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AUTHOR(S): Chin, Lawrence S., M.D.;
Raffel, Corey, M.D., Ph.D.; GonzalezGomez, Ignacio, M.D.; Giannotta, Steven L., M.D.;
McComb, J. Gordon, M.D.
Divisions of Neurological Surgery (LSC, CR, SLG,
JGM) and Neuropathology (IG-G), Childrens
Hospital of Los Angeles, and the Department of
Neurological Surgery (LSC, CR, SLG, JGM),
University of Southern California School of
Medicine, Los Angeles, California
Neurosurgery 31; 863-869, 1992
ABSTRACT: IN A REVIEW of our series of patients
with arteriovenous malformations (AVMs), a group
with atypical angiographic and histopathological
characteristics was discovered. Unlike the typical
AVM, these lesions contained normal cerebral tissue
between the abnormal vessels. We call these lesions
diffuse AVMs, and think that this AVM represents
one end of the AVM spectrum from a tight nidus to a
diffuse lesion. The mean age of these patients was
18.1 years. Eight patients presented with an
intracerebral hemorrhage, two with seizures, one with
headache without hemorrhage, and one with ischemic
symptoms compatible with vascular steal. Cerebral
angiography revealed three AVMs to be 2 to 4 cm in
diameter, four were 4 to 6 cm in diameter, and five
were >6 cm in diameter. Characteristic angiographic
features included multiple small arterial feeders,
small ectatic vessels in the malformation itself,
multiple small draining veins, and a diffuse, puddling
appearance of the contrast dye. Despite 16 operations
in 11 patients, complete resection of the AVM was
accomplished in only 8. The four patients with
residual disease have received radiation therapy.
Histopathology of the surgical specimens found
AVM vessels interspersed among normal appearing
neurons and white matter. Leptomeningeal
angiodysplasia was noted when the cerebral cortex
was involved. Gliosis was noted in some cases.
Diffuse AVMs represent a difficult surgical challenge
and recognition of the lesion aids in surgical
planning.
KEY WORDS: Angiography;
Arteriovenous malformation;
Central nervous system; Headache;
Intracerebral hemorrhage; Seizures;
Vascular abnormality
The typical arteriovenous malformation (AVM) is a
tangle of abnormal arteries and veins without an
intervening capillary bed. Furthermore, parenchyma
found among the abnormal vasculature is usually
reported as absent or highly gliotic and nonfunctional
(1,14)
. The AVM that appears diffuse on angiography
has been studied far less (26). In fact, no series in the
neurosurgical literature could be found that addressed
this lesion in a comprehensive manner. This subtype
of AVM, representing the diffuse end of the spectrum
of AVMs, has a distinct angiographic appearance and
implies the existence of neural tissue within the
malformation. In a review of our series of AVMs, we
have encountered 12 examples of diffuse AVMs. The
cases are described for their characteristic
radiological and pathological findings as well as the
treatment dilemmas caused by their diffuse nature.
PATIENTS AND METHODS
During the period from 1978 to 1990, all AVMs
treated at the Childrens Hospital of Los Angeles (30
patients) and from the personal series of adult AVMs
of one of the authors (SLG) (150 patients) were
reviewed radiologically and histopathologically.
Twelve examples of diffuse AVMs were found.
Hospital records, angiograms, magnetic resonance
imaging (MRI) scans and surgical specimens from
these patients were studied. The histopathology of the
typical AVMs resected were examined and compared
with those AVMs subsequently classified as diffuse
AVMs. Size of the AVM was determined by
measuring the maximum diameter in a lateral
projection with correction for magnification error.
Based on size, a grade was assigned using the system
of Luessenhop and Rosa (13): Grade I, <2 cm; Grade
II, 2-4 cm; Grade III, 4-6 cm; Grade IV, >6 cm (13). A
grade was also assigned according to the Spetzler
classification which takes into account the size of the
lesion, its relationship to eloquent areas of the brain,
and its venous drainage patterns (21). A cerebral
angiogram was obtained postoperatively in all
surgical cases.
Neurological outcome was considered excellent if
the patient was neurologically normal, good if
improvement in an existing deficit occurred but some
deficit remained, unchanged if an existing deficit
persisted, and poor if the neurological status changed
either by appearance of a new deficit or worsening of
a preexisting deficit.
RESULTS
The 12 examples of diffuse AVMs represented 7%
of the total number of patients with AVMs, and the
11 pediatric patients comprised 27% of the AVMs in
this age group. Table 1 lists the pertinent clinical
information. The mean age was 18.1 years (range, 937 yr) with a 1:1 sex ratio. Eight patients had
hemorrhage, two had seizures, one had episodes of
transient hemiparesis and hemisensory loss
compatible with steal phenomenon, and one had
headaches alone. No patient had a history consistent
with previous hemorrhage. The two most common
neurological findings were hemiparesis (3 patients) or
altered mental status (3 patients). Other neurological
findings were coma (2 patients) and an expressive
aphasia (1 patient). Five patients were neurologically
normal.
By the Luessenhop scale, 3 AVMs were Grade II (24 cm), 4 were Grade III (4-6 cm), and 5 were Grade
IV (>6cm). Using the Spetzler classification, there
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Neurosurgery 1992-98
November 1992, Volume 31, Number 5
863 Diffuse Arteriovenous Malformations: A
Clinical, Radiological, and Pathological Description
Clinical Study
DISCUSSION
The classification of vascular malformations in the
central nervous system into AVMs, cavernous
angiomas, venous malformations, and capillary
telangiectasias is well established (15,26). This
categorization allows for a uniform grouping
anatomically, pathologically, angiographically, and
clinically. The category of AVM, however, represents
a spectrum of lesions ranging from a small compact
nidus of abnormal vessels to the diffuse pattern we
describe here. Recognition of the angiographic
pattern of a diffuse AVM is important in subsequent
surgical planning.
Clinical features
In this series, diffuse AVMs were seen primarily in
the older pediatric patient (mean age, 18.1 yr) and
appears distinct from vein of Galen malformations
and other giant AVMs of infancy, in that patients
with diffuse AVM lack symptoms of cardiac failure
and do not develop hydrocephalus (11,12). This age
distribution may reflect a population bias caused by
the inclusion of patients from a large pediatric center.
The incidence of patients presenting with
intracerebral hemorrhage in our small series (8 of 12)
was less than the reported 75 to 85% in childhood
series of AVMs, but more than the 50% incidence
reported for adults (5-7,9,14,17,19,20,24).
Imaging features
Diffuse AVMs appear on cerebral angiograms as a
large collection of tortuous vessels with multiple
arterial feeders and multiple draining veins. Deep
venous drainage is common. An identifiable compact
nidus is not seen and an entire lobe of the brain may
be involved. Deep gray nuclei may be involved in
some cases. Yasargil (26) has reported a similar
angiographic appearance of diffuse AVMs. In
addition, we have observed a scattered, puddling
appearance of contrast dye, which persisted into the
late arterial and early venous phase, perhaps
signifying an element of stasis or low flow within the
malformation.
The presence of intervening neural tissue in the
malformation can only be inferred from the diffuse
appearance of the angiograms. Three patients in this
series underwent MRI scans. The MRI scans detected
the presence of acute hemorrhage; evidence of old
hemorrhage was not seen. In addition, the MRI scans
were not helpful in identifying the nature of the
neural tissue between the abnormal vessels of the
malformation.
Histological appearance
On histological examination, the vessels of diffuse
AVMs and compact AVMs have similar features. A
striking difference is seen in the amount of
intervening neural tissue, which is either absent or
highly gliotic in the compact AVMs. In all of our 11
patients with surgical specimens, the diffuse AVM
was noted to contain normal neurons with varying
amount of gliosis. The implication is that the brain
interspersed between the abnormal vessels is
functional. In this respect, these AVMs are similar to
venous malformations and capillary telangiectasias
which also have normal brain between the vessels of
the anomaly (15,26).
Embryological considerations
The nature of the abnormal embryogenesis of
AVMs is unresolved. Two main theories have been
promulgated. One assumes failure of capillary bed
formation and therefore development of abnormal
artery to vein connections in the fetal brain (3,8,10,19,
24)
. The second theory suggests that AVMs result
from a primary abnormality in the proliferation and
metamorphosis of capillaries. The failure of
subsequent normal development or remodeling of the
capillary plexus results in the final morphology of the
malformation (26).
The second theory appears to be more compatible
with the AVMs we describe. The development of an
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
were 3 Grade II, 3 Grade III, 4 Grade IV, and 2 Grade
V.
On angiography, the AVMs were large, wedgeshaped, and often appeared to occupy the entire lobe
(Figs. 1 and 2). Multiple small arterial feeders and a
diffuse, puddling appearance of the contrast agent
were seen in all cases. Multiple draining veins were
noted in every case, and in 10 of 12 cases, venous
drainage was to the deep system. In the 3 patients in
whom MRI scans were obtained, the nature of the
parenchyma between abnormal vessels was not
evident.
Histopathological examination of the resected
diffuse AVM specimens showed the presence of
abnormal arteries and veins typical of an AVM in all
cases as well as normal appearing neurons and, in
some cases, mild gliosis (Fig. 3A). By contrast,
neural tissue, when present, between the abnormal
blood vessels of the typical AVM was restricted to
thin gliotic bands without identifiable neurons
(Fig. 3B). When a diffuse malformation came near
the cortical surface, focal leptomeningeal
angiodysplasia, consisting of an increased number of
leptomeningeal vessels with abnormally thickened
walls, was noted (Fig. 3C).
Eleven patients underwent craniotomy, and one
patient was deemed inoperable and received
conventional external beam radiation therapy (30
Gy). Five patients with residual AVM underwent a
second craniotomy, and in three the remaining AVM
was removed completely. Of the three patients with
residual AVM, two underwent stereotactic
radiosurgery and one has received no further therapy.
The clinical outcome was excellent for eight
patients. In the remaining four patients there were
two good outcomes, one unchanged, and one poor.
The patient with the poor result was left with an
expressive aphasia and an increased hemiparesis.
There was no surgical mortality or evidence of normal perfusion pressure breakthrough (23). No
definitive correlation can be made between
preoperative grading and outcome because of the
small number of patients, but the two patients with
the worst clinical outcomes were Spetzler Grades IV
and V.
Treatment
Diffuse AVMs are difficult to treat effectively as
they are both large and complex. This is reflected in
the high scores given to the patients in our series
using the Spetzler scale (21). The absence of a gliotic
plane around a well defined nidus makes total
surgical removal more of a challenge. In addition, the
presence of normal brain within the lesion means that
surgical excision or radiation therapy will result in
the sacrifice of normal parenchyma. This precludes
surgical treatment when these lesions are located
exclusively in cortex with critical function.
Anterior frontal, anterior or non-dominant
temporal, or parieto-occipital lesions are amenable to
surgery, which provides the only opportunity for
immediate cure. The traditional principles of AVM
resection must be modified (13,14,26). An en bloc
approach, such as a lobectomy, may be required for
complete removal of all abnormal vessels. The
attempt to remove all of the malformation must
obviously be weighed against the danger of
producing an unacceptable neurological deficit. If
there is extension of abnormal vessels into critical
areas of the brain such as the thalamus, stereotactic
radiosurgery may be useful in obliterating remaining
malformation.
Our surgical results with incomplete removal of the
AVM in 6 of 11 patients with the first attempt, and in
2 of 5 after the second, demonstrate the difficulty in
determining the extent of resection intraoperatively.
Because of the low rate of flow through the AVM, the
surgeon can cut through the lesion without noticing
the small, abnormal vessels. The difficulty is
increased by the lack of a gliotic plane around the
lesion. Intraoperative angiography was not available
at the time of these operations. Although small
residual portions of the AVM can be missed with
intraoperative angiography, it will be used in future
cases. Postoperative angiography is essential to verify
complete removal.
There were four patients with residual AVMs. Two
underwent stereotactic radiosurgery. This modality
has had some success in obliterating small AVMs
(18)
. Colombo et al. (2) achieved obliteration at 2 years
in 90% of AVMs <15 mm and 80% of AVMs
between 15 and 25 mm. Follow-up on these two
patients has not been long enough to know whether
the treatment has been effective. One patient had a
poor result after the initial surgical attempt at
removal, and further treatment of his residual AVM
has not been undertaken. One patient with a >6 cm
AVM involving the left basal ganglia and thalamus
never underwent surgical intervention. This lesion
was too large for stereotactic radiosurgery and the
multiple small feeders made embolization impossible.
She underwent conventional radiation therapy with
30 Gy with resolution of the steal phenomenon. The
status of her AVM is not known, because repeat
angiography has been refused. Conventional
radiation therapy has been found to be of modest
efficacy in the treatment of AVMs (18).
Staged embolization with operative excision of
large AVMs has been advocated to lessen the risk of
normal perfusion pressure breakthrough (22).
Embolization was only used in two patients in our
series, yet we did not encounter this complication in
any of our patients. The low flow nature of these
malformations, despite their large size, is likely the
reason that normal perfusion pressure breakthrough
was not noted.
Diffuse AVMs are large vascular malformations
with a tendency to hemorrhage in late childhood and
early adulthood. The unique angiographic features
can be recognized preoperatively and aid in surgical
planning. The presence of normal neural tissue
interspersed among the vessels of the malformation
requires caution during resection. Nonetheless, an en
bloc resection of brain may be necessary to
completely remove the malformation.
Received, March 25, 1992.
Accepted, May 11, 1992.
Reprint requests: Corey Raffel, M.D., Ph.D., 1300
North Vermont Avenue, Suite 906, Los Angeles, CA
90027.
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Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
abnormal capillary bed into a large plexus of vessels
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COMMENTS
Chin et al. have reported 12 interesting cases of socalled diffuse arteriovenous malformations (AVMs).
The authors suggest that these lesions are a subtype
of AVMs that reflect the diffuse end of the spectrum
of AVM morphology. The critical characteristic for
differentiating these lesions from typical AVMs is
significant amounts of presumably normal brain
parenchyma within the diffuse AVM nidus. The
excess parenchyma makes surgical treatment difficult
when these AVMs are located in eloquent areas of the
brain. Nonetheless, the authors report favorable
results after surgery in most cases (with additional
radiosurgery in a few cases). The cases span a 12-year
period during which adjuvant treatments such as
stereotactic radiosurgery and advanced embolization
techniques become an important part of the treatment
for AVMs.
We have also seen many cases of large diffuse
AVMs, most of which have not been localized
sufficiently within the anterior frontal or temporal
regions to permit complete excision or lobectomy.
Several of these AVMs extended into the thalamus
and other critical subcortical areas. Our recent
attempts to treat these deep lesions by intraoperative
glue embolization appear to be promising. We
combined this technique with surgical excision of
accessible portions of the AVM and, when necessary,
with stereotactic radiosurgery of the residual
portions. Chin et al. used embolization to treat two of
their patients but did not discuss the efficacy of this
preoperative treatment.
We agree that these large, diffuse lesions represent
an extremely challenging type of AVM to treat safely.
Chin et al. have made a valuable contribution by
demonstrating the presence of normal brain tissue
within the diffuse nidus. Some of their cases predate
radiosurgery and advances in endovascular
techniques, which now offer additional means of
treating these AVMs. Nonetheless, it is important to
recognize these lesions as one end of the spectrum of
AVM morphology and that their treatment carries a
high risk to interspersed normal brain. With careful
use of combined therapies, however, most of these
AVMs can be treated effectively.
John A. Anson
Robert F. Spetzler
Phoenix, Arizona
Chin et al. have very carefully described what I
think is a very important neurovascular entity that has
substantial importance to the patient and must be
recognized preoperatively. Diffuse AVMs with
intervening functional brain tissue carry a substantial
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
8.
risk of incomplete resection, as the authors have
demonstrated, as well as neurological injury with
complete resection. We have clearly seen evidence on
magnetic resonance imaging scan of diffuse
malformations with definite intervening gray and
white matter among the vascular flow voids. At
surgery, one can be deceived by an apparent gliotic
tissue plane apparently marginating the malformation
when, in fact, one is simply cutting across a small
tuft. In addition to the obvious hazard of resecting an
eloquently located malformation of this type, I am
concerned about the impact of stereotactically
delivered high dose radiotherapy because of the risk
of symptomatic brain necrosis in the intervening
brain tissue. We have seen this entity in a number of
middle-age and older adults, and I suspect the skew
in the present series toward younger people simply
reflects the inclusion of a population based at the
Childrens Hospital. Based on the authors' experience,
for a grading scale to be truly predictive, the actual
physical characteristics of the malformation (diffuse
or compact) must be taken into consideration.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
H. Hunt Batjer
Dallas, Texas
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 1. Right internal carotid angiogram in the
anteroposterior projection showing the typical
features of a juvenile diffuse AVM. A, arterial phase
angiogram revealing multiple small feeding vessels
arising from the anterior and middle cerebral arteries.
B, a slightly later film demonstrates the small caliber
of the vessels in the ill-defined nidus.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 2. Right internal carotid angiogram in the
lateral projection demonstrating the typical features
of a juvenile diffuse AVM. A, arterial phase
angiogram demonstrating the diffuse, ill-defined
nidus made up of small vessels. B, late venous phase
angiogram showing the puddling appearance with
persistence of the contrast agent in the vessels of the
malformation.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 3. Photomicrographs demonstrating the
typical features of juvenile diffuse AVMs. A, juvenile
diffuse AVM involving both cerebral cortex and
white matter. Some blood vessels have an internal
elastic lamina (arrow) and are easily identified as
arteries; others are clearly veins. The majority of
vessels, however, are difficult to classify (VerhoeffVan Gieson stain, ×200). B, abnormal, dilated vessels
Table 1. Clinical Data for Diffuse AVMs
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