Paraclinoid aneurysms arise near the internal carotid artery (ICA) just distal to the cavernous sinus. They are classified based on their location along the ICA segments. Clinical presentation can include headaches, visual issues, and endocrine abnormalities. Treatment is recommended for symptomatic or rapidly growing aneurysms over 1cm. Surgical techniques involve craniotomy, anterior clinoidectomy to access the aneurysm, and clipping or trapping. Endovascular coiling is also used. Complications include visual and cranial nerve deficits, which often improve after treatment. Larger aneurysms may be treated with flow diverters.

1. Paraclinoid Aneurysms

2. • Introduction
• Anatomy
• Classification
• Indications for Treatment
• Pre-op evaluation
• Management techniques

3. Paraclinoid aneurysms
• Nutik
• Arise from the ICA distal to the cavernous
sinus but proximal to the PCoM
• 5 – 10% of all intracranial aneurysms arise
from this segment of the ICA

4. • Female preponderance - 9:1(Shimizu et al; AJNR 2016)
• High incidence of being multiple
• Rupture rate is lower than supra-clinoid
aneurysms
• Half of pts with C6 segment aneurysms have
additional intracranial aneurysms elsewhere

6. Seven segments
• Cervical – C1
• Petrous – C2
• Lacerum – C3
• Cavernous – C4
• Clinoid – C5
• Ophthalmic – C6
• Communicating/Terminal segment – C7

9. C5 and C6 segments
• Clinoid segment
▫ Optic strut
▫ ACP
▫ Superiorly – DR
▫ Inferiorly – COM
▫ Interdural
• Ophthalmic segment
▫ Sub-arachnoid space
▫ Ophthalmic artery
▫ Sup Hypophyseal artery

12. Anterior Clinoid process
• Cline – Greek – bed
• Lesser sphenoid wing
• Superior orbital fissure
• Optic canal
• Cavernous sinus

16. • Carotid sulcus
• Infra-clinoid carotid groove

17. Dural reflections off ACP
• Falciform ligament
▫ Covers posterior optic canal
• Dural ring
▫ Superior dural surface fuses with ICA adventitia
▫ Distal dural ring
▫ Diaphragma sellae
• Carotid-oculomotor membrane(COM)
▫ Periosteal dura
▫ Marks exit of ICA from C.S

21. Distal Dural ring
• Slopes down
▫ Anterior to posterior
▫ Lateral to medial
• Medial to ICA - subarachnoid recess –
Carotid cave

23. Carotid cave
• Kobayashi(1989)
• Sup – Medial surface of DR
• Lat – Medial wall of ICA
• Medially – Carotid groove
• Cave communicates with the
clinoidal venous plexus
• Subarachnoid space
• 3 patterns
▫ Slit (34%)
▫ Pocket(24%)
▫ Mesh(10%)

24. • Carotid collar attaches to
ICA only at Upper dural ring
• Space between collar and ICA
– Clinoid venous plexus
• Lower ring – Perneczky’s
ring

25. • Middle clinoid process
• Osseous bridge
• Carotico-clinoidal
foramen

26. Neural relationship
• Optic Nerve
▫ Optic canal
▫ Optic strut
▫ Falciform ligament

28. Arterial bends - 2
• 1st
▫ Sharp posterior turn
▫ Superior vector stress on the anterior and dorsal
wall
• 2nd
▫ Medial to lateral curve
▫ Stress on the medial aspect

30. Branch points
• Ophthalmic artery
▫ Dorso-medial ICA surface
▫ Just above DR
▫ Infero-lateral to Optic nerve
▫ Optic canal

32. • Superior hypophyseal
artery
▫ Largest perforator from
Ophthalmic segment
▫ Runs medially
▫ Optic chiasm
▫ Optic tracts

34. Barami classification(2003)
• Type Ia – Arising from the ophthalmic segment of the ICA and
related to the ophthalmic artery
• Type Ib – arising from the superior ophthalmic segment but
without relationship with ICA branches
•
• Type II – from ventral ophthalmic segment of ICA without ICA
branches relation

36. • Type IIIa – from medial ophthalmic segment of the ICA and
related to the SHA
• Type IIIb – from the medial clinoid segment below the DR
• Type IV –Large aneurysms involving the clinoid and the
ophthalmic segment of the ICA
• Ia – Most common - 43%

37. • Clinoidal segment
▫ Antero-lateral variant
▫ Medial variant
• Ophthalmic segment
▫ Ophthalmic artery aneurysms
▫ Sup Hypophyseal artery aneurysms
▫ Dorsal variant
• Carotid cave aneurysms
• Transitional aneurysms

39. Anterolateral variant
• From anterolateral surface of C5
• Superior projecting towards ACP
• Erode optic strut – visual loss

40. Medial variant
• From medial surface of clinoidal segment
• Enlarges towards sella and sphenoid sinus
• Expands beneath the diaphragma sellae into the pituitary fossa
• Hypopituitarism
• Visual loss
• Rupture - Simulate apoplexy

46. Ophthalmic artery aneurysms
• From posterior bend of ICA just distal to origin
of Ophthalmic artery and DR
• Project dorsally or dorsomedially
• Can elevate the Optic nerve against the falciform
ligament

47. • Monocular inferior nasal field defect
• Entire nasal field
• Superior temporal field loss in C/L eye

48. Large ophthalmic artery aneurysms
• Thickened or calcified walls
• Antero-inferior portion

49. Superior hypophyseal artery
aneurysms
• Medial surface of ICA
• Just distal to the DR
• Surrounded by Superior hypophyseal artery perforators
• Can project into the carotid cave – unlikely to rupture
when small

51. • When it fills the cave and extends into the
suprasellar region – Risk of hemorrhage rises
• Thickening or calcification along the anterior
medial aspect near the origin
• Giant aneurysms – compress chiasm like
pituitary tumors

52. Dorsal variant aneurysms
• Dorsal aspect of ICA
• Distal to ophthalmic artery origin
• Blisters
• Hemorrhage when small and expand as fusiform lesions
externally
• Very fragile

54. Carotid cave aneurysms
• Arises proximal to ophthalmic artery
• Below distal dural ring
• Points ventromedially into the cave

55. Clinical presentation
• Sudden severe headache
• Decreased visual acuity/field
defects
• Changes in colour vision
• Diplopia
• Panhypopituitarism
• Pituitary apoplexy
• Epistaxis
• Facial numbness

56. Indication for treatment
• Small <1cm asymptomatic
clinoid segment aneurysms –
conservative
• Small symptomatic lesions
(visual deficits, focal
unrelenting headaches) –
Rx
• Lesion whose protective ACP
roof has been removed - Rx
• >1cm – often extend into
subarachnoid space –
Increased risk of rupture – Rx
even if asymptomatic

57. • Ophthalmic segment aneurysms – low risk of
rupture. Expn – dorsal variant
• All symptomatic aneurysms > 1cm – Rx
• Large or giant lesions – Flow diverters

58. Pre-operative evaluation
• Cranial nerve deficits
▫ Visual acuity and fields
▫ EOM
▫ Facial sensations
• Endocrine status
• DSA
• CT angiography – DR can be
identified. Atheroma +
calcifications
• Anterolat v/s Ophthalmic in
CT
▫ Erosion of ACP
▫ Proximal origin
▫ Dorsolat v/s dorsomedial
▫ Angiographic waist

59. Clinoidal medial Sup Hypophyseal
• Projects medially
• Originates below diaphragma
sellae
• Superior surface is flattened
by the diaphragma
• Narrow neck(b/w DR and
COM)
• Projects medially
• Originates above diaphragma
sellae
• Not flattened
• Wide neck

61. • EVD or Lumbar drain
• Positioned supine with a shoulder roll ipsilateral
to the lesion
• Head is elevated above the heart
• Rotated 45 to 60 degrees away from the side of
the aneurysm

62. • Cervical carotid exposed
• Skin incision
• Pterional craniotomy with an orbital osteotomy
• Lesser wing is removed extra-durally down to
the base of ACP

64. Anterior clinoidectomy
• Extradural – Dolenc approach
• Intradural approach
• Intradural advantage – visualisation of
aneurysm throughout the procedure

65. Extradural ACP removal -EDAC
• Avoid extradural ACP removal if a clinoidal segment
anterolateral variant is suspected
• Extend medial dissection
• Diamond drill
• Dural attachments released

68. Intradural ACP removal
• Basal removal
• Dura opened in a curvilinear fashion
• Sylvian fissure split
• Aneurysm, ICA and optic apparatus visualised

70. • Falciform ligament sectioned
• Better visualization of optic apparatus and
aneurysm
• Optic canal – unroofed
• Optic strut drilled down
• Optic nerve sheath - sectioned

72. • DR sectioned circumferetially
• ICA can me mobilized

74. Techniques
• Temporary proximal cervical carotid ligation
• Trapping of aneurysm
• Intra-aneurysmal suction decompression
• Fenestrated clips – calcified lesion
• ICG – perforator patency
• Intraoperative angiography

75. Clinoidal segment
• Anterolateral variant – gently curved or side
angled clip parallel to the anterolateral surface
of ICA
• Medial variant

76. Ophthalmic segment
• Calcification along anterior aspect
• Sup Hypophyseal - Right angled fenestrated clip
• Dorsal wall aneurysms
▫ Blister variety – Clipping after trapping
▫ Sling of fascia or PTFE – wrap and clip

84. Complications
• Delayed stenosis or thrombosis
• Post-operative visual deterioration – 8.7%
(Nanda and Javalkar et al – Neurosurgery 2011)
• Heat from drilling
• Manipulation of Optic nerve
• Perforators
• Most patients have improved visual function after
surgery(De Oliveira et al – Neurosurg Focus 2009)

85. • 3rd, 4th, 6th nerve palsies
• Avoid excessive cranial nerve manipulation or
cavernous sinus packing
• CSF rhinorrhea – ACP drilling – Yo –Yo
technique

87. • Detachable coils
• Stenting and flow diverters
• Balloon assisted coiling
• Adjunct to surgery – Suction decompression +
Intraop angiography

88. Complications
• Coil compaction – refilling of aneurysm
• Blockage of parent vessel
• Progression of aneurysm thrombosis to parent
vessel
• Embolization of aneurysm thrombus

90. PED v/s Coiling v/s Clipping(JNS 2018 – Michael A
silva et al)
• PED has highest rate of visual improvement –
93%
• Complication rates 9% - PED
• Complete occlusion – Clipping(97) > PED(89) >
Coiling(78)

91. • CN palsy – 29% clipping > 13% PED > 0%
coiling
• SHA – coiling
• Ophthalmic – clipping
• Large aneurysms – PED and coiling

92. Bibliography
• Youmans
• Ramamurthi
• 7 Aneurysms