Ossifi cation of caroticoclinoid Srijit Das Rajesh Suri ligament and its clinical importance Vijay Kapur in skull-based surgery Department of Anatomy, Universiti Kebangsaan Malaysia, Kuala Case Report Lumpur, Malaysia INTRODUCTION Knowledge about the ossifi cation of the ABSTRACT The medial end of the lesser wing of the CCL may be immensely benefi cial for skull sphenoid bone forms the anterior clinoid process surgeons. Considering the fact that anatomy CONTEXT: The medial end of the posterior border 1 of the sphenoid bone presents the anterior clinoid (ACP). The ACP provides attachment to the free textbooks do not provide a detailed descrip- process (ACP), which is usually accessed for margin of the tentorium cerebelli and is grooved tion of the anatomoradiological characteristics operations involving the clinoid space and the medially by the internal carotid artery.1 The ACP of the CCL or CCF, the present study may cavernous sinus. The ACP is often connected to is joined to the middle clinoid process (MCP) prove especially relevant to neurosurgeons and the middle clinoid process (MCP) by a ligament known as the caroticoclinoid ligament (CCL), by the caroticoclinoid ligament (CCL), which radiologists in day-to-day clinical practice. which may be ossifi ed, forming the caroticocli- is sometimes ossifi ed. A dural fold extending noid foramen (CCF). Variations in the ACP other between the anterior and middle clinoid processes CASE REPORT than ossifi cation are rare. The ossifi ed CCL may have compressive effects on the internal carotid or ossifi cation of the CCL may result in the forma- The skull bones kept in the Department of artery. Thus, anatomical and radiological know- tion of the caroticoclinoid foramen (CCF).1 Anatomy are prepared by means of initial wash- ledge of the ACP and the clinoid space is also In neurosurgical operations, the ACP is ing, followed by autoclaving and treatment with important when operating on the internal carotid artery. Excision of the ACP may be required for usually accessed in order to gain entry into the ethylene oxide, and are fi nally freeze-dried. Dur- many skull-based surgical procedures, and the 2 clinoid space. After the internal carotid artery ing routine osteology teaching for undergraduate presence of any anomalies such as ossifi ed CCL leaves the cavernous sinus, it is related medially medical students, we observed an anomalous may pose a problem for neurosurgeons. to the ACP. The presence of an ossifi ed CCL CCL in a skull bone. Anomalous ossifi cation of CASE REPORT: We observed the presence of ossi- may form a potential site for compression of the CCL was noted and the specimen was pho- fi ed CCL in a skull bone. A detailed radiological study of the CCL and the CCF was conducted. the internal carotid artery. Abnormal variations tographed (Figure 1). Appropriate morphometric Morphometric measurements were recorded in the ACP may pose a risk while it is being measurements were recorded and a proper radio- and photographs were taken. The ACP was removed in regional surgical procedures.2 logical evaluation was also conducted (Figure 2). connected to the MCP and was converted into a CCF. Considering the fact that standard anatomy textbooks do not provide morphological descrip- tions and radiological evaluations of the CCL, the present study may be important for neurosur- geons operating in the region of the ACP. KEY WORDS: Skull. Sphenoid bone. Skull. Abnormalities. Anatomy. Figure 1. Photograph of interior of skull Figure 2. X ray photograph of skull (lat- showing:1. Frontal crest; 2. Orbital part eral view), with wires inside optic canal of frontal bone; 3. Jugum sphenoidale; and caroticoclinoid foramen. a. Upper 4. Anterior clinoid process; 5. Pituitary end of bent wire inside optic canal; b. fossa; 6. Posterior clinoid process; 7. Lower end of bent wire inside optic canal; Foramen magnum; 8. Petrous part of tem- c. Posterior end of bent wire inside ca- poral bone. The ossifi ed caroticoclinoid roticoclinoid foramen; d. Anterior end of ligament extending between the anterior bent wire inside caroticoclinoid foramen. and middle clinoid processes is marked The ossifi ed caroticoclinoid ligament is by vertical arrows. shown with an arrow. Sao Paulo Med J. 2007;125(6):351-3. 352 The ossified CCL (shown by vertical osteological study has ever been supplemented occurrence in dried human skulls.6 That par- arrows in Figure 1) was found to extend with additional radiological fi ndings of a CCL, ticular anatomical study laid less emphasis on between the ACP (marked as “4” in Figure and the present case is a humble attempt to the radiological aspects of the ossifi ed CCL.6 1) and the MCP (marked with an vertical highlight this fi nding. A skiagram was taken In comparison to earlier anatomical studies, arrows in Figure 1), in the bone specimen. using separate wires inserted into two different the present study has not only described the The ossifi ed CCL was found bilaterally, on openings, i.e. the optic canal and CCF, for easy morphological and clinical characteristics of both sides of the skull. The anterior clinoid differentiation (Figure 2). an ossifi ed CCL, but also displayed the radio- processes on the two sides were separated The internal carotid artery is present in logical features of an ossifi ed CCL, which may by a distance of 2.1 cm. The anterior and the medial groove of the ACP and it may be be benefi cial for radiologists. posterior clinoid processes were separated compressed by the ossifi ed CCL, giving rise Another important clinical characteristic by a distance of 0.7 cm and 0.6 m on the to vascular complications. The presence of is the pneumatization of the ACP, which has right and left sides, respectively. The sulcus an ossifi ed CCL is likely to cause compres- to be evaluated pre-operatively, in order to chiasmaticus was situated at a distance of 0.5 sion and straightening of the internal carotid avoid serious complications like pneumo- cm behind the jugum sphenoidale. The right artery.3 In the present case, the clinical history cephalus and rhinorrhea.7 For any surgery posterior clinoid process was found to be more of the patient was not available to corroborate involving the ACP, preoperative imaging may prominent (marked as “6” in Figure 1) than this observation. be advised, to keep such anomalies in view. on the left side. The ossifi ed CCL measured The internal carotid artery is convention- Interestingly, 60% of ACP cases are pierced approximately 1.5 cm on each side. The CCF ally divided into six segments and the clinoid by narrow venous canals arising from the an- was prominently formed as a result of the segment of the artery is located between the terior cavernous sinus and traversing through presence of the ossifi ed CCL. The maximum proximal and distal dural rings.4 In any surgi- the clinoid space. These are considered to be transversal dimension between the optic canals cal operation involving exposure of the clinoid a potential source of bleeding during removal on each side was 1.5 cm. segment of the internal carotid artery, excision of the ACP.8 It must also be remembered that of the anterior clinoid process is mandatory. the extraocular nerves traverse to the superior DISCUSSION Even to expose the cavernous sinus superiorly orbital fi ssure inferolaterally to the ACP, and The ACP forms the attachment site for and to manage paraclinoid aneurysm, the it is essential for surgeons to adopt a careful the free anterior margin of the tentorium ACP has to be removed.2,5 The clustering of approach when operating on the ACP.9 cerebelli, whereas the MCP provides the the neurovascular structures in the vicinity of attachment for the diaphragma sellae.1 the ACP renders the surgery more risky.2 Prior CONCLUSION The parts of the sphenoid bone that are usu- anatomical knowledge is essential for identi- If an ossifi ed CCL is present, it is likely ally reported as capable of ossifi cation are the fying any inadvertent injury to the internal to cause compression of the internal carotid pterygospinous and interclinoid processes.1 carotid artery. artery. A detailed anatomical report of such As described in conventional textbooks of Research studies have also reported the an anomaly was presented in the present anatomy, the ACP may be joined to the fact that an ossifi ed CCL makes the removal of case. Radiological studies on the CCF and its MCP by a ligament or dural fold.1 The bony the ACP more diffi cult, especially in the pres- differentiation from the optic canal may be bridge joining the ACP and MCP converts ence of any aneurysm.2 Drilling of the ACP, clinically important for radiologists. Anatomi- the distal end of the carotid sulcus into an when required, may cause inadvertent injury cal knowledge about ossifi cation of the CCL ostium known as the CCL.2 to the internal carotid artery and optic nerve. may be useful in cases of surgery involving To the best of our knowledge, no single There have been previous reports of CCF removal of the ACP, for which additional risk is involved. REFERENCES 1. Standring S. Overview of the Development of the Head and 5. Dolenc VV. A combined epi- and subdural direct approach to carotid- 9. Huynh-Le P, Natori Y, Sasaki T. Surgical anatomy of the anterior Neck Head: Skull and Mandible. In: Standring S, editor. Gray’s ophthalmic artery aneurysms. J Neurosurg. 1985;62(5):667-72. clinoid process. J Clin Neurosci. 2004;11(3):283-7. anatomy: the anatomical basis of clinical practice. New York: 6. Gupta N, Ray B, Ghosh S.