ICA anatomy

Segments and relations to the ICA

1. Internal Carotid Artery Anatomy and segments Mohamed Elsayed Elsebaey Neurosurgery Registrar Egypt, Ismailia Ministry of Health [email protected] Mohamed E Elsebaey

2. Surface anatomy of the CCA

3. C1

4. Cervical segment C1 Begins in the neck at the carotid bifurcation where the CCA divides into internal & external Goes within the carotid sheath with IJV & vagus Encircled with PGSN Ends where the ICA enter carotid canal of petrous bone branches ??? Mention them

5. Carotid sheath Fibrous connective tissue that surrounds the vascular compartment of the neck. Part of the Deep Cervical Fascia of the neck, that include : The investing layer (encloses the SCM and Trapezius ) The carotid sheath (encloses the vascular region of the neck ) The pretracheal fascia (encloses the visceral region of the neck ) The prevertebral fascia (encloses the vertebral region of the neck

6. Located at the lateral border of the retropharyngeal space , at the level of the oropharynx on each side, deep to the SCM muscle , extending from the base of the skull to the sternum and 1 st rib. Contain :

7. Cr. Ns. 9, 11 & 12 pierces the carotid sheath in the upper part. How ? Ansa Cervicalis is embedded in the Anterior wall of the sheath.

8. PostGanglionic Sympathetic Nerves PGSN Internal Carotid plexus is mainly located in the lateral side of the Carotid A. PGSN ascend from the superior cervical ganglion Creep on the ICA wall Enter the ICA plexus then Emerge into Superior Tarsal Ms & Pupillary dilator Ms Some fibers converge and form the Deep petrosal N .

9. para

10. How many Nucleui of the 3 rd Cr. N. ??? Edenger Westephal N Motor Nucleus Nucleus of Perli  Medial rectus M alone

11. C2

12. Temporal Bone Parts : Squamous part Petrous Mastoid Styloid

13. Petrous segment C2 Still surrounded by PGSN Ends at the posterior edge of foramen lacerum. Three divisions: Vertical segment Posterior segment Horizontal segment

14. Petrous Bone Part of the Temporal Bone Very complicated bone Many so important relations Like the pyramid

15. Base  fused with the internal surfaces of the squamous and mastoid parts of temporal bone. Apex  rough, forms the Postero lateral boundary of the F. lacerum. Surfaces  Anterior , Posterior & Inferior . Angles  superior, anterior & posterior.

16. In this surface: large circular opening  do tunnel ascends vertically then Do bend then Runs horizontally forward and medially ICA passes

17. C3

18. Lacerum segment C3 C3 is the shortest segment Passes over foramen lacerum forming the lateral loop ICA does not go through the F lacerum but walks over it Ascends in the canalicular portion of the foramen lacerum to the juxtasellar position Piercing the Dura Passes the petrolingual ligament to become the cavernous segment Branches : Caroticotympanic artery Pterygoid ( Vidian artery )

19. Foramen Lacerum Triangular hole in the base of the skull. Located between the sphenoid, Apex of petrous bone & basilar part of occipital bone. Situated Anteromedial to the carotid canal C canal F L Mid line

20. Gasserian Ganglion It is a sensory ganglion of the trigeminal nerve that occupies a cavity ( Meckel's cave ) in the dura mater, covering the trigeminal impression near the apex of the petrous part of the temporal bone.

21. Meckel’s cave Known also as Trigeminal cave It is an Arachnoidal pouch containing cerebrospinal fluid formed by two layers of dura mater near the apex of the petrous part of the temporal bone Contains the trigeminal Ganglion Bounded by Tentorium cerebelli superolaterally Cavernous sinus superomedially Clivus medially Posterior petrous inferiolaterally

22. Superficial Petrosal nerve Nerve in the skull that branches from the facial nerve. forms part of a chain of nerves that innervate the lacrimal gland It proceeds towards the foramen lacerum, where it joins the deep petrosal nerve to form the nerve of the pterygoid canal, which passes over the foramen lacerum

23. Petrolingual ligament The petrolingual ligament is the posteroinferior attachment of the lateral wall of the cavernous sinus, where the internal carotid artery enters the cavernous sinus.

24. The petrous segment of the internal carotid artery finishes and the cavernous segment begins at the superior margin of this ligament. The ligament is surgically important due to its identification as a landmark for dissection of the internal carotid artery during the approaches to posterolateral intracavernous and extracavernous lesions. It can be well exposed after mobilization of the gasserian ganglion, or after the trigeminal root and ganglion have been split along the junction of V2 and V3 (the transtrigeminal approach).

25. C4

26. Cavernous segment C4 Covered by vascular membrane lining the sinus Still surrounded by the PGSNs The Pathway : Pass anteriorly,  superomedially bends posteriorly( Medial loop )  travels horizontally  bends anteriorly ( anterior loop ) Ends at the proximal dural ring

27. Branches of C4 Meningio hypophyseal trunk Anterior meningeal artery A to inferior portion of the cavernous sinus Capsular aa that supply the capsule of pituitary Mention Blood supply of Pituitary. Ant. Lobe of pituitary has no specific Blood supply

28. N.B. Rupture aneurysm of ICA ( C4 ) does not cause SAH As it is still not intra subdural space It is just penetrates the outer Dural layer

29. C5

30. Clinoid segment C5 The ICA becomes Intradural Begins at the proximal Dural ring Ends at the distal Dural ring

31. C6

32. Ophthalmic segment C6 Begins at the distal Dural ring Ends just proximal to P- Com- A Branches: Ophthalmic A Superior hypophyseal a.

33. C7

34. Communicating segment C7 Begins proximal to P- comm origin Ends just below anterior perforated substance where terminates into ACA & MCA

35. Carotid siphon Not a segment , but region Incorporating the Cavernous, opthalmic & comm segment “ When viewed from laterally, the cavernous(C3 ) and intracranial (C4) portions have several curves that forman S -shape, and together these portions are called the carotid S iphon .” Rhoton,2002 . Begins at the posterior bend of cavernous ICA Ends at the ICA bifurcation

36. Thank You