ARTERIOVENOUS MALFORMATIONS AVM: a TLA for the CNS CEREBRAL ARTERIOVENOUS MALFORMATIONS

Incidence 0.52% at autopsy Slight male preponderance (1.09 to 1.94) Congenital lesions (although rarely familial)

Embryology First half of third week of gestation epiblastic cells migrate to form mesoderm mesodermal cells differentiate to arterial and venous vessels on the surface of the embryonic nervous system

Embryology First half of third week of gestation epiblastic cells migrate to form mesoderm mesodermal cells differentaite to arterial and venous vessels on the surface of the embryonic nervous system Seventh gestational week vessels sprout branches & penetrate developing brain reach the gray-white interface, either loop back to pial surface or traverse entire neural tube, thus epicerebral & transcerebral circ'n eventually connect arterial and venous systems by around the twelfth week

Pathology & Pathophysiology absence of normal capillary system

Pathology & Pathophysiology absence of normal capillary system usual function displaced

Pathology & Pathophysiology absence of normal capillary system usual function displaced asymptomatic at birth

Pathology & Pathophysiology absence of normal capillary system usual function displaced asymptomatic at birth vessels change with time may develop aneurysms

Pathology & Pathophysiology absence of normal capillary system usual function displaced asymptomatic at birth vessels change with time may develop aneurysms parenchymal changes within and around the lesion

Pathology & Pathophysiology absence of normal capillary system usual function displaced asymptomatic at birth vessels change with time may develop aneurysms parenchymal changes within and around the lesion site frequency is proportional to brain volume

Clinical presentation 95% have symptoms by age of 70 years

Clinical presentation 95% have symptoms by age of 70 years peak presentation second to fourth decade

Clinical presentation 95% have symptoms by age of 70 years peak presentation second to fourth decade high output failure, neonate, vein of Galen hydrocephalus, first decade headache, hemorrhage, seizures, 2nd & 3rd

Clinical presentation factors contributing to symptoms vessel walls, flow and pressures

Clinical presentation factors contributing to symptoms vessel walls, flow and pressures enlargement and encroachment

Clinical presentation factors contributing to symptoms vessel walls, flow and pressures enlargement and encroachment dural sinuses

Clinical presentation factors contributing to symptoms vessel walls, flow and pressures enlargement and encroachment dural sinuses ischaemia

Clinical presentation factors contributing to symptoms vessel walls, flow and pressures enlargement and encroachment dural sinuses ischaemia cardiac output

Clinical presentation

Hemorrhage AVM Aneurysm rupture not a function of size rupture related to aneurysm size

Hemorrhage AVM Aneurysm rupture not a function of size no marked increase with exercise, pregnancy, trauma Aneurysm rupture related to aneurysm size increase with trauma exercise, end pregnancy

Hemorrhage AVM Aneurysm rupture not a function of size no marked increase with exercise, pregnancy, trauma arteriovenous, therefore less severe Aneurysm rupture related to aneurysm size increase with trauma exercise, end pregnancy arterial, therefore more severe

Hemorrhage AVM Aneurysm rupture not a function of size no marked increase with exercise, pregnancy, trauma arteriovenous, therefore less severe mortality 6 to 13.6% Aneurysm rupture related to aneurysm size increase with trauma exercise, end pregnancy arterial, therefore more severe mortality 30-50%

Hemorrhage AVM Aneurysm rupture not a function of size no marked increase with exercise, pregnancy, trauma arteriovenous, therefore less severe mortality 6 to 13.6% lower rebleed mortality rate (1%) Aneurysm rupture related to aneurysm size increase with trauma exercise, end pregnancy arterial, therefore more severe mortality 30-50% higher rebleed mortality rate (13%)

Hemorrhage AVM Aneurysm rupture not a function of size no marked increase with exercise, pregnancy, trauma arteriovenous, therefore less severe mortality 6 to 13.6% lower rebleed mortality rate (1%) vasospasm rare Aneurysm rupture related to aneurysm size increase with trauma exercise, end pregnancy arterial, therefore more severe mortality 30-50% higher rebleed mortality rate (13%) vasospasm common

Hemorrhage - AVM Nonetheless, risk of major, incapacitating, or fatal hemorrhage in untreated lesion is 40 to 50%

Hemorrhage - AVM Nonetheless, risk of major, incapacitating, or fatal hemorrhage in untreated lesion is 40 to 50% Yearly risk of initial hemorrhage ~3% Rebleed in first subsequent year 6-18%, reducing to ~3% again thereafter Pediatric prognosis worse than adult

Spetzler & Martin Grading System Criteria Score Size of Nidus Spetzler & Martin Grading System Small (<3cm) 1 Medium (3-6cm) 2 Large (>6cm) 3 Eloquence of Adjacent Brain No Yes 1 Deep Vascular Component No Yes 1

Treatment Options Surgical Resection

Treatment Options Surgical Resection Endovascular Embolisation

Treatment Options Surgical Resection Endovascular Embolisation Stereotatic Radiosurgery

Treatment Options Surgical Resection Endovascular Embolisation Stereotatic Radiosurgery Multimodal Therapy

Treatment Options Surgical Resection Endovascular Embolisation Stereotatic Radiosurgery Multimodal Therapy Conservative Management

Normal Perfusion Pressure Breakthrough Theory R.F. Spetzler et al

Normal perfusion pressure breakthrough theory Loss of autoregulation and carbon dioxide reactivity in presence of large arteriovenous malformation.

Normal perfusion pressure breakthrough theory Loss of autoregulation and carbon dioxide reactivity in presence of large arteriovenous malformation. Normal hemispheric vessels are chronically maximally dilated to attempt to divert flow from the AVM

Normal perfusion pressure breakthrough theory Loss of autoregulation and carbon dioxide reactivity in presence of large arteriovenous malformation. Normal hemispheric vessels are chronically maximally dilated to attempt to divert flow from the AVM Obliteration of the AVM diverts all flow to these maximally dilated vessels which have lost their normal control mechanisms

Normal perfusion pressure breakthrough theory Loss of autoregulation and carbon dioxide reactivity in presence of large arteriovenous malformation. Normal hemispheric vessels are chronically maximally dilated to attempt to divert flow from the AVM Obliteration of the AVM diverts all flow to these maximally dilated vessels which have lost their normal control mechanisms Results in loss of protection of the capillary bed, with edema and hemorrhage

Mathematical Models Arterial inflow

Mathematical Models Arterial inflow Nidus

Mathematical Models Arterial inflow Nidus Venous Outflow

Anaesthesia Technique