Surgery for Cerebral AVMs

Posted by Dr. Thamburaj Dr. Thamburaj
Conventional surgery remains the gold standard in the management of cerebral AVMs; other modalities are considered only if a safe surgical excision without any long-lasting morbidity is not feasible.
The natural history of an individual AVM is difficult to predict; however, left untreated, they have the potential of causing significant hemorrhage, which may result in serious neurological deficits or death. Best course of therapy must be made on a case-by-case basis.

Conventional surgery is most appropriate when an AVM is located in a superficial portion of the brain and can be performed even in an eloquent area in experienced hands. Recent advances in anesthesia, laser photocoagulation, evoked potential monitoring, facilities for intra operative DSA and cortical mapping have contributed in total excision of these lesions. Stereotactic localizing helps in deep seated AVMs.

Essential surgical steps include

·         A generous craniotomy is advised.
·         Associated dural component, if any, should be excised. Any injury to an adherent vein while opening the dura must be avoided.Prominent landmarks at surgery are the large arterialized veins, which need to be protected until the arterial  feeders are coagulated.Bleeding vein may be controlled with gelfoam and cottonoids and dissection should be continued.
·         Intermittent hypotension helps on occasions.
·         As the major feeders are coagulated, the malformation shrinks. Clipping a feeder shrinks the draining vein whereas clipping the arterialized vein produces venous engorgement.
·         Temporary clipping helps in differentiation of the feeders from the arterialized veins, which, perhaps, is the most important part of the surgery.
·         Presence of hematoma helps in delineation of the malformation and the adjacent gliotic ‘pseudocapsule’ offers a plane for dissection. Such gliotic areas are encountered, more often, in deeper areas.
·         Dissection is kept close to the malformation. As the superficial feeders are secured, the deeper ones appear to collateralize and coagulation may be difficult. Use of gel foam and judicious use of hypotension help.
·         In case of persistent oozing from the bed, a residual nidus must be looked for.