1) The document discusses various types of intracranial aneurysms including their presentation, incidence, diagnosis, and radiographic features. 2) Saccular aneurysms are the most common type and can cause subarachnoid hemorrhage from rupture. They are often detected on CT/CTA or catheter angiography. 3) Other aneurysm types discussed include fusiform, dissecting, mycotic, oncotic, and traumatic pseudoaneurysms. These have different etiologies and features on imaging.

1. C.N.S.
Intracranial Aneurysms

2. Mohamed Zaitoun
Assistant Lecturer-Diagnostic Radiology
Department , Zagazig University Hospitals
Egypt
FINR (Fellowship of Interventional
Neuroradiology)-Switzerland
zaitoun82@gmail.com

5. Knowing as much as
possible about your enemy
precedes successful battle
and learning about the
disease process precedes
successful management

6. Aneurysm
1-Presentation
2-Incidence
3-Diagnosis
4-Types

7. 1-Presentation :
a) Sudden onset of severe headache
b) Mass effect
c) Thromboembolic events

8. a) Sudden onset of severe headache :
-Sudden onset of severe headache +/- neurological
signs + /- reduced level of consciousness with
scan findings of :
1-Subarachnoid Hemorrhage
2-Parenchymal Hemorrhage (usually with
associated SAH )
3-Intraventricular Hemorrhage (most often
secondary to bleeding in the general
subarachnoid space , occasionally primary)

9. b) Mass effect :
1-Cranial nerve palsies (especially 3rd
nerve palsy
with PCOM aneurysms)
2-Horner’s syndrome
3-Brainstem dysfunction
4-Hydrocephalus
c) Thromboembolic events

10. 2-Incidence :
-Incidence in general population is 2-3 %
-Overall risk of rupture = 0.5-1.5 % per annum ,
variable according to size and position of
aneurysm , sex , smoking , etc

11. 3-Diagnosis :
a) CT & CTA
b) MR & MRA
c) Catheter Angiography

12. a) CT & CTA :
-Extra-axial mass in subarachnoid space
-Enhances if patent
-May be thrombosed and / or have calcification
(especially giant aneurysms)
-CTA demonstrates site and morphology of
aneurysm and may allow planning of
treatment (neurointervention versus surgery)
without need for catheter angiography

13. Nonenhanced CT scan of a middle-aged man with headaches, the patient had
a giant aneurysm of the LT ICA in its intracavernous segment, this
aneurysm is densely calcified and is easily depicted

14. CTC shows a basilar tip aneurysm

15. Coronal reformatted MIP images from a CTA demonstrates a 5 mm aneurysm
(straight arrow) of the anterior communicating artery (arrowhead)

16. RT MCA aneurysm seen on both CTA and MRA), A, Coronal section on CTA reveals
aneurysm in RT MCA bifurcation, B, MRA also displays aneurysm with less
definition, C, 3D reconstruction of CTA better defines saccular appearance of this
aneurysm

17. A, Catheter angiography lateral view, following left ICA injection, shows
aneurysm originating from supraclinoid portion of ICA, B, CTA axial source
image reveals lobulated aneurysm (arrow)

18. CTA obtained on day 6 after occurrence of aneurysmal subarachnoid
hemorrhage shows severe spasm of the right MCA (arrows) and a midline
hematoma surrounding a thrombosed aneurysm of the anterior
communicating artery

19. b) MR & MRA :
-Patent aneurysm will show flow void
-Giant or partially thrombosed aneurysms can
show complex flow patterns with
heterogeneous signals on standard sequences
-Not reliable for treatment planning

20. T1 of a middle-aged woman with progressive headaches, aphasia, and right-
sided hemiparesis, a large intracerebral mass with a significant amount of
surrounding edema is depicted, the lesion is a giant internal carotid artery
aneurysm

21. T2 of a middle-aged woman with progressive headaches, aphasia, and right-
sided hemiparesis, the lesion is a giant internal carotid artery aneurysm,
note the flow void, the blood breakdown products within the layers of
mural thrombus, and calcification within the aneurysm that produces a
marked hypointense signal, significant surrounding edema is depicted

22. T2 shows 7-mm basilar artery terminus aneurysm (arrow)

23. MRA shows basilar tip aneurysm (arrow) and very small (1.5
mm) P1 segment aneurysm (arrowhead)

24. Coronal T2 through the chiasmatic cistern , the optic chiasm is displaced to the left (arrow) and
the anterior cerebral arteries elevated by a large right carotid-ophthalmic aneurysm , this
patient present with visual disturbance and examination revealed an ipsilateral temporal
quadrantanopia

25. (a) Axial T2 and (b) oblique frontal intra-arterial digital subtraction
angiography showing a giant aneurysm of the intrapetrous right carotid
artery , this patient presented complaining of deafness and was treated
by balloon occlusion of the carotid artery

26. c) Catheter Angiography :
-Invasive with 0.1-0.5 % inherent stroke risk
-Still considered gold standard but may soon be
superimposed by CTA

27. Left oblique cerebral angiogram in a patient with multiple intracranial
aneurysms shows an anterior communicating aneurysm and a middle
cerebral artery aneurysm

28. (a) Axial CT showing acute SAH with intra parenchymal and intraventricular
hemorrhage , (b, c) DSA by right (b) and left (c) ICA injection 2 days after the
hemorrhage shows no evidence of vasospasm and only faint filling of a small
saccular aneurysm of the anterior communicating artery on b (arrow) , (d, e) A
repeat study was performed 4 days later and shows the aneurysm filling from the
left side (e) and intense vasospasm of right (d) and left (e) anterior cerebral
arteries

29. (a) Left carotid angiography showing a saccular ACOM aneurysm 24 h after
rupture , (b) the aneurysm rebleed before treatment and a second
angiogram 8 days later (immediately prior to coil embolisation) shows a
daughter lobule at the fundus

30. (a) Very large aneurysm arising from the lCA distal to the ophthalmic artery origin ; pointing
upwards and medially , aneurysms at this site are variously described as carotid-ophthalmic ,
paraclinoid or global ICA aneurysms , the neck is very wide and this lesion was treated by
parent artery occlusion , (b) T1 showing the aneurysm filling the chiasmatic cistern with the
chiasm displaced to the right , (c) T1 shortly after left ICA balloon occlusion , the aneurysm
sac is substantially thrombosed

31. ICA DSA showing a small superior hypophyseal aneurysm arising from the
supraclinoid artery and pointing medially , the aneurysm arises at the
level of the superior hypophyseal artery , but this vessel is rarely visible on
angiography

32. Oblique frontal angiograms of a large aneurysm of ICA , (a) before and (b) 6 months after coil
embolisation , aneurysms at this site often have wide necks which increases the risk of
recurrence after coil embolisation , a microcatheter has been positioned in the central part of
the aneurysm sac in (a) , at follow-up (b) there is a small neck remnant (arrow) which will be
monitored by further intra-arterial angiography

33. Lateral intra-arterial DSA showing a small aneurysm at the origin of the
anterior inferior frontal artery , the angiogram was performed soon after
SAH

34. Left MCA arising at the bifurcation , the orbitofrontal artery arises from the
superior trunk (arrow) and its origin is intimately related to the aneurysm
neck , an early branch of the M2 arteries such as this may be difficult to
separate , on imaging , from the aneurysm neck

35. Basilar artery (BA) termination aneurysm on frontal (a) and oblique (b) intra-arterial DSA , this
aneurysm points upwards and to the right side , lateral deviation of the aneurysm sac is due
to asymmetry of the inflow , the bifurcation of the BA , in this case , is low relative to the
dorsum sella and the P1 arteries are therefore directed vertically , the right P1 is obscured
and oblique views (b) are used to show the relationship of the aneurysm neck to the
posterior cerebral artery origins , note that both PCOMs fill and the proximity

36. Oblique lateral intra-arterial DSA following vertebral artery (VA) injection , there is a
small saccular aneurysm arising from the PICA , the neck of the aneurysm is clearly
separate from VA ; arising from the apex of the initial downward turn of the lateral
medullary section of PICA , the aneurysm points upwards and medially

37. 4-Types :
a) Saccular aneurysm
b) Fusiform aneurysm
c) Dissecting aneurysm
d) Mycotic aneurysm
e) Oncotic aneurysm
f) Traumatic pseudoaneurysm

38. a) Saccular Aneurysm :
1-Incidence
2-Etiology
3-Radiographic Features
4-Complications
5-Multiple aneurysms
6-Giant aneurysm

40. 1-Incidence >>
-Present in approximately 2% of population ,
multiple in 20% , 25% are giant aneurysms
(>25 mm)

41. -Increased incidence of aneurysm in :
a) Adult dominant polycystic kidney disease
(ADPKD)
b) Aortic Coarctation
c) FMD
d) Structural collagen disorders (Marfan syndrome ,
Ehlers-Danlos syndrome)
e) Spontaneous dissections

42. 2-Etiology :
-Degenerative vascular injury (previously
thought to be congenital) > trauma ,
infection , tumor & vasculopathies

43. 3-Radiographic Features :
a) CT & CTA
b) MR & MRA
c) Catheter Angiography

44. a) CT & CTA :
-See before
b) MR & MRA :
-See before

45. c) Catheter Angiography :
-Number of aneurysms : multiple in 20%
-Location , 90% in anterior circulation
-Size
-Relation to parent vessels
-Presence and size of aneurysm neck

46. 4-Complications :
a) Rupture >>
-SAH
-Parenchymal hematoma
-Hydrocephalus
b) Vasospasm >>
-Occurs 4 to 5 days after rupture
-Causes secondary infarctions
-Leading cause of death / morbidity from rupture

47. c) Mass effect >>
-Cranial nerve palsies
-Headache
d) Death >> 30 %
e) Rebleeding >>
-50% rebleed within 6 months
-50% mortality

48. 5-Multiple Aneurysms :
-In the presence of multiple aneurysms , one may
identify the bleeding aneurysm using the following
criteria :
a) Location of SAH or hematoma adjacent to or around
bleeding aneurysm
b) Largest aneurysm is the one most likely to bleed
c) Most irregular aneurysm is the one most likely to
bleed
d) Extravasation of contrast (rarely seen)
e) Vasospasm adjacent to bleeding aneurysm

49. 6-Giant aneurysm :
a) Definition :
-Aneurysm > 25 mm in diameter
b) C/P :
-Mass effect (cranial nerve palsies , retro-orbital
pain )
-Hemorrhage

50. c) Radiographic Features :
1-Large mass lesion with internal blood
degradation products
2-Signet sign : eccentric vessel lumen with
surrounding thrombus
3-Curvilinear peripheral calcification
4-Ring enhancement : fibrous outer wall
enhances after complete thrombosis

51. 5-Mass effect on adjacent parenchyma
6-Slow erosion of bone :
*Sloping of sellar floor
*Undercutting of anterior clinoid
*Enlarged superior orbital fissure

52. b) Fusiform (Atherosclerotic) Aneurysm :
1-Etiology & Incidence
2-Radiographic Features
3-Complications

54. 1-Etiology & Incidence :
-Elongated aneurysm caused by atherosclerotic
disease
-Most located in the vertebrobasilar system
-Often associated with dolichoectasia
(elongation and distention of the
vertebrobasilar system)

55. 2-Radiographic Features :
-Vertebrobasilar arteries are elongated ,
tortuous and dilated
-Tip of basilar artery may indent 3rd ventricle
-Aneurysm may be thrombosed :
CT: Hyperdense
T1W: Hyperintense

56. 3-Complications :
a) Brainstem infarction due to thrombosis
b) Mass effect (cranial nerve palsies)

57. c) Dissecting Aneurysm :
1-Etiology
2-Radiographic Features

60. 1-Etiology :
-Following a dissection an intramural hematoma
may organize and result in a saclike out
pouching
-Causes : Trauma > vasculopathy ( SLE , FMD ) >
spontaneous dissection
-Location: Extracranial ICA > vertebral artery

61. 2-Radiographic Features :
Elongated contrast collections extending beyond
the vessel lumen
Angiography is sometimes required for imaging
of vascular detail (dissection site)

62. Patient presenting with SAH) due to rupture of a dissecting aneurysm of the
right intracranial vertebral artery (VA) (arrow) , this is a common site for a
dissecting aneurysm to cause SAH

63. (a) Diffusion shows lesion of restricted diffusion on the left side (arrow), which was consistent
with acute posterior choroidal-artery infarction, (b) T2, (c) MRA and CTA (d) show a dilatation
of the left posterior cerebral artery, with a double lumen, that is, a true circulating lumen
(lower arrows) and a false noncirculating lumen (upper arrows) divided by an intimal flap (b,
arrowheads), suggesting a dissecting aneurysm, (e) Angiography confirmed an aneurysm of
the posterior cerebral artery , (f) shows the coiling of the aneurysm

64. d) Infectious (Mycotic Aneurysm) :
1-Causes :
-Bacterial endocarditis , IVDA (intravenous drug
abuse) 80 %
-Meningitis , 10 %
-Septic thrombophlebitis , 10 %

65. 2-Radiographic Features :
-Aneurysm itself is rarely visualized by CT
-Most often located peripherally and multiple
-Intense enhancement adjacent to vessel
-Conventional angiography is the imaging study
of choice

66. Coronal CT angiography showing a large irregularly shaped
presumed mycotic middle cerebral artery aneurysm

69. e) Oncotic aneurysm :
-Is an aneurysm caused by neoplasm
-A benign left atrial myxoma may predominantly
embolize and cause a distal oncotic aneurysm

70. Oncotic IAA in a 14-year-old girl with Maffucci syndrome and a skull base
chondrosarcoma, (a) Axial T2 through the circle of Willis shows bulbous
dilatation of the right ICA (arrow) where it abuts the skull base
chondrosarcoma (arrowheads), (b) Axial CTA at the same level shows the
aneurysmally dilated right ICA (straight arrow), mildly aneurysmal left ICA
(curved arrow), and normal-caliber basilar artery (arrowhead)

71. f) Traumatic Pseudoaneurysm :
-Aneurysms due to trauma are most commonly
pseudoaneurysms which don’t contain the typical
three histologic layers of the vessel wall, usually the
vessel wall exhibit abnormal luminal narrowing
proximal to the aneurysm
-Similar to mycotic aneurysms, traumatic
pseudoaneurysms tend to occur distally
-Arteries close to bony structures (such as the basilar &
vertebral artery) are prone to dissecting aneurysms

72. (a) Preoperative T1+C shows a 3-cm tuberculum sellae meningioma encasing the
ACOM, (b) Preoperative RT ICA angiogram shows elevation of the right A1 portion
and occlusion of the left A1 portion, but no aneurysms (c) RT ICA angiogram, 1
month after surgery, shows a newly developed 3- × 5-mm aneurysm of the ACOM,
(d) RT ICA angiogram, 2 months after surgery, shows a 6- × 8-mm aneurysm that
enlarged progressively