	Aetiology	Pathology	Prevalence	Haemorrhage risk
With AV Shunting
AVM	Congenital (dysregulated angiogenesis)	Nidus +arterial feeders, draining vein, no capillary bed	Up to 0.14% of population	Very high 2-4%/year
Dural AV fistula	Acquired (trauma, thrombosis)	Network of multiple AV microfistulas	Up to 0.05%	Variable
Vein of Galen Malformation	Congenital	Large venous pouch	Rare	Low
Without AV shunting
Developmental venous anomaly	Congenital (arrested foetal medullary vein development	Dilated WM veins (normal brain in between)	2-9% of population	Very low
Sinus pericranii	Congenital	Blood filled, subcutaneous scalp mass	Rare	Very low
Cavernous malformation	Congenital	Collection of blood filled caverns with no normal brain.	Up to 0.6% of population	High ~0.5%/year
Capillary telangiectasia	Congenital	Dilated capillaries, normal brain in between.	Moderately common	Very low

AVMs

Definition

• Tangle of arteries and veins without a capillary bed in between them

• Three components:

o Feeder artery

o Nidus

o Draining vein

• There is often an associated saccular aneurysm (up to 15%)

Epidemiology

• Of ‘detection’ of AVM - 1/100,000 per year

• 0.02-0.14% of population

• Peak presentation 20-40

• In young patients with ICH an AVM is the cause in about 1/3

Aetiology

• Most are congenital due to a focal abnormality of angiogenesis

• Can occur in genetic syndromes:

o Hereditary haemorrhagic telgiectasia

Clinical manifestations

• Haemorrhage – 50%

• Epilepsy – 25%

• Asymptomatic

Imaging

• 85% are supratentorial

• CT

o Bag of worms

o Calcification common

o All three elements enhance with contrast

• MRI

o Flow void honeycomb mass

o Brain parenchyma within lesion is usually gliotic and hyperintense on T2

o May be surrounding T2* bloom due to haemorrhage

• May be associated flow related aneurysm in up to 15%

Prognosis

• Rate of (re)rupture

o If associated aneurysm – 7%/year

o If no aneurysm – 2-3%/year

Treatment

• Very controversial

• ARUBA study (Lancet 2014 383:614)

o 223 patients randomised to surgery vs medical management

o Stopped early

o Primary endpoint (death or symptomatic stroke) 10% vs 30% (in favour of medical management.

• Observational trial (JAMA 2014 311:1661) confirmed similar results.

Dural AV Fistula

Aetiology and pathology

• Acquired

• Usually secondary to venous thrombosis in a sinus. Thought that upregulated angiogenesis causes proliferation of microvascular networks and multiple tiny arterial fistulas

Clinical features

• Often benign

• Some can progress and enlarge with a high rate of haemorrhage

Imaging

• Often associated venous thrombosis

• Enlarged dural sinus

• Multiple small dilated vessels

Carotid-cavernous fistula

• A special type of dural fistula

• Two types”

o Direct – rupture into sinus

o Indirect – slow-flow via arteriovenous connections

• Accquired

o Direct – trauma

o Indirect – degeneration

Cerebral Cavernous malformations (Cavernoma)

Aetiology and pathology

• Lesions consisting of tightly packed epithelium lined vascular channels (“Caverns”) in collagenous stroma

• Thin walled caverns containing haemorrhage in different stages of evolution

• Low flow arterial supply and normal venous drainage

• Do not contain brain parenchyma

• 1mm to several cm

• Mulberry-like conglomerates

• Can variably enlarge over time

Incidence

• 0.5% of routine post-mortems

• 2/3 solitary

• 1/3 multiple

• Can be associated with DVA

Clinical

• Epilepsy

• Haemorrhage

o Risk of haemorrhage highly variable – 0.25% to 6%/year

o Often small haemorrhage causing limited focal deficits

o If in brain stem however small bleed can cause large deficit

• Focal deficits from enlarging lesions

· Meta-analysis of risks

o Lancet Neurology Horne et al.

Mode of presentation leading to CCM diagnosis

	Incidental	Seizure	ICH	Focal Neurological deficit
Lobar	65%	86%	27	50
Deep	10%	5	7	8
Cerebellum	11%	4	4	62%
Brainstem	14%	4	62	35

5 year risk of ICH

ICH or FND presentation Brainstem location	31%
ICH or FND presentation Non-brainstem location	18%
Other presentation Brainstem location	8%
Other presentation Non-brainstem location	4%

Imaging

• Can occur anywhere in CNS

• CT

o Hyperdense lesion, often subtle, sometimes with calcification.

• MRI

o Mixed signal popcorn ball

o Surrounding rim of T2* bloom

o Usually not contrast enhancing

Treatment

• Surgical resection – often considered for brainstem lesions given risks if haemorrhage occurs

Suggested treatment and monitoring protocol (From paper Surgical Neurology 63 (2005) 319– 328):

• Cases of suspected cavernous angioma should undergo MRI scan with gradient echo imaging (to exclude or define multifocal lesions and likely genetic substrate) and gadolinium-enhanced study (to exclude or define associated venous angioma).

• Asymptomatic lesions in any location are generally observed carefully with follow-up MRI at a yearly or 2 year intervals. The relatively benign nature of the lesion obviates the need for any immediate resection unless they grow or become symptomatic

• Superficial lesions in accessible noneloquent areas with overt hemorrhagic presentation should undergo resection with frameless stereotactic guidance. Lesions in eloquent location should be observed or resected depending on balanced risk benefit analysis in the individual patient.

• Progressive enlargement of cavernoma with mass effect–related symptoms should be resected using frameless stereotaxy and functional magnetic resonance imaging guidance.

• Patients with accessible single lesion presenting with seizure disorders are strong candidates for surgical extirpation of lesion and surrounding abnormal brain parenchyma. The threshold for intervention depends on lesion accessibility, eloquent location, and severity of seizure disorder as well as resistance to medical management.

• Cases with single lesion and temporal lobe seizures should undergo lesionectomy. If this fails to correct the seizure disorder, detailed cortical and electrode electroencephalographic mapping should be performed followed by possible epilepsy surgery such as amygdalohippocampectomy.

• If the lesion features deep location, observe unless repetitive hemorrhage occurs and ventricular representation is noted. Pial surface or ventricular presentation provides surgical access to the lesion.

• Patients with multifocal lesions should generally be followed expectantly, with intervention reserved for expanding lesions with new symptoms. Cases with epilepsy and refractory multiple lesions should be studied extensively to decide if one or more lesions are responsible for intractable seizures.

• Associated venous anomalies should be spared during surgery for cavernous angioma.

Developmental Venous Anomaly (Venous angioma or Venous Malformation)

Aetiology and Pathology

• Umbrella shaped congenital malformation composed of mature venous elements

• Abnormal dilated veins that are associated with corresponding arteries which are normal.

• Possibily due to arrested development of medullary veins

• Occur in at least 2% of normal brains

• Occur in deep white matter - usually adjacent to frontal horn of lateral ventricles or next to the 4^th ventricle

• Can be associated with “Blue rubber bleb nevus syndrome”

Clinical

• Majority asymptomatic and essentially can be considered normal variants

• Haemorrhage (rare) – usually due to associated cavernoma

Imaging

• CT – usually normal

• MRI

o Detectable on contrast enhanced scans – stellate collection of veins converging on collector vein

o Slow flow may result in increased T2* signal

•

Treatment

• Surgery can often make things worse given subsequent problems with cerebral venous drainage

Capillary Telangiectasia

• Dilated capillaries

• Can occur anywhere – more common in pons, cerebellum and spinal cord

• Quite common

• MRI – subtle increased