A proposed grading system for arteriovenous malformations

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✓ An important factor in making a recommendation for treatment of a patient with arteriovenous malformation (AVM) is to estimate the risk of surgery for that patient. A simple, broadly applicable grading system that is designed to predict the risk of morbidity and mortality attending the operative treatment of specific AVM's is proposed. The lesion is graded on the basis of size, pattern of venous drainage, and neurological eloquence of adjacent brain. All AVM's fall into one of six grades. Grade I malformations are small, superficial, and located in non-eloquent cortex; Grade V lesions are large, deep, and situated in neurologically critical areas; and Grade VI lesions are essentially inoperable AVM's.

Retrospective application of this grading scheme to a series of surgically excised AVM's has demonstrated its correlation with the incidence of postoperative neurological complications. The application of a standardized grading scheme will enable a comparison of results between various clinical series and between different treatment techniques, and will assist in the process of management decision-making.

Article Information

Address reprint requests to: Robert F. Spetzler, M.D., Editorial Office, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, Arizona 85013.

© AANS, except where prohibited by US copyright law.

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Figures

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    The anatomic areas considered neurologically eloquent for the purposes of the grading system are indicated. The deep eloquent areas (hypothalamus, thalamus, brain stem, and cerebellar peduncles) are highlighted in the upper image. The eloquent regions of the cerebral cortex (sensorimotor areas, language areas, and primary visual area) are identified on the lower image.

  • View in gallery

    Carotid angiograms, lateral view (left) and anteroposterior view (right), showing a Grade I arteriovenous malformation (AVM). This AVM is less than 3 cm in diameter (small: 1 point), located in the anterior frontal lobe (noneloquent: 0 points), and drains through cortical veins (arrows) (superficial drainage: 0 points).

  • View in gallery

    Vertebral angiograms, lateral view (left) and anteroposterior view (right), showing a Grade I arteriovenous malformation (AVM). This cerebellar AVM is less than 3 cm in diameter (small: 1 point), located superficially on the cerebellar cortex (non-eloquent: 0 points), and drains only through superficial cerebellar hemispheric veins (arrows) (superficial drainage: 0 points).

  • View in gallery

    Carotid angiograms, arterial phase (left) and venous phase (right), showing a Grade V arteriovenous malformation (AVM). This AVM is larger than 6 cm in its greatest diameter (large: 3 points), located in the corpus callosum with a deep thalamic component (eloquent: 1 point), and drains predominantly into a hugely dilated internal cerebral vein (arrow) (deep drainage: 1 point).

  • View in gallery

    Vertebral angiograms, anteroposterior view (left) and lateral view, venous phase (right), showing a Grade V arteriovenous malformation (AVM). This posterior fossa AVM is larger than 6 cm (large: 3 points), located in the cerebellar hemisphere with extension into the inferior cerebellar peduncle and region of the deep cerebellar nuclei (eloquent: 1 point), and drains primarily into the galenic system (deep drainage: 1 point).

  • View in gallery

    Carotid angiograms, lateral view (left) and anteroposterior view (right), showing a Grade II arteriovenous malformation (AVM). The AVM is less than 3 cm (small: 1 point), located in the dominant hemisphere adjacent to the receptive language area (Wernicke's area) (eloquent: 1 point), and has exclusively superficial venous drainage (arrow) (superficial drainage: 0 points).

  • View in gallery

    Carotid angiograms, lateral view (left) and anteroposterior view (right), showing a Grade III arteriovenous malformation (AVM). The AVM is less than 3 cm (small: 1 point), located adjacent to the thalamus (eloquent: 1 point), and drains into the galenic venous system (arrow) (deep drainage: 1 point).

  • View in gallery

    Carotid angiograms, lateral view (left) and anteroposterior views, arterial phase (center) and venous phase (right), showing a Grade IV arteriovenous malformation (AVM). This AVM is slightly less than 6 cm in diameter (medium: 2 points), located in the dominant parietal lobe adjacent to Wernicke's area (eloquent: 1 point), and drains in part into the galenic system (arrow) (deep drainage: 1 point).

  • View in gallery

    Diagrammatic representation of the combinations of graded variables (size, eloquence, and venous drainage) that are possible for each grade of arteriovenous malformation. There is one combination each for Grades I and V, three combinations each for Grades II and IV, and four possible combinations for Grade III.

  • View in gallery

    Vertebral angiograms, anteroposterior view (left) and lateral view, arterial phase (right), showing an inoperable (Grade VI) arteriovenous malformation (AVM). This AVM is fed by multiple vessels from the rostral basilar artery, encircling and infiltrating the mesencephalon. The diffuse involvement of the brain stem renders this lesion inoperable.

  • View in gallery

    Correlation of arteriovenous malformation grades with surgical results. See also Table 2.

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