OSSIFICATION OF CAROTICOCLINOID AND PETROSPHENOIDAL LIGAMENTS OF SKULL: A CASE REPORT

Int J Anat Res 2015, 3(2):1039-42. ISSN 2321-4287 1039

Case Report

OSSIFICATION OF CAROTICOCLINOID AND PETROSPHENOIDAL

LIGAM ENTS OF SKULL

Kavitha Kamath.B *

_{, Vinayak Kamath}

_.

ABSTRACT

Address for Correspondence: Dr. Kavit ha Kamat h.B, Assistant Professor, Depart ment of Anat omy, Shimoga Inst it ut e of M edical Sciences, Sagar Road, Shimoga, Karnat aka. 577201, India.

E-M ail: drkavit hakamat [email protected]

* 1 _{Assistant Professor, Dept of Anatomy, Shimoga Inst it ute of M edical Sciences, Shimoga, Karnataka,}

India.

2 _{Lect urer, Dept of Public healt h dent ist ry, A.B Shett y Inst it ute of Dental Sciences, Derlakatte,}

M angalore, Karnat aka, India.

Ossi f icat i on of var ious ligam ent s in t he bo dy m ay r esult in cli nical sym pt om s due t o com p r essio n of neighbouring st ruct ures and com plicat ions in r egional surgeries. This case repor t s of a dr y skull t hat present ed w it h t w o rar e bony anom alies - carot icoclinoid and pet r osphenoid bridges. Sim ult aneous occurr ence of bot h t hese anom alies is a unique m orphological event w it h neurovascular im plicat ions. Consider ing t he f act t hat m ajorit y of t ext books in anat om y do not provide a det ailed descript ion of t hese ent it ies, t he present r eport is ver y m uch relevant for neur osur geons and radiologist s in day t o day pract ice.

KEY W ORDS: Car ot icoclinoid ligam ent , pet rosphenoidal ligam ent , clinoid processes, abducent ner ve, int er nal carot id art ery.

INTRODUCTION

Int ernat ional Journal of Anatomy and Research, Int J Anat Res 2015, Vol 3(2):1039-42. ISSN 2321- 4287 DOI: ht t p:/ / dx.doi.org/10.16965/ ijar.2015.152

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Received: 30 M ar 2015 Accept ed: 27 Apr 2015 Peer Review : 30 M ar 2015 Published (O):31 M ay 2015 Revised: None Published (P):30 June 2015 Int ernat ional Journal of Anat omy and Research

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DOI: 10.16965/ ijar.2015.152

A myriad of int ricat e st ruct ures are found in t he p et r o cl i v al r egi o n, w hi ch ar e esp eci all y import ant in procedures involving the skull base. Know ledge of anat omy of t his area is essent ial for successful surgical t reat ment of lesions in t his region. Surgical approaches t o t he clivus, pet roclival region and cavernous sinus require an excellent know ledge of t he anat omy of t his region [1].

Ossi f icat io n of li gam ent s ar oun d t he sella t ur cica m ay give rise t o bony br idges t hat con n ect t he cl i no i d pr o cesses w i t h o t her surrounding st ructures. These sellar bridges can develop unilat erally or bilat erally and vary in frequency [2]. As a result of abnormal

develop-ment in anterior, middle and posterior clinoid processes, t hese bony st ruct ures could fuse, forming osseous bridges. Bridge formation could eit her occur bet w een t he ant erior and middle (carot icoclinoid bridge forming carot icoclinoid foramen of Henle), t he ant erior and posterior or bet w een middle and posterior clinoid processes. In addit ion, a bony bridge could also develop bet w een t he post erior clinoid pr ocess and superior margin of petrous part of temporal bone, t he sphenopet rous bridge [3].

Int J Anat Res 2015, 3(2):1039-42. ISSN 2321-4287 1040

Kavit ha Kamat h.B, Vinayak Kam at h. OSSIFICATION OF CAROTICOCLINOID AND PETROSPHENOIDAL LIGAM ENTS OF SKULL: A CASE REPORT.

CASE REPORT

clinoid segment of int ernal carot id art ery as it t ur ns upw ar ds t o supply t he brain [ 4] . The presence of ossified carot icoclinoid ligament is li kel y t o cau se com pr ession, t ight eni ng or st ret ching of int ernal carot id art ery [5].

Th e p et r o sph en oi d al l i gam ent (Gr u b er ’s ligament ) is locat ed bet w een t he pet rous apex and posterior clinoid process and forms t he roof of Dorello’s canal t hrough w hich t he abducent nerve passes [1]. Dorello’s canal was described by Gruber in 1859 as an ost eofibrous canal (foram en pet ro-sphenoideum) locat ed at t he apex of pet rous bone cont aining t he abducent n er v e, i n f er i or p et r o sal si n u s an d d o r sal m eniningeal branch of m eningohypophyseal t r u n k [ 1,6,7] . Cl in i cian s m i ght con si der ossif icat ion of pet r osphenoidal ligam ent in unexplained cases of abducent nerve palsy [6].

Records of t he variat ions st at ed above are very few in medical lit erat ure and t heir simult aneous occur rence in sam e skull is except ional and requires report ing. Descript ions of such ent it ies are import ant because of t heir applicabilit y in su r gi cal i nt er ven t io n s in v o lv i n g r egi o n surrounding t he sella t urcica.

During rout ine ost eology classes for first year m edical st udent s of 2013-14 bat ch, bilat eral com plet e carot icoclinoid bridges w ere seen ext endi ng f r om ant er i or t o m i ddle clin oid process result ing in t he form at ion of bilat eral carot icoclinoid foramina w hich w ere circular in shape w it h smoot h out line. They w ere locat ed

Fig. 1: Sh o w i n g b i l at e r al co m p l et e

car ot icoclinoid bridges and right sided com plet e pet rosphenoidal bridge.

( CCB- Car o t i co cl i n o i d b r i d ge, CCF-Car ot icoclinoid f or am en, ACP-Ant erior cli no id p r o cess, M CP- M id dl e cl in oi d process, PCP- Post erior clinoid process, PSB- Pe t r o sp h e n o i d al b r i d ge, PTB-Pet rous part of t em poral bone. OC- Opt ic can al)

ant er ol at er al t o sel l a t u r ci ca, m ed i al t o superior orbit al fissure and behind t he opt ic canal on bot h sides. In addit ion, a complet ely ossified pet rosphenoidal ligam ent w as seen ext ending from apex of pet rous t emporal bone t o t he post erior surface of post erior clinoid p r o cess on r i ght sid e o f sk u ll f o r m i n g an ellipt ical bony foramen beneat h t his bridge.

DISCUSSION

Incidence of carot icoclinoid foramen in various st udies r anged bet w een 6.27-36% [4,8-10]. Uni l at eral an d i nco m p l et e car ot i co cli n oi d foramen are more common t han bilat eral and com plet e f or am en [ 4,10,11] . The incidence show s racial t rends; show ing high occurrence in Turks, Americans, Port uguese, Nepalese and low in Brazilians, Japanese, Koreans and Indians [4,9-13].

-Int J Anat Res 2015, 3(2):1039-42. ISSN 2321-4287 1041 -izat ion or m arrow assessm ent s of ant erior

cl in oi d p r o cess. It poses accessib ili t y and bleeding problems during neurosurgical invasive procedures of t he region [11].

Th e i n t er n al car o t id ar t er y en t er s t h e subarachnoid space t hrough a t hick ring of dur am at er called t he dist al dur al ring. The int ernal carot id art ery is also surrounded w it h anot her ring of dura, t he proximal dural ring w hich is exposed af t er t he ant er ior clinoid process is removed. The area in bet w een t hese t w o r ings is called t he clinoidal space. The clinoidal segment of t he int ernal carot id art ery locat ed in t his space is exposed by rem oving t he ant erior clinoid process. During surgical approaches t o t he sellar region for t umors or aneur ysm s, t he ant er ior clinoid pr ocess is removed carrying risk of damage t o t he int ernal carot id art ery during t hese approaches [10]. Approach t o t he cavernous sinus com m only involves removal of ant erior clinoid process t o expose t he st ruct ures in t he superior part of cavernous sinus. Presence of carot icoclinoid bridge makes removal of anterior clinoid process m or e di f f icu l t an d i n cr eases t h e r i sk o f complications, especially if aneurysm is present . Oculomot or nerve may also be damaged during t he rem oval of ant er ior clinoid pr ocess. So ser i ou s w ei gh i ng o f r isk s an d b en ef i t s o f operat ive approaches must be done before t he o per at i o n b ecau se o f t h e m agn it u d e o f operat ing procedure and risks of neural and vascular injury [3].

In pr esence of carot icoclinoid foram en it is impossible t o ret ract or mobilize t he cavernous segment of carot id art ery even aft er releasing t h e p r oxi m al and d ist al car o t i d r i ngs. Preoper at ive r ecognit ion of carot icoclinoid foramen is import ant because undue ret ract ion of cavernous segment of int ernal carot id art ery may t ear or rupt ure it and cause fat al cerebral infarct ion [12].

Incidence of pet rosphenoidal bridges in various st udies w as found t o be 5-17.7% [1,3,7,14]. An ossified pet rosphenoidal ligament may play a role in abducent nerve palsy and can be detect ed by mult idetector comput ed tomogaphy [14]. The abducent nerve m ay be com pressed w it hin Dorello’s canal by an accompanying artery

u sual l y t h e d o r sal m en in geal b r an ch o f meningohypophyseal trunk. If Gruber ’s ligament is ossified t hen vascular compression may be more likely [6].

The pet rosphenoidal ligament is an import ant st ruct ure in t he pet roclival area, not only from anat omical point of view but also for surgical and endovascular pract ice. This ligam ent is locat ed at t he p et r o veno us co nf lu ence of superolat eral part of t he basilar plexus, t he post erior port ion of cavernous sinus, superior part of inferior pet rosal sinus and ant erior part of sphenopariet al sinus. This int erdural region is com m only used f or t reat m ent of carot id cavernous sinus fist ulas. The main funct ion of pet rosphenoidal ligam ent is report ed t o be f i xat i on o f sh eat h o f abd u cen t ner v e i n pet roclival venous confluence. The nerve is also prot ect ed by t his ligament during pet rous bone drilling during ant erior pet rosal approach [1].

Ossificat ion of fibrous ligament s is considered a normal physiological process t hat occurs w it h age [ 10] . Th er e i s st at i st i call y si gn if i can t associat ion bet w een calcificat ion of pet roclinoid and int erclinoid ligament s because of possibilit y t hat t hese ligament s are part s of same dural folds. Hence age may be a significant fact or in risk of ossificat ion of cranial ligam ent s [15]. How ever t his process is an except ion in t he format ion of carot icoclinoid foramen since it is present in foet uses and children [16,17 ]. Sellar bridges are laid dow n in cart ilage during early st age of sphenoid development and ossify in early childhood [18].

Alt hough Dorello’s canal in modern human is an ost eofibrous st ruct ure and ellipt ical in shape, in primat es it is round osseous opening closed superiorly by t he f used pet r osal spine and accessory clinoid process. These differences betw een the primat e and human configurat ions are t he source of abducent nerve vulnerabilit y. Changes in t he anat omy of t he cranial base during t he course of human evolution, st emming po ssi bly f r om t h e i ncr ease i n end ocr ani al capacit y have br ought about dist ancing of d o r su m sel la and p et r o us apex, t h er eb y elongat ing t he horizontal axis of Dorello’s canal and causing t he discont inuit y of it s osseous perimeter. Hence t he pet rosphenoidal ligament

Int J Anat Res 2015, 3(2):1039-42. ISSN 2321-4287 1042 of Gruber replaced t he bony bridge and Dorello’s

canal becam e an o sseo f i br o u s st r u ct ur e, r en d er i n g i t s co n t en t s su scep t i b l e t o compression against t he cranial base. A bony p et r o sph en oi d al b r id ge i s f ar m o r e advant ageous than a fibrous one as deformat ion inflict ed on a ligament by int racranial masses w ou ld be great er. Ap es ar e l ess pr o ne t o abd u cen t neu r op at hi es r esul t i ng f r o m compression of t he nerve t han humans as t he nerve is prot ect ed by an osseous canal [19].

CONCLUSION

Considering t he fact t hat anat omy t extbooks do no t pr ov ide d et ai led d escr ip t io n of t hese ent it ies, t he present st udy is of relevance t o neurosurgeons and radiologist s in day t o day clinical pract ice for underst anding t he et iology o f cl in i cal sym p t om s, r ed uci n g er r o r s i n diagnost ic procedures and increasing success of surgical pr ocedures. It is concluded t hat presence of t hese anom alies have import ant clinical im plicat ions and t heir know ledge is r eq u i r ed f o r bet t er p lan n in g of sur gi cal t reat ment s involving t his region.

List of abbreviations:

Conflicts of Interests: None

REFERENCES

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