10 triangles 360°

1. 10 Triangles 360 ° 31-10-2015

2. Great teachers – All this is their work . I am just the reader of their books . Prof. Paolo castelnuovo Prof. Aldo Stamm Prof. Mario Sanna Prof. Magnan

3. For Other powerpoint presentatioins of “ Skull base 360° ” I will update continuosly with date tag at the end as I am getting more & more information click www.skullbase360.in   - you have to login to   slideshare.net  with Facebook account for downloading.

4. 10 Triangles = 4 Cavernous Sinus Triangles + 6 Middle Fossa Triangles 4 Cavernous Sinus Triangles Clinoidal ( Anteromedial ) Triangle Oculomotor (Medial or Hakuba's ) Triangle Supratrochlear ( Paramedian ) Triangle Parkinson's ( Infratrochlear ) Triangle 6 Middle Fossa Triangles Anteromedial ( Mullan's ) Triangle Anterolateral Triangle Posterolateral (Glasscock's) Triangle Posteromedial ( Kawase's ) Triangle Inferolateral Triangle Inferomedial Triangle

5. Cavernous Sinus Triangles 1.   Clinoidal ( Anteromedial ) Triangle · Borders: 1. Optic Nerve 2. Occulomotor Nerve 3. Tentorial Edge · Contents: 1. Anterior Clinoid Process 2. Clinoidal ICA 2. Oculomotor (Medial or Hakuba's ) Triangle · Borders: 1. Anterior petroclinoid dural fold. 2. Posterior petroclinoid dural fold. 3. Interclinoid dural fold. · Contents: 1. Occulomotor Nerve 2. Horizontal Segment of ICA

6. cavernous Roof has - two triangles: 1. clinoid (anterior ) 2. oculomotor (posterior ) ACP anterior clinoid process, APCF anterior petroclinoid fold, DS dorsum sellae , ICF interclinoid fold, PF pituitary fossa, PLL petrolingual ligament (inferior sphenopetrosal ligament), PPCF posterior petroclinoid fold, PS planum sphenoidale , SSPL superior sphenopetrosal ligament (Gruber’s ligament), TS tuberculum sellae , black asterisk middle clinoid process , CSR cavernous sinus roof , white asterisk oculomotor nerve If the Gruber’s ligament is ossificated it is called Wegener’s bridge .

7. The lower dural ring is given by the COM, that lines the inferior surface of the ACP. It can be visible, through a transcranial route, only by removing the ACP. The lower dural ring is also called Perneczky’s ring . Medially the COM blends with the dura that lines the carotid sulcus (Yasuda et al. 2005 ) Endoscopic supraorbital view of the anterior clinoid region. The right portion of the planum sphenoidale is seen from above. The anterior clinoid process has been removed. Vision obtained through a right supraorbital approach with a 30° down-facing lens focusing on the cavernous sinus roof. ACP anterior clinoid process (removed ), COM carotid oculomotor membrane , ICAc cavernous portion of the internal carotid artery, ICAi intracranial portion of the internal carotid artery, OA ophthalmic artery, ON optic nerve, LWS lesser wing of the sphenoid, IIIcn oculomotor nerve

8. The lower dural ring is given by the COM [ Carotid- oculomotor membrane ] , that lines the inferior surface of the ACP. It can be visible, through a transcranial route, only by removing the ACP. The lower dural ring is also called Perneczky’s ring . Medially the COM blends with the dura that lines the carotid sulcus (Yasuda et al. 2005 ) Endoscopic supraorbital view with a 30° down-facing lens -The right portion of the planum sphenoidale is seen from above. Right side

9. COM = carotico – oculomotor membrane Superior view of the right ophthalmic artery in the right paraclinoid area. The anterior clinoid process, which is situated on the lateral side of the optic nerve, has been removed. The optic canal has been unroofed, the optic sheath opened, and the optic nerve elevated to expose the origin of the ophthalmic artery under the medial half of the optic nerve. In the optic canal, the ophthalmic artery courses within the dural sheath of the optic nerve. It exits the optic canal and the optic sheath to enter the orbital apex on the inferolateral aspect of the optic nerve. The oculomotor nerve courses just below the dura covering the lower margin of the anterior clinoid process. The clinoid segment of the internal carotid artery is the segment that courses on the medial side of the anterior clinoid process and is exposed by removing the anterior clinoid process. The upper edge of the clinoid segment is defined by a dural ring, called the upper dural ring, formed by the dura , which extends medially from the upper surface of the anterior clinoid process. The lower edge of the clinoid segment is defined by the lower dural ring, which is formed by the dura that line1 the lower surface of the anterior clinoid process and separates the clinoid process from the upper surface of the oculomotor nerve and continues medially as the carotid- oculomotor membrane to surround the carotid artery The ophthalmic artery usually arises just above the clinoid segmenl However, it may infrequently arise from the clinoid segment.

10. Fig. 22.31 Clinoidal and oculomotor triangles have been opened and the anterior clinoid removed up to the optic strut, exposing the carotido-oculomotor membrane. The optic strut has two neural-facing surfaces( yellow dotted lines) and one vascular-facing surface (red dotted line). CN: cranial nerve; Falc .: falciform ; ICA: internal carotid artery; Inf.: inferior ; Lig .: ligament; Pet.: petrosal ; V1: first division; V2: second division; V3: third division of trigeminal nerve. ACP anterior clinoid process, APCF anterior petroclinoid fold, DS dorsum sellae , ICF interclinoid fold, PF pituitary fossa , PLL petrolingual ligament (inferior sphenopetrosal ligament), PPCF posterior petroclinoid fold, PS planum sphenoidale , SSPL superior sphenopetrosal ligament (Gruber’s ligament), TS tuberculum sellae , black asterisk middle clinoid process

11. The optic strut has two neural-facing surfaces( yellow dotted lines) and one vascular-facing surface (red dotted line). [ COM= Lower dural ring – Carotico-Occulomotor membrane seperates 3 rd N from Clinoidal carotid ]

12. 3 rd & 4 th nerves below optic nerve

13. Roof - two triangles: 1. clinoid (anterior) 2. oculomotor (posterior) Anterior skull base approach – see clinoid triangle in below photo

14. Oculomotor triangle is seen [ 3 rd N. , 4 th N. & Pcom ] seen in Posterosuperior compartment [ virtual compartment ] of cavernous sinus –better understanding see cavernous sinus PPT http:// www.slideshare.net/muralichandnallamothu/cavernous-sinus-360

15. Note the aperture for 3 rd nerve & 4 th nerve anterior & posterior to posterior petro- clival fold [ PPCF ]

16. Oculomotor cistern Cranial nerve III enters the roof included in its own cistern ( oculomotor cistern). Oculomotor cistern goes upto anterior clinoid tip

17. The lower dural ring is given by the COM [ Carotid- oculomotor membrane ] , that lines the inferior surface of the ACP. It can be visible, through a transcranial route, only by removing the ACP. The lower dural ring is also called Perneczky’s ring . Medially the COM blends with the dura that lines the carotid sulcus (Yasuda et al. 2005 ) Endoscopic supraorbital view with a 30° down-facing lens -The right portion of the planum sphenoidale is seen from above. Right side

18. The trochlear nerve in 80 % of cases enters at the posterior end of the roof of the cavernous sinus ( CS ) and in 20 % at the lower surface of the TC (Lang 1995 ) . 80 % of cases enters at the posterior end of the roof of the cavernous sinus ( CS ) ------ Note the aperture for 3 rd nerve & 4 th nerve anterior & posterior to posterior petro- clival fold [ PPCF ] in 20 % at the lower surface of the TC (Lang 1995 )

19. The trochlear nerve is divided into 5 segments: cisternal , tentorial , cavernous, fissural ( in superior orbital fissure ) and orbital. The cisternal segment exits the midbrain and courses through the quadrigeminal and ambiens cisterns towards the TC. The tentorial segment starts when the nerve pierces the TC, usually posterior to the postero -lateral margin of the oculomotor triangle. This segment ends at the level of the anterior petroclinoid fold . This portion is in close relationship with the spheno -petro- clival venous gulf and the petrous apex ( Iaconetta et al. 2012 ).

20. The TC [ tentorium cerebelli ], with the trochlear nerve inside , can be visualized passing inferiorly to the IIIcn . endoscopic transclival view

21. 1. In the posterior part of the CS the trochlear nerve is below the oculomotor nerve, while anteriorly it turns upward and becomes the most superior structure of the CS (at the level of the optic strut) ( Iaconetta et al. 2012 ) . 2. Trochlear nerve is always superior to V1.

22. L-OCR – Triangle 1. Upper boarder – Optic nerve & Opthalmic artery 2. Posterior boarder – Clinoidal carotid 3. Lower boarder – 3 rd N. [ COM – Carotico-Occulomotor membrane seperates 3 rd N f rom Clinoidal carotid ] [ 6 th N. & 4 th N . & V1 present inferior to 3 rd N. ]

23. Oculomotor triangle is seen [ 3 rd N. , 4 th N. & Pcom ] seen in Posterosuperior compartment [ virtual compartment ] of cavernous sinus –better understanding see cavernous sinus PPT http:// www.slideshare.net/muralichandnallamothu/cavernous-sinus-360

24. Antero-inferior compartment 1. The abducens nerve and the sympathetic plexus around the intracavernous carotid artery are the only nerves which have a real intracavernous course . 2. The anteroinferior and lateral compartments contain the abducens nerve and, as surgical corridors, they are exposed to the risk of injury to the VIth nerve . BS basisphenoid , CS cavernous sinus, CSd dura of the cavernous sinus, ET eustachian tube, ICAc cavernous portion of the internal carotid artery, ICAh horizontal portion of the internal carotid artery, ICAp parapharyngeal portion of the internal carotid artery, ILT inferolateral trunk , LVPM levator veli palatini muscle, MHT meningohypophyseal trunk, PAp petrous apex, PCFd posterior cranial fossa dura and periosteum , PG pituitary gland, TVPM tensor veli palatini muscle , VN vidian nerve, IIIcn oculomotor nerve, IVcn trochlear nerve, V1 fi rst branch of the trigeminal nerve, V2 second branch of the trigeminal nerve, V3 third branch of the trigeminal nerve , VIcn abducens nerve, XIIcn hypoglossal nerve, white asterisks sympathetic fi bres connecting the VIcn

25. Cavernous Sinus Triangles 3. Supratrochlear ( Paramedian ) Triangle · Borders: 1. Occulomotor Nerve 2. Trochlear Nerve 3. Tentorial Edge · Contents: 1. Meningohypophyseal Trunk 4. Parkinson's ( Infratrochlear ) Triangle · Borders: 1. Trochelar Nerve Middle_fossa_triangles Clinoidal ( Anteromedial ) Triangle 2 2. Opthalmic Division (V1) 3. Tentorial Edge · Contents: 1.  Cavernous ICA 2. Abducens Nerve

26. Supra-trochlear triangle Infra-trochlear triangle

27. http://www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study - Endoscopic view of the right cavernous sinus and neurovascular relations , demonstrating the ‘S’ shaped configuration formed by the oculomotor , the abducens and the vidian nerves. III oculomotor nerve , V1 ophthalmic nerve, V2 maxillary nerve, V3 mandibular nerve , VI abducens nerve , C clivus , ICA-Sa anterior bend of the internal carotid artery– parasellar segment, ICA- Sp posterior bend of the internal carotid artery– parasellar segment, ICA-C paraclival segment of the internal carotid artery, ICA-L lacerum segment of the internal carotid artery, ICA-P petrous segment of the internal carotid artery, PG pituitary gland, VC vidian canal, VN vidian nerve 6 th nerve is parallel to V1 – in the same direction of V1

28. 6 th nerve is parallel to V1 – in the same direction of V1

29. STA is devided into 1. Supra-Trochlear triangle 2. Infra-Trochlear triangle

30. http:// www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study- Endoscopic view of the right cavernous sinus and its neurovascular relations, demonstrating the triangular area formed by the medial pterygoid process laterally, the parasellar ICA medially and the vidian nerve inferiorly at the base. III oculomotor nerve , V1 ophthalmic nerve, V2 maxillary nerve, V3 mandibular nerve, VI abducens nerve, C clivus , ICA-Sa anterior bend of the internal carotid artery– parasellar segment, ICA- Sp posterior bend of the internal carotid artery– parasellar segment, ICA-C paraclival segment of the internal carotid artery, ICA-L lacerum segment of the internal carotid artery , ICA-P petrous segment of the internal carotid artery, PG pituitary gland, VC vidian canal, VN vidian nerve

31. 1.Supra Trochanteric & Infratrochanteric Triangles 2. Upper & lower dural rings

32. http://www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study -Endoscopic view of the right cavernous sinus showing its neurovascular relations and the main anatomic areas . III oculomotor nerve , V1 ophthalmic nerve, V2 maxillary nerve, V3 mandibular nerve , VI abducens nerve, C clivus , ICA-Sa anterior bend of the internal carotid artery– parasellar segment, ICA Sp posterior bend of the internal carotid artery– parasellar segment, ICA-C paraclival segment of the internal carotid artery, ICA-L lacerum segment of the internal carotid artery, ICA-P petrous segment of the internal carotid artery, PG pituitary gland, VC vidian canal, VN vidian nerve, STA superior triangular area, SQA superior quadrangular area, IQA inferior quadrangular area 1.Supra Trochanteric & Infratrochanteric Triangles 2. Upper & lower dural rings

33. http://www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study - Endoscopic view (a ), and a drawing (b) of the right cavernous sinus demonstrating its neurovascular relations. c A drawing of the right cavernous sinus demonstrating the exposure of the trochlear nerve after retracting the oculomotor nerve. III oculomotor nerve, IV trochlear nerve , V1 ophthalmic nerve, VI abducens nerve, ICA internal carotid artery, OA ophthalmic artery , OCh optic chiasm , ON optic nerve, PG pituitary gland

34. http://www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study - Endoscopic view of the right cavernous sinus and neurovascular relations , demonstrating the ‘S’ shaped configuration formed by the oculomotor , the abducens , carotid nerve ( paraclival carotid ) and the vidian nerves. III oculomotor nerve , V1 ophthalmic nerve, V2 maxillary nerve, V3 mandibular nerve , VI abducens nerve , C clivus , ICA-Sa anterior bend of the internal carotid artery– parasellar segment, ICA- Sp posterior bend of the internal carotid artery– parasellar segment, ICA-C paraclival segment of the internal carotid artery, ICA-L lacerum segment of the internal carotid artery, ICA-P petrous segment of the internal carotid artery, PG pituitary gland, VC vidian canal, VN vidian nerve VI nerve is parallel & medial to V1 – in the same direction of V1 [ Mneumonic – VI & V1 in same direction ]

35. Meningo-hypophyseal trunk & carotid nerve

36. 1. 6 th N. crossing carotid at Petro- clival junction when viewing in lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve ( VI ) at the entrance of both [ 6 th nerve & carotid ] structures into the cavernous sinus. 2. The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges- Coll et al. 2010 ).

37. 1. 6 th N. crossing carotid at Petro- clival junction when viewing in lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve ( VI ) at the entrance of both [ 6 th nerve & carotid ] structures into the cavernous sinus. 2. The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges- Coll et al. 2010 ).

38. Carotid nerve – part of S’ shaped configuration formed by the oculomotor , the abducens , carotid nerve ( paraclival carotid ) and the vidian nerves.

39. VI nerve is parallel & medial to V1 – in the same direction of V1 [ Mneumonic – VI & V1 in same direction ]

40. STA is devided into 1. Supra-Trochlear triangle 2. Infra-Trochlear triangle 1.Supra Trochanteric & Infratrochanteric Triangles 2. Upper & lower dural rings 3. lower dural ring is COM ( Carotico-Oculomotor Membrane ) I n the below picture superior cerebellar artery mislabelled as meningohypophyseal trunk .

41. STA is devided into 1. Supra-Trochlear triangle 2. Infra-Trochlear triangle 1.Supra Trochanteric & Infratrochanteric Triangles 2. Upper & lower dural rings 3. lower dural ring is COM ( Carotico-Oculomotor Membrane ) Right lateral view of the inferolateral trunk or artery of the inferior cavernous sinus, a branch of the horizontal part of the internal carotid artery (ICA) that provides blood to the dura of the lateral wall of the cavernous sinus as well as to the cranial nerves running along the lateral wall of the cavernous sinus. The trochlear nerve has been displaced inferiorly and the oculomotor nerve has been displaced superiorly. A recurrent branch from the inferolateral trunk is observed in this specimen. This branch heads back toward the tentorium cerebelli forming the so-called marginal tentorial artery. 1=horizontal segment of cavernous ICA, 2= clinoid segment of ICA, 3= supraclinoid ICA, 4= inferolateral trunk or artery of the inferior cavernous sinus, 5=marginal tentorial artery, 6=optic nerve, 7= oculomotor nerve, 8=trochlear nerve, 9=ophthalmic nerve, 10= abducent nerve, and 11=sphenoid sinus.

42. 1. In the posterior part of the CS the trochlear nerve is below the oculomotor nerve, while anteriorly it turns upward and becomes the most superior structure of the CS (at the level of the optic strut) ( Iaconetta et al. 2012 ) . 2. Trochlear nerve is always superior to V1.

43. From lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve (VI)

44. The abducens nerve in most case is a single trunk throughout its entire course (Zhang et al. 2012 ) . There are some variants, and one should be aware that the nerve can fuse with the oculomotor nerve for all its course (Zhang et al. 2012 ) . The surgeon must be prepared to face other rare variations, such as different fasciculi within the CS. Globally, the incidence of a duplicated abducens nerve has been reported , ranging from 8 % to 18 % (Nathan et al. 1974 ; Iaconetta et al. 2001 ; Ozveren et al. 2003 ) . In the prepontine cistern, when the duplication is present, AICA passes through the bundles. Furthermore , the incidence of a bilaterally duplicated nerve has been reported as frequently as 8 % of the time (Nathan et al. 1974 ; Ozveren et al. 2003 ) . The abducens nerve can pass above the Gruber’s ligament in 12 % of cases (Lang 1995 ) . Endoscopic vision of the cavernous sinus. Vision obtained through a right supraorbital approach with a 30° down-facing lens focusing on the cavernous sinus ICAc cavernous portion of the internal carotid artery, lwCS lateral wall of the cavernous sinus, SCA superior cerebellar artery, IIIcn oculomotor nerve, IVcn trochlear nerve, Vcn root of the trigeminal nerve, VIcn abducens nerve, blue arrow Gruber’s ligament, white asterisk Dorello’s canal .

45. Blue arrow in Left picture ; * in Right picture - Gruber’s ligament

46. http://www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study - Endoscopic view (a ), and a drawing (b) of the right cavernous sinus demonstrating its neurovascular relations. c A drawing of the right cavernous sinus demonstrating the exposure of the trochlear nerve after retracting the oculomotor nerve. III oculomotor nerve, IV trochlear nerve , V1 ophthalmic nerve, VI abducens nerve, ICA internal carotid artery, OA ophthalmic artery , OCh optic chiasm , ON optic nerve, PG pituitary gland

47. Middle Fossa Triangles 5.   Anteromedial ( Mullan's ) Triangle · Borders: 1. Opthalmic Nerve (V1) 2. Maxillary Nerve (V2) 3. A line connecting Superior Orbital Fissure and Foramen Rotundum · Contents: 1. Sphenoid Sinus 2. Opthalmic Vein 3. Abducens Nerve 6. Anterolateral Triangle · Borders: 1. Maxillary Nerve (V2) 2. Mandibular Nerve (V3) 3. A line connecting Foramen Rotundum and Foramen Ovale · Contents: 1. Lateral sphenoid wing 2. Spenoid emmissary vein 3. Cavernous- Pterygoid Venous Anastamosis

48. The space between V1 & V 2 and V2 & V3 is sphenoid sinus Middle cranial fossa approach – the nerve between V2 & V3 is VN Anaterior skull base

49. http:// www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus-cadaver-study- Endoscopic view of the right cavernous sinus and its neurovascular relations, demonstrating the triangular area formed by the medial pterygoid process laterally, the parasellar ICA medially and the vidian nerve inferiorly at the base. III oculomotor nerve , V1 ophthalmic nerve, V2 maxillary nerve, V3 mandibular nerve, VI abducens nerve, C clivus , ICA-Sa anterior bend of the internal carotid artery– parasellar segment, ICA- Sp posterior bend of the internal carotid artery– parasellar segment, ICA-C paraclival segment of the internal carotid artery, ICA-L lacerum segment of the internal carotid artery , ICA-P petrous segment of the internal carotid artery, PG pituitary gland, VC vidian canal, VN vidian nerve

50. JNA DISSECTION IN ANTEROLATERAL TRIANGLE .. NOTE V3

51. VI nerve is parallel & medial to V1 – in the same direction of V1 [ Mneumonic – VI & V1 in same direction ]

52. Middle Fossa Triangles 7. Posterolateral (Glasscock's) Triangle · Borders: 1. Mandibular Nerve (V3) 2. Greater Superficial Petrosal Nerve 3. A line from Foramen Spinosum to Arcuate Eminence · Contents: 1. Foramen Spinosum 2. Horizontal Petrous ICA (for anastamosis ) 3. Infratemporal Fossa 8. Posteromedial ( Kawase's ) Triangle This area is also known as The Rhomboid. Removal of the petrous bone within this triangle/quadrangle is an anterior petrosectomy . · Borders: 1. Mandibular Nerve (V3) 2. GSPN 3. Arcuate Eminence 4. Superior Petrosal Sinus -or- 1. GSPN 2. Arcuate Eminence 3. A line connecting the hiatus fallopii and Meckel's Cave · Contents: 1. Petrous Apex 2. IAC 3. Vertebrobasilar Junction Contains cochlea

53. Posterolateral (Glasscock's) Triangle

54. Posterolateral (Glasscock's) Triangle approach in Trans-temporal skull base approaches is called “ Infra-temporal fossa B approach “ by Prof. Mario sanna The petrous apex as viewed through the infratemporal fossa type B approach. Structures lying lateral to the internal carotid artery ( ICA ). The mandibular nerve ( V3 ) and the middle meningeal artery have been cut. The instrument points to the position of the already drilled bony eustachian tube ( ET ).

55. Infratemporal fossa anatomy line diagram in both anterior & lateral skull base ( Infratemporal fossa approach A, B, C , D )

56. Iatrogenic chances of injury of cochlea in infratemporal fossa transpetrous approach

57. The skin incision. The external auditory canal (arrow) is closed as cul-de-sac.

58. The temporalis muscle is detached anteriorly. The zygomatic arch is transected. Arrows point to the transection sites .

59. Subtotal petrosectomy . The facial nerve ( FN ) is skeletonized and the vertical internal carotid artery ( ICA ) is identified.

60. A minicraniotomy helps positioning the infratemporal fossa retractor . Identification of the middle meningeal artery ( MMA ) crossing lateral to the eustachian tube ( ET ).

61. Coagulation of the middle meningeal artery ( MMA ). Cutting the middle meningeal artery ( MMA ).

62. Identification of the mandibular nerve ( V3 ). The mandibular nerve ( V3 ) is cut.

63. Suturing the eustachian tube ( ET ) at the end of the procedure. Closure and drain insertion.

64. Infratemporal fossa approach B in cadaver

65. The temporalis muscle (TM ) of a left temporal bone has been reflected anteriorly after it has been dissected from the squamous bone (S) . TL Temporalis line, ZR Root of the zygomatic process

66. The periosteum (P) overlying the zygomatic arch (ZA) is being dissected away. This step helps avoid the laterally lying frontal branch of the facial nerve. SB Squamous bone The view after dissection of the periosteum (P) from the zygomatic arch (ZA) . SB Squamous bone, TM Temporalis muscle

67. The zygomatic arch has been transected. EAC External auditory canal, SB Squamous bone, TM Temporalis muscle, ZR Zygomatic root The skin of the external auditory canal (S) is being dissected away under the microscope. TM Tympanic membrane

68. After complete removal of the external auditory canal skin and tympanic membrane, the incudostapedial joint is disarticulated in order to remove the ossicular chain. C Chorda tympani, I Incus, M Malleus, S Stapes The mastoid cavity and the posterior and superior walls of the external auditory canal have been partially drilled. FB Facial bridge, FR Facial ridge, MFP Middle fossa plate, SS Sigmoid sinus

69. A radical mastoidectomy has been carried out, and the facial nerve has been skeletonized. AR Anterior attic recess, C Basal turn of the cochlea (promontory), DR Digastric ridge, FN(m) Mastoid segment of the facial nerve, FN(t) Tympanic segment of the facial nerve, LSC Lateral semicircular canal, MFP Middle fossa plate, PSC Posterior semicircular canal, RW Round window, S Stapes, SS Sigmoid sinus, SSC Superior semicircular canal, TT Tensor tympani The retrofacial and infralabyrinthine air cells are being drilled using an appropriately sized diamond drill. Attention must be paid during this step to avoid injuring the laterally lying facial nerve with the burr or the shaft. ELS Endolymphatic sac, FN(m) Mastoid segment of the facial nerve, ICA Internal carotid artery, SS Sigmoid sinus

70. The anterior wall of the external auditory canal has been partially drilled, and the vertical segment of the internal carotid artery (ICA) has been identified. FN(m) Mastoid segment of the facial nerve, FN(t) Tympanic segment of the facial nerve, JB Jugular bulb, LSC Lateral semicircular canal, S Stapes, SS Sigmoid sinus, TT Tensor tympani Dissecting the articular disk (AD) of the temporomandibular joint. ACW Anterior canal wall, SB Squamous bone, ZR Zygomatic root

71. A small craniotomy (CT) has been created in the squamous bone. ACW Anterior canal wall, AD Articular disk A self-retaining retractor is used to keep the mandible retracted inferiorly. ACW Anterior canal wall, AZT Anterior zygomatic tubercle, GF Glenoid fossa

72. The rest of the anterior canal wall has been drilled away, and the internal carotid artery is better skeletonized. C Basal turn of the cochlea (promontory), ET Eustachian tube, FN(m) Mastoid segment of the facial nerve. G Genu of the internal carotid artery, ICA(v) Vertical segment of the internal carotid artery To obtain control of the horizontal segment of the internal carotid artery, the eustachian tube (ET) , glenoid fossa bone (GF) , and the anterior zygomatic tubercle (AZT) have to be carefully drilled away. ICA Vertical segment of the internal carotid artery

73. In live surgery, the middle meningeal artery (MMA) should be coagulated to prevent bleeding. ICA Internal carotid artery, MFP Middle fossa plate The middle meningeal artery (MMA) is being sharply cut. ET Eustachian tube, ICA Internal carotid artery, MFP Middle fossa plate

74. Further anterior drilling uncovers the mandibular nerve (MN) . This nerve also has to be coagulated in live surgery before it is cut. ET Eustachian tube, ICA Internal carotid artery, MFP Middle fossa plate Sharply cutting the mandibular nerve (MN) . ET Eustachian tube, ICA Internal carotid artery, MFP Middle fossa plate

75. The stumps of the mandibular nerve (*) . ET Eustachian tube, ICA Internal carotid artery, MFP Middle fossa plate The eustachian tube (ET) and tensor tympani muscles (TT) are the last structures lying lateral to the horizontal segment of the facial nerve and should be removed. ICA Internal carotid artery, JB Jugular bulb, MN The cut end of the mandibular nerve

76. The lateral, thin part of the eustachian tube (ET) that remains can be removed with forceps. C Basal turn of the cochlea (promontory), ICA Internal carotid artery, MFP Middle fossa plate The tensor tympani muscle has been dissected away from its canal (TTC) . ET Medial wall of the eustachian tube, ICA Internal carotid artery, MFP Middle fossa plate

77. A large diamond burr is used to remove the remaining bone overlying the horizontal segment of the internal carotid artery. C Basal turn of the cochlea (promontory), ICA Vertical segment of the internal carotid artery, MFP Middle fossa plate, MMA Stump of the middle meningeal artery, MN Stump of the mandibular nerve The horizontal segment of the internal carotid artery ( ICAh ) has been skeletonized. Note that the greater petrosal nerve (GPN) is adherent to the dura , and that retracting the dura will lead to stress on the facial nerve at the geniculate ganglion (GG) level. Thus, if dural retraction is needed, cutting the petrosal nerve will prevent this injury. C Basal turn of the cochlea (promontory), CL Clivus bone, G Genu, ICA(v) Vertical segment of the internal carotid artery

78. The tip of the suction is used to displace the internal carotid artery (ICA) laterally while the medially lying bone is being drilled. C Basal turn of the cochlea (promontory), FN(m) Mastoid segment of the facial nerve, FN(t) Tympanic segment of the facial nerve, GPN Greater petrosal nerve, MFP Middle fossa plate, MMA middle meningeal artery stump Drilling of the clivus has been completed. C Basal turn of the cochlea (promontory), FN(m) Mastoid segment of the facial nerve, FN(t) Tympanic segment of the facial nerve, GG Geniculate ganglion, GPN Greater petrosal nerve, ICA Internal carotid artery, RW Round window

79. The full course of the intratemporal internal carotid artery has been freed. AFL Anterior foramen lacerum , CF Carotid foramen, CL Dura overlying the clivus area, ICA(h) Horizontal segment of the internal carotid artery, ICA(v) Vertical segment of the internal carotid artery, MN Stump of the mandibular nerve The view after completion of the approach.

80. The relationship of the internal carotid artery (ICA) to the tympanic membrane (TM) and middle ear in a right temporal bone. A Annulus, FN(m) Mastoid segment of the facial nerve, I Incus, JB Jugular bulb, LSC Lateral semicircular canal, M Malleus, MFD Middle fossa dura, PSC Posterior semicircular canal, SSC Superior semicircular canal

81. Kawase triangle

82. Two bissections in skull base 1. vertical part of facial nerve bisects jugular bulb 2. GSPN bisects V3& petrous carotid Vertical part of facial nerve bisects jugular bulb GSPN bisects V3 & petrous carotid

83. Triangles of Middle cranial fossa – see Ant. Medial & Ant. Lateral triangles in both photos. http://www.eneurosurgery.com/surgicaltrianglesofthecavernoussinus.html Postero -medial Triangle = KAWASE triangle [ Prof.KAWASE , JAPAN Neurosurgeon -below photo]

84. Neurosurgeons are doing FTOZ + kawase approach to get control of middle cranial fossa & posterior cranial fossa respectively 1. For FTOZ click 1. https :// www.youtube.com/watch?v=es-U3QitxdY 2. https :// www.youtube.com/watch?v=vDGO4kVy0Gc 3. https :// www.youtube.com/results?search_query=frontotemporal+orbitozygomatic+approach 2. For kawase approch click 1. http ://www.aiimsnets.org/skull_base_tumors.asp 2. https :// www.youtube.com/results?search_query=kawase+approach

85. FTOZ + kawase approch cadaver albums https ://www.facebook.com/groups/383508355070291/permalink/896897763731345 / https://www.facebook.com/groups/383508355070291/permalink/897122833708838/

86. Modified Anterior Transpetrosal Posterior Cavernous Posteromedial Rhomboid ( Dolenc-Kawase Rhomboid) Approach to Posterior Cavernous and Petroclival Lesions –AIIMS , INDIA https:// www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0034-1370530

87. The same approach what you get in FTOZ + KAWASE approach , you get in Type C Modified transcochlear approach without any brain retraction

88. Various types of Modified transcochlear approach Don't give too much importance to the jargon of approaches . Approaches developed from anatomy . Anatomy not developed from approaches. Know the www.skullbase360.in  anatomy. Automatically you can individualize the approach for the tumor .

89. a Schematic drawing showing the extent of the modified transcochlear type C approach. Note the superior extent of the craniotomy and the cut of the tentorium. b The markings of the skin incision to be made.

90. Drawing showing the structures exposed. Incision of the middle fossa dura . The vein of Labbé ( vL ) is clearly seen.

91. Cutting the tentorium ( Ten ). The last part of the tentorium is still to be cut to reach the tentorial notch .

92. The different structures seen after completion of the approach. With mild retraction of the temporal lobe, the bifurcation of the internal carotid artery ( ICA ) into the anterior ( ACA ) and middle cerebral ( MCA ) arteries is seen. The ipsilateral ( ON ) and contralateral ( ONc ) optic nerves are seen. The oculomotor nerve ( III ) is embraced by the posterior cerebral artery ( PCA ) superiorly and the superior cerebellar artery ( SCA ) inferiorly.

93. Middle Fossa Triangles 9. Inferolateral Triangle · Borders: 1. A line from the dural entries of the Trochlear and Abducens Nerve 2. A line from the dural entries of the Abducens Nerve and the Petrosal Vein 3. The petrous apex Middle_fossa_triangles Posterolateral (Glasscock's) Triangle  · Contents: 1. Porous Trigeminii (Dural opening into Meckel's Cave) 10. Inferomedial Triangle · Borders: 1. A line from the dural entries of the Trochlear and Abducens Nerve 2. A line from the dural entries of the Abducens Nerve and the Posterior Clinoid 3. The petrous apex · Contents: 1. Porous Abducens (Dural opening into Dorello's Canal) 2. Gruber's Ligament

94. inferomedial triangle – remember that 6 th nerve below the grubers ligament passes in this triangle · Borders: 1. A line from the dural entries of the Trochlear and Abducens Nerve 2. A line from the dural entries of the Abducens Nerve and the Posterior Clinoid 3. The petrous apex · Contents: 1. Porous Abducens (Dural opening into Dorello's Canal) 2. Gruber's Ligament

95. Anterior skull base view of Inferomedial triangle - 6 th nerve – enters the dorellos canal – Intradural course clinical importance = Gradenigo Syndrome - Infection & inflammation of petrous apex involves 6 th  cranial nerve at the Dorello's canal and 5 th  cranial nerve in the Meckel's cave

96. The basilar artery ( BA) can be seen very tortuous.

97. Cadaveric dissection of the middle third of the clivus with removal of the basilar plexus and exposing the dura . The abducens nerves ( CN VI ) can be seen bilaterally as they perforate the meningeal dura and become the interdural segments of CN VI. CS , cavernous sinus; PCA , paraclival carotid arteries; P , pituitary gland.

98. Gulfar segment of 6 th nerve ( GS in left picture ) ( gVIcn in right picture ) - The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges- Coll et al. 2010 ). 6 th nerve enters dorello’s canal between the meningeal layer of dura and the periosteal layer of dura ( POD ).

99. 1. 6 th N. crossing carotid at Petro- clival junction when viewing in lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve ( VI ) at the entrance of both [ 6 th nerve & carotid ] structures into the cavernous sinus. 2. The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges- Coll et al. 2010 ).

100. 1. 6 th N. crossing carotid at Petro- clival junction when viewing in lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve ( VI ) at the entrance of both [ 6 th nerve & carotid ] structures into the cavernous sinus. 2. The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges- Coll et al. 2010 ).

101. AICA anterior-inferior cerebellar artery, Cl clivus , CS cavernous sinus, ICAc cavernous portion of the internal carotid artery, IPS inferior petrosal sinus, LPMVN lateropontomesencephalic venous network, PBs pontine branches, PG pituitary gland, TPV transverse pontine vein, VA vertebral artery, VN vidian nerve (bordered in yellow ), Vcn trigeminal nerve, VIcn abducens nerve, yellow arrow cavernous portion of the abducens nerve

102. Blue arrow in Left picture ; * in Right picture - Gruber’s ligament

103. inferolateral triangle – remember that 5 th nerve passes in this triangle · Borders: 1. A line from the dural entries of the Trochlear and Abducens Nerve 2. A line from the dural entries of the Abducens Nerve and the Petrosal Vein 3. The petrous apex Middle_fossa_triangles Posterolateral (Glasscock's) Triangle  · Contents: 1. Porous Trigeminii (Dural opening into Meckel's Cave)

104. Anterior skull base view of Inferolateral triangle - “Front door” to Meckel’s cave – the space between trigeminal ganglion & laceral carotid is called quadrangular space – suprapetrous approach PLL - It can be considered the border between the horizontal and cavernous portions of the internal carotid artery.

105. For Other powerpoint presentatioins of “ Skull base 360° ” I will update continuosly with date tag at the end as I am getting more & more information click www.skullbase360.in   - you have to login to   slideshare.net  with Facebook account for downloading.