Size, location dictates radiosurgical success for deep eloquent AVMs
MedWire News: Clinicians have reported radiosurgery outcomes for the largest series of patients with deep eloquent arteriovenous malformations (AVMs) to date.
The study was conducted by Andras Kemeny and co-workers from The National Centre for Stereotactic Radiosurgery in Sheffield, UK. Being a national center for the UK, it serves around 60 million people, and the team has treated 356 patients with thalamic/basal ganglia AVMs and 160 with brainstem AVMs over a period of more than 20 years.
The researchers report good outcomes for radiosurgical treatment of pontine/medullar and thalamic/basal ganglia AVMs smaller than 4 cm3, with obliteration rates of 69-89% and low rates of permanent disability related to radiation effects - up to 14% of patients had mild, lasting disability.
For larger thalamic/basal ganglia lesions, Kemeny et al achieved AVM obliteration with low complication rates for about 50% of the patients under "optimal treatment conditions," which they describe as use of magnetic resonance imaging during planning and no embolization before radiosurgery.
Initial obliteration rates for AVMs in the midbrain and in the peritectal diencephalon were low, ranging from 17% to 70% depending on the size. However, complication rates were again low, and repeat treatment resulted in an obliteration rate of 80-90%.
"Therefore, we advocate radiosurgical treatment for these lesions," the researchers write in Neurosurgery.
But they say: "All of our treatment efforts for brainstem lesions >4 cm3 failed, even with improving treatment planning."
AVM bleeding rates were generally lower after than before treatment, with posttreatment bleeding of lesions smaller than 4 cm3 causing little mortality or permanent morbidity. But larger lesions, when they bled, had a more serious impact, causing the death of 19% of patients in the case of those with thalamic/basal ganglia AVMs larger than 8 cm3.
Kemeny et al stress that bleeding outcomes are misleading for previously ruptured AVMs unless the posttreatment bleeding rate is compared with pretreatment rebleed rates, ie, bleeds occurring after the initial AVM rupture.
"The high rebleed rate in the largest thalamic/basal ganglia AVMs is of concern," says the team. "However, optimal radiosurgical treatment of such ruptured AVMs should be considered because of their poor natural history, unless complete surgical elimination is possible."
By Eleanor McDermid