Full text of DOI:10.1017/S0317167100001591

CASE REPORT
Dissecting Hematoma of Intracranial
Internal Carotid Artery in an
8
-year-old Girl
Roy H. Rhodes, Susan Phillips, Frances A. Booth, Kenneth G. Magnus
ABSTRACT: Background: An 8-year-old girl had a minor fall without head trauma and she collapsed the following day while play-
ing. She was awake but mute with focal neurologic signs when admitted to hospital. Radiologic imaging studies showed a progressive
left cerebral infarct with left hemisphere vascular narrowing and beading. She died on the third hospital day. Methods: Autopsy includ-
ing exploration of neck vessels and neuropathological examination was performed. Postmortem studies included immunostaining for
immunoglobulins and fixed complement. Results: Subtotal subintimal dissections of both proximal supraclinoid internal carotid arter-
ies were found microscopically. On the left, the subintimal dissection extended into the major branches of the left internal carotid artery
as dissecting hematomas with a major compromise of the arterial lumina. Specific IgM deposition at the dissection sites was found. A
literature review shows that subintimal dissection of the intracranial internal carotid artery or its branches occurs rarely, it is often fatal,
and it is present in patients with a mean age of 17.5 years in cases studied pathologically. Trauma and physical exertion are the most
common associated factors. Conclusions: Among the causes of ischemic stroke in young individuals, dissecting hematomas of the
intracranial portions of the internal carotid artery system rank low. Few reported cases have identifiable pre-existing pathology. The
pathogenesis of dissecting hematomas in this region is reviewed and expanded with speculation regarding relevant developmental,
anatomical, flow stress and possibly humoral factors that are involved in the disruption of the arterial elastica and subsequent develop-
ment and extension of a subintimal hematoma resulting in luminal closure and often death.
RÉSUMÉ: Hématome disséquant de la carotide interne intracrânienne chez une fillette de 8 ans. Introduction: Une fillette âgée de 8 ans a fait
une chute mineure sans traumatisme crânien et elle s’est affaissée en jouant le lendemain. Elle était consciente mais ne pouvait parler et présentait des
signes neurologiques focaux à l’admission. Des études radiologiques ont montré un infarctus cérébral gauche progressif avec un rétrécissement vascu-
laire à l’hémisphère gauche avec aspect en chapelet. Elle est décédée trois jours après son admission à l’hôpital. Méthodes: Une autopsie a été pra-
tiquée, incluant une exploration des vaisseaux du cou et un examen neuropathologique incluant des études immunohistochimiques pour les
immunoglobulines et la fixation du complément. Résultats: À la microscopie, on a constaté la présence de dissection sous-intimale subtotale de la por-
tion supraclinoïdienne proximale des carotides internes. À gauche, la dissection sous-intimale s’étendait aux branches majeures de la carotide interne
gauche sous forme d’hématomes disséquants qui compromettaient de façon importante la lumière artérielle. Des IgM spécifiques étaient présentes aux
sites de dissection. Une revue de la littérature a montré que la dissection sous-intimale de la carotide interne intracrânienne ou de ses branches est rare,
souvent fatale, et se retrouve chez des patients dont l’âge moyen est 17.5 ans dans les cas ayant subi un examen anatomopathologique. Un traumatisme
ou l’activité physique intense sont les facteurs les plus souvent associés. Conclusions: Parmi les causes d’accident vasculaire cérébral chez les jeunes,
l’hématome disséquant de la portion intracrânienne du système carotidien interne est une cause peu fréquente. Parmi les cas rapportés, peu ont une
pathologie préexistante identifiable. Nous revoyons la pathogénèse des hématomes disséquants de cette région et nous discutons de facteurs du
développement, de l’anatomie, des forces de cisaillement et de facteurs humoraux potentiels qui sont impliqués dans la perturbation de la couche élas-
tique artérielle, et le développement subséquent et l’extension d’un hématome sous-intimal menant à l’oblitération luminale et souvent au décès.
Can. J. Neurol. Sci. 2001; 28: 357-364
Intracranial internal carotid artery system dissection is
infrequently reported, its course is typically short and enigmatic,
of the intracranial vertebrobasilar system can be accompanied by
14-16
rupture of the arterial wall with subarachnoid hemorrhage.
1-7
and it is often fatal. By comparison, magnetic resonance (MR)
imaging has helped to establish arterial dissection in the
extracranial internal carotid arteries as an important and more
Dissecting hematomas of the intracranial internal carotid
artery system differ from neck vessel dissections by occurring in
8
-10
commonly survivable cause of cerebral infarction in adults.
The mean age of patients with dissection in the neck vessels is
From the Department of Pathology, (RHR, SP); Department of Pediatrics and Child
Health, (FAB); Department of Radiology, (KGM); University of Manitoba, Health
Sciences Centre, Winnipeg, Manitoba, Canada.
RECEIVED DECEMBER 11, 2000. ACCEPTED IN FINAL FORM JUNE 27, 2001.
Reprint requests to: R.H. Rhodes, Health Sciences Centre, Department of Pathology,
MS-459, 820 Sherbrook Street, Winnipeg, MB R3A 1R9, Canada
4
1
0 to 45 years, and the incidence is close to three cases per
11
00,000 population. Dissection through the medial layer in the
neck vessels may be spontaneous, but there is often a history of
trauma, including trivial head or neck trauma.5
,6,9,12,13
Dissection
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THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES
much younger patients and by having a plane of dissection that
is subintimal and splits the internal elastic lamina from the
media. Few of these patients have histologic evidence of a
with friends. No adult witnessed the event. Later history from her mother
described a fall from a countertop without head trauma the previous day.
During transfer to hospital, she opened her eyes and withdrew to pain. In
the Emergency Department, she had a transient increase in systolic
blood pressure to 140 mm Hg associated with a heart rate of 50 to 60
beats per minute. Otherwise, vital signs were stable and she was afebrile.
On initial neurological examination, she was awake, vocalizing but not
verbalizing, had persistent eye deviation to the left, right upper motor
neuron facial weakness, right extremity weakness and increased tone,
right-sided hyperreflexia, right ankle clonus, and a right extensor plantar
response with an equivocal left plantar response.
Her initial noninfused computed tomography scan showed subtle,
decreased gray/white differentiation of the left cerebral hemisphere with
small basal cisterns and cerebral ventricles, suggesting mild cerebral
edema and a left-sided infarct. A repeat study 24 hours later showed
progression of the lesion with some mass effect and petechial
hemorrhages in the parenchyma of the left middle cerebral artery
territory. MR imaging and MR angiography confirmed the presence of
an almost total, acute, left-sided cerebral infarct involving the internal
carotid artery distribution. The parenchyma of the left cerebral
hemisphere was swollen resulting in mass effect on adjacent structures.
Arterial calibre was reduced in the left supraclinoid internal carotid
artery, A1 segment of the left anterior cerebral artery, M1 segment of the
left middle cerebral artery and the entire left posterior cerebral artery.
Vascular “beading” was also present in this distribution. The left
thalamostriate vessels were more prominent when compared to the right
side (Figure 1).
17
previous vasculopathy. Typically, these children and young
adults have sudden onset of a lateralizing headache associated
with trauma, including trivial head trauma with or without a
delay, or with intense physical exertion and there is simultaneous
or subsequent development of neurologic symptoms. The delay
18
can be hours and sometimes days, and there is one report
19
documenting a one year delay. There is a relatively rapid
development of signs of cerebral ischemia with a progressive and
6
,17
fatal development of cerebral infarction in many instances.
Naturally-occurring defects in the internal elastic lamina
combined with hypertensive episodes have been linked to the
2
0
initiation of the dissections of the anterior cerebral circulation.
These dissections close the lumen and prevent blood flow, so
they do not generally form a grossly-identifiable aneurysm, even
6
though the artery can be expanded or beaded in imaging studies.
Vertebrobasilar dissections may differ in that they can have
significant disruption of the elastic layer and outer layers with
demonstrable aneurysmal formation and subarachnoid
1
4-16
hemorrhage.
In the anterior circulation, a dissecting
hematoma rather than aneurysmal formation is the focus of
pathologic attention. Anatomic location, age differences and the
physical properties of the intracranial internal carotid artery
system under flow stress have not been accounted for in a unified
theory of the mechanisms of intramural blood dissection. We
present a case of an extensive dissecting hematoma of the
intracranial internal carotid artery system in a child who had a
minor fall and collapsed at play the following day. We review
patients with similar findings and offer a contribution to the
possible pathogenesis of the entity.
Routine laboratory values were within reference ranges. There were
no abnormalities from viral titres; cultures; metabolic screens, including
the thermolabile 5,10-methylenetetrahydrofolate reductase variant and
homocysteine levels; C3 and C4 levels; antinuclear, anti-DNA and anti-
cardiolipin antibodies; antinuclear cytoplasmic antibody screens,
including myeloperoxidase cytoplasmic enzyme; or coagulation studies.
Carotid sonogram (left carotid and vertebral arteries) revealed no
evidence of dissection. She remained stable until 60 hours after
admission when she deteriorated suddenly and failed to respond to
ventilation, mannitol and steroids. She was declared brain dead and
removed from ventilatory support.
CASE REPORT
This 8-year-old, previously well, right-handed caucasian girl was
reported to collapse suddenly and become unresponsive while playing
After autopsy, brain examination showed that the cerebrum was
swollen and the cerebellar tonsils were herniated. The arteries at the base
A
B
C
Figure 1: A – T2-weighted axial MR imaging shows high signal intensity of entire left cerebral hemisphere and basal ganglia. L = left. B – Frontal
view of circle of Willis using MR angiography shows vascular narrowing and beading of supraclinoid left internal carotid and left posterior cerebral
arteries, and M1 segment of left middle cerebral artery (arrowhead). Note prominent left thalamostriate vessels (curved arrow). C – Frontal view of
posterior circulation with MR angiography show vascular narrowing and beading of left posterior cerebral artery.
3
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LE JOURNAL CANADIEN DES SCIENCES NEUROLOGIQUES
A
B
Figure 2: H&E-stained sections of left (A) and right (B) proximal supraclinoid internal carotid arteries show partial dissection of the internal elastic
lamina from the media, leaving a space between the mural layers (*). The elastica is ruptured with free ends curled in the lumen. A, bar = 100 µm; B,
bar = 300 µm.
A
B
Figure 3: Elastin-stained section of subintimal
dissecting hematoma of supraclinoid left internal
carotid artery distal to the segment shown in
Figure 2A. The hematoma separates the elastica
Figure 4: A – H&E-stained section of left posterior cerebral artery with dissecting hematoma. B
– Infarcted left occipital cortex has shrunken neurons (H&E stain). A, bar = 250 µm; B, bar =
100 µm.
(
arrow) from the media, leaving a restricted
luminal opening (*). Bar = 250 µm.
A
B
C
Figure 5: A – Proximal supraclinoid left internal carotid artery immunostained for IgM with deposition of IgM in media (long arrow) and on elastica
where subintimal dissection has occurred. Media is mostly negative for IgM where the elastica remains attached (short arrowhead). B – Distal to A,
subintimal hematoma is heavily IgM-immunoreactive. The media beneath the hematoma is also heavily immunostained for IgM, giving a stippled
appearance (long arrow), but the medial layer beneath attached elastica is negative (short arrowhead). C – Two adjacent branches of the left middle
cerebral artery have medial layer IgM immunoreactivity of varying intensity under subintimal hematomas (long arrows). Short arrowheads mark points
of dissection of elastica from media. Bar = 100 µm.
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THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES
of the brain were congested and they had a normal configuration.
Coronal sections of cerebrum revealed softened tissue and a distinct
corticomedullary junction. No deep white matter or cortical changes
were seen, but the lateral ventricles were small and the anterior horns
were almost closed. There was a small anterior shift of midline
structures from left to right. The superior aspect of the cerebellum was
narrowed from supratentorial pressure along the tentorium cerebelli and
the upper midbrain was slightly narrowed. No intraventricular
hemorrhage was present. The caudal half of the medulla near the
herniations had subarachnoid hemorrhage around it.
Microscopically, a subtotal subintimal dissection between the
internal elastic lamina and the muscular medial layer was found in the
right and left internal carotid arteries in their proximal portions that had
been in an immediately supraclinoid position. The internal elastic lamina
of the supraclinoid segment of both the left and right internal carotid
arteries was ruptured and the broken ends were curled up in the lumen
relatively closely related to rapid collapse. The most common
dissecting hematoma of limited extent is of the right (nine cases)
or left (eight cases) middle cerebral arteries alone, although
middle cerebral artery dissection is found in 37/42 patients.
Internal carotid artery dissection is present in 21/42 cases, with
the intramural hematoma continuing into the middle and anterior
cerebral arteries in 3/42 cases. A left anterior cerebral artery is
dissected alone in 1/42 cases. Bilateral dissections in 2/42 cases
involve the internal carotid and middle cerebral arteries and
another bilateral case has in addition anterior cerebral artery
dissections on both sides. One case has an extensive dissecting
hematoma of the right internal carotid, middle, anterior and
posterior cerebral arteries. Our case has a similarly extensive
dissecting hematoma of the left internal carotid artery system and
an early separation of the right internal carotid and middle
cerebral artery intimal layer from the media. The posterior
cerebral artery has not been involved alone in cases with
histologic data (Table).
(
Figure 2). An extensive dissecting hematoma involved the left internal
carotid artery several millimetres distal to the supraclinoid subintimal
dissection (Figure 3). The subintimal hematoma dissected into the left
middle, anterior and posterior cerebral arteries in each of several
sections made of these vessels. Each microscopic section had the same
histologic appearance with blood between the elevated elastica and the
otherwise normal-appearing media (Figure 4). The subintimal
hematomas compromised the lumen by up to 80%, while 40-70% of the
circumferential extent of the elastica was dissected away from the
media. There was a recent thrombus in the right anterior cerebral artery,
and a proximal segment of the right middle cerebral artery had a
scalloped appearance of the elastica that seemed to represent early
separation from the media. No hematoma was found in the right internal
carotid artery system. No medial degenerative findings were observed in
any vessels. Basilar and intracranial vertebral arteries and all major neck
vessels were normal. Recent infarcts were seen in the left frontal and
occipital lobes (Figure 4B) and in Sommer’s sector on the left.
DISCUSSION
Frequent causes of ischemic stroke in young adults include
extracranial arterial dissection, cardioembolism, premature
atherosclerosis, migraine, and hematologic and immunologic
disorders, as well as drug abuse, primary angiitis of the central
nervous system, connective tissue disorders, mitochondrial
5
2
cytopathies and cerebral autosomal dominant arteriopathy.
Dissecting hematomas appear to be a relatively common cause of
5
,9,11,53
extracranial internal carotid artery obstruction
and of
5
4
vertebrobasilar artery-related infratentorial infarcts.
Immunostains for IgG (rabbit polyclonal antibody, 1:2000, trypsin
predigestion; DAKO, Denmark) showed heavy infiltration of infarcted
cerebral tissue and moderately heavy immunolabeling of the entire
medial layer of all of the major branches of the circle of Willis. IgM
immunostaining (monoclonal antibody, 1:30, trypsin predigestion;
DAKO) of each section containing the left intracranial internal carotid
artery system showed a distinct staining pattern in most of the arterial
segments with little or no IgM in the part of the arterial wall
circumference that was intact, but with patchy to almost homogeneous
IgM deposition in the medial layer adjacent to the subintimal
dissections. IgM staining included the left internal carotid artery
supraclinoid segments where no hematoma was found as well as the
media adjacent to the hematoma (Figure 5). None of the normal arterial
branches had IgM deposition. IgA immunoreactivity (monoclonal
antibody, 1:20, microwave antigen retrieval; DAKO) was negative.
Immunoreactivity for fixed complement component C3 (monoclonal
antibody, 1:100, trypsin predigestion; DAKO) was equivocally present
in the medial layer of arteries with dissections, while normal-appearing
arteries were negative.
Intracranial arterial dissection is decidedly more uncommonly
found than dissecting hematomas of neck vessels. Only
histologically confirmed cases of intracranial internal carotid
artery system dissection are compared here and these are fatal
with the exception of the youngest patients. Fibromuscular
4
0,55
dysplasia may be a rare cause of arterial dissection,
most cases of intracranial arterial dissection that invoke this
although
2
0
disease may be showing only focal arterial healing.
Radiologic identification of patients, such as by the “pearl-
5
6
and-string” sign of beading in anterior and rarely in posterior
5
7
branches of cerebral arteries, is important in diagnosis.
However, whether cases of intracranial arterial dissection with
known histology differ pathologically from surviving cases
5,56-60
studied by radiologic imaging methods is not clear.
Therapy
provided to survivors has included resection with or without a
6
0
bypass procedure,
occlusion, entrapment, wrapping,
5
6
58
endovascular embolization, balloons, and detachable coils.
5
8
Angioplasty and stents may hold promise but relatively few
cases are on record and treatment avenues require further
REVIEW OF THE LITERATURE AND CURRENT FINDINGS
5
9
consideration. The rationale for anticoagulation in these
patients is empirical. Rapid recognition and intervention are
probably the keys to a successful outcome.
The 41 cases with intracranial internal carotid artery system
dissecting hematomas studied histologically in previous
publications, with the addition of the present case, average 17.5
years of age at presentation. The only long-term survivors
In our patient, the right internal carotid and middle cerebral
arteries appear to be undergoing separation of the intimal layer
with no intramural hematoma or significant compromise of the
lumen. This could be an early event leading to a delayed
hematoma or even to recovery when a significant hematoma
does not form. Such a pathologic progression might be a cause
of delay in symptoms, and it might also provide the degree of
2
-
include three patients with onset at one year of age or younger.
4
Of the 42 total cases, 18 had trauma, including 10 with mild or
trivial head trauma, while 10 had physical exertion, two had
migraines, and one had emotional exertion. These cases include
two instances with both mild trauma and physical exertion
3
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LE JOURNAL CANADIEN DES SCIENCES NEUROLOGIQUES
Table: Intracranial Carotid Artery System Dissecting Hematomas with Histologic Findings
Case No.
Age (yr)
Gender
Arterial Site
History
/
2
2
2
2
2
3
3
2
1
1
2
3
4
1
2
3
4
5
6
7
8
9
1
42/M
21/F
47/M
27/F
0.5/M
16/M
0/F
29/F
17/M
11/F
30/F
21/F
30/F
15/M
20/F
1/M
5/M
7/F
7/M
34/M
6/M
17/M
14/M
8/M
15/F
16/M
6/F
Right middle cerebral artery
Left internal carotid, middle and anterior cerebral arteries
Right middle cerebral artery
Right middle cerebral artery
Right middle cerebral artery
Right middle and anterior cerebral arteries
Left middle cerebral artery
Right internal carotid artery
Left internal carotid and middle cerebral arteries
Right internal carotid, middle and anterior cerebral arteries
Right internal carotid and middle cerebral arteries
Left middle cerebral artery
Right middle cerebral artery
Left middle cerebral artery
Right middle cerebral artery
Right middle cerebral artery
Left anterior cerebral artery
Left middle cerebral artey
Left internal carotid artery
Left middle cerebral artery
Moderate head trauma
Moderate head trauma
—
Migraines; Hashimoto's thyroiditis
—
Physical exertion
Head compression at birth?
Post-tonsillectomy
Remote trauma
Remote mild head trauma
Migraine
Recent trauma
Collapsed drinking alcohol
Trauma
Emotional distress
Mild head trauma
Mild trauma
Collapsed at play
Homocystinuria
5
8
1
9
0
1
2
6
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
2
2
2
3
4
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
1
4
2
2
2
4
4
4
5
5
7
8
9
0
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
7
6
0
0
0
7
8
9
0
1
Physical exertion
—
Physical exertion
Mild head trauma
No trauma; ANA weakly positive
Headache followed by trivial trauma
Left middle cerebral artery
Left internal carotid, middle and anterior cerebral arteries
Bilateral internal carotid and middle cerebral arteries
Bilateral internal carotid, middle, and anterior cerebral arteries
Right internal carotid, middle and anterior cerebral arteries
Right internal carotid, middle, anterior and posterior cerebral arteries Systemic fibromuscular dysplasia
Right middle cerebral artery
Right internal carotid, middle and anterior cerebral arteries
Right internal carotid, middle and anterior cerebral arteries
Left middle and anterior cerebral arteries
Right internal carotid and middle cerebral arteries
Left middle cerebral artery
Bilateral internal carotid and middle cerebral arteries
Left internal carotid and middle cerebral arteries
Right internal carotid, middle and anterior cerebral arteries
Right internal carotid artery
—
8/M
9/F
Trivial head trauma
—
No trauma history
—
Mild head trauma
No trauma; platelet hyperaggregation
Playing tug of war
Raking leaves; long-term estrogen treatment
Motor vehicle accident
No head trauma
23/M
13/M
19/M
8/M
20/M
31/F
18/M
46/F
19/M
17/M
12/F
22/M
Left internal carotid and middle cerebral arteries
Left middle and anterior cerebral arteries
Right middle cerebral artery
Left middle cerebral artery
Right internal carotid artery
Head trauma
Physical exertion
Mild head trauma
Mild head trauma and physical exertion
2 (Present case) 8/F
Left internal carotid, middle, anterior and posterior cerebral arteries Recent mild trauma; collapsed at play
right internal carotid and middle cerebral artery intimal
separation without hematoma)
(
ANA = antinuclear antibody.
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THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES
severity of luminal closure that could be an important difference
between surviving and autopsied cases.
One speculative mechanism of exacerbation of arterial wall
7
0
damage involves pre-existing inflammatory disease. Vella et al
Intramural dissections of the intracranial internal carotid
artery system are generally thought to arise when normal gaps in
report an 8-year-old girl with neck trauma followed by radiologic
evidence of an aneurysm developing in a cervical internal carotid
artery in association with circulating antibodies to antiprotease 3.
Case 24 in the Table, with bilateral subintimal dissecting
hematomas of the intracranial internal carotid arteries, has a
2
0
the internal elastic lamina are altered by episodic hypertension.
Sudden stretching from acutely increased blood pressure during
trauma or exertion is thought to cause enlargement of the
openings in the honeycomb structure of the elastica at proximal
3
8
weakly positive serum antinuclear factor. Cystic medial
necrosis as the cause of a focal dissecting hematoma of an
internal carotid artery in case 41 is associated with an elevated
leukocyte elastase content at the lesion site that may have been
2
0,61,62
bifurcations.
It is speculated here that the anatomic site of
the initial elastica disruption is related to tethering of the
supraclinoid internal carotid artery at the anterior clinoid
process. The supraclinoid segment and its middle and anterior
5
1
24
related to arterial damage. Case 4 has autoimmune thyroiditis.
63
cerebral artery branches are mobile, and the cardiac cycle
would cause sudden lengthening and an abrupt recoil of these
arterial branches. Systolic pressure at bifurcations flattens the
These findings suggest a possible place for humoral as well as
for cellular mechanisms to influence the initiation or
enlargement of dissecting mural hematomas.
6
4
apical tissue situated between the two daughter channels and
sequential systolic flattening and diastolic narrowing cause
A possible humoral influence is from preformed
autoantibodies to normally hidden mural antigens. For example,
rare individuals, with preformed antibodies to their cerebral
artery walls, are found in primary angiitis of the central nervous
system. These patients have a variety of comorbidity factors, the
most common being a previous viral infection with supposed
6
5
maximal stress at these apical regions. Cerebral artery
6
6
bifurcations are optimized to avoid such hemodynamic stress
and arteriosclerotic lesions accumulated at bifurcations with age
may play a protective role that further prevents arterial
67
71
dissections after early middle age. In fact, the thickness of
intimal pads at bifurcations increases during childhood and early
molecular mimicry being responsible for autoimmunity. An
analogous mechanism could explain the acute reactivity of IgM
in the subintimal muscle layer preferentially where the elastica
has been lifted off. Although the initial mechanical dissection
should be all that is required to cause severe clinical problems,
we speculate that extensive subintimal dissections may require
additional factors. Thus, cases with limited mural dissection
might have only mechanical subintimal pad damage while very
rare patients with an extensive dissection could have underlying
autoimmunity as one potential factor in their lesion. For
6
8
adulthood and it reaches its greatest thickness at middle age.
This may leave younger people less protected at proximal
bifurcations. It may be that raised blood pressure flowing against
a maturing but still thin intimal pad not too distant from the
tethered proximal supraclinoid internal carotid artery helps to
dislodge the intimal layer over the internal elastic lamina as the
arterial system is translocated longitudinally and vertically
during each cardiac cycle. Tethering at the anterior clinoid
process might therefore translate high stress-strain forces
maximally to initial branches of the intracranial internal carotid
artery, aiding in damage to the intima and honeycomb structure.
Significant damage to the endothelium and elastica appears to be
rapidly amplified into a clinically significant breach of the
internal elastic lamina. The elastica network appears to be
sufficiently strong but its openings are large enough to admit
blood cells into the subintimal layer should the endothelial layer
5
1
example, Thal et al found no immunoglobulin immuno-
reactivity in a short supraclinoid dissecting hematoma that did
not extend far into the middle cerebral artery in case 41, while in
our patient the extensive dissection is associated with an
apparent immunopathologic event.
In support of such mechanisms of vascular damage,
autoantibodies and fixed complement components have been
localized on subintimal and medial smooth muscle elastic
6
2
72
become torn. Thus, as blood pressure increases, a small tear in
the endothelium over the stretching elastica may admit
subintimal blood and the elastica itself may tear, as is sometimes
found histologically. The breach then becomes symptomatic over
minutes to days as the subintimal dissection of blood forces an
initially short segment of the arterial lumen shut. The initial
breach need not be at a bifurcation, but that it involves only the
elastica may be explained by the relative fragility of the internal
elastic lamina compared to the media and adventitia under
microfibrils. In addition, reactivity for IgM and C3 in
intracranial arterial aneurysms has been demonstrated after
7
3
subarachnoid hemorrhage,
while circulating immune
complexes and raised plasma C3 levels are found with post-
7
4
rupture vasospasm. The relatively selective localization of IgM
present in our case appears in the proximal vessels bilaterally,
where no underlying hematoma is seen, as well as distally and it
is deposited where vascular damage is most pronounced. Heavy
IgG deposition is probably reflective of generalized tissue
69
75
tensile extension of the arterial wall. The relatively proximal
location of most intracranial dissections is consistent with this
mechanism. The clinical severity may depend in part on the
extent of dissection, although other factors that would be critical
include the rapidity of cerebral edema formation, the rate of
intracranial pressure increase that may lead to vascular collapse,
and any associated vasculopathy such as medial degeneration or
homocystinuria. Severe vasospasm during migraines may play a
similar role.
damage associated with infarction, while IgA staining serves as
a negative staining control.
Vascular damage, including subintimal dissolution, might
progress relatively rapidly, and most likely independently, by a
second humoral mechanism. Arterial smooth muscle cells under
7
6
high in vitro shear stress, or with the influence of plasma
thrombin, elaborate significant amounts of tissue plasminogen
activator, and plasmin depolymerizes vascular smooth muscle
7
7
elastic fibrils within a few hours. Thrombin might have other
7
8
Our patient experienced such an extensive dissection of the
vascular system that consideration of its magnitude is in order.
direct actions causing vasospasm and complement activation
79-81
after it is activated by exposed vascular smooth muscle cells.
3
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ACKNOWLEDGEMENTS
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091.
We thank Mrs. Sharon Allen, Mrs. Susan Janeczko and Ms. Vicki
Brown for excellent technical assistance. Mr. Gary Burgess provided
photographic assistance. Supported in part by the University of
Manitoba Department of Pathology Research Donations Fund.
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