Northeast Florida Medicine
Vol. 66, No. 3 2015
25
Endovascular Neurosurgery
AVM. Circumferential embolization of the AVM, rather
than fragmentation of the nidus, is the preferred strategy
as a fragmented nidus may result in multiple targets for
radiation dosing. This could make radiosurgery planning
difficult, thereby negating the benefits of embolization.
Some limited evidence exists to support the embolization
of large AVMs to a size that is amenable to radiosurgery.
14,15
Endovascular treatment alone is rarely curative.
15
In
general, this strategy works for some small AVMs with
limited arterial feeders and draining veins (Figure 3). Rarely,
a medium-size AVM can be embolized over the course of
months until a cure is achieved.
Embolization solely for palliation of symptoms is rarely
indicated. Some AVMs may be too dangerous to treat
because of size and/or location. Conversely, an AVM may
be responsible for debilitating symptoms such as severe
headaches or ischemia related to steal phenomena. In
these situations, partial embolization may help reduce flow
through the AVM and ameliorate the patient’s symptoms.
Embolizing dural feeders may be particularly helpful in
reducing headaches. Steal symptoms can be reduced by
embolizing large “incurable” AVMs.
16
Embolization techniques can be used to treat associated
aneurysms. Owing to the risk of rupture of proximal aneu-
rysms during AVM embolization or excision, treatment of
these lesions should precede AVM treatment when possible.
If the aneurysm is appropriate for coiling, it can potentially
be occluded during the first embolization session before
the AVM nidus is addressed. If the aneurysm appears to be
better suited to surgery, surgical clipping can be performed
before AVMembolization. Aneurysms on feeding pedicles of
the AVM, known as flow-related aneurysms, can be treated
in one of two ways. They can be occluded primarily using
detachable coils. Alternatively, an aneurysm that is close to
the AVM nidus can often be occluded by embolization of
the pedicle that harbors the aneurysm, while injecting glue
from themicrocatheter (the glue refluxes from the nidus into
the pedicle and aneurysm). This occlusion can result from
infiltration of glue into the aneurysm sac or secondarily as
the feeding pedicle becomes occluded. Attention should
be paid to intranidal aneurysms during embolization. If a
hemorrhage has occurred, an intranidal aneurysm should be
suspected as a rupture site.When possible, the pedicle feeding
the nidus harboring the aneurysm should be treated first.
Controversies in the
Management of Unruptured AVMs
Management of unruptured brain AVMs has been a
subject of significant debate in recent medical literature,
especially after the publication of two large trials.
17,18
Simplistically speaking, if left untreated, AVMs confer
a risk for neurologic morbidity and mortality; however,
treatment is associated with risks, but offers the potential
for lifetime eradication.
The first important trial on unruptured brain AVMs, enti-
tled A Randomized Trial of Unruptured Brain AVMs study
(ARUBA) 17was a randomized,multi-center trial comparing
“best possible AVMeradication” withmedical management.
The primary endpoint was a composite of symptomatic
stroke or death.Treatment modalities included radiosurgery,
microsurgical resection, and endovascular embolization,
alone or in combination. The secondary outcome measure
was disability at five years post-randomization. The initial
study design had called for enrollment of 800 patients, but
this number was later reduced to 400; however, the study
enrolled only 223 patients from 65 certified sites. AVMs
in the study cohorts were relatively well-matched for size,
location, and venous drainage pattern, and Spetzler-Martin
Grade. The majority were comprised of S-M grade 1, 2, or
3 (approximately equal) with 10 percent grade 4 patients
and no grade 5 patients. Based on intent-to-treat analysis,
ten adverse events (7.9 percent), defined as death or stroke,
occurred in the medical management arm while 34 adverse
events (35.1 percent) occurred in the interventional therapy
arm. There was no significant difference in the number of
deaths.When analyzed according to S-MGrade, patients with
grade 1 AVMs fared better in the interventional group while
adverse events were much higher in patients with grades 2 to
4 lesions. In addition, the trial was not powered to evaluate
treatment effect by modality. Additional criticisms of the
trial include patient selection and short follow-up times.
An even more recent trial, published in JAMA by
Al-Shahi Salman and colleagues, prospectively watched 204
patients with unruptured AVMs over 12 years.
18
Morbidity
andmortality rates amongst patientsmanaged conservatively
versus those who underwent interventions were compared.
Over a four-year period, the authors reported 36 events
leading to sustained handicap or death in the conservative
arm versus 39 in the interventional group. The number of
AVM-associated symptomatic strokes or deaths in patients
managed conservatively versus those who underwent in-
tervention was 14 and 38, respectively. Interestingly, the
authors documented an obliteration rate of 66 percent in
patients who underwent interventions, an extremely poor
outcome given that 90 percent of the treated AVMs were
low grade. In comparison, ameta-analysis of 13,698 patients
documented a surgical obliteration rate of 96 percent for
low-grade AVMs.
19
Moreover, the complication rate in the
treatment arm of the study was 27.1 percent, as compared
to the 5.7 percent rate reported in the meta-analysis.
Given the very heterogeneous populations within the
interventional groups included in the two trials, the nu-
