georges rodesch md phd dept of diagnostic and therapeutic ...€¦ · dissecting aneurysms stehbens...
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Aneurismi dissecanti e patologia della parete
Georges Rodesch MD PhD
Dept of Diagnostic and Therapeutic Neuroradiology
Hôpital Foch, Suresnes, France
Pathological mechanism and 3D structure of cerebral dissecting aneurysmsMizutani T et al , JNS 2001
The substantial pathological mechanism creating a dissecting aneurysm is createdby a sudden widespread disruption of the IEL
IEL : *mainly elastic fibers *most important layer of cerebral arterial wall for protection against
hemodynamic stress* supports blood pressure of 600 mm Hg (Glynn LE, J Pathol Bacteriol, 1940)
Endoth cellsconjonctive t
Smooth m cExtracell components (elastin, collagen, proteoglycanes…)
CollagenThick elastic fFibroblasts
Media is always disrupted adjacent to disrupted IEL
Plane of dissection extends through loose portion of media and is determinedby the extent of disruption of the media
If disruption of media is minimal, dissecting plane is between IEL and media
If the media is totally disrupted, dissecting plane is between media and adventicia
Dissecting aneurysms accompanied by infarction have less medial damage than those with SAH
Usually occurs in pts in 5 th or 6 th decades
Primary cause of dissection is unknown : Infection? Ischemia? Mechanical constraints? HTA?
Since Turnbull 1915 : syphilitic arteritis, rupture of vasa vasorum, medial degeneration, congenital defect in media and/or IEL…
Dissections : mechanical or biological phenomenon?
The tear…
« Entry only » vs. « Entry- Exit »
Immune: inflammatory, infectious, deficiency (HIV, candidosis…)Hemodynamic (BAVM+ AA…)Genetical: NF1, PKD, ED, FMD, Marfan…
Intracranial dissection
Surgical removal D35 post SAH
Disruption of IEL
Wall adjacent to rupture: thin fibrin and collagen
Most frequent type (?)Age at time of SAH: hrs-1w(no healing process)
Pseudolumen is « dead end »Blood flow unstable. Rebleed++If thrombosis: stenosis at A°Mizutani JNS 2001
Autopsy D35 post SAH
Disrupture of IEL + media« Entry only »
« Entry only »
Mizutani JNS 2001
Dense collagen proliferation atsurface of pseudo lumen
A°: smooth margins if patentpseudolumen
Age of « Entry-Exit » aneurysm?
Several weeks till time of bleeding because of dense proliferation of collagen at surface of pseudolumen
Constant stable flow throughpseudolumen for long periodswithout clinical symptoms
« Entry- Exit »
42y M
HIV+SAH
Dissecting Aneurysms
Stehbens (1963) MCA 41%VB 23%ICA 21%ACA 13%other 2%
Segmental vulnerability
Angiographic diagnosis (may be challenging)
arterial pouch/focal enlargement/fusiformstenosis proximal/distal
82% were subintimal (without SAH)
If distally located AA (PICA, PCA, MCA, ACA…): raise the possibility of dissection
Difficult to distinguish effects produced by triggersvessel wall diseaserepair processes
Stagnation in (false) AA, stenosis arterial segment, fusiform aspect artery…
Interest of MRI
Horie N et al, JNS 2011
Day 7
Mizutani 1999 4 types
1. Classic dissecting AA SAHfusiform; irregular wallrebleeding ++; death ++
disruption of elastic laminano intimal thickeningfalse lumenfragile adventiciano thrombus in AA
Acute process
EL regeneration in healed dissecting AA
61 Y maleSudden loss of consciousness
2. Segmental ectasia fusiform AA, smooth walllarge lumenno thrombus
stretched/fragmented ELmoderately thick intima
« placid » evolutionEL compensation by intimaChronic response?
3. Dolichoectatic dissecting AA
tortuous fusiform appearanceintraluminal organized thrombiintimal flapprogression giant size
fragmented ELdissections thickened intimathrombus at site intimal dissection
Recurrent hemorrhages inside walland thrombus
CourtesyT Siniluoto
4. Saccular AA unrelated to branchingSAH +++
EL disrupted, fragmenteddistended fragile adventicia
Blister AA
High frequency of rebleed in dissecting AA with SAH (57.1% within 1 week after initial SAH) (10% after 1 month)
Mizutani et al Recurrent SAH from untreated ruptured VB dissecting aneurysms
Neurosurgery 1995
Rebleed rate decreases after 1 WLongest interval between first SAH and rebleeding : 41 days=> Some healing mechanisms (scar…) are at work after SAH
Mizutani et alHealing process for cerebral dissecting aneurysms presenting with SAH
Neurosurgery 2004
13 pts: 9 VA, 2 ICA, 1 ICA, 1 SCA
43 y female dissection L VA autopsy D14Ruptured media + IEL no neo intima ruptured portion covered by thrombus
Healing process for cerebral dissecting aneurysms presenting with SAHMizutani T et al, Neurosurgery 2004
67 Y male Dissect VA Prox clipping D1Autopsy D14
Silent repair of IEL disruptionLocal thickening of neointima
Disrupted ends of IELDisruptend ends of adventicia
AA at the ruptured portion
34 y female Dissection L SCA. Resection D 23
Disruption of IEL Circumferential prolif of neointima
The time of genesis of dissecting AA can be determined on the basis ofclinical presentation (headaches, SAH, stroke…)
According to the time after presentation: chronological changes in arterial wall(healing process)
Injured arterial wall is repaired with other matrix components in a biological reaction (and many repairs can occur silently)
1st day: leucocytes + macrophages3-5 days: endothelial coverage4 days: smooth muscle cells1 week: neo intima (ceases at 3 months)
Pool et al Am J Pathol 1971Mizutani et al , JNS, 2004
*Newly synthetized smooth muscle cells (in neo intima)(from the disruptured ends of media towards ruptured part)*Extracellular matrix (collagen, elastic fibers, proteoglycans etc)
( determines the strength of the repaired vessel)
consists
4th dimension….Time
Healing mechanism may be delayed in certain conditions
*A longer time is needed for repair tissue over the whole vessel circumference : large dissecting aneurysms carry rebleed risk for a long time
*if thrombus in AA (neointima may appear in accordance to retraction of thrombus)
•AA where IEL and media are completely separated from adventitia
Theoretically: wall repair completed after full coverage of arterial wall by neointima
Rate of rebleed after one week ~ standard time for appearance of neointima
Mizutani 2004: neointima did not reach ruptured portion of dissection in most cases=> Pathological confirmation of safety from the risk of rebleed is not obtained…
Mizutani 2004
Initial FU
Decision to treat (sacrifice) when
progressive enlargement
Angio when trtt was decided. E° withdrawn at that stage
Further control
Because first « deflatening » of the sac was obtained during A°under GA and hypoAT, pt was proposed GA and hypoAT for 24hrs in ICU to promote
thrombosis. Angio confirmed the previous finding
Control shows
appearance of stenosis
on AICA proximal to AA
Healing process was
Suspected.
P1-P2 dissecting AA presenting with CVA treated with anticoagulation
Courtesy KTB
Intracranial Aneurysms in the pediatric population
• Traumatic
• Associated with BAVM
• Dissecting
• Inflammatory and infectious
• Hereditary (Familial)
• Collagen disorders
• “Congenital” or berry type (ruptured, unruptured)
• Atherosclerotic (fusiform, giant size etc)
1 y boy
3w earlier V+, « not well »gastroenteritis ? 1st HB ?
Dissection from mural hematoma
ExtrinsicFactors
Inflammation(Auto) immune
IschemiaAtherosclerosisHemodynamics
TraumaHTA
IntrinsicFactors
Systemic diseaseSegment. vulner.Dysplastic wallVasa Vasorum (?)Altered repair
mechanisms
Sub adventicial(transmural)
Subintimal
Reopeningof vessel lumen
Completerepair
SAH Distal emboli Normal aspect orfusiform dolicho a
Acute Subacute
Modified from P Lasjaunias 2006
Dissection from mural hematoma
ExtrinsicFactors
Inflammation(Auto) immune
IschemiaAtherosclerosisHemodynamics
TraumaHTA
IntrinsicFactors
Systemic diseaseSegment. vulner.Dysplastic wallVasa Vasorum (?)Altered repair
mechanisms
Sub adventicial(transmural)
Subintimal
Reopeningof vessel lumen
Completerepair
Recurrentdissections
SAH Distal emboli Normal aspect orfusiform dolicho a
Partiallythromb.AA
Acute Subacute Chronic
Modified from P Lasjaunias 2006
A form of « chronic » dissection: partially thrombosed AA
Schubiger et al, Neuroradiology 1987
« slow growth by recurrent hemorrhagesinto the lesion »
« recurrent hemorrhages from capillaries sprouting within the membrane of the lesion »
« the highly vascularized membranous wallof a giant intracranial aneurysm seems tobehave like the membrane of a chronic subdural hematoma »
«the giant intracranial aneurysm grows byrecurrent hemorrhage into its wall and behaves like growing encapsulated hematomas »
Zhao et al, Nat Med 2004 Krings et al, Neuroradiology, 2005
5-LO expressed in mast ¢,leucytesand macrophages
Once these ¢ are activated, 5-LO creates mediators of inflammation(leukotrienes) =>activation +recruitment
mast¢,leucytes,macrophages
Inflammatory process of vessel wall
Leucotriene binding to vasa vasorum leucocyte extravasation
proliferation of vasa vasorumweakening of vessel wall
arterial aneurysm formation »
Growth and rupture of these lesions depend on biological
factorsthat are induced from the outside with help of vasa
vasorum(« abluminal aneurysmal
vasculopathy »)P. Lasjaunias
Partially thrombosed AA
Other names?
AA with intramural haemorrhageChronic dissecting AA
Key words : vasa vasorum dissectioninflammation
Consequences: mass effectthrombus different agescontinuous growing (sometimes even after vessel occlusion)spontaneous thrombosis
PRE EMBO
Cause of dissection is unclear triggers: infection, ischemia ?...underlying disease ?biological disorders ?
Evolution variable : repeated ischemia /Hbspontaneous healing
no recurrence after healing/trtt
Sacrifice. Stent. FD? . Anatomy
SUMMARY
Frequent rebleed if presentation with hemorrhageRare bleeds if initial non hemorrhagic presentation