1100

Spontaneous Intracranial Carotid
Artery Dissection
Michael S. Pessin, MD, Lester S. Adelman, MD, and Nancy R. Barbas, MD
A previously healthy 46-year-old woman had the abrupt onset of aphasia and right hemiplegia
from a large left-hemisphere infarct. At postmortem examination the cause of the infarct was
dissection and occlusion of the intracranial carotid artery. No preexisting abnormality was
found to account for the dissection. This uncommon cause of stroke and its pathogenesis are
discussed. (Stroke 1989;20:1100-1103)

S
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pontaneous (nontraumatic) intracranial internal carotid artery (ICA) dissection is an
uncommon cause of cerebral infarction. The
diagnosis may be suggested by angiography when
an irregular, thin column of dye (the string sign1-3)
is seen as part of the occlusive process, but often
only an intracranial occlusion, which may be indistinguishable from embolism,4-9 is noted. Pathologic
documentation is usually required to establish the
diagnosis of dissection and to clarify its pathogenesis.
Several conditions have been implicated in the
pathogenesis of spontaneous intracranial dissection. These include congenital defects in the media
or internal elastic lamina, fibromuscular dysplasia,
cystic medial necrosis, trivial trauma, and
migraine.4-6-12 In a few patients, no preexisting
abnormalities have been discovered, adding further
to the mystery of this condition. - > The present
patient falls in the latter category, in which no cause
for the dissection was identified.
Case Report

A 46-year-old woman arose and prepared for
work at 6:00 AM and was found on the floor shortly
thereafter by her husband. She was vomiting but
awake and mute, not moving her right side. She was
taken to a local hospital and then to New England
Medial Center. On examination, her blood pressure
was 130/80 mm Hg and her pulse was 58 beats/min.
She was lethargic and followed no verbal instructions. A left gaze preference was noted, but her
eyes moved fully to the right with oculocephalic
maneuvers. She had right lower face weakness, and
her right arm and leg moved poorly to painful
From the Departments of Neurology (M.S.P., L.S.A., N.R.B.)
and Pathology (L.S.A.), Tufts University School of Medicine and
the New England Medical Center, Boston, Massachusetts.
Address for reprints: Michael S. Pessin, MD, New England
Medical Center, Box 314, 750 Washington Street, Boston, MA
02111.
Received March 3, 1989; accepted April 3, 1989.

stimulation compared with her left arm and leg.
Bilateral extensor plantar responses were present.
There were no carotid or ocular bruits.
There was no history of transient ischemic attacks,
migraine, or neck or head trauma. She did not have
hypertension, diabetes, or heart disease, and she
was not taking oral contraceptives. She smoked
cigarettes.
Results of computed tomography (CT scan) and
lumbar puncture were normal. Eight hours later she
was comatose, with bilateral decorticate posturing
and pupils poorly reactive to light. CT scan (Figure
1) at that time showed a large infarct in the territories of the anterior cerebral artery (ACA), middle
cerebral artery (MCA), and posterior cerebral artery
(PCA). Despite medical measures to control her
increased intracranial pressure, she died on the
second hospital day.
Gross examination of the brain revealed massive
swelling and softening of the left cerebral hemisphere involving the territories of the ACA, MCA,
and PCA. There was a medial temporal lobe herniation on the left. The left posterior communicating
artery was large; the PI segment of the PCA was
small. The anterior communicating artery (AComA)
was of average size. The left ICA, as it entered the
cavernous sinus, had a hematoma in its wall, without significant narrowing of the lumen. The distal
intracavernous ICA was grossly normal. Redbrown, granular material obstructed the lumen of
the left ICA in its most proximal intracranial portion. It was not possible to tell grossly if this
material was in the lumen of the vessel or in its wall.
This process extended along the ICA, past the
orifice of the ACA, and involved the proximal MCA
in the sylvian fissure (Figure 2). The carotid arteries
in the neck were widely patent and showed only
mild atherosclerosis. Horizontal sections of the
cerebral hemispheres showed a recent infarct involving almost all of the left cerebral hemisphere, includ-

Pessin et al

Carotid Artery Dissection

1101

ACA
MCA

ICA

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FIGURE 1. Noncontrast computed tomogram in 46year-old woman showing low-attenuation area involving
anterior, middle, and posterior cerebral artery territories
with marked midline shift and compression of left lateral
ventricle.
ing the basal ganglia. Transverse sections of the
brainstem showed elongation and distortion of the
midbrain and rostral pons, but no secondary brainstem hemorrhages.
Microscopic examination of the intracavernous
portion of the left ICA showed a recent dissection
with an intimal tear and an intramural hematoma
located in the center of the media (Figure 3, left).
The vessel showed no preexisting abnormality. A
section of the grossly spared distal intracavernous
artery showed no dissection and no other abnormality of the vessel wall. The intracranial ICA was
severely narrowed by an intramural dissection
between the internal elastica and the media (Figure
3, right). There was recent thrombus in the lumen,
some attached to the wall and some lying free in the
lumen. Similar changes were seen in the proximal
portion of the MCA. The dissection did not involve
the ACA, but a microscopic bit of recent thrombus
was seen in the lumen of this vessel. The distal left
MCA, right MCA, and the right ICA were all
histologically normal.
Discussion
Postmortem examination established dissection
as the mechanism for this patient's intracranial ICA
occlusion and massive hemispheric infarct. Dissection was present in two separate areas of the ICA,

FIGURE 2. Diagram of location of lesions found in left
carotid artery. Sites of dissection in siphon (A) and in
intracranial vessels (B) are indicated. Area uninvolved by
dissection is seen between A and B. ICA, internal carotid
artery; MCA, middle cerebral artery; ACA, anterior
cerebral artery.

with a "skip" area between them free of any
abnormality (Figure 2). These separate areas of ICA
dissection probably occurred nearly simultaneously
since both hematomas showed recent blood clot
histologically. The reason for the normal skip area
is unclear, but its length of >1 centimeter suggests
that there was more than one dissection. This case
reemphasizes the difficulty in deciding on the importance of intimal tears in the pathogenesis of dissections since an intimal tear was found in one area of
dissection but not in the other. The intramural
hematomas were in slightly different locations in the
two areas of dissection. The hematoma in the
intracavernous dissection, associated with the intimal tear, was located in the center of the media; the
hematoma in the intracranial dissection was found
between the elastica and media. Dissections have
been reported in both locations, but those in the
media are more often found in the vertebrobasilar
system and are associated with hemorrhage, whereas
subendothelial hematomas are more characteristic
of carotid dissection with resulting luminal stenosis
and occlusion.9-11'12-14
The inclusion of the ACA territory in the hemispheric infarct is unexpected in a patient with a
patent AComA and ACA. It may have resulted
from local embolism of the ICA thrombus to the

1102

Stroke Vol 20, No 8, August 1989

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FIGURE 3. Photomicrographs of two areas of dissection. Left is from siphon (A in Figure 2). There is defect in intima
elastica and part of media at lowerpart of photomicrograph. Dissection is indicated by arrows. Elastica stain, x34. Right
is from intracranial carotid artery (B in Figure 2). Large dissection between elastica and media has reduced lumen to slit.
Elastica stain, x34.

ACA with subsequent fragmentation. This hypothesis is supported by the microscopic particle of
thrombus found in the ACA. Either local embolism
or hemodynamic insufficiency affecting the left PCA
may have resulted in the inclusion of the PCA
territory in the huge hemispheric infarct since the
left PCA arose primarily from the ICA.
Our patient had no preexisting arterial condition
to explain the occurrence of her dissection, nor was
trauma, infection, or migraine a factor. Histologic
examinations of intracranial dissection have frequently identified defects, presumably congenital,
in the internal elastic lamina.4'6-12 Gaps in, fragmentation of, or disruption of the internal elastic lamina
have been the usual findings implicated in the
pathogenesis of dissection. In some cases there has
been an association with other conditions such as
fibromuscular dysplasia, moyamoya disease, and
migraine.9-11 Other patients have not shown preexisting arterial abnormalities.2'5'13 Whether trivial
trauma, such as persistent coughing, sneezing, or
vomiting, can precipitate dissection even with preexisting defects remains unknown.
Our patient is unusual because of the two distinct
areas of dissection and the absence of any preexisting underlying defect. Further pathologic studies of

such cases may help clarify the pathogenesis and
may help identify patients at risk for stroke.
References
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1103

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KEYWORDS • carotid artery diseases • dissection

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