From the Istituto di Clinica delle Malattie Nervose e Mentali (S.P.) and
Istituto di Scienze Eidologiche e Radiologiche (G.F.), Università di
Siena (Italy).
Correspondence to Stefano Passero, MD, Istituto di Clinica delle Malattie Nervose e Mentali, Università di Siena, Viale Bracci, I-53100 Siena, Italy.
Methods—We studied 40 consecutive stroke patients with associated
VBD. All were evaluated by CT scan (n=9), MRI (n=6), or both (n=25).
The diameter of the basilar artery (BA), height of bifurcation, and
transverse position were evaluated. Clinical and imaging findings were
compared with those found in a group of 40 VBD patients without stroke.
Results—More than half of the patients (24 of 40) had
infratentorial infarcts, located mainly in the midpons. Sixteen
patients had supratentorial lesions localized in
the thalamus (n=8) or in the superficial arterial territory
of the posterior cerebral artery (PCA; n=8). The diameter and height of
the bifurcation of the BA were correlated with the location of the
lesion (PCA territory versus BA territory), in that severe ectasia and
vertical elongation of the BA were significantly more often observed in
patients with infarcts in PCA territory than in patients with infarcts
in territories supplied by branches of the BA. Comparison of VBD
patients with and without stroke showed that the incidence of
arterial hypertension and the degree of ectasia and lateral
displacement of the BA were not significantly different in the two
groups. Patients with stroke more often had atherosclerotic changes of
the posterior circulation (P=.0006) and a higher degree
of vertical elongation of the BA (P=.025).
Conclusions—In patients with VBD, superimposed
atheromatous changes of the posterior circulation may
have an important role in precipitating ischemia. However,
other factors related to the severity of the dolichoectasia also favor
ischemia and in some cases are the only factors responsible.
This study was undertaken to systematically examine and characterize
clinical and imaging findings in patients with stroke associated with
VBD and to compare this data with that of patients with VBD but no
stroke.
The following risk factors for cerebrovascular disease were examined:
history of hypertension (previous diagnosis of arterial
hypertension, ie, systolic blood pressure >160 mm Hg
or diastolic >90 mm Hg or both and/or past or
present use of antihypertensive agents), diabetes mellitus
(previous diagnosis of diabetes and/or past or present use of
antidiabetic agents), current smoking, alcohol abuse (ingestion of
>400 mL/wk pure ethanol), hyperlipidemia
(cholesterol level of >250 mg/100 mL or
triglyceride level of >180 mg/100 mL or both), previous
coronary artery disease (or myocardial infarction), and
potential cardiac source of embolism.
Ischemic lesions in the posterior circulation were classified
according to the anatomic site and the presumed vascular territory
involved using the templates proposed by
Pullicino,23 Tatu et al,24
and Damasio.25 The diameter of the BA, height of
bifurcation, and lateral displacement were evaluated as suggested by
Smoker et al.22 The height of the BA bifurcation
was scored as 1 (within the suprasellar cistern), 2 (at level of third
ventricle floor), or 3 (indenting and elevating the floor of the third
ventricle); lateral displacement was scored as 1 (medial to lateral
margin of clivus or dorsum sellae), 2 (lateral to lateral margin of
clivus or dorsum sellae), or 3 (in cerebellopontine angle cistern). A
global index of dolichoectasia was calculated by adding the single
scores.
Some clinical and imaging findings (parameters of the BA,
presence of hypertension, and presence of atherosclerotic changes of
the posterior circulation) were compared with those found in a group of
40 patients (9 women and 31 men; mean age, 61.6±8.6 years; median age,
63.0 years; range, 45 to 82 years) with VBD but no history of
cerebrovascular events. None of these patients showed evidence of
ischemic lesions in the posterior circulation on CT (n=9) or
MRI (n=31) examinations. Sixteen patients also underwent conventional
angiographic examination.
The
Vascular Concomitants
Infarcts in Posterior Circulation
In 22 patients the lesion was located in arterial
territories supplied by branches of the BA or vertebral artery,
specifically, the penetrating arteries (anteromedial and anterolateral
perforators) in 12 patients and the short and long circumferential
arteries (lateral pontine artery, superior cerebellar artery, anterior
inferior cerebellar artery, and posterior
inferior cerebellar artery) in 10 patients. In the other 18
patients, the arterial territory involved was supplied by
deep branches of the PCA, such as the anteromedial and anterolateral
midbrain arteries (n=2), inferolateral thalamic arteries (n=5),
paramedian thalamic arteries (n=2), posterior choroidal arteries (n=1),
or by the superficial branches of the PCA (n=8). The latter included
patients with infarct involving the entire superficial territory of the
PCA (n=1), the territory of the posterior division (n=6), and the
territory of the anterior division (n=1).
Other Infarcts and Lesions
Arterial Lesions
The diameter of the BA ranged in size from 4.8 to 10.9 mm. In 20
patients, elongation of the BA was very pronounced, with the
bifurcation of the artery indenting the floor of the third ventricle or
the artery lying in the cerebellopontine angle cistern. The most
frequent deformation of the BA was C shaped (n=24), other types were S-
(n=13) and J-shaped (n=3) deformities.
An attempt was made to correlate some aspects of the BA (diameter of
the artery, degree of the lateral displacement, and height of the
bifurcation) with the location of the ischemic lesions (PCA
territory versus BA territory). Among these variables, diameter and
height of the bifurcation of the BA were correlated with the location
of the lesion, in that severe ectasia and vertical elongation of the BA
were observed significantly more often in patients with infarcts in the
PCA territory than in patients with infarcts in territories supplied by
branches of the BA (Table 3
Other Causes of Stroke
Clinical Aspects
Thirty-eight patients survived the acute event, 32 with mild to
moderate disability and 6 with severe deficit. Two patients (cases 13
and 24) died of the stroke within 6 days of onset.
Comparison of VBD Patients With and Without Stroke
Unlike those in other series,4 9 11 13 our
patients showed a higher incidence of
supratentorial infarcts, especially in the
superficial PCA territory. This discrepancy may result from many
factors, including different patient enrollment criteria and different
imaging methods. MRI has certainly aided recognition of small infarcts
not detectable by CT. Moreover, in patients with acute stroke, CT scan
often cannot detect the simultaneous presence of VBD unless
the BA has calcifications or a contrast medium is used.
The precise pathophysiology of cerebral ischemic events
associated with VBD is not clear. In this condition, mechanisms
commonly observed in patients with cerebrovascular disease, such as
arteriolar lipohyalinosis, obstruction by atheroma or
intraluminal thrombus, and artery-to-artery embolism, may be operant.
However, in VBD other specific mechanisms, such as distortion of
branches of the BA due to elongation and tortuosity of this vessel and
hemodynamic factors related to the significant
reduction of flow velocity in the BA, may contribute to
ischemia.
On the basis of the imaging and angiographic findings and exclusion of
patients with other potential cause of stroke, two
pathophysiological mechanisms of infarction can be
identified in our series: (1) infarcts in distal territories (thalamus,
superficial PCA territory, cerebellum) that may be associated with
artery-to-artery embolism8 28 and (2) brain stem
and some cerebellar infarcts that may be associated with
atherothrombotic occlusion at the origin of BA branches (branch
atheromatous disease).40
Our study reveals three interesting aspects. The first is the fact that
the infarcts located in the PCA territory were significantly associated
with more severe ectasia and vertical elongation of the BA than those
located in territories supplied by branches of the basilar or vertebral
arteries. This suggests the involvement of hemodynamic
or thromboembolic mechanisms related to the reduced blood flow velocity
in severe dolichoectasia (as demonstrated by angiographic study and
transcranial Doppler
examination)12 and to the distortion of the PCAs
and their small branches. Another aspect suggesting a
hemodynamic mechanism is the fact that half of the
patients with infarcts in the superficial PCA territory had occlusion
or severe stenosis of the anterior circulation. This feature
was also observed by Steel et al8 in a patient
with an occipital infarct associated with VBD and a severe
stenosis of the internal carotid artery.
Among infratentorial infarcts, we observed that the majority of the
lesions in the arterial territories supplied by branches of
the BA were contralateral to the side of the lateral displacement of
the BA, which suggests a relationship between ischemia and
distortion and/or stretching of the branches of the BA.
Some authors21 41 have suggested that
atherosclerotic degeneration of the vascular wall, either alone or
associated with arterial hypertension, is the initial
pathogenetic factor in the development of this condition. Other authors
maintain that atherosclerosis does not play a
substantial role in the pathogenesis of arterial ectasia
and that VBD is a congenital anomaly. The second hypothesis is backed
by histological studies that show defects in the
internal elastic lamina, with thinning of the media secondary to smooth
muscle atrophy20 32 42 ; by the frequent absence
of atherosclerosis42 43 ; and by
the occurrence of arterial ectasia in all age
groups.13 44 45 46 47 Furthermore, VBD may be (1) a
component of generalized ectasia of the cerebral vessels, as indicated
in our and other
series1 4 6 7 10 11 26 32 42 43 46 48 ; (2)
associated with aneurysm of the abdominal
aorta4 13 21 32 43 44 46 ; or (3) associated with
ectasia of other vascular districts,43 46 which
suggests a more diffuse arterial defect.
It seems likely that a defect in the development of the
arterial wall is responsible for ectasia, which may also be
favored by arterial hypertension, associated in some cases
with an atheromatous process that further damages the
elastic elements. Thus VBD may occur in the absence of
atheroma or with superimposed atheromatous
changes, as in the present series and
others.1 21 42 43 44 Superimposed
atheromatous changes may have an important role in
precipitating ischemia, as suggested by our comparison of VBD
patients with and without stroke, which showed that ischemic
complications of VBD were significantly more often observed in patients
who had superimposed atheromatous changes of the
posterior circulation. However, the present study shows that other
factors related to the severity of the dolichoectasia also favor
ischemia and in some cases are the only factors
responsible.
Although our series does not necessarily describe the entire spectrum
of ischemic lesions associated with VBD, it nevertheless gives
a sufficiently complete view of the possible ischemic
complications associated with this pathology.
Received November 3, 1997;
revision received December 18, 1997;
accepted January 6, 1998.
© 1998 American Heart Association, Inc.
Original Contributions
Posterior Circulation Infarcts in Patients With Vertebrobasilar Dolichoectasia
Abstract
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Background and
Purpose—Vertebrobasilar dolichoectasia (VBD) may produce symptoms
by direct compression of cranial nerves or the brain stem, by
obstructive hydrocephalus, or by ischemia in the
vertebrobasilar arterial territory. This study was
undertaken to examine and characterize clinical and imaging findings in
patients with stroke associated with VBD and compare these data with
those for patients with VBD who did not have a stroke.
Key Words: stroke, ischemic • vertebrobasilar circulation • vertebrobasilar dolichoectasia
Introduction
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Vertebrobasilar
dolichoectasia is an uncommon but well-recognized vascular anomaly, the
diagnosis of which has been simplified by CT and MRI. An ectatic,
elongated BA may produce symptoms by direct compression of cranial
nerves or the brain stem, by obstructive hydrocephalus, or by
ischemia in vertebrobasilar arterial
territory.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Bleeding associated with VBD has
also been reported.4 10 13 17 18 19 20 21 There are many
reports of patients with VBD complicated by compression of neural
structures, whereas studies of ischemic complications are few
and no attempt has been made to characterize this
aspect.4 9 11 13
Subjects and Methods
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
We studied 40 consecutive stroke patients with associated VBD.
All were evaluated by CT scan (n=9), MRI (n=6), or both (n=25).
Eighteen patients underwent additional angiographic examination
performed by the Seldinger method, and 11 underwent MRA. Other
investigations included standard blood tests, Doppler
ultrasonography, ECG, and transthoracic
echocardiography. MR was performed with a 0.5-T
superconducting magnet unit with use of spin-echo, multi-echo, and FAST
techniques. The images (T1- and T2-weighted and proton density) were
obtained in the sagittal, axial, and coronal planes. Slice thickness
was 5.0 mm, with a 2.0-mm interval between successive slices.
According to Smoker et al,22 the BA was judged
elongated if at any point along its course it lay lateral to the margin
of the clivus or dorsum sellae or bifurcated above the plane of the
suprasellar cistern. Ectasia was diagnosed if the diameter of the
artery was greater than 4.5 mm. 
2 test was used in the statistical
procedures.
Results
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
The 40 patients (9 women and 31 men) ranged in age from 47 to 83
years (mean, 62.8±8.9 years; median, 63.0 years). Of these patients,
25 had experienced no previous cerebrovascular events. Twelve patients
had suffered one or more previous transient ischemic attacks,
and 3 patients had previous cerebral hemorrhages (1 thalamic, 1
putaminal, and 1 lobar). At the time of stroke all patients without
previous history of cerebrovascular events and the 3 patients with
previous cerebral hemorrhage were not being treated with
antithrombotic drugs. Among the 12 patients with previous transient
ischemic attacks, 5 were treated with aspirin (325 to 500 mg/d)
and 5 with dipyridamole, while 2 patients were not
under treatment at the time of stroke.
The most common risk factor was arterial hypertension,
which was present in 29 patients. Six patients had diabetes, 20
patients hyperlipidemia, 17 patients were current
smokers, 8 patients were alcohol abusers, and 6 patients had a history
of coronary artery disease (4 angina pectoris and 2 old
myocardial infarct) (Table 1
). None had
arrhythmia at the time of the event, and
echocardiography performed in 37 patients revealed
the presence of possible emboligenic abnormalities in 2 patients (left
ventricular hypokinetic segment). Only 1 patient was free
of risk factors; 7 patients had one, and 32 had more than one risk
factor.
View this table:
[in a new window]
Table 1. Demographic and Clinical Characteristics of 40
Patients With Stroke Associated With Vertebrobasilar Dolichoectasia
More than half of the patients (24 of 40) had infratentorial
infarcts localized in the midbrain (n=4), pons (n=14), medulla (n=1),
and cerebellum (n=5). Pontine lesions were mainly located in the
midpons (9 of 14). Sixteen patients had
supratentorial lesions localized in the thalamus
(n=8) or in the superficial arterial territory of the PCA
(n=8) (Table 2).
View this table:
[in a new window]
Table 2. Posterior Circulation Infarcts in 40 Patients With
Vertebrobasilar Dolichoectasia
One patient had an old asymptomatic occipital infarct
(case 38) and 3 had supratentorial scars due to
previous cerebral hemorrhage. Thirty-two patients had white
matter lesions, with areas of focal abnormalities in 26 and a
multifocal diffuse pattern (leukoencephalopathy) in 5 (cases 12, 13,
20, 31, and 32). In 7 patients (cases 11, 17, 21, 23, 28, and 40) no
other lesions were found.
None of the 29 patients in whom angiography or MRA was performed
had occlusion or stenosis of >50% of the vertebral, basilar,
and posterior cerebral arteries; 4 had unilateral or bilateral
stenosis of >50% of the carotid arteries (cases 33, 34, 35,
and 39); and 7 had stenosis of <50% of the anterior
circulation (n=4), posterior circulation (n=2), or both (n=1). Diffuse
atherosclerotic changes were observed in 13 patients, and in 2 patients
(cases 19 and 23) no arterial lesions other than VBD were
found . Other findings were ectasia (cases 6, 14, and 30) and saccular
aneurysm (case 1) of the anterior circulation. One patient
(case 6) had ectasia of the abdominal aorta on MRA. Ten of the 11
patients who were not examined by angiographic study underwent MRI,
which showed no abnormal vertebrobasilar artery flow void signal.
Doppler sonography showed atherosclerotic changes in all 11
patients. One patient (case 24) underwent CT examination only; however,
a contrast-enhanced scan showed no evidence of BA intraluminal
thrombus. ). The same
was true even when the analysis was repeated with the exclusion
of patients with possible causes of posterior circulation infarct other
than VBD. Among the 19 patients with pontine or cerebellar lesions
(superior cerebellar and anterior inferior cerebellar
artery territories), the location of infarct was opposite to the side
of lateral displacement of the BA in 11 patients, on the same side in 5
patients, and at the same level as the side-to-side transition of the
BA in 3 patients with S-shaped BAs.
View this table:
[in a new window]
Table 3. Location of Lesions and Severity of Vertebrobasilar
Dolichoectasia
In 23 patients there was no potential cause of posterior
circulation infarct other than VBD. In 17 patients another possible
cause of stroke coexisted with VBD. These included arteriolar
lipohyalinosis in 15 hypertensive patients with lacunar infarcts in the
thalamus or brain stem and a potential cardiac source of embolism (left
ventricular hypokinetic segment) in 2 patients with
infarcts in the superficial territory of the PCA.
Classic lacunar syndromes were observed in 14 patients: 3
had pure motor hemiparesis with contralateral pontine infarcts; 4 had
pure sensory stroke, with contralateral thalamic infarcts in 3 and a
contralateral pontine infarct in the other; and 7 had sensory motor
stroke, with contralateral thalamic infarcts in 3 and contralateral
pontine infarcts in 4. Acute unilateral pseudobulbar palsy was observed
in 4 patients, with contralateral midbrain infarcts in 3 and a
contralateral pontine infarct in the other. One patient had hemichorea
with a contralateral thalamic infarct. Alternating syndromes, including
Weber's and Raymond's syndromes, were observed in 5 patients (Table 2
).
The incidence of arterial hypertension and the degree
of ectasia and lateral displacement of the BA were not significantly
different in the two groups. Patients with stroke more often had
atherosclerotic changes of the posterior circulation
(P=.0006) and a higher degree of vertical elongation of the
BA (P=.025; Table 4).
View this table:
[in a new window]
Table 4. Clinical and Imaging Findings in VBD Patients With
and Without Stroke
Discussion
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
The relationship between cerebrovascular events and VBD has been
described in occasional cases and in a few patient series. In those
reports with sufficient clinical and imaging
data,3 4 5 8 9 10 11 13 15 26 27 28 29 30 31 32 the most frequently
described ischemic lesion was brain stem infarction, observed
in 39 of 56 patients. Ten patients were reported to have cerebellar
infarcts, 4 thalamic infarcts, and 3 infarcts in the superficial PCA
territory (Table 5). Brain stem infarcts
were most often located in the pons (29 of 39). Other authors have
observed VBD in study series of patients with
cerebellar,33 34 pontine,35
medullary,36 37 and
thalamic38 infarcts or in patients with posterior
circulation strokes.39
View this table:
[in a new window]
Table 5. Location of Ischemic Lesion as Demonstrated
by CT Scan, MRI, or Autopsy in 96 Patients With Stroke Associated With
Vertebrobasilar Dolichoectasia1
Selected Abbreviations and Acronyms
BA
=
basilar artery
MRA
=
magnetic resonance angiography
PCA
=
posterior cerebral artery
VBD
=
vertebrobasilar dolichoectasia
Acknowledgments
Supported in part by research grants from the University of
Siena (Contributi per la Ricerca Scientifica, fondi 60%).
References
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
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