Vascular malformation
Definition: congenital abnormalities that involve the neurovascular system, they may affect the AV system as in AVM, the venous system as in DVA and cavernous malformation or the capillaries as in capillary telangectasia.
AVMs are the most common clinically encountered abnormality
Data from surgical and autopsy findings ( Stehbens)
Type / Supratentorial / InfratentorialAVM / 62.7% / 42.7%
Cavernous malformation / 17.1% / 12.8%
DVA / 13.3% / 18.9%
Varix / o.6% / 2.4%
Pathologically
Type / Vascular component / Parenchymal component / Old hemorrhageAVM / Arteries, veins, arterialized veins,atherosclerotic changes, vessel wall calcification, thrombosed vesseles,A4 amyloid in the elderly / Dysplastic ,gliotic brain, Rosenthal fibers /-necrosis / Hemosiderin/hematoidin common
Cavernous malformation / Thick haylinized channeles, no elastic lamina, frequent thrombosis of a single channel / No intervening neural tissue ,gliosis around them / Almost always
DVA / Thin walled, patent channels usually > 30-50m / Normal / Rare
Telangectasia / Capillary with normal thin walls / Normal / Almost never
Venous Varix / Single channel / Normal / Rare
AVMs
Congenital lesions
1/7 the incidence of aneurysms
no sex predilection
70-90% supratentorial location most commonly involves the MCA distribution, followed by the ACA, then PCA.
Classification of AVMs:
1)Parenchymal (pial AVMs)
2)Dural AVMs
3)Mixed .
Parenchymal AVMs:
They are made of arterial feeders , nidus and draining veins
May contain gliotic brain tissue,
Grossly they are wedge shaped with apex toward the ventricular surface (most difficult part during resection)
Secondary pathological changes within and around pial AVMs:
1)thickening of the overlying leptomeninges.
2)Flow related aneurysms (10-15%) I) pre nidal
II) post nidal
III) nidal
3)Degenerative angiopathic changes including thrombosis, stenosis
4)Ischemia and gliosis in the surrounding brain due to steal phenomenon.
Microscopic changes:
Arteries with IEL that is split and fragmented at certain areas
Localized smooth muscle hyperplasia infiltrated with fibroblasts and interstitial connective tissue, the changes are similar to the non-complicated atherosclerosis . no cholesterol clefts ,ulceration or necrosis.
Veins no elastica, thickened walls in arterialized veins
It is difficult to pinpoint the site of bleeding in AVMs.
Multiple AVMs
98% of AVMs are solitary.
Occasionally multiple in certain syndromes
Wyburn-Mason syndrome : multiple cutaneous nevi and multiple brain and retinal Avms.
Rendu-Osler-Weber syndrome: multiple cutaneous and mucocutaneous telangectasia, pulmonary AVF and brain AVMs
Clinical presentation
I) Hemorrhage is the commonest presenting sign , about 50% of patients with AVM present with hemorrhage. Includes ICH, SAH, SDH and IVH
Phase I of the cooperative study for IC aneurysms & SAH from 24 Centers . 453 patients with AVMs.
Supratentorial------421
Infratentorial------32
236 patients presented with hemorrhage as the initial presentation.
What are the factors associated with increased risk of hemorrhage from an AVM?
a) Patient related factors:
1)Age
2)Sex
3)pregnancy
b) factors related to the AVM (angiographic):
1)Size :smaller AVMs have higher chances of hemorrhage
Waltimo et al 45pts 22 /45 presented with hemorrhage , the average volume of the AVM 2.8Cm Vs 11.5cm average volume for those presented with seizures(23).
Morello and Borghi 50/58 with small AVM presented with hemorrhage
37/49 medium size AVM presented with hemorrhage
22/47 large AVMs ======hemorrhage
Spetzler et al in a series of 92 pts
AVM size / <3Cm / 3Cm-6Cm / >6CmNumber of patients / 44 / 31 / 17
%hemorrhage / 82% / 29% / 12%
Hematoma size / 4.9Cm / 2.7Cm / 2Cm
Feeding artery pressure / 66mmhg / 47mmhg / 35mmhg
2)venous drainage : venous out flow obstruction, deep venous drainage and fewer number of draining veins is associated with increased risk of bleeding.
3)The presence of intranidal aneurysm increases the risk of hemorrhage.
4)Location of the AVM: ed risk of bleeding in AVMs located in the periventricular , intraventricular ,and insular areas
II) seizures: the 2nd commonest presenting feature 34%
More common with larger AVM
Can be focal, generalized, petit mal or psychomotor seizures.
The incidence of seizure after hemorrhage is 1%/yr
The longer the seizure history the more refractory it gets.
III) Headache : as an early symptom in 5-30% ;may present with CP of pseudotumor cerebri
IV) Steal effect , intellectual decline and stroke
Diagnosis
a)Clinical
b) Neuroimaging
CT scan changes
MRI
Angiogram
Natural history of AVM
1)what is the annual risk of hemorrhage from an AVM?
Author / No of patients / Hemorrhage rate / Mortality / MorbidityRobert et al / 168 over 8 yrs / 2.2%/yr / 29% / 23%
Graf et al / 66 pts / 2-3%
Brown et al / 168 pts over8.5 yrs / 2.25%/yr / 10-13%
Torner / 110 over 20 yrs / 2-3%/yr / 9.8%
2)What is the annual rebleeding rate?
Torner , the cooperative study 144 patients with hemorrhage followed up for 20 years no treatment the rate of bleeding was 6% in the 1st yr. after the initial hemorrhage followed by decline to 3%per yr. .
Ondra et al in a series of prospectively followed untreated AVMs F/U period 23.7yrs
114 ----hemorrhage
38------seizures
8---others
during the F/U 64 pts had at least one bleed , total bleeds 147
the annual rate of bleeding is 4%per yr., and that did not change throughout the study regardless the mode of presentation.
Samson and Batjar in their review of literature concluded
1)The annual rate of presentation is 3-4% regardless the mode of presentation, there is a slightly greater risk in the 1st yr. after the initial hemorrhage
3)The risk of death from each hemorrhage 10-15% ( 1%per yr.)
4)The risk of permanent neurological deficit is twice the death rate 20-30% (2-3% per yr.)
5)Rebleeding is not related to the size of the AVM, sex, or age.
Do AVMs change in size spontaneously?
Author / Number of pts / F/U / / / No changeHook / 13 / 3.5-21yrs / 8 / 1 disappeared / 4
Watimo / 21 / >44 months / 12 / 1 / 8
Minakawa / 20 / 5-28yrs / 4 / 4 &4 completely disappeared / 8
AVM Grading system
Spetzler and Martin
1)size of the nidus as measured on the angio or MRI
small <3cm ----1
medium 3-6Cm---2
large >6Cm------3
2)eloquence of the adjacent brain
sensorimotor cortex ,visual cortex,hypothalamus, basal ganglia ,thalamus , deep cerebellar nuclei cerebellar peduncles and brain stem
no----0
yes----1
4)Deep venous drainage (deep vascular component)
Any deep drainage
In the post fossa only drainage to the cerebellar cortical veins is considered superficial
Only superficial ----0
Deep ------1
AVM grade (size +eloquence +venous drainage)
Grade VI non-operable e.g. small AVM in the internal capsule, or hypothalamus or large one involving the whole cortex.
It merely predicts the treatment outcome , not the prognosis or the natural history
Treatment
a)surgery
Certain considerations
1-timing
2-larger flaps
3-use of hypotension intraop and post op
4- circumferential dissection around the wedge
5- interrupt the inflow before the outflow
6-staging
7-pre op embolization
b) Radiosurgery
Author / Number of pts / Type of SRS / Length of f/u Yrs / 2yr obliteration %Kjelberg / 800 / Proton beam / 20 / 15-40%
Fabrikant / 375 / Helium / 2-7 / 70-90%
Lunsford / 346 / knife / 5 / 71%
Colombo / 92 / Linear accelerator / 80%
.
C) Endovascular
Dural AVF
Abnormal AVF that occur within the dural leaflets ( essential for the Dx)
Usually related to dural sinuses
The venous drainage is to either 1) venous sinus
2) dural veins
3) cortical vein
congenital Vs acquired
common in women in particular those with cortical venous drainage
they account for 10-15% of all AVM
Classification of DAVF
Group I drain directly to the dural sinus or vein
Group II drainage into the sinus is accompanied by reflux into a cortical vein
Group III direct drainage into a cortical vein with retrograde flow
Group IV drainage into a dural venous lake .
Distribution
Transverse and sigmoid sinus ------62%
Cavernous sinus ------12%
Tentorial incisura ------8%
Convexity------6%
Sylvian middle fossa ------4%
CCF:
Feeders either ICA or ECA
Venous drainage anterior to the ophthalmic veins
Posterior IPS, SPS
And occasionally to the MCV
Classification of CCF
Type A direct shunt between the ICA and the CS
Type B shunt between meningeal branches of ICA and CS
Type C shunt between meningeal branches of ECA and CS
Type D shunt between CS and meningeal branches of both ICA & ECA
A is traumatic in origin 70-85% , younger patients. Spontaneous occlusion in20%
B,C and D are spontaneous 15-20%, elderly females , spontaneous occlusion in 10-60%
Clinical presentation is related to the venous drainage
Tentorial DAVF
almost always present with SAH or ICH
Vein of Galen aneurysm (DAVF):
Presentation:
1)Neonates presents with high output heart failure, the venous system is usually normal , no hydro
2)Infants , hydrocephalus and minimally enlarged heart, abnormal venous system
3)Older children and young adults , mass effect on the tectal plate area or SAH , abnormal venous system.
Natural history of vein of Galen malformation
Neonates progressive heart failure , will die if not treated, brain damage because of steel effect
Older children progressive hydro and hemorrhage .
Treatment of DAVF :
Observation
Surgical
Endovascular
Radiosurgery
Rererrences
1-Intarcranial AVMs –AANS publication by Barrow DL 1990
2- Dural AVF- AANS publication by Awad I 1993
3-spetzler and Martin proposed grading of AVM , J of Neurosurgery 65.1986 476-48
4- Ondra et al Natural history of symptomatic AVM. J.Neurosurgery 73: 387-391 1990