Large Arteriovenous Malformations: The Role Of Staged Treatment

Meriem Amarouche1, Hari Chandran1, Philip Blackburn1

1The London Gamma Knife Centre, St Bartholomew’s Hospital, London, U.K.

Keywords: arteriovenous malformation, radiosurgery, gamma knife, technique, outcome

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     Staged Gamma Knife Radiosurgery (GKS) for large AVMs may offer benefits such that an outcome can be achieved which is superior to that of the known natural history.
     This study retrospectively analyses the clinical and radiological outcome of this treatment for otherwise untreatable AVMs.
     Over a period of 64 months nine patients have been selected for staged treatment of a large AVM, six of whom have received both stages of treatment. Of these six, all lesions were Spetzler-Martin grade 4 or 5. Presenting features were haemorrhage in three patients, seizures in two patients, and both in one patient. Five lesions were supratentorial in lobar parenchyma, and the remaining lesion was cerebellar.
     Mean interval between GKS stages = 18.6 months (7-37), median 14.5 months. Mean Target Volume (TV) for first stage = 12.8cc(2.5cc-22.8cc), median 12.4cc, mean Prescription Dose 17.7Gy (14.5Gy – 22Gy) to 46% to 54% isodose. Mean TV for second stage = 11.0cc(6.7cc – 18.6cc), median 10.2cc, mean prescription dose 17.2Gy (15Gy – 20Gy) to 41% to 53% isodose. Two patients had required craniotomy for evacuation of haematoma; two had failed embolisation. Mean follow-up from first stage was 67 months (49-99), median 62 months, and from second stage was 48.5 months (34-92), median 39 months.
     Of six patients, one suffered cognitive impairment and left sided sensory/motor deficit one month following 2nd stage, attributed to post-Rx radionecrosis. This is slowly improving. Two patients were asymptomatic pre and post treatment, at 34 months and 92 months respectively. One patient improved in cognitive, motor, and other function. One patient suffered spontaneous haemorrhage 15 months after 2nd stage, associated with cognitive impairment and persisting but improving left hemiparesis. Nevertheless, at 17 months seizure activity was much improved. One patient, with associated flow aneurysm, died from haemorrhage at 41 months post 2nd stage. The patient with the cerebellar lesion obtained angiographically confirmed complete obliteration of the nidus 36 months after 2nd stage. In 3 other patients significant reduction in lesion size has been observed at 25 – 28 months, and it is hoped that these will go on to obliterate.
     This is a retrospective sudy.
     Our preliminary results suggest that staged radiosurgery is a safe approach in patients with large AVMs. 
     In common with previously published results, our experience seems to suggest that obliteration of the lesion takes longer, and is less certain than for smaller lesions. However, it may be that this reduced clear up rate is somewhat offset by the possibility of relieving associated co-morbidity, thereby justifying such an approach.


Project Roles:

M. Amarouche (), H. Chandran (), P. Blackburn ()