Definition Abnormal arteriovenous shunts within the dural leaflets

Definition Abnormal arteriovenous shunts within the dural leaflets in AVMs: nidus in pia mater, no dural feeders

d. AVFs • 5 -20% of all intracranial malformations • Most common acquired intracranial vascular malformation • 6 th – 7 th decade • Arterial supply from dural arteries (less common: osseous branches) • Venous drainage via dural venous sinus, cortical veins or both • Symptoms secondary to venous congestion • 8% multiple d. AVFs

Pathogenesis ? Head injury ? Craniotomy ? Hypercoagulability ? ? ? Recanalisation Venous hypertension Pre-existing dural microvascular channels Sinus thrombosis • Enlarged by venous hypertension Neoangiogenesis • BFGF, VEGF Dural AVF formation

Clinical Presentation • Pulsatile tinnitus, objective bruit • Haemorrhage (ICH, SDH, SAH, IVH) • NHND (Non-hemorragic neurological deficit) • Focal • Global • Visual disturbances • • Opthalmoplegia Visual loss Glaucoma Papilledema • Facial pain (compression of V 1, V 2 at the lateral wall of the cavernous sinus)

Diagnosis • Golden Standard: 6 -vessel angiography • Presence or absence of CVR (determination of the exact site) • Venous sinus occlusion * • Direction of flow in sinuses • Venous drainage pattern of brain • ? MRI/MRA * Careful in symptomatic patients!! - deficits may improve with restoration of normal flow

Classification Borden Classification Cognard Classification Type I: Drainage into venous sinus or meningeal vein only Type I: Drainage into dural venous sinus only, antegrade flow Type IIa: Drainage into dural venous sinus only, retrograde flow Type II: Drainage into dural venous sinus or meningeal vein + CVR* Type IIb: Drainage into dural venous sinus (antegrade flow) + CVR Type IIa+b: Drainage into dural venous sinus (retrograde flow) + CVR Type III: CVR only without venous ectasia Type IV: CVR only with venous ectasia *CVR: Cortical Vein Reflux Type V: Drainage into spinal perimedullary veins

Natural History Borden Type I II III Aggressive Presentation % 2% 39% 79% Aggressive presentation defined as ICH, NHND or death as the presenting symptom Davies et al. , “The validity of classification for the clinical presentation of intracranial d. AVFs”, J Neurosurg 1996

Management Options Observation • For d. AVFs without CVR • ANY change in symptoms might signal development of CVR (2 -3%) • Serial MRI/MRA + angiogram after 3 years Endovascular • Transarterial embolization (palliative or preoperative) • Transvenous embolisation Surgical • Venous access + direct packing of sinus • Surgical excision • CVR disconnection

Borden type I • Benign natural history: 2% of ICH, NHND (Van Dijk et al, 2002) • 2 -3% to develop CVR • Palliative or no treatment Right occipital artery, antegrade flow into transverse/sigmoid sinus (Cognard I) Left vertebral artery, retrograde flow into transverse/sigmoid sinus (Cognard IIa)

Management Strategy No CVR (Borden I, Cognard I, IIa) Asymptomatic or tolerable symptoms Intolerable symptoms Observation Palliative treatment (e. g. , endovascular transarterial embolization of feeders) Benign Fistulas No change in Symptoms Worse OR Better Continue Observation Serial MRI + MRA Repeat angiogram in 3 years Repeat angiogram

Borden type II • Type II + III: 15% annual risk of rebleeding • 35% rebleed within 2 weeks (one series) • Complex management strategy – multidisciplinary approach LECA angiogram, superficial temporal artery, antegrade flow into SSS, with CVR (Cognard IIb) LECA angiogram, occipital artery, retrograde flow into transverse sinus, with CVR (Cognard IIa+b)

Management Strategy CVR and sinosal drainage (Borden II, Cognard IIb, IIa+b) Aggressive Fistulas (with sinus drainage) No neurological deficit Neurological deficit secondary to venous congestion Assess venous phase of angiogram Interruption of feeding arteries only (transarterial endovascular or surgical) Sinus not used by brain Sinus used by brain Complete obliteration or excision of lesion including sinus sacrifice OR CVR disconnection only (endovascular transvenour or surgical) CVR disconnection only (endovascular transvenous or surgical)

Borden type III RECA angiogram, superficial temporal artery, CVR, no ectasia (Cognard III) RECA angiogram, posterior branch of MMA, ectatic cortical vein drainage(Cognard IV)

Management Strategy CVR only (Borden III, Cognard III, IV, V) Aggressive Fistulas (without sinus drainage) No neurological deficit Neurological deficit secondary to venous congestion Assess venous phase of angiogram Interruption of feeding arteries only (endovascular transarterial or surgical Refluxing cortical vein not used for drainage of brain Refluxing cortical vein used for drainage of brain CVR disconnection (endovascular transvenous or surgical) Interruption of arterial feeders only (endovascular transarterial or surgical)

Transverse/Sigmoid Sinus d. AVFs - Most common (40 -60%) Arterial Supply ECA (occipital, posterior auricular , MMA, ascending pharyngeal) VA (posterior meningeal branch) ICA (meningohypophyseal trunk) Petrous bone Venous drainage Ipsilateral or contralateral sinus (if thrombosed) Cortical veins (temporal, occipital, cerebellar)

Transverse/Sigmoid d. AVFs Complete CVR: excision: • Dural Drill flap bonebased laterally on sinus (mastoid & petrous) to expose sigmoid • Disconnect sinus (anterolateral ALL arterialized dura) • veins Dura incision above & below TS (medial to lateral) • Occlude & cut TS medially • Expose and cut tentorium • Extend to junction • Evaluate venous anatomy (Labbe, sigmoid sinus patency)

Cavernous Sinus fistulas Barrow et al classification of carotid-cavernous fistulas Type Feeding arteries A Direct fistula between ICA & CS B ICA meningeal br. C ECA meningeal br. D ICA + ECA meningeal br. Spontaneous Resolution? High-flow No Low-flow Yes …presented next week…

Anterior Cranial Fossa d. AVFs • Arterial supply: anterior and posterior ethmoidal a. • Venous drainage: ALWAYS cortical veins (frontal, olfactory) • Aggressive lesions • Treatment: Surgery (unilateral frontal or bifrontal craniotomy) • !Embolisation risk of central retinal artery occlusion

Convexity d. AVFs • Arterial supply: MMA • Venous drainage: SSS +/- CVR • Treatment: Surgery • Other options for high-flow fistula into SSS (without CVR) associated with papilledema: • LP shunt • Optic nerve sheath decompression

Deep venous d. AVFs • Arterial supply: ECA, ICA, VA, PCAs (tentorial dural branches) • ? Hypertrophic dural arteries (including Bernasconi, Davidoff) • Venous drainage: Rosenthal, LMVs, Galen • Aggressive lesions • If drainage into LMV quadriparesis • Treatment: Surgery (CVR disconnection)

Superior petrosal sinus d. AVFs • Arterial supply: ECA, ICA, vertebrobasilar (dural branches) • Venous drainage: Usually (94%) CVR with SPS thrombosis • Presentation: • ICH 50% • Ocular symptoms (w/ reflux into CS & SOV) • Trigeminal neuralgia • Treatment: Surgery (subtemporal craniotomy, posterior petrosectomy, suboccipital craniotomy) • Aim for CVR disconnection

Inferior petrosal sinus d. AVFs • Arterial supply: Vertebrtal a. , ECA (ascending pharyngeal, MMA, occipital) • Venous drainage: • Retrograde to IPS CS • Jugular bulb (tinnitus) • Retrograde to transverse/sigmoid sinus • Treatment: Surgery (far lateral approach) • Aim at CVR disconnection

Results • Van Dijk et al, Toronto, 2004: • • 94. 1% cure (25% endovascular, 25% surgical, 44% combined) All complications transient (17. 56% surgical, 4% endovascular) No deaths or permanent neurological deficits CVR disconnection equal to total excision • Ambekar et al, Miami, 2015: • 14. 3% recurrence following endovascular treatment alone • Baltsavias et al, Zurich, 2014: • 85% complete occlusion following endovascular treatment alone

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