] | Lateral cephalometric radiographs of 255 subjects presenting for orthodontic evaluation | USA | 8–76 years | 23% | 9% | 32% | Very weak correlation with advancing age. |
Inal et al. [16] | 130 temporal bone CTs | Turkey | 20–78 years | 26.6% (right); 29.5% (left) | 5.2% (right), 4.6% (left) | – | Neurosurgical implications. Anatomical features that may predispose to cranial nerve palsy. |
Kimball et al. [18] | 15 cadaveric head halves; 71 dry skulls | Grenada | 68–93 years | 13% (of cadaveric head halves) | 20% (of cadaveric head halves) | 9% skulls had large (> 2 mm) trigeminal protuberances | Neurosurgical implications. Potential role in trigeminal neuralgia. |
Ozdede et al. [46] | 290 cone beam CTs | Turkey | 24–81 years | – | – | 33.4% (calcification in general) | Male preponderance. |
Patwardhan [47] | Case report | India | – | – | – | – | Anatomical features that may predispose to oculomotor palsy. |
Sedghizadeh, Nguyen, and Enciso [48] | 500 cone beam CTs | USA | 13–82 years | – | – | 8% (calcification in general bilateral only) | Common finding on dental cone beam CTs. |
Skrzat et al. [49] | 24 fixed specimens, 73 dry skulls (reviewed for ligament remnants) | Poland | – | – | – | 1.4% (1 of 73 skulls) | Anatomy of non-calcified ligament and relationship with oculomotor nerve. |
Wysiadecki et al. [50] | 1 | Poland | 76 years | – | – | – | Association with oculomotor palsy. |
Pterygospinous ligament | |||||||
Current study | 240 CT studies | UK | 6–80 years | 12.5% | 2.1% | 17.1% (includes mixed 2.5%) | – |
Goyal and Jain [51] | 55 dried adult skulls and 20 sphenoid bones | India | – | 14.67% | 2.67% | 17.33% | Implications for surgery and neural compression. |
Shivanni and Yuvaraj Babu [52] | 40 dry skulls | India | – | 8% | – | 8% | Surgical implications. |
Yadav, Kumar, and Niranjan [53] | 500 skulls | India | – | 6.2% | 4% | 10.2% | Implications for neural compression. |
Saran et al. [54] | 50 dried skulls and 30 dried sphenoid bones | India | – | 7.50% | 1.25% | 8.75% | Implications for surgery and neural compression. |
Shinde, Mallikarjun, and Patil [55] | 65 skulls | India | – | 3.07% | – | 3.07% | Implications for surgery and neural compression. |
Tubbs et al. [56] | 154 skulls | USA | – | 0.645% | 0.645% | 1.3% | Implications for surgery. |
Antonopoulou, Piagou, and Anagnostopoulou [57] | 50 skulls | Greece | 30–60 years | 25% | 2% | 27% | Implications for neural impingement. |
Nayak et al. 2007 [58] | 416 dry skulls | India | – | 3.84% | 5.76% | 9.61% | Phylogenetic origins and differences. |
Das and Paul [59] | 50 sphenoid bones | India | – | 1% | 0% | 1% | Implications for surgery and neural compression. |
von Lüdinghausen et al. [60] | 100 skull bases. 54 halves of fixed cadaveric head and neck specimens | Japan and Germany | – | – | 6% | – | Anatomical relationships on dissection. Phylogenetic differences. |
Peuker, Fischer, and Filler [9] | 1 | Germany | – | – | – | – | Neural entrapment in a dissection specimen. |
Tebo [61] | 516 skulls | Skulls imported from India | – | 33% (includes spines) | 3.90% | – | Visibility on panoramic radiographs—can be mistaken for fracture. |
Lepp and Sandner [22] | Not specified | Venezuela | – | – | – | – | Morphology anatomical review of the ligaments and implications for access to the foramen ovale. |
Chouké [1] | n/a | USA | – | – | – | – | Technique modification for percutaneous access to the foramen ovale. |
Chouké [62] | 2745 skulls (in addition to skulls examined in 1946 paper) | USA | 16–93 years | 28.71% | 5.46% | – | Implications for access to the foramen ovale. |
Chouké [20] | 1544 skulls | USA | 16–101 years | – | 6.28% | – | Anatomical description of the courses of the mineralised ligaments. |
Shaw [63] | 454 skulls | UK | Known in 80 cases: 18-60 years | 11.7% partial or complete formation of a pterygospinous bar 16.1% (complete 4.4%) | 4.4% | 16.1% | Potential association with trigeminal neuralgia |
Krmpotić-Nemanić et al. [7] | 100 skulls; 50 isolated macerated sphenoid bones | Poland | Skulls 18–95 years; sphenoid bones 5–17 years | – | 5% | – | Potential mechanisms for neural entrapment. |
Ryu et al. [21] | 142 skulls | Korea | Unknown | 16.6% | 1.4% | 18% | Implications for neural impingement and surgical access. |
Kamath and Kuberappa [64] | 100 skulls | India | – | 16% | 1% | 17% | Implications for neural impingement and surgical access. |
Rosa et al. [65] | 93 skulls (radiographed using the Hirtz axial technique) | Brazil | – | 19.36% | 8.61% | 27.97% | Implications for neural impingement and surgical access. |
Peker et al. [8] | 452 skulls + mandibular nerves of 9 fixed cadavers | Turkey | – | – | 5.50% (fixed); 8.8% (skulls) | – | Potential mechanism for neural entrapment. |
Aggarwal, Gupta and Kumar [37] | 67 dry skulls | India | – | 6.7% (9 of 134 sides) | 3.0% (4 of 134 sides) | 9.7% (13 of 134 sides) | Implications for neural impingement and surgical access. |
Pterygoalar ligament | |||||||
Current study | 240 CT studies | UK | 6–80 years | 4.2% | 1.3% | 6.3% (includes mixed 0.8%) | – |
Tubbs et al. [56] | 154 skulls | USA | – | 0.645% | 0.645% | 1.3% | Implications for surgical access. |
Antonopoulou, Piagou, and Anagnostopoulou [57] | 50 skulls | Greece | 30–60 years | 1% | 7% | 8% | Implications for neural impingement. |
Lepp and Sandner [22] | Not specified | Venezuela | – | – | – | – | Morphology of the ligaments and implications for access to the foramen ovale. |
Chouké [1] | n/a | USA | – | – | – | – | Technique modification for percutaneous access to the foramen ovale. |
Chouké [62] | 2745 skulls (in addition to skulls examined in 1946 paper) | USA | 16–93 years | 17.76% | 5.94% | – | Anatomical characteristics of ligamentous mineralisation. No relationship with age. |
Chouké [20] | 1544 skulls | USA | 16–101 years | – | 10.30% | – | Anatomical characteristics of ligamentous mineralisation. |
Shaw [63] | 454 skulls | UK | Known in 80 cases: 18–60 years | – | 0.67% | – | Relationship with trigeminal neuralgia. |
Ryu et al. [21] | 142 skulls | Korea | – | 5.60% | 2.80% | 8.40% | Implications for surgical access and neural impingement. |
Kamath and Kuberappa [64] | 100 skulls | India | – | 29% | 1% | 30% | Implications for surgical access and neural impingement. |
Rosa et al. [65] | 93 skulls (radiographed using the Hirtz axial technique) | Brazil | – | 49.44% | 12.91% | 62.35% | Implications for neural impingement. Use of dedicated radiographic projections. |
Peker et al. [8] | 452 skulls + mandibular nerves of 9 fixed cadavers | Turkey | – | – | 4.90% (fixed); 7.9% (skulls) | – | Potential mechanism for neural impingement. |
Natsis et al. [66] | 145 skulls | Greece | 18–91 years | 27.60% | 4.10% | 31.70% | Implications for neural impingement. |
Pękala et al. [67] | Meta-analysis 25 studies | – | – | 8.4% (overall pooled prevalence) | 4.4% (overall pooled prevalence) | – | Meta-analysis. |