Application of Single-Stage Stereotactic Radiosurgery for
Cerebral Arteriovenous Malformations >10 cm3
Shunya Hanakita, MD; Tomoyuki Koga, MD, PhD; Masahiro Shin, MD, PhD;
Hiroshi Igaki, MD, PhD; Nobuhito Saito, MD, PhD
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Background and Purpose—Stereotactic radiosurgery (SRS) is a safe and effective treatment for small arteriovenous
malformations (AVMs), the use of this modality for the treatment of large AVMs is still controversial, although it has
been used in difficult cases. The aim of this study was to evaluate the treatment outcomes of patients who underwent
single-stage SRS for large AVMs and to discuss the role of SRS in the treatment of these challenging lesions.
Methods—Between 1998 and 2010, 65 patients with AVMs >10 cm3 underwent single-stage SRS using the Leksell Gamma
Knife. Patients who had prospective volume-staged SRS were excluded from this series. Outcomes including the rates of
obliteration, hemorrhage after treatment, and adverse events were retrospectively evaluated.
Results—The mean nidus volume was 14.9 cm3 (±3.8 cm3), and a mean margin dose of 20 Gy (±1.5 Gy) was applied. The
mean observation period was 60 months (range, 7–178 months). The nidus obliteration rates after SRS were 44%, 76%,
and 81% at 3, 5, and 6 years, respectively. The annual hemorrhage rate after SRS was 1.94% and permanent adverse
events were observed in 2 patients (3%).
Conclusions—For large AVMs <20 cm3, single-stage radiosurgery by applying >16 Gy marginal dose presented favorable
obliteration rates with relatively low rate of morbidity. Further accumulation of cases is awaited to fully evaluate the
results of single-stage radiosurgery for large AVMs. (Stroke. 2014;45:3543-3548.)
Key Words: arteriovenous malformations ◼ Gamma Knife radiosurgery ◼ radiosurgery
D
account. Lesions with volume less than ≈10 cm3 can be good
candidates for radiosurgery.7 However, there are still many
cases with larger lesions that are also difficult to be treat with
other options. For those cases, staged radiosurgery has been
applied in some centers. This approach seems to have treatment effects to certain extent, but the results are not favorable, showing <30% obliteration rates at 5 years with adverse
events observed in 11% to 13% of the cases.9,10
Here, we review the results of a single-session SRS for a
nidus volume ranging from 10 to ≈20 cm3 and speculate the
efficacy and volume limit for a single-session SRS treatment
strategy for patients with AVMs.
espite recent progress in microsurgical techniques, endovascular treatments and radiosurgery that allow for the
safer treatment of even the deep cerebral arteriovenous malformations (AVMs), large AVMs still remain difficult to treat.1
In addition, some of these lesions are associated with repetitive hemorrhage, which necessitates proper treatment.2 As for
stereotactic radiosurgery (SRS), previous studies have shown
that nidus volume was one of the most important factors for
predicting outcomes.3,4 When single, high-dose irradiation is
applied, as in Gamma Knife radiosurgery, the irradiated margin dose must be lowered when the target lesions are larger
to avoid unacceptable morbidity; thus, the efficacy of treatment is reduced according to the dose–response curve.3–6 SRS
has often been recommended for small, deep-seated lesions,
where direct surgery is difficult.7 Although the size limitation in radiosurgery for AVM is often a maximum diameter
of 3 cm, diameter cannot be a strict criterion for treatment
decision because volume is not always correlated with maximum diameter. Even lesions with a diameter >3 cm can sometimes be safely treated because of their thin and long, shape,
as often observed in the corpus callosum lesions.8 Therefore,
when considering the indications for SRS, not only the maximum diameter but also the nidus volume should be taken into
Methods
Patients and Characteristics of Lesions
Between September 1998 and October 2010, 67 patients with cerebral AVM with a nidus volume >10 cm3 underwent single-stage SRS
using the Leksell Gamma Knife at our institute. Of these, 2 patients
died of unrelated events within 3 months of their SRS procedures.
As a result, we retrospectively reviewed the medical records of 65
patients. If the lesions were too large to apply ≥16 Gy for keeping
the volume receiving 12 Gy smaller than ≈20 to 25 cm3, which was
considered as the safety limit,4 we decided to treat them with staged
radiosurgery. Patients who underwent prospective volume-staged
Received August 19, 2014; final revision received September 18, 2014; accepted September 22, 2014.
From the Departments of Neurosurgery (S.H., T.K., M.S., N.S.) and Radiology (H.I.), The University of Tokyo Hospital, Tokyo, Japan.
Correspondence to Shunya Hanakita, MD, Department of Neurosurgery, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655,
Japan. E-mail [email protected]
© 2014 American Heart Association, Inc.
Stroke is available at http://stroke.ahajournals.org
DOI: 10.1161/STROKEAHA.114.007162
3543
3544 Stroke December 2014
Downloaded from http://stroke.ahajournals.org/ by guest on June 14, 2017
SRS for large AVMs were excluded from this study. The institutional
review board of our institute approved the study protocol, and written
informed consent was obtained from all patients.
In all patients, the diagnosis of AVM was confirmed with cerebral
angiography in combination with computed tomography or MRI.
Twelve patients (18%) were initially treated with other modalities (surgical resection in 2, endovascular treatment in 10) and were referred
to our hospital to receive SRS for the residual nidus. In the other 53
patients, SRS was the primary treatment. The treatment decisions for
patients with AVM were made based on neurosurgical conferences.
Radiation oncologists jointly discussed treatment strategies that included radiosurgery. The radiosurgery-based grading score (AVM
score) proposed by Pollock and Flickinger11 was used to evaluate patient outcomes. The score was calculated according to the following
equation: AVM score=0.1×(AVM volume in cm3)+0.02×(patient age
in years)+0.5×(location: hemispheric/corpus callosum/cerebellar=0;
basal ganglia/thalamus/brain stem=1). The clinical characteristics of all
patients are summarized in Table 1. In total, 65 patients were followed
up for 7 to 178 months (mean, 60 months; median, 55 months) after
SRS. Among these, 49 patients (75%) were followed up for >3 years.
The patient age at the time of SRS ranged from 9 to 66 years (mean,
35 years; median, 34 years). When graded using the Spetzler–Martin
classification,12 16 (25%) were grade II, 38 (58%) were grade III, and
11 (17%) were grade IV. There were no patients in grade V or grade VI.
The maximum nidus diameter ranged from 25 to 68 mm (mean±SD,
Table 1. Clinical Characteristics and Radiosurgical
Dosimetry for Patients With AVMs >10 cm3
Characteristics
No. of patients in analysis
Male/female
65
34/31
39±7.7 mm; median, 36 mm; interquartile range, 35–43 mm). Sixtyone patients (94%) had nidi of maximum diameter >3 cm. Of these,
2 had nidi of maximum diameter >6 cm. The nidus volume ranged
from 10 to 23.5 cm3 (mean±SD, 14.9±3.8 cm3; median, 14.2 cm3; interquartile range, 11.3–18.1 cm3; Figure 1). The mean radiosurgery-based
AVM score was 2.25±0.49 (range, 1.2–3.4). For SRS using the Gamma
Knife, the marginal dose ranging from 15 to 20 Gy (mean, 18.9±1.5 Gy;
median, 20 Gy; interquartile range, 18–20 Gy) was applied. Twenty patients (31%) experienced 37 hemorrhagic events before SRS. Between
the time of diagnosis and SRS, excluding the first hemorrhagic event
in 17 patients who presented with hemorrhage, 20 hemorrhagic events
were observed >180 patient-years. Using the person-years method, the
annual hemorrhage rate after initial presentation until SRS was 11.1%.
Radiosurgical Treatment
After the Leksell stereotactic frame was fixed on the patient’s head,
the patient underwent stereotactic imaging to obtain precise information on the shape, volume, and 3-dimensional coordinates of the AVM
nidus using computed tomography or MRI in combination with angiography. Treatment planning was performed jointly by neurosurgeons
and radiation oncologists using commercially available software. The
planning software (Leksell GammaPlan, Elekta Instruments AB) allowed for the display of multiple radiographic images on a computer
screen with simultaneous superimposition of isodose lines. The nidus
volume was calculated using the Leksell Gamma Plan by depicting
the nidus based on the judgment of neurosurgeons and radiation oncologists. In principle, the ideal dose applied to the margin of each
AVM nidus was 20 Gy. To avoid complications when the nidus volume was larger, the marginal dose was reduced (but not to <16 Gy),
which resulted in an obliteration rate of ≈70% in previous reports.4,13
Only 1 patient was treated with a marginal dose of <16 Gy (15 Gy) to
reduce irradiation of the optic nerve.
Age at SRS, y
Mean/median (range)
35/34 (9–66)
Clinical presentation, n
Seizure
20 (31%)
Hemorrhage
17 (26%)
Incidental
17 (26%)
Headache
9 (14%)
Previous treatment, n
Endovascular treatment
Surgical resection
10 (15%)
2 (3%)
Follow-up period, mo
Mean/median (range)
60/55 (7–178)
Maximum diameter, mm
Mean/median (range)
38/36 (25–68)
Nidus volume, cm3
Mean/median (range)
14.9/14.2 (10–23.5)
Marginal dose, Gy
Mean/median (range)
18.9/20 (15–20)
AVM score, range
Mean/median (range)
2.25/2.22 (1.20–3.40)
Spetzler–Martin grade, n
II
Maximum diameter >30 mm
III
Maximum diameter >30 mm
IV
16 (23%)
14
38 (58%)
36
11 (17%)
AVM indicates arteriovenous malformation; and SRS, stereotactic
radiosurgery.
Figure 1. Distribution of maximum nidus diameter and nidus
volume. A, Maximum nidus diameter ranged from 25 to 68 mm
(mean±SD, 39±7.7 mm; median, 36 mm; interquartile range [IQR,
35–43 mm]). B, The nidus volume ranged from 10 to 23.5 cm3
(mean±SD, 14.9±3.8 cm3; median, 14.2 cm3; IQR [11.3–18.1 cm3]).
Hanakita et al Radiosurgery for Large Arteriovenous Malformations 3545
Follow-Up Evaluation and Statistical Analysis
After SRS, follow-up clinical examinations were performed either
at our hospital or by the referring physicians. The patients underwent radiological imaging (mainly MRI) every 6 months on a regular basis, and additional imaging was performed when the patients
presented with new or worsened symptoms. Images were evaluated
independently by neurosurgeons and radiologists. Angiography was
performed when the results of these imaging modalities strongly suggested nidus obliteration.
Statistical analyses were performed using JMP 10 (SAS Institute,
Inc, Cary, NC). The actuarial obliteration rate was calculated using
the Kaplan–Meier method. A Cox proportional hazards model was
used for univariate and multivariate analyses to evaluate factors that
could potentially affect nidus obliteration. Factors associated with
adverse events were also evaluated by univariate and multivariate logistic regression models.
Table 2. Factors Associated With Nidus Obliteration in
Univariate and Multivariate Analyses
Univariate Analysis
Multivariate Analysis
Factors
HR (95% CI)
P Value
HR (95% CI)
Age, y
0.99 (0.97–1.03)
0.88
0.99 (0.97–1.03) 0.77
Male/female
1.22 (0.65–2.30)
0.52
1.29 (0.64–2.61) 0.47
AVM volume
0.97 (0.89–1.89)
0.42
1.07 (0.94–1.19) 0.31
AVM score
NT
P Value
0.79 (0.40–1.57)
0.50
History of hemorrhage 1.21 (0.58–2.84)
0.62
0.72 (0.26–1.76) 0.49
NT
Previous endovascular 0.98 (0.34–2.32)
treatment
0.97
1.41 (0.58–3.83) 0.46
Deep location
0.86 (0.26–2.18)
0.78
0.60 (0.16–1.83) 0.39
Deep drainer
1.07 (0.57–1.97)
0.83
1.53 (0.62–3.61) 0.35
Maximum diameter
0.99 (0.98–1.03
0.99
0.99 (0.94–1.04) 0.80
Obliteration Rate
Eloquent area
0.91 (0.49–1.73)
0.76
1.34 (0.66–2.77) 0.43
In this series, 18 patients achieved nidus obliteration within
3 years and 23 patients had nidus obliteration after >3 years
of follow-up as assessed by angiography (n=32) or MRI
(n=9) at a mean time of 40 months after SRS (range, 15–73
months). Thus, among 53 patients who were followed up for
>3 years or had confirmed nidus obliteration within 3 years,
41 patients (77%) had nidus obliteration. When calculated
by the Kaplan–Meier method, the actuarial obliteration rates
were 44%, 76%, and 81% at 3, 5, and 6 years, respectively.
When the group of patients with AVMs ≥14 cm3 (approximate volume of a 3 cm diameter sphere) was assessed, 14
of 23 patients (61%) who were followed up for >3 years
showed obliteration. Using the Kaplan–Meier method, the
accumulated obliteration rates for AVMs ≥14 cm3 at 3, 5, and
6 years were 36%, 74%, and 74%, respectively, and there was
no significant difference between lesions with volume of 10
to 14 cm3 and larger lesions (P=0.31; Figure 2). When we
analyzed the factors for successful obliteration, higher margin dose was the only significant associated factor in the univariate analysis (hazard ratio, 1.30; 95% confidence interval,
Margin dose
1.30 (1.04–1.67)
0.02*
1.50 (1.11–2.06) 0.009*
Results
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Figure 2. Kaplan–Meier curves for obliteration after single-stage
stereotactic radiosurgery (SRS) for arteriovenous malformation
(AVM) >10 cm3. In the entire series, obliteration rates at 3, 5, and
6 years were 42, 76, and 81%, respectively. When patients were
stratified based on an AVM volume of 14 cm3, the obliteration
rates in the group with volumes <14 cm3 at 3, 5, and 6 years
were 51, 79, and 84%, respectively (solid line), whereas the
obliteration rates in the group with volume ≥14 cm3 at 3, 5, and
6 years were 41, 73 and 73%, respectively (dotted line). There
was no significant difference between these 2 curves (P=0.28) in
univariate analysis.
AVM indicates arteriovenous malformation; CI, confidence interval; deep
location, AVMs at the basal ganglia or thalamus; HR, hazard ratio; and NT, not
tested.
*P value <0.05 is significant.
1.04–1.67; P=0.02). In multivariate analyses, there was no
significant factor for higher obliteration rate. Factors, including target volume, AVM score, history of hemorrhage, previous endovascular treatment, deep location (basal ganglia or
thalamus), and deep drainage, did not significantly influence
the obliteration rate (Table 2). The largest volume of angiographically obliterated case was 21.5 cm3.
Among 41 patients whose lesions were obliterated, the
lesions in 18 patients showed complete obliteration until 3 years
after treatment. Univariate analysis for age, volume, maximum
diameter, previous treatment, location (eloquent area or deep
seated), deep draining vein, and presentation (hemorrhagic
versus nonhemorrhagic presentation) did not reveal any significant factors associated with the earlier response.
Based on our early experience in which nidus obliteration
in most cases was obtained by 5 years after treatment,14 we
considered additional treatment if the nidi were still present
5 years after initial treatments. The outcome was analyzed
based on the results of the initial treatments and those patients
who received additional treatments were censored at the time
of those procedures for the Kaplan–Meier analysis. In this
series, 3 patients received additional SRS for their residual
nidus after a 5-year follow-up. Two achieved nidus obliteration on angiography at 27 and 28 months after their second
SRS, respectively. None of these patients presented with neurological deterioration after additional treatment. One patient
received resection of his residual nidus 64 months after SRS.
This patient was discharged without neurological events and
showed no adverse events during the follow-up period.
Complications and Hemorrhagic Events
Thirty-one patients (48%) developed T2 hyperintense regions
around the irradiated field that were confirmed by MRI at 3 to
24 months (mean, 10 months; median, 11 months) after SRS.
Adverse events were observed in 11 patients (17%) at 3 to
17 months (mean, 10 months; median, 11 months) after SRS.
3546 Stroke December 2014
Table 3. Factors Associated With Neurological Events After
Stereotactic Radiosurgery
Univariate Analysis
HR (95% CI)
Factors
Multivariate Analysis
P Value
HR (95% CI)
P Value
Age, y
0.47 (0.02–8.41) 0.61
0.97 (0.90–1.03)
0.97
Male/female
2.82 (0.74–14.2) 0.13
4.03 (0.84–25.7)
0.47
AVM volume
1.02 (0.86–1.21) 0.83
1.02 (0.76–1.35)
0.89
AVM score
1.35 (0.35–5.23) 0.41
NT
NT
History of hemorrhage 0.64 (0.09–2.85) 0.58
2.67 (0.21–32.9)
0.42
Previous endovascular 2.99 (0.55–14.1) 0.19
treatment
3.16 (0.43–22.7)
0.25
Deep location
2.18 (0.28–12.0) 0.41
6.92 (0.54–115.1)
0.13
Deep drainer
0.28 (0.04–25.1) 0.09
0.16 (0.06–1.67)
0.14
Maximum diameter
0.98 (0.88–1.07) 0.71
0.99 (0.84–1.14)
0.89
Eloquent area
8.62 (1.49–163)
Margin dose
0.99 (0.65–1.58) 0.96
0.01* 8.02 (0.0.85–233)
1.10 (0.59–2.04)
0.07
0.76
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AVM indicates arteriovenous malformation; CI, confidence interval; deep
location, AVMs at the basal ganglia or thalamus; HR, hazard ratio; and NT, not
tested.
*P value <0.05 is significant.
Of these 11 patients, 9 patients (14%) had newly developed
symptoms (3 had seizures, 2 hemiparesis, 3 dysesthesia, 1
visual field defect, and 1 aphasia). When the patients developed neurological symptoms related to T2 signal changes
surrounding the lesions, we principally administrated oral
corticosteroids. Fortunately, these symptoms resolved during
the follow-up period, and no patient had a permanent deficit.
For 2 other patients who had existing symptoms that worsened
(1 had hemiparesis, 1 dysarthria, and 1 increasing frequency
of seizures), both patients (3%) showed permanent symptoms (one showed mild hemiparesis and the other showed
mild dysarthria). Therefore, in a single-stage SRS, transient
neurological events were observed in 9 patients (14%) and
permanent neurological consequences were observed in 2
patients (3%). The presence of lesions at the eloquent area was
the only significant factor associated with the adverse events
after SRS in the univariate analysis (hazard ratio, 8.62; 95%
confidence interval, 1.49–163; P=0.01); however, there was
no significant factor associated with adverse events in multivariate analyses (Table 3).
Five patients experienced 6 hemorrhagic events 6 to 24
months (median, 17 months) after the treatment during 309
patient-years. The annual hemorrhage risk after SRS was
1.94%. The status of these 5 patients scored with modified
Rankin scale (mRS) was mRS 4 for 3 patients and mRS 5 for 2
patients. Pretreatment mRS of these patients was mRS 0 for 4
patients and mRS 1 for 1 patient. All the post-treatment hemorrhagic events occurred before radiological confirmation of
nidus obliteration. There was no bleeding after nidus obliteration in this cohort during 90 patient-years. About correlation
between the nidus volume and treatment outcomes, the annual
bleeding rate after SRS was 1.93% for AVM with volume of
10 to 14 and ≥14 cm3 were 1.93% and 1.96%, respectively
(P=0.62), and the rate of adverse events was 19% and 15%,
respectively (Table 4).
Discussion
In this study, we showed that the single-stage SRS for the
treatment of AVMs >10 cm3 achieved a 78% obliteration rate
at 5 years with a 2% rate of adverse events. Because AVMs
have a complex shape in many cases, there are diverse treatment strategies for this disease.7 SRS is particularly recommended for deep-seated lesions, where surgical resection can
be difficult and a functional field probably exists.7 The use of
SRS for the treatment of small- or medium-sized AVMs has
been accepted widely in the past.5,21 However, because larger
AVMs require higher radiation doses that increase the risk of
Table 4. Results of Radiosurgery and Radiotherapy for Arteriovenous Malformations >10 cm3 in Previous Studies
Authors/Modality
No. of Pts
Volume, cm3
Obliteration
Rate at 5 y, %
Adverse Events
ABR After Treatment, %
Miyawaki et al /LINAC
23
>14
22
27% required medication
6.6
Pan et al16/single GKS
28
10–15
77
3.9% in entire series
NA
48
>15
40
15
Pollock et al17/single GKS
25
>14
36
NA
NA
11 LINAC
35 GKS
>14
38
NA
3.0
Xiao et al19/HSRT
20
>12.5 (median 47)
NA
10%
2.06
Kano et al9/volume-staged GKS
47
>10 (median 22)
28
13%
5.1
Huang et al10/volume-staged GKS
18
>15 (median 22.9)
29
11%
4.2
Yamamoto et al20/dose-staged GKS
31
>10 (median 14)
52
6.5%
9.1 at first year
16.1 at second years
Present series/single GKS
65
>10 (median 14)
76
Transient symptoms 13.8%
Permanent symptoms 3%
1.94
31
10–14
79
Transient symptoms 19%
1.93
34
>14
74
Transient symptoms 8.8%
Permanent symptoms 5.9%
1.96
Yang et al18/LINAC and GKS
ABR indicates annual bleeding rate; GKS, Gamma Knife surgery; HSRT, hypofractionated stereotactic radiotherapy; LINAC, linear accelerator; and NA,
data not available.
Hanakita et al Radiosurgery for Large Arteriovenous Malformations 3547
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radiosurgery-induced complications,3 there has been skepticism over their use for larger lesions. Therefore, there is still
controversy over which treatment strategy, including conservative management, is optimal for larger AVMs.22–24
In our series, patients with nidi volumes ranging from 10 to
23 cm3 were treated. The limit for SRS is usually considered as
3 cm, which means ≈14 cm3 when lesions are sphere shaped.
However, not all AVMs are spheres. They often show complex shapes from which it is difficult to predict nidus volume.
Considering radiosurgery, volume >10 cm3 is still challenging
because related complications have been well reported.15–18
We mainly applied ≥16 Gy to the margin of the lesions aiming
for favorable obliteration. However, it was impossible to apply
>16 Gy for lesions >20 cm3 while keeping the volume receiving >12 Gy smaller than ≈20 to 25 cm3, which is one of the
possible safety limits suggested by a dose–response analysis,
although it should be noted that they are variable depending
on the location of AVMs.4 Indeed, the largest lesion for which
complete obliteration was obtained in our series was 21.5 cm3,
and 2 among 6 patients with lesions >20 cm3 experienced
post-treatment adverse events. Therefore, we speculate that
the size limit of AVM for which single-session radiosurgery
can safely and effectively be applied is ≈20 cm3.
Five-year obliteration rate in our series was 76%, which was
higher than or similar to that of single-session radiosurgery
for large AVMs in other series (22%–77%; Table 4), whereas
the rate of morbidity was comparable (3% versus 3.9%–27%;
Table 4). A possible cause for this difference may be because
of the higher doses applied in our series compared with others (15–20 Gy [mean, 18.9 Gy] in our series versus 10–20 Gy
[mean, 14.1 Gy] in others). We tried not to reduce the marginal doses to <16 Gy, which was a suggested dose that can
obliterate ≈70% of AVM in a dose–response analysis.13 Thus,
the upper limit of the volume in our study cohort was ≈20 cm,3
whereas other studies contained large number of patients
with AVMs >30 cm3 and this may have resulted in different
outcomes.15,16,18
For excessively large AVMs (>20 cm3), single-session SRS
may be limited because of the high frequency of treatmentrelated complications despite of low efficacy.15,16 For treating
excessively large AVM, there are few reports mainly using
radiotherapy procedure. Historically, conventional fractionated radiotherapy for large AVM was known to be less effective25; therefore , hypofractionated radiotherapy was applied.
Although the results were not conclusive, the author mentioned
the possibility of volume reduction by hypofractionated radiotherapy and a combined therapy with other modalities was
recommended.19 Some institutes have reported the preliminary results of staged SRS, particularly using Gamma Knife.
There are scarce reports on staged SRS that showed 28% to
29% rate of angiographic obliteration with 11% to 13% of
adverse events and 4% to 5% risk of hemorrhage in the latency
period.9,10 Although these results may not seem promising, it
must be noted that the majority of patients included in these
series had excessively large volumes (>20 cm3) relatively low
marginal doses <18 Gy were applied to avoid adverse radiation effects in the earlier cases and additional SRS increased
the obliteration rates to 56% at 10 years.9 Evidently, the
reduction of hemorrhage risk in the present series from 11.1%
before treatment to 1.9% after treatment seemed preferable.
However, because the goal of AVM treatment is to eliminate
bleeding, and having considered the severity of morbidity
experienced by 5 patients in our series after hemorrhage, the
residual nidus should be treated with multimodal approaches,
such as additional SRS, endovascular treatment, and surgical
resection after a sufficient follow-up to further eliminate the
risk of bleeding.
The limitations of this study include a selection bias. As for
the analysis of hemorrhagic risk before and after treatment,
the relatively short observation period before treatment (mean,
29 months; median, 5 months) may have elevated the apparent
pretreatment risk and thus the risk of hemorrhage after treatment may seem to have reduced. Another limitation of this
study is the limited number of patients in this series. Although
we could not see any significant factors related to higher obliteration rate or morbidities in multivariate analyses, absence
of certain, well-known factors associated with the outcomes
such as volume and history of hemorrhage may suggest the
lack of statistical power in these analyses.3,26 For example, the
fact that the lesions in the eloquent regions did not result in a
significantly higher morbidity (P=0.07) does not allow us to
treat those lesions in the same way as the lesions in noneloquent areas.
Conclusions
Single-stage radiosurgery was safely and effectively applied
to limited cases of AVMs with nidus volume between and 20
cm3. Delivering ≥16 Gy to the margin of the lesions in one
session resulted in favorable obliteration rates with relatively
low morbidity for this size range of AVM. About the severe
morbidity associated with post-treatment hemorrhage, additional treatment for the residual nidus after a sufficient followup should be considered. Further accumulation of cases is
awaited to fully evaluate the results of single-stage radiosurgery for large AVMs.
Disclosures
None.
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Application of Single-Stage Stereotactic Radiosurgery for Cerebral Arteriovenous
Malformations >10 cm 3
Shunya Hanakita, Tomoyuki Koga, Masahiro Shin, Hiroshi Igaki and Nobuhito Saito
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Stroke. 2014;45:3543-3548; originally published online October 7, 2014;
doi: 10.1161/STROKEAHA.114.007162
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